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Track Design Handbook for Light Rail Transit, Second Edition (2012)

Chapter: Chapter 5 - Track Components and Materials

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Suggested Citation:"Chapter 5 - Track Components and Materials." National Academies of Sciences, Engineering, and Medicine. 2012. Track Design Handbook for Light Rail Transit, Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22800.
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5-i Chapter 5—Track Components and Materials Table of Contents 5.1 INTRODUCTION 5-1  5.2 RAILS 5-1  5.2.1 Introduction 5-1  5.2.1.1 Types of Rail for Light Rail Transit 5-1  5.2.1.2 Rail Lengths 5-1  5.2.1.3 Joining Rails 5-2  5.2.1.4 Rail in Curves 5-2  5.2.1.5 Rail Handling 5-2  5.2.1.6 Rail/Wheel Interface Issues 5-2  5.2.2 Tee Rail 5-3  5.2.2.1 Rail Section—115 RE 5-3  5.2.2.2 Rail Strength and Metallurgy 5-5  5.2.2.3 Rail Straightness 5-6  5.2.2.4 Rail Running Surface Finish 5-6  5.2.2.5 Precurving of Tee Rail 5-7  5.2.2.6 Procurement of Tee Rail 5-8  5.2.3 Groove Rail 5-9  5.2.3.1 Advantages of Groove Rail for Embedded Track 5-9  5.2.3.2 Available Groove Rail Sections 5-9  5.2.3.3 Groove Rail Head Profile Compatibility with Tee Rails 5-11  5.2.3.4 Groove Rail Strength and Chemistry 5-16  5.2.3.5 Precurving of Groove Rail 5-18  5.2.3.6 Procurement of Groove Rail 5-18  5.2.3.7 Block Rail 5-19  5.2.4 Rail Wear 5-20  5.2.5 Wear-Resistant Rail 5-21  5.3 RESTRAINING RAIL DESIGNS FOR GUARDED TRACK 5-22  5.3.1 Groove Guard Rail for Embedded Track 5-22  5.3.1.1 North American Girder Guard Rail—Background 5-22  5.3.1.2 Restraining Rail Issues with CEN Groove Rails 5-23  5.3.1.3 The Possibility of a New North American Groove Rail 5-23  5.3.1.4 Alternatives to Groove Rail for Guarded Embedded Track 5-24  5.3.2 Restraining Rail Options for Use with Tee Rail Construction 5-25  5.3.2.1 Vertically Mounted Restraining Rails 5-25  5.3.2.2 Horizontally Mounted Restraining Rails 5-27  5.3.2.3 Strap Guard Rail 5-27  5.3.2.4 33C1 Restraining Rail 5-30  5.3.3 Restraining Rail Recommendations 5-32  5.3.4 Restraining Rail Thermal Expansion and Contraction 5-33  5.3.5 Restraining Rail Restrictions 5-33 

Track Design Handbook for Light Rail Transit, Second Edition 5-ii 5.4 RAIL FASTENINGS AND FASTENERS 5-34  5.4.1 Definitions 5-34  5.4.2 An Introduction to Common Designs 5-34  5.4.3 Insulated Fastenings and Fasteners 5-35  5.4.3.1 Isolation at the Rail Base 5-36  5.4.3.2 Isolation at the Fastener Base 5-36  5.4.4 Elastic Rail Clips 5-36  5.4.5 Fastenings for Timber and Concrete Cross Ties for Ballasted Track 5-38  5.4.6 Fasteners for Direct Fixation Track 5-40  5.4.6.1 Fastener Design Consideration 5-40  5.4.6.1.1 Vertical Static Stiffness 5-41  5.4.6.1.2 Ratio of Dynamic to Static Stiffness (Vertical) 5-41  5.4.6.1.3 Lateral Restraint 5-41  5.4.6.1.4 Lateral Stiffness at the Rail Head 5-42  5.4.6.2 Shims beneath Direct Fixation Rail Fasteners 5-42  5.4.7 Fasteners and Fastenings for Embedded Track 5-43  5.5 CROSS TIES AND SWITCH TIES 5-45  5.5.1 Timber Cross Ties 5-45  5.5.2 Concrete Cross Ties 5-47  5.5.2.1 Concrete Cross Tie Design 5-48  5.5.2.2 Concrete Cross Tie Testing 5-48  5.5.3 Switch Ties—Timber and Concrete 5-48  5.5.3.1 Timber Switch Ties 5-48  5.5.3.2 Concrete Switch Ties 5-49  5.6 JOINING RAIL 5-50  5.6.1 Welded Joints 5-51  5.6.1.1 Electric Pressure Flash Butt Weld 5-52  5.6.1.2 Exothermic (“Thermite”) Rail Welding 5-53  5.6.2 Insulated and Non-Insulated Bolted Rail Joints 5-54  5.6.2.1 Non-Glued Insulated Rail Joints 5-54  5.6.2.2 Glued Bolted Insulated Rail Joints 5-55  5.6.2.3 Bolted Rail Joints 5-55  5.6.3 Compromise Joints and Compromise Rails 5-56  5.7 BALLAST AND SUBBALLAST 5-56  5.7.1 Ballast 5-57  5.7.1.1 Ballast Materials 5-57  5.7.1.2 Ballast Gradation 5-58  5.7.1.3 Testing Ballast Materials 5-59  5.7.2 Subballast Materials 5-61  5.8 HIGHWAY/RAILWAY AT-GRADE CROSSINGS 5-61  5.9 TRACK DERAILS 5-63  5.10 RAIL EXPANSION JOINTS 5-64  5.10.1 Rail Expansion Joint Theory 5-64 

Track Components and Materials iii-5 56-5 noitarugifnoC larutcurtS 2.01.5 5.10.3 Rail Expansion Joint Track Details 5-65 5.10.3.1 Rail Expansion Joints for Open Trackforms 5-65 5.10.3.2 Rail Expansion Joints for Embedded Track 5-66 5.10.4 Rail Anchorages 5-67 5.11 END-OF-TRACK BUMPERS AND BUFFERS 5-68 5.11.1 Warning Signs/Signals 5-69 5.11.2 Fixed Non-Energy-Absorbing Devices 5-69 5.11.3 Fixed Energy-Absorbing Devices 5-70 5.11.3.1 Non-Resetting Fixed Devices 5-71 5.11.3.2 Resetting Fixed Devices 5-71 5.11.4 Friction (or Sliding) End Stops 5-71 5.12 REFERENCES 5-72 List of Figures 4-5Figure 5.2.1 115 RE tee rail with 8-inch crown radius Figure 5.2.2 CEN 51R1 and 59R2 groove rail sections 5-12 Figure 5.2.3 CEN 53R1 and 60R2 groove rail sections 5-13 Figure 5.2.4 CEN 62R1 and 67R1 groove rail sections 5-14 Figure 5.2.5 CEN 56R1 groove rail and 76C1 construction rail sections 5-15 Figure 5.2.6 LK1 block rail section 5-19 Figure 5.3.1 Typical restraining (guard) rail arrangements 5-26 Figure 5.3.2 Strap guard rail 5-28 Figure 5.3.3 33C1 restraining rail 5-30 Figure 5.4.1 Isolation at the rail base 5-37 Figure 5.4.2 Isolation at the fastener base 5-37 Figure 5.4.3 Threadless plate fastenings on concrete switch ties 5-39 Figure 5.4.4 Elastic rail clip assembly for embedded track 5-44 Figure 5.6.1 Machined central block for compromise rail 5-57 Figure 5.10.1 Double-ended sliding rail expansion joint 5-66 Figure 5.10.2 Rail anchorage 5-67 Figure 5.11.1 Friction energy buffer stop 5-71 List of Tables Table 5.2.1 Chemical composition of CEN groove rail steel 5-17 Table 5.2.2 Brinell and Rockwell hardness related to tensile strength 5-17 Table 5.7.1 Ballast gradations 5-58 Table 5.7.2 Limiting values of testing for ballast material 5-60

5-1 CHAPTER 5—TRACK COMPONENTS AND MATERIALS 5.1 INTRODUCTION The track components that form the track structure generally include steel rails, a rail fastening system, and an underlying structure that provides overall stability and strength. The most familiar form of trackwork is ballasted track, where cross ties embedded in ballast rock provide the last function. However, light rail transit includes several other types of trackforms, each designed to meet the needs of a particular trackway condition, such as public streets, aerial structures, and subway tunnels. This chapter discusses all of these trackforms and the sundry components used in each, as well as elaborating on the various designs and requirements. The information in this chapter pertains to light rail transit systems that use overhead contact system (OCS) electric traction power distribution, with the running rail providing the negative return path. In addition, the rails are often used as a component of the signal system. While this discussion is specific to LRT, many LRT track components are common with those used on heavy rail metro transit systems and freight, commuter, and intercity railway lines. 5.2 RAILS 5.2.1 Introduction Rail is the most important—and most expensive—element of the track structure. It is the point of contact with the vehicle wheel, the structural beam supporting the vehicle load, and one location where noise is generated. Hundreds of different rail sections have been created since the first strip of iron was placed over a longitudinal timber beam nearly 200 years ago. Each new rail section has been developed to satisfy a particular combination of wheel/rail loading in a specific trackway environment. 5.2.1.1 Types of Rail for Light Rail Transit Two types of rail are in common use on light rail transit: tee rails and groove rails. Tee rails, so called because they vaguely resemble an inverted upper case letter T, were first developed for use in ballasted track. When rails were placed in paved streets, groove rails (commonly called girder rails in North America) were developed to provide the needed flangeway. 5.2.1.2 Rail Lengths When manufactured for use by a railroad, rails are naturally delivered on railroad freight cars and because of the evolution of railroad freight cars, rail lengths have increased over the years. In recent times, North American standards for rail lengths have increased from the 39-foot [11.8- meter] lengths that prevailed until about 1975, up to 78-, 80-, and 82-foot [23.8-, 24.4- and 25- meter] lengths. The actual length of these longer rails varies due to each manufacturer’s equipment. Since about 2005, some North American and European rail mills can now produce tee rail as long as 400 feet [122 meters]. These extremely long rails were developed in response to freight railroads’ interest in reducing the number of rail welds necessary to produce continuous strings of rail. However, extremely long rails require special handling methods and equipment so as to avoid damage and obviously cannot be routinely moved over the highway. Should

Track Design Handbook for Light Rail Transit, Second Edition 5-2 favorable conditions for delivery and handling of such lengths prevail, rail transit projects could consider procuring such longer rail sections. 5.2.1.3 Joining Rails Bolted rail joints between contiguous rails have always been the weak link in the track. Welding of the individual rolled rail lengths (sometimes called “sticks”) into continuous welded rail (CWR) (called “strings”) is now customary to eliminate bolted rail joints, improve the performance of the rail in track, and provide a quieter track system. On an electrified railway and any railway using track-circuit-based signaling, welded rail has the advantage of providing a better path for electric current. Continuous welded rail has been made possible by the development of rail welding systems. The two most prevalent rail welding systems are electric flash butt welding and exothermic (also known as “thermite”) welding. Both types of welding are discussed in Article 5.6.1 of this chapter. Flash butt welded CWR is the recommended standard for transit trackwork. The only exceptions are locations, such as within special trackwork and very sharp curves using precurved rail, where the flash butt welding equipment cannot be clamped to the rail. Thermite welding is therefore used in such locations. Rarely, under specific or unusual conditions, bolted jointed rail may be more practical to suit specific site conditions and future maintenance procedures. However, wherever a segment of bolted rail is proposed immediately contiguous to a CWR string, an analysis of the ability of the rail anchoring system to resist thermal forces should be undertaken so that “pull-aparts” do not occur during cold weather. 5.2.1.4 Rail in Curves While generally very stiff, rail can be surprisingly ductile, particularly as long strings of CWR, and it can be field curved down to fairly tight radii without any special equipment. In the case of 115 RE rail, CWR can usually be laid down to a 300-foot [about 90-meter] radius without difficulty. Below that threshold, it is common practice to precurve the rail so as to eliminate internal stresses that attempt to straighten the rail. For additional information about the precurving of both groove rail and tee rail, refer Articles 5.2.2.5 and 5.2.3.5 in this chapter. 5.2.1.5 Rail Handling See Chapter 13 of this Handbook, Article 13.3, for discussions concerning the handling of rail and other trackwork materials during construction. 5.2.1.6 Rail/Wheel Interface Issues Wheel/rail interface is one of the most important issues in the design of the wheel profile and the railhead section. Trackwork engineers on freight railroads have a difficult time maintaining an optimized rail/wheel interface because they must accommodate an extremely wide array of rolling stock and wheel maintenance conditions. The sheer number of freight cars in North America, which are owned by hundreds of business concerns, makes it virtually impossible to maintain freight car wheels to tight standards. By contrast, light rail transit systems usually have relatively small fleets, often of only one or two vehicle types, and do not have to contend with vehicles from other owners. These “captive” vehicle fleets provide the opportunity to custom design and maintain an optimal wheel/rail interface, with a single standard for wheel profile that is designed to match the types of rail used on the system.

Track Components and Materials 5-3 Vehicle operational and ride performance is highly dependent on the primary and secondary suspension systems that allow the vehicle to traverse the track system and negotiate track curves. The manner in which the wheels and axles are incorporated into the vehicle truck, together with the wheel and rail profiles, control how well the vehicle truck steers in curves and at what speed truck hunting will commence on tangent track. On trucks with tapered wheels rigidly mounted on conventional solid axles, the contact zone between the wheel and rail will migrate to a position near the gauge corner on the high outside rail of curves to improve steering. The contact zone on the low rail is best located toward the field side of the rail head. These two distinct contact zone locations take advantage of the tapered wheel rolling radius differential so as to automatically provide axle steering due to the conical shape formed by the different rolling radii between the two wheels. This action does not occur on trucks equipped with either independently rotating wheels or non-tapered (also known as “cylindrical”) wheel tread profiles. Wheel and rail design that produces a wider conformal contact zone, or a wider contact and wear pattern, will, after a short period of service life, result in poor vehicle tracking performance through curved track. A wider contact band can also exacerbate any tendency for truck hunting, which in turn is one cause of corrugations on the rail head. Conformal contact conditions are produced when the rail head radius is worn to a relatively flat condition and the wheel is worn to a similar flat or hollow condition. This stimulates rail head corrugation growth, producing an irregular wavy wear zone across the head of the rail. These corrugations result in unsatisfactory ride quality and excessive noise. 5.2.2 Tee Rail Tee rail is the prevalent section for running rail on contemporary light rail systems for all three types of track structure (ballasted, direct fixation, and embedded). Overseas, tee rails are commonly referred to as either “Vignole rails” or “flat bottom rails,” and dozens of sections are still manufactured. In North America, tee rail sections have evolved from about a hundred sections circa 1900 down to the American Railway Engineering and Maintenance-of-Way Association’s (AREMA’s) four standard sections—115 RE, 132 RE, 136 RE, and 141 RE. Several other rail sections (not documented here) are still manufactured for specific customers, generally in very small quantities and on an irregular schedule. Rail section designs, the composition of the steel rails are rolled from, and the post-rolling treatments used to increase their strength and resistance to wear all continue to evolve and be improved worldwide. 5.2.2.1 Rail Section—115 RE Selection of the running rail section must be performed with consideration for economy, strength, and availability. The 115 RE rail section (see Figure 5.2.1) is the primary section used on current North American light rail track systems. This is largely because, as a recognized and popular standard section for freight railroad use, there is a guaranteed continuous supply from many manufacturers. The 115 RE section has more than adequate beam strength to support light rail vehicle wheel loads on standard spacings for cross ties and direct fixation fasteners and has sufficient cross-sectional area to provide a low-resistance negative return conductor in the traction power circuitry. As of 2011, because of the popularity, economics, and ready availability of 115 RE rail, there is virtually no reason to consider tee rails of non-North American standard designs.

Track Design Handbook for Light Rail Transit, Second Edition 5-4 Figure 5.2.1 115 RE tee rail with 8-inch crown radius

Track Components and Materials 5-5 The “115” and the “RE” in the rail section identification 115 RE mean the following: • 115 is the mass (weight) in pounds per one yard length. It is rounded from the exact mass of 114.3757 pounds per yard and is equivalent to 56.737 kilograms per meter. • RE = AREMA standard rail section. From a structural perspective and quite likely from an electrical perspective, a rail weighing about 100 pounds per yard [roughly 49.6 kg/m] would be sufficient for rail transit. Notably, many European tramways and Stadtbahn operations use the CEN 49E1 section, which weighs very nearly 100 pounds per yard, for open track areas. The only 100-pound rail commonly available in the United States is “100-8,” a modification of the former 100 ARA-B section incorporating an 8- inch crown radius. It is rolled by only one manufacturer, mostly for the needs of one very large transit agency. 5.2.2.2 Rail Strength and Metallurgy Chemical composition guidelines for the steel used to make running rail are standardized in the AREMA Manual for Railway Engineering, Chapter 4, for both standard rail and high-strength rail. The use of alloy rail is not recommended to obtain high-strength standards because of the additional complexities of welding alloy rail. The current AREMA standards for standard strength and high-strength rail hardness (developed by the head hardening procedure) are the following: • Standard Rail—321 minimum Brinell Hardness Number (BHN). • High-Strength Rail—341 to 388 BHN (may be exceeded provided a fully pearlitic microstructure is maintained). The life of the rail can be extended [3] by increasing the rail’s resistance to • Wear. • Surface fatigue-damage. • Fatigue defects. Fatigue is rarely an issue in rail transit service since the loadings are much less than they are for railroad service and the plastic deformation that results from high contact stresses occurs much less often. Wear, on the other hand, is a significant issue in transit service, particularly in sharp curves. Rail steel hardness, cleanliness, and fracture toughness can increase resistance to wear. The effect of rail hardness in resisting gauge corner and gauge face wear is a known fact. Increased rail hardness in combination with minimized sulfide inclusions reduces the likelihood of rolling contact fatigue. This, in turn, reduces development of subsequent surface defects such as head checks, flaking, and shelly spots. Clean steel, free of oxide inclusions, combined with good fracture toughness, reduces the likelihood of deep-seated shell formations. Both shelly spots and deep-seated shells can initiate transverse defects, which ultimately cause broken rails. Current rail standards include increased rail hardness and improved rail steel cleanliness, with the pearlitic steels peaking at 390 BHN. Research commencing in the 1990s focused on other metallurgies such as bainitic steels. Although bainitic steels of the same hardness as pearlitic steel are not as wear resistant, high-hardness low-carbon bainitic steel offers wear resistance superior to that of pearlitic steel.

Track Design Handbook for Light Rail Transit, Second Edition 5-6 A general guideline for transit installations is the use of clean rail steel with a hardness not less than • 300–320 BHN (standard rail) in tangent tracks, except at station stops (and similar locations of heavy traction or braking) and gradients steeper than 4%. • 380–390 BHN in tangent tracks at station stops, gradients steeper than 4%, curved track with radii less than 1640 feet [500 meters] and all special trackwork components including switch points, stock rails, guard rails, frog rails, and rails within the special trackwork area. However, experiences during the 1990s and early 2000s suggest that there may be benefits to specifying head hardened rail steel in all primary tracks. Hardened rail is known to retard the growth of corrugations, reduce rail head flanging wear, and increase overall rail life. In addition, specifying a single rail type throughout a project simplifies both construction and future maintenance. Serious consideration should be given to this option for locations such as embedded track, where rail grinding with conventional equipment is difficult. Directly related to rail chemistry is the matter of rail conductivity. So that the rail provides sufficient capacity for the negative return side of the traction power circuit, guidelines suggest that its electrical resistance should be a maximum of 0.0092 ohm/1000 ft at 68 degrees F [0.0302 ohm/km at 20 degrees C). Normal rail steel chemistry for any rail section likely to be used for LRT service meets this requirement. As a practical matter, any attempt to alter the rail chemistry so as to increase its conductivity (such as increasing the percentage of copper) would likely have adverse effects on the rail’s mechanical properties. It is unlikely that commercial rolling mills would provide warranties for rail that has not been rolled to a recognized standard such as AREMA or an applicable European Norm. 5.2.2.3 Rail Straightness An additional measure worth considering for locations where noise and vibration are particularly sensitive issues is the selective use of so-called “super straight” rail to improve ride quality and reduce noise by providing a more consistent contact band. For additional information on rail straightness and noise refer to Chapter 9, Article 9.3.3.7. 5.2.2.4 Rail Running Surface Finish Running rails are rolled to specifications that have very tight tolerances on dimensions, including the profile of the rail head. Manufacturers generally have little difficulty meeting those tolerances when measured at the actual clean surface of the rolled steel. However, rail is generally delivered from the manufacturer with a bluish to black surface residue called “mill scale.” Mill scale is composed of iron oxides, is typically about 1/32 inch [1 mm] thick, and is a byproduct of the hot rolling process. Mill scale is generally only loosely attached to the underlying steel, is usually discontinuous, and will frequently, albeit somewhat irregularly, flake off during handling of the rail from the steel mill to the track. So long as the mill scale is intact, it provides the underlying steel with an unintended but reasonably effective protective coating from corrosion. Mill scale is of no real consequence on the base or web of the rail except that it must be removed from the vicinity of a rail weld before welding. In railroad service, any mill scale on the running surfaces of the rail is very quickly removed by abrasion due to the extremely high contact

Track Components and Materials 5-7 stresses between the rail and the wheels. However, under transit wheel loadings, mill scale on the running surfaces of the rail will not wear away as quickly and can cause several problems: • It can interfere with the reliable shunting of low-voltage signal circuits. • It can interfere with traction power ground, causing arcing as the traction power current burns through the mill scale to find good ground on the underlying rail steel. This arcing can result in appreciable damage to the rail head and the vehicle wheels. • The residual mill scale, together with any damage caused by arcing, can cause the contact band between the top of rail and the wheel to become irregular, resulting in degraded performance. This can initiate wheel dynamic responses that subsequently result in higher noise and, at worst, possible corrugation of the rail’s running surface. Because of these issues, it is customary for rail transit projects to lightly grind the running surface of newly laid rail so as to remove the mill scale and thereby provide a clean and uniform running surface for the wheels. The problem is that the grinding process itself can possibly damage the surface of the rail. Even under the best of circumstances, grinding alters the as-rolled geometry of the rail head and thereby possibly invalidates some of the assumptions made concerning how the wheel will interface with the rail. If the rail is in embedded track or has an adjoining restraining rail, the chances that grinding will alter the as-rolled rail profile into an undesirable contour are even higher. These issues could be relieved if there was a reliable method of removing the mill scale on a production basis before the rail is laid in track and perhaps even at the time it is rolled. However, as of this writing, no such methods are commonly available for production use. Circa 1990, some success was achieved using the equivalent of a “belt sander,” but the process was very slow, not well adapted to embedded track, and was thus never adopted as a standard practice. Blast cleaning methods might be promising, but it is not believed this has ever been attempted on any sort of production basis. The development of a production method for removing mill scale from the rail head, perhaps at the rolling mill, could result in a much better wheel/rail interface from the very start of rail operations. Additional research and development is very much needed in this area. 5.2.2.5 Precurving of Tee Rail Where the track radius is sharp enough that springing the rail to radius and keeping it there would be difficult or perhaps even dangerous, the rail must be precurved. Precurving rail essentially requires stretching the rail beyond the elastic limit of the steel so that it cannot spring back to its original straight configuration. Precurving is sometimes desirable even when the radius is within the range where the rail can be sprung into alignment. Refer to discussions in Article 6.11 in Chapter 6 and Article 13.3.2.2 in Chapter 13. These are the general guidelines for precurving 115 RE tee rail: • Standard Rail − Precurve rail horizontally for curve radii below 300 feet (91 meters). − Precurve rail vertically for curve radii below 755 feet (230 meters).

Track Design Handbook for Light Rail Transit, Second Edition 5-8 • High-Strength Rail − Precurve rail horizontally for curve radii below 400 feet (120 meters). − Precurve rail vertically for curve radii below 980 feet (300 meters). Rail should be precurved in the vertical plane whenever the mid-ordinate of the vertical geometry exceeds the natural sag or droop of the rail length being used. “Sag” means when the rail is supported only at the ends. “Droop” is when the rail is supported only in the middle. Vertical precurving can often be required when embedded track rails must conform to severely warped pavement surfaces in a street intersection. Precurved rails are often needed in high-wear locations where the rail is replaced more frequently. These locations are sometimes designed with standard bolted rail joints rather than welded joints to facilitate rail change out. This does not necessarily work in practice since change out of individual rails in a worn sharp curve could result in significant gauge face mismatch between old and new rails. The traditional process for precurving rail was the use of a “gag press,” holding the rail at two points and using a hydraulic ram to place a tiny kink in the rail at an intermediate point. The process was repeated at intervals through the required length of the rail to produce a reasonable approximation of the desired circular curve radius. This process has largely been replaced by roller bending equipment that still uses three points, but produces an absolutely uniform curve rather than a series of kinks. Regardless of the equipment used, it is typically not possible to get a true curve in the last 18 inches [about 0.5 meter] of the rail. On extremely sharp radius curves, typically anything sharper than a 100-foot [30-meter] radius, it is therefore usually necessary to crop off these straight ends so that the joints are not kinked. For much the same reason, in bolted rail construction, it is often necessary to precurve the joint bars for extremely tight curves. It is typically possible to spring long strings of CWR to fairly tight radii, and some track constructors will use that as a reason why they don’t need to precurve the rail. However, springing the rail leaves it in a state of high internal stress. Obviously, the sharper the curve, the higher the stress, and that stress can make track maintenance more difficult. For example, a sprung curve in ballasted track is more likely to develop a sun kink at a single weak spot in the ballast section. The same curve using precurved rail will maintain line better. A broken rail that had been sprung into alignment may be nearly impossible to fix since the maintenance staff could have great difficulty getting the rail ends to line up squarely so that they could be rejoined by either a bolted joint or a field weld. Some contractors have brought roller rail bending equipment onto jobsites and precurved previously welded strings of CWR for immediate installation in track. This method eliminates both the need to crop straight rail ends and the use of thermite welds and can thereby save both time and costs, provided the jobsite provides sufficient room to do the work. 5.2.2.6 Procurement of Tee Rail Procurement of rail should be done in accordance with AREMA Chapter 4, Part 2, Section 2.1, supplemented by any specific requirements of the transit project. A major consideration for rail procurement is the proposed methods for shipping, handling, and welding. These issues should

Track Components and Materials 5-9 be thought through before finalizing the rail procurement methodology and specifications. See Chapter 13 for additional considerations about procurement of rail and other track materials. 5.2.3 Groove Rail While tee rail can be and is commonly used in embedded track, groove rail is arguably the preferred rail section for such construction. As the name implies, groove rails have a preformed flangeway in their top surface. On one side of the flangeway is the head of the rail, where the rail vehicle wheel treads roll in the usual manner. On the opposite side of the flangeway is a thinner segment of rail steel, variously called the “tram,” “lip,” or “guard.” The tram defines the inner edge of the flangeway and, in embedded track, conveniently excludes the adjoining pavement material from encroaching on the flangeway. Such rails were popularly known as “girder rails” in North America, but have not been rolled in the United States since the 1980s. Overseas, they are known as “groove rails” in the English language. The equivalent term in German is rillenschiene. The French call these rails rail à orniére or rail à gorge profonde. This Handbook will use the English version of the European terminology unless specifically referring to one of the girder rail sections formerly rolled in the United States. 5.2.3.1 Advantages of Groove Rail for Embedded Track Groove rail has two principal advantages for use in embedded track: • The preformed flangeway eliminates the tedious process of forming a flangeway in the embedding pavement. Instead, the constructor need only screed and finish the pavement between the trams of the parallel groove rails. This translates directly into construction cost savings by eliminating an appreciable amount of labor. • It is easier to achieve a high level of electrical isolation using groove rail than it is with tee rail, especially when using a rail boot for isolation. The flangeways in embedded track, particularly track that is longitudinally level or only on a slight gradient, tend to fill up with the dirt, grit, and debris that is endemic to any street environment. This detritus, especially when wet, can be electrically conductive. When a flangeway is formed adjacent to tee rail, the debris will bridge the top of the rail boot in the floor of the flangeway, resulting in trace amounts of stray traction power current. However, groove rail can be completely wrapped in the rail boot on both sides of the rail, and stray current leakage can be appreciably less. Groove rail has a distinct advantage when it is deemed desirable to use paving stones or bricks in the track area so as to achieve some architectural goal or ambiance. Such pavers can be laid directly up against the booted rail without going to extra measures to keep them from encroaching on the flangeway. See Chapter 4, Figure 4.7.13, for an alternative detail using brick pavers with tee rail. 5.2.3.2 Available Groove Rail Sections The European Committee for Standardization (in French, Comité Européen de Normalisation, hence the usual abbreviation “CEN”) has developed European Norm specification EN 14811 that

Track Design Handbook for Light Rail Transit, Second Edition 5-10 lists and illustrates the groove rail profiles available and stipulates requirements for their manufacture. There are about a dozen groove rail sections still being manufactured, most of which have been adopted as standard sections under the European Norms. Several of these sections are older designs that were kept in the Norms only because some transit agencies were still using them and apparently disinclined to change to newer designs. Because of this, not all the groove rails shown in EN 14811 should be considered for North American use. In most cases, use of these groove rails is not suggested due to gauge corner radii that are dramatically inconsistent with 115 RE tee rail and flangeways that are too narrow for most wheel flanges in use in North America. Not all groove rail sections are available from all European rolling mills, and some mills offer proprietary post-rolling treatment processes. Readers should confer with North American sales representatives of these rolling mills for current information concerning available sections and associated technical data. As of 2010, five CEN groove rail sections are in common use in North America. These are listed below with both the current CEN identifiers and the names by which they were formerly known: • Section 51R1 (formerly Ri52N) shown in Figure 5.2.2. • Section 53R1 (formerly Ri53N) shown in Figure 5.2.3. • Section 59R2 (formerly Ri59N) shown in Figure 5.2.2. • Section 60R2 (formerly Ri60N) shown in Figure 5.2.3. • Section 62R1 (formerly NP4aS) shown in Figure 5.2.4. In addition, one other groove rail is worthy of consideration since it is one of only a few sections that can easily accommodate AAR wheel profiles and gauges: Section 67R1 (formerly Ph37a) shown in Figure 5.2.4. So as to simplify the images, the dimensional information provided in Figures 5.2.2 through 5.2.5 has been abbreviated so that only key dimensions are shown. Complete dimensional data are readily available from vendors or by consulting EN 14811. The flangeway in 67R1 is dramatically wider than the flangeways of the other groove rail sections. Nevertheless, despite first appearances, the 67R1 flangeway is actually in compliance with the rules set out in the Americans with Disabilities Act Accessibility Guidelines (ADAAG) for LRT flangeways in pedestrian areas. The CEN 46G1 and 68R1 sections can also accommodate railroad wheel flanges and gauges, and the former has the advantage of being somewhat shorter than the 67R1 section. Nonetheless, neither the CEN 46G1 section nor the 68R1 section are as common as the 67R1, and sources of supply are more limited. Groove rails that could reliably be used as a restraining rail are limited. The following three sections are suggested based on the thickness and height of the tram. • Section 56R1 (formerly Ri1c), as shown in Figure 5.2.5, has a raised tram and more closely resembles the former ATEA and AREA girder guard rails than any other groove rail section. However, it has a very small (6-millimeter [0.24-inch] ) gauge corner radius and an exceptionally narrow flangeway. Unless a correspondingly small wheel profile is used, the 56R1 section likely can be used in North American LRT tracks only by

Track Components and Materials 5-11 extensively machining the groove to increase the gauge corner radius and widen the flangeway. • Section 62R1 (formerly NP4aS), shown in Figure 5.2.4, has been used successfully by three legacy streetcar systems in North America, all of whom use small wheel flanges. However, the narrow flangeway and steep guard face are far less than optimal compared to the former North American girder guard rail sections. • Section 76C1, shown in Figure 5.2.5, is “construction rail” section most commonly used for fabrication of special trackwork components such as flange-bearing frogs. At some expense, it would be possible to have a customized flangeway of whatever shape milled into the head of this section. Other groove rail sections listed in CEN Standard EN 14811 include 46G1, 52R1, 55G1, 55G2, 57R1, 59R1, 60R1, 60R3, 62R1, 63R1, 68R1, and 68G1. These are not recommended for North American use due to small gauge corner radii and insufficient flangeway width or depth. The 55G1 and 55G2 sections have a base width equal to that of 115 RE tee rail, but the base thickness and slope are radically different than 115 RE. Also, the relationship between each rail’s gauge line and web vertical axis is appreciably different, so the common base width is of little advantage when considering rail fastening systems. EN 14811 includes several other sections of rail that are classified as “construction rail profiles.” These sections are primarily used as base materials for fabrication of special trackwork components. Several other groove rail sections are rolled that were not adopted as CEN standards. For example, there is a GP41 section that is very similar to the CEN-adopted GP35 section but has a 41-mm (1.61-inch) groove as opposed to the 35-mm (1.38-inch) groove of GP35. The selection of groove rail currently available is limited to the European standards listed above. To use these narrow flange girder rails, the wheel gauge and track gauge must be compatible with a reduced gauge clearance between wheel and rail to allow for wheel passage. The wheel flange profile may need to be customized. For additional information on wheel profiles and groove rail, refer to Chapters 2 and 4. 5.2.3.3 Groove Rail Head Profile Compatibility with Tee Rails Wheel compatibility based on head radii and wheel contact zone is possible if the wheel profile is designed to suit both tee rail and girder rail sections. The vehicle/wheel designer and the track designer must consider the impacts of wheel/rail performance resulting from standardized rail sections. For additional information on wheel/rail conformance refer to Chapter 2. When the former Ri59 and Ri60 rail sections were redesigned to incorporate a 13-mm [about ½- inch] gauge corner radius, the crown of the head was also reprofiled. Together, these changes achieved a close compatibility with the former S49 (now 49E1) Vignole rail section, which is the predominant tee rail used in open track areas of European tramways and Stadtbahn systems. Coincidentally, this change in the groove rail design also made them, when fastened to a flat base, a reasonably good match with the original design 115 RE tee rail when it is installed at a standard cant of 1:40.

Track Design Handbook for Light Rail Transit, Second Edition 5-12 Figure 5.2.2 CEN 51R1 and 59R2 groove rail sections

Track Components and Materials 5-13 Figure 5.2.3 CEN 53R1 and 60R2 groove rail sections

Track Design Handbook for Light Rail Transit, Second Edition 5-14 Figure 5.2.4 CEN 62R1 and 67R1 groove rail sections

Track Components and Materials 5-15 Figure 5.2.5 CEN 56R1 groove rail and 76C1 construction rail sections

Track Design Handbook for Light Rail Transit, Second Edition 5-16 Until 2009, the 115 RE rail section, which was first rolled shortly after World War II, included a 10- inch (254-millimeter) crown head radius. That radius is a reasonably good match to popular European groove rail sections that have a 300-mm [11.81-inch] crown radius. The 300-mm radius matches the 49E1 Vignole rail section often used on European light rail systems. However, in 2009, AREMA modified the design of the 115 RE rail to a crown radius of 8 inches, [203 mm] so as to match other modern North American tee rails, such as a the 141 RE section. The smaller radius is designed to better handle high loadings from average worn freight car wheels. With this change to the head radius of the 115 RE section, compatibility with European groove rails has been diminished. Nevertheless, a smaller crown radius reduces the contact band along the rail to a well-defined ½- to 5/8-inch [12- to 15-millimeter] width. Light rail transit operations that have relatively little or no groove rail in track will likely benefit from this reduced contact band, as it can help control truck hunting in tangent track. Several transit agencies have incorporated more radical improvements, such as asymmetrical rail grinding (See Chapter 4, Article 4.2.5.3) for outside and inside rail in track curves, with documented operational improvements in wheel/rail performance. For additional information on rail grinding refer to Chapter 9, Article 9.2.1.3.3, and Chapter 14, Article 14.6.2.2. When a groove rail track system is designed to match transit wheel profiles and gauges, off-the- shelf track construction/maintenance-of-way equipment (constructed to AREMA and AAR standards) will usually not fit the track. Damage to new track has been experienced under these circumstances. 5.2.3.4 Groove Rail Strength and Chemistry The customary European steel manufacturing practice is to roll standard groove rail sections in accordance with the current CEN EN14811. The standard groove rails are produced in many grades of rail steel as shown in Table 5.2.1. Each designation classifies the groove rail per chemical composition by percent of mass, tensile strength, elongation in percent, and hardness. Hardness is designated as “HBW,” which is equivalent to the Brinell Hardness Number (BHN) customarily used in North America. To meet North American requirements for surface hardness a groove rail section must have a minimum tensile strength of 1,131 MPa (N/mm2), which equates to approximately 340 BHN according to Table 5.2.2. So as to match AREMA high-strength tee rail, an optimal CEN groove rail steel designation from Table 5.2.1 would be R340GHT, a rolled rail section with a minimum tensile strength of 1175 MPa or 1175 N/mm2, having a hardness of 340 to 390 BHN. Groove rail of this hardness can be obtained only through a combination of rail chemistry and post-rolling hardening procedures and may not be available from all manufacturers. Since groove rail is a manufactured product, its metallurgy is subject to changes and improvements. Manufacturers also have proprietary processes that may be beneficial for specific LRT projects. Users of this Handbook are encouraged to confer with sales representatives of the various competing steel companies for current information.

Track Components and Materials 71-5 Table 5.2.1 Chemical composition of CEN groove rail steel CEN Steel Designation Percent by Mass of Liquid Steel H, max in PPM Tensile Strength, MPa, min Running Surface Hardness, HBW C Si Mn P (max) S (max) R200 0.40 to 0.60 0.15 to 0.58 0.70 to 1.20 0.035 0.035 3.0 680 200to 240 R220G1 0.50 to 0.65 0.15 to 0.58 1.00 to 1.25 0.025 0.025 3.0 780 220 to 260 R260 0.62 to 0.80 0.15 to 0.58 0.70 to 1.20 0.025 0.025 2.5 880 260 to 300 R260GHT 0.40 to 0.60 0.15 to 0.58 0.70 to 1.20 0.035 0.035 2.5 880 260 to 300 R290GHT 0.50 to 0.65 0.15 to 0.58 1.00 to 1.25 0.025 0.025 2.5 960 290 to 330 R340GHT 0.62 to 0.80 0.15 to 0.58 0.70 to 1.20 0.025 0.025 2.5 1175 340 to 390 Table 5.2.2 Brinell and Rockwell hardness related to tensile strength Brinell Hardness Number Rockwell Hardness Number Rockwell Superficial Hardness Number, Superficial Diamond Penetrator Brinell Indentation Diameter (mm) Standard Ball Tungsten Carbide Ball B Scale C Scale 15-N Scale 30-N Scale 45-N Scale Tensile Strength (Mpa)= (N/mm2)* 2.50 601 57.3 89.0 75.1 63.5 2262 2.60 555 54.7 87.8 72.7 60.6 2055 2.70 514 52.1 86.5 70.3 47.6 1890 2.80 477 49.5 85.3 68.2 54.5 1738 2.90 444 47.1 84.0 65.8 51.5 1586 3.00 416 415 44.5 82.8 63.5 48.4 1462 3.10 388 388 41.8 81.4 61.1 45.3 1331 3.20 363 363 39.1 80.0 58.7 42.0 1220 3.30 341 341 36.6 78.6 56.4 39.1 1131 3.40 321 321 34.3 77.3 54.3 36.4 1055 3.50 302 302 32.1 76.1 52.2 33.8 1007 3.60 285 285 29.9 75.0 50.3 31.2 952 3.70 269 269 27.6 73.7 48.3 28.5 897 3.80 255 255 25.4 72.5 46.2 26.0 855 3.90 241 241 100.0 22.8 70.9 43.9 22.8 800 4.00 229 229 98.2 20.5 69.7 41.9 20.1 766 4.10 217 217 96.4 710 4.20 207 207 94.6 682 * 1 MegaPascal = 1 Newton/millimeter2 As a guideline, groove rail should have a running surface hardness not less than 340 BHN. Higher hardness is difficult to obtain in groove rails since the asymmetric shape of the rail makes it difficult to head harden by conventional heat treatment methods. However, at least one

Track Design Handbook for Light Rail Transit, Second Edition 5-18 European rail manufacturer has developed a proprietary head hardening process for groove rail. Their rail is categorized as Head Special Hardened (HSH) and has a test hardness of about 365 BHN in the rail head and tram (lip) of the groove section. Their product was utilized on one LRT system in North America with 100% of the main tracks built using HSH groove rail. After several years of operation, the rail shows exceptional resistance to corrugation and very little wear. 5.2.3.5 Precurving of Groove Rail Like tee rail, groove rail must be precurved if the curve radius is sharp enough to make springing the rail impractical. The radius thresholds for precurving groove rail are generally higher than for tee rail. This is because the asymmetrical shape of the groove rail causes it to curl when sprung horizontally so that the base no longer lies flat. For this reason, it is often necessary to camber groove rail vertically prior to bending it horizontally, particularly when using a gag press rail bending method. The amount of camber will vary by both the rail section and the horizontal radius desired. The direction and amount of camber will vary depending on the rail section and whether the rail is on the inside or outside of the curve. Typically, inner rails will require a negative camber (a “smile”) while outer rails will require a positive camber (a “frown”) prior to being curved horizontally. Cambering is sometimes not necessary when precurving groove rails using a roller bender that tightly clamps the rail to constrain vertical movement. General guidelines for precurving groove rails are the following: • Horizontal Curves—precurve groove rail for curve radii below 450 feet [137 meters]. • Vertical Curves—precurve girder rail for vertical curve radii below 1000 feet [300 meters]. 5.2.3.6 Procurement of Groove Rail Procurement of groove rail requires specific contract language stating the requirements as to rail section, strength, special treatments, and potential precurving requirements in specific lengths of rail. The incorporation by reference of the most recent version of CEN European standard EN14811 is acceptable as long as additional special provisions are included. As a guideline, the special provisions section for procurement of groove rail should include the following: • The ultimate tensile strength of the rail to be supplied, in particular, the minimum Brinell Hardness Number at the two wearing surfaces—the groove rail head and tram. • The compatibility of welding and providing guidelines as to welding—both electric flash butt and thermite welding. • Precurving requirements, including specific length of rails. Since, as of 2010, groove rail is only rolled in Europe, delivery to a project in North America will involve several stages of handling and transport by multiple parties, including transatlantic shipment. So responsibilities for any damage are clear, it is recommended that specifiers avoid specific handling methods and instead focus on the condition that the rail must be in upon

Track Components and Materials 5-19 delivery to the project. It should be very clear that acceptance and payment for the rail is conditional on meeting the stated requirements. Federally funded rail transit projects in the United States are subject to the requirements of 49 CFR 661, commonly known as “Buy America.” Briefly stated, “Buy America” provisions stipulate that products purchased for construction of a federally funded transit project must have been made in the United States unless either (1) the item is not made in the United States or (2) the item is not made in the United States in sufficient quantities to satisfy the needs of the project. Project owners wishing to procure a foreign-made product under either of those exemptions must first obtain a waiver from the Federal Transit Administration. Up until 2010, such waivers were routinely granted for procurement of groove rail since no comparable product was made here. However, during 2010, the FTA began to interpret “Buy America” very strictly and waivers for groove rail were no being longer granted. As of this writing, it is unclear whether this restrictive policy will continue. Project owners that are considering the use of groove rail should very closely consider whether their funding mechanisms will permit them to do so. In that regard, it should be noted that similar restrictions may be attached to state or local funding. 5.2.3.7 Block Rail Late in 2010, as a direct result of the “Buy America” issue mentioned in the paragraph above and as this second edition of the Handbook was undergoing final editing, it was announced that a variation of groove rail would be manufactured in the United States. Called “block rail,” this product effectively eliminates the customary web of the rail and places the head and tram directly on the base of the rail. Figure 5.2.6 illustrates a typical block rail section. Photo courtesy of HDR Engineering Figure 5.2.6 LK1 block rail section There are at least three distinct sections of block rail rolled in Europe, where it has been used for decades for two purposes:

Track Design Handbook for Light Rail Transit, Second Edition 5-20 • Fabrication of temporary tracks, particularly temporary crossover tracks that sit on top of existing embedded trackwork. • Construction of modular embedded tracks using precast concrete panels. This was fairly common in the former Soviet Bloc countries up through the 1990s, but is reported to have fallen out of favor with some (but not all) transit agencies there due to maintenance issues with existing installations. As of this writing, an initial rolling of block rail has occurred at a steel mill in Pennsylvania and some block rail has been installed on a streetcar project in Portland, Oregon. Full details of that installation are, as of this writing, not yet public; however, preliminary information presented at an APTA conference in June 2011 suggests that details used in Eastern Europe are not proposed. Some industry observers have noted that block rail has a very low section modulus and hence has very limited beam strength. Because of that, block rail likely should be continuously supported so that the sinusoidal wave action response that all rails have to a rolling load does not result in a permanent vertical warping of the rail. Photographs of block rail installations in Eastern Europe suggest that this problem may be common. The Portland installation will therefore generate great interest as it is designed, built, and brought into revenue operation. Handbook users who believe they might have an application for block rail are strongly encouraged to consult recent trade publications and obtain current information from manufacturers before suggesting the concept to their project management. 5.2.4 Rail Wear Rail continually suffers from abrasive wear due to the steel wheel running on and against it. Surface head wear is due to the constant running of the wheels and is further compounded by the additional forces generated by braking and traction during deceleration and acceleration, respectively. In curved track, there is added surface wear, where wheel slippage and load transfers occur due to the changing direction of the vehicle truck. Gauge corner and eventually gauge face rail wear occur due to the steering function of the rail. Steering contact is at the outer rail of a curve, which guides the outside wheel of the lead axle. The action commences when the vehicle wheels negotiate the outside rail of the track curve to the point where the wheel flange makes contact with the gauge corner due to the designed freeplay between the wheels and the rail head. Because of the freeplay, the wheel contact is virtually never normal to the direction of the rail, but at a slight angle that is referred to and measured as the "angle of attack."[4] This attack on the outer rail is not caused by the vehicle’s centrifugal force, but by the constant change in the track alignment that results in changing the vehicle’s direction. The outer rail constantly steers the outer leading wheel inwards towards the curve center. This function requires the truck to rotate (“skew” or “yaw”), and, in a conventional truck, that rotation is resisted by friction in the connections between the truck and the car body. For additional information on truck skew, refer to Chapter 4 and the discussions concerning Nytram plots at Article 4.2.4. The wheel acts as a cutting tool, or grinding stone, that actually machines the steel at the gauge corner and eventually the face of the running rail. This is caused by several factors, such as the severity of the wheel’s angle of attack to the rail, the friction between wheel and rail, and the

Track Components and Materials 5-21 stiffness against rotation of the vehicle truck. The latter increases the force against the rail, increasing friction and wear, and concurrently reduces the speed of the vehicle. Another rail wear phenomenon is the formation of metal flow. The wheel/rail interaction causes the rail and steel surfaces to deform at the point of contact due to the concentrated load. This contact pressure is extreme to the point where the stress is greater than the yield point of the rail steel, which causes plastic deformation of the surrounding surface steel. This action leads to metal flow accumulation on the surface edges of the rail head. Metal flow may collect at the gauge corner of rail in tangent track, where the wheel is seldom in contact with the rail gauge corner or face. Metal flow collection also occurs on the field side of the inside rails in curves, where the rail head metal flow migrates toward the field side and accumulates as a pronounced lip. Slivers of metal flow have been known to eventually wear through completely, forming a long slender metal strip that drops off the rail, generally at the base of the gauge side rail head due to full depth rail gauge face wear. This condition is far less prevalent in transit track than it is on freight railroads, but, as rail ages, the possibility of metal flow grows and this is with the lightest of vehicles. Corrugation of rail is another rail wear phenomenon that severely impacts ride quality and noise generation. Corrugation is discussed in detail in Chapter 9, Article 9.2.1.1.3. 5.2.5 Wear-Resistant Rail Transit systems have historically suffered from worn rails and the need for rail replacement due to accumulative wear limits of the rail head and/or gauge face. To combat the wheel machining of the rail gauge face and loss of metal, an abrasion-resistant steel is required. Improvements in the chemical composition and treating process of rail steel have led to the development of wear- resistant grades of steel. Research has shown that a fine grade of tempered pearlitic steel with sufficient hardness will be resistant to both wear and abrasion (or machining) of the steel and the formation of corrugations.[5] The hardness of rail steel is proportional to its toughness or its ultimate tensile strength (UTS). UTS is used to measure the quality of the steel. Up until about the mid-1990s, European groove rails, like North American girder rails, were rolled from very soft steel. Typical surface hardness was in the range of 220 to 240 BHN. Soft metallurgy was used because groove rails need to make more passes through the rolling equipment than tee rails of similar weight. Since the string loses heat during each pass, the chemistry needed to be soft so that the steel would stay sufficiently ductile for the last pass through the rolls, when the tram is bent up to form the flangeway. However, because the metallurgy was soft, such rails wore rapidly, particularly under the heavier loadings of modern light rail vehicles. In response to this rapid wearing of rails, European steel companies developed the harder grades of steel that are now available for groove rail. Prior to the development of harder grades of steel, proprietary processes for head hardening groove rails were sometimes used to provide a more wear-resistant surface to the rail. For example, a special surface weldment known as Riflex[6], which also featured anti-squeal characteristics, was popular circa 2000. However, Riflex and similar processes were expensive.

Track Design Handbook for Light Rail Transit, Second Edition 5-22 Such post-manufacturing treatments are now seldom used as more wear-resistant grades of groove rail are now readily available directly from the rail mills. 5.3 RESTRAINING RAIL DESIGNS FOR GUARDED TRACK Guarded track in light rail transit design, as described in Chapter 4, Article 4.3, can reduce outer rail gauge face wear on sharp curves by restricting movement of the wheels toward the outer rail. The guard (or restraining) rail is positioned close to the inside rail of the curve and contacts the back of the inside wheel flange. In an optimal condition, steering action can be realized at both wheels of the axle. The designs of restraining rails can differ dramatically between projects, and over the years various designs have been used. Traditionally, curve guarding on North American street railway systems was usually achieved using a girder guard rail section somewhat similar to the 56R1 groove rail section illustrated in Figure 5.2.5. Ballasted and direct fixation track requiring guarding typically used a separate restraining rail mounted adjacent to the running rail. However, then as now, exceptions can be found, depending on the requirements and circumstances of a particular light rail system. Sharp curves with restraining rail are very complicated to design, fabricate, and construct in the field. Prefabrication of restraining rail curves, including full assembly on a shop floor for initial acceptance inspection, can improve quality and reduce field installation time by detecting and correcting fabrication errors. The following articles discuss the various designs and hardware for providing guarded track. 5.3.1 Groove Guard Rail for Embedded Track Groove rail can be employed for two purposes: • To provide a uniform flangeway in embedded track without needing to form one in the pavement. • To provide a restraining rail that is integral with the running rail, thereby simplifying the design by eliminating one rail and the associated mounting and connection hardware. These two purposes are not necessarily linked. It can be desirable to use a groove rail for curve guarding purposes even if tee rail is used in the same track segment when guarding is not required. 5.3.1.1 North American Girder Guard Rail—Background While dozens of different girder guard rail sections were once rolled in North America, the most common sections after about 1930 were the 140ER7B and 152ER9B sections (designed for transit use) and the 149RE7A section (designed for use with railroad wheel flanges). These sections were developed specifically for embedded street track and North American wheel profiles and provided a robust tram on the side of the flangeway to act as a working guard face. Unfortunately, these sections are no longer rolled. The last North American rolling mill to produce them got out of the business in the mid-1980s when the rolls used to produce girder rail were too

Track Components and Materials 5-23 worn to meet quality requirements. For various reasons, the product line was not sufficiently profitable to justify the investment in new rolls, so production ceased. Once the North American girder rail sections were no longer available, transit agencies turned to European groove rail sections. Up through about 2000, the most popular European sections were Ri59 (now known as 59R1 and 59R2), Ri60 (now 60R1 and 60R2), and a section known as GGR-118, which is no longer available. These sections were all designed solely for transit vehicle wheels with relatively small flanges. Other groove rail sections rolled in Europe that can be considered for transit use in North America are listed in Article 5.2.3.2 of this chapter. With the exception of the CEN 67R1 section (formerly Ph37), the European groove rails shown are not compatible with freight operations. 5.3.1.2 Restraining Rail Issues with CEN Groove Rails With the exception of the CEN 67R1 section (and two other similar non-CEN rails), the European groove rail sections are adaptable to North American use only if a transit wheel gauge is selected for the wheel set. The AAR wheel gauge of 55.6875 inches [1414 millimeters] is not compatible with the other groove rail sections. However, CEN 67R1 is not configured as a restraining rail. The flangeway, 58.66 millimeters [2.309 inches], is too wide and the tram, 16.31 millimeters [0.642 inch] thick and positioned 3.00 millimeters [0.12 inches] below top of rail, is both too thin and too low. The other few available groove rail sections with wider flangeways are similarly configured. The dilemma confronting the North American light rail track designers whose projects need to comply with AAR railroad gauge standards is the lack of a suitable groove rail section that has the increased flangeway width required to accommodate railroad wheel sets and has a curve guard for embedded sharp radius curves. Even if the freight railroad does not operate over a particular track segment, the standards used elsewhere on the system may set requirements that must be met in the embedded track area. As a solution, consideration could be given to machining a flangeway of an appropriate shape into the head of one of the several “construction rail” sections available from European manufacturers. Primarily designed for fabricating special trackwork (such as flange-bearing frogs), these sections could be machined to just about any head profile desired. This method has been employed on some U.S. LRT properties, but it is expensive. As noted in Chapter 4, Article 4.3, the use of restraining rail is technically optional. Many LRT operations, both abroad and in the United States, successfully operate without restraining rail, albeit with increased rail gauge face wear. As a guideline, for systems using a transit wheel profile with a transit wheel gauge of 56 inches (1422.4 millimeters), most CEN groove rail sections rolled and treated to the hardest grade of steel possible will generally provide satisfactory service in tangent track and flat radius curves. Service life on sharp curves can be expected to be appreciably shorter. 5.3.1.3 The Possibility of a New North American Groove Rail There has been appreciable discussion in the industry as to whether a new design of groove rail could be made that more closely matches North American needs. For that to occur, there are two principal issues to be addressed and resolved:

Track Design Handbook for Light Rail Transit, Second Edition 5-24 • What should the new section look like? • Where can it be rolled? It is unlikely that any previously rolled section would be totally satisfactory, and detailed investigation would be necessary to make certain that all reasonable issues are addressed. The short-lived GGR-118 rail, which was intended for North American use, was deliberately designed with a 139.7 mm [5 ½ inch] wide base for nominal compatibility with 115 RE rail, but the thickness and top slope of its base were totally different. Accordingly, it was not possible to use the same rail fastening hardware. The tram was also too thin to be an effective restraining rail over the long term. Hence, resurrection of GGR-118 is not a likely solution. A new groove rail section is likely required, one with both a wide flangeway and a guard/tram that is thick enough to take decades of wear and is raised to at least the rail running surface. Such a section might closely resemble the former 149RE-7A girder guard rail section with revisions to the shape of the head (for compatibility with wheels that spend most of their time running on canted 115 RE) and the height (for compatibility with 115 RE). Consideration might also be given to configuring the base so as to be compatible with rail fastenings used with 115 RE. If an organization such as APTA and/or AREMA Committee 12 were to undertake this project, it would probably be possible to work toward one or two designs that would meet the needs of the majority of North American LRT systems. The “where” question is more problematic. North American steelmakers withdrew from the girder rail business because it wasn’t sufficiently lucrative to justify the investment. The current resurgence of LRT and streetcar projects is unlikely to change their perspective. Rail mills in the United States understandably prefer to continue catering to the needs and requests of their biggest customers—the freight railroads of North America. The rolling of block rail at a U.S. mill came about in part because the steel company involved politely declined to roll groove rail. They agreed to instead roll the block rail because it was both a relatively simple section to roll and, more importantly, they could roll it on existing machinery at a location other than their rail mill. Such experience suggests that pursuing the rolling of a groove rail in the United States is likely to be an exercise in futility. The TCRP Project D-14 research team is under the impression that European rolling mills can be relatively cooperative concerning rolling of special sections for customers. An example is a non- CEN groove rail section, Ri5, which Voest Alpine rolled specifically for Yarra Trams in Melbourne, Australia. If consensus can be reached on an appropriate girder guard rail section for North American use, it might be possible to interest one or more European mills to provide quotations. However, the more significant problem is the “Buy America” issue discussed in Article 5.2.3.6. 5.3.1.4 Alternatives to Groove Rail for Guarded Embedded Track Where curve guarding is desired in embedded track and groove rail is not used, alternate designs are available. The two most common details include • Conventional vertically mounted tee rail restraining rail, similar to the details described in Article 5.3.2.1 of this chapter.

Track Components and Materials 5-25 • Strap guard rail, bolted to 115 RE tee running rail, as described in Article 5.3.2.3 of this chapter. 5.3.2 Restraining Rail Options for Use with Tee Rail Construction When groove rail is not used, but a restraining rail is desired, tracks with sharp curves have been equipped with various designs to provide the required restraint. Guarding is typically provided by mounting a separate “restraining rail” parallel and concentric to the inside running rail, with the horizontal distance between the two rail heads set at the required flangeway width dimension. See Chapter 4, Article 4.2.4.2, for guidance on determination of the appropriate restraining rail flangeway width using the Nytram Plot procedure. The restraining rail can be fabricated from one of several steel shapes and may or may not be physically attached to the running rail. In versions that are physically bolted to the running rail, the restraining rail/running rail assembly must be designed as a unit so that curvature is consistent and bolt holes in both rails are aligned. 5.3.2.1 Vertically Mounted Restraining Rails The most common type of restraining rail is a vertically mounted tee rail as shown in Figure 5.3.1. The restraining rail is fabricated by planing away a portion of the rail base of a standard tee rail, which is then bolted to the running rail at intervals of 24 to 36 inches [roughly 600 to 900 millimeters]. Cast or machined steel spacer blocks are placed between the running rail and the restraining rail to provide the desired flangeway. Some designs fabricate the spacer blocks in two pieces and insert shims between them to adjust the flangeway width so that the flangeway width can be restored to the design dimension as the guard rail face wears. Although this design feature appears sound, experience has shown that few transit systems actually ever take advantage of this maintenance feature. The restraining rail and the running rail webs must be match drilled to insert connecting bolts. The bolt hole spacing must be detailed on the shop drawings because the restraining rail is on a slightly larger horizontal radius than the inside running rail to which it is attached. In addition, the bolt hole spacing will be different on each rail. While this differential is minor between any pair of bolt holes, it will become significant when accumulated over the full length of a rail. For curves using 115 RE rail with radii less than 300 feet [91 meters], the combined running and restraining rails are typically precurved, fabricated, and assembled together on a shop floor. Each piece is numbered and match marked similar to special trackwork assemblies such as turnouts. For ease of shipment, these precurved segments are usually 36 feet [11 meters] long or shorter. It is suggested that the precurved running rail not be shop drilled to match the restraining rail. Instead, drilling can take place after the running rail is thermite welded in track and placed in final position, matching the as-built locations of the predrilled holes in the restraining rail. By working from one hole to the next, drilling and bolting the rails together in a continuous process, it is possible to keep the holes closely aligned. During field assembly, should any of the shop-drilled holes coincide with or be within 6 inches [150 mm] of a weld in the running rail, it is necessary to abandon the shop-drilled hole in the restraining rail and drill a new one at an appropriate longitudinal distance from the rail weld.

Track Design Handbook for Light Rail Transit, Second Edition 5-26 Figure 5.3.1 Typical restraining (guard) rail arrangements For curves with radii greater than 300 feet [91 meters] and through curve spiral segments with instantaneous radii above that threshold, both the CWR running rail and the restraining rail can usually be field sprung to the desired curvature. In such cases, shop curving of both running and restraining rails is typically not essential. The restraining rail is often the same rail section as the running rail. In cases where the restraining rail is elevated above the head of the running rail, the restraining rail is sometimes fabricated from the next larger rail section (e.g., 115 RE running rail would be paired with a 132 RE restraining rail). In other designs, the same rail section is used, but a riser shim is welded to the rail fastening plate beneath the restraining rail to elevate it. See Chapter 4, Article 4.2, for additional discussion concerning restraining rail configuration, including height, flangeway width, and guard face angle. See also TCRP Research Results Digest 82, which contains extensive discussion concerning restraining rail height and application. If elastic rail fastenings are used, the spacing between the restraining rail bolts and the cross tie or rail fastener should be coordinated to ensure that the bolt assembly will not interfere with either insertion or removal of the elastic rail clip. Similarly, it should be possible to either tighten or remove the bolt assembly without removing the rail clip.

Track Components and Materials 5-27 On timber cross ties, the combined running rail/restraining rail assembly will usually be installed on a common extended rail fastener or tie plate unlike those used under single running rails. Restraining rail installed on concrete cross ties will require a special restraining rail cross tie with a wider shoulder mounting. Some designers support the restraining rail only at every other cross tie or rail fastener location. Restraining rails that are physically attached to the running rail can compromise broken running rail detection by providing an alternate path for signal circuit current around the break. Similarly, mounting plates shared by the running rail and restraining rail can create a circuit path around a rail break. Groove rail, as a single entity, does not have this problem since the guard face would be included with the break. A similar situation exists at running rail insulated joint locations. Both the running rail and the restraining rail must be designed with an insulated assembly. For vertically mounted tee restraining rail, there usually is a common double rail end post configuration that suits the flangeway width. Vertically mounted restraining rails have been used in all the types of track structures. Nonetheless, when vertically mounted restraining rails are employed in embedded track, it is necessary to attempt to completely seal the flangeway to keep out moisture and accumulating debris. The insulating rubber rail boot in a two-rail configuration is available and can be included in the track design. A restraining rail assembly in embedded track will have multiple paths for water to seep into the boot. Even with sealants, it is critical to provide drainage to keep the rail enclosure relatively dry. Track drains with open rail boot areas at the transverse track drains can provide this drainage relief. See Chapter 4, Article 4.7.4.4, for additional discussion of embedded track drainage. In embedded track, vertically mounted restraining rail has the problem of sealing the floor of the flangeway against water intrusion. In the absence of a seal, the flangeway (and the rail boot, if used) could fill up with storm water and debris, possibly leading to problems, particularly in cold winter climates. The depth of the open flangeway can also be a safety issue for pedestrians; see Chapter 4, Article 4.3.5.3, for additional discussion on this point. 5.3.2.2 Horizontally Mounted Restraining Rails Transit systems have used horizontal designs where the restraining rail is mounted with the rail’s Y axis oriented horizontally, as shown in Figure 5.3.1. This is a relatively old design that is currently seen only in older rail transit installations. Horizontally mounted restraining rail cannot be used in embedded track areas. The mounting hardware is bulky and expensive. Similar results can likely be achieved at a lower cost by using the 33C1 guard rail section discussed below. While some legacy rail transit systems used and/or still use horizontally mounted restraining rail in open trackforms, it is not suggested for new light rail installations. 5.3.2.3 Strap Guard Rail An innovative restraining rail design uses a special rolled steel section known as “strap guard” with 115 RE rail (see Figure 5.3.2). The strap guard section is bolted directly to the web area of the running rail similar to a joint bar.

Track Design Handbook for Light Rail Transit, Second Edition 5-28 Figure 5.3.2 Strap guard rail The strap guard section was developed for the Pittsburgh light rail transit system in the early 1980s based on similar sections that were rolled for use with ASCE tee rails in the early 20th century. Pittsburgh is the still the largest user of strap guard, using it in all trackforms, and considering nothing else for restraining rail. However, strap guard has seen limited application outside of Pittsburgh. There are short installations in Baltimore, Dallas, Galveston, Tampa, and Kenosha. Boston’s MBTA tried a short section, but opted for a different design instead. Advantages of strap guard include the following: It does not require special rail tie plates, rail fasteners or cross ties. The only requirement is a specially designed rail clip that can bear on the lower flange of the guard on the gauge side of the assembly. The field-side rail hold-down device can be the same as that used in ordinary single rail installations. This facilitates adding strap guard to an existing curve in open track that is experiencing unacceptable levels of gauge face rail wear. It is a universal guarding system that can be used in ballasted, direct fixation, and embedded track. In embedded track, when compared to a vertically mounted tee restraining rail assembly, strap guard has an advantage since the configuration provides a solid floor to the flangeway. By contrast, the opening in the flangeway area in the vertically mounted tee rail and restraining rail assembly requires a substantial amount of filler material to exclude moisture and address safety concerns.

Track Components and Materials 5-29 • When considering rail breaks in areas of strap guarded rail, the strap guard rail actually provides some minimal security against both a wide gap and rail end mismatch since its shape effectively places a joint bar across the rail break. On the other hand, the resulting electrical continuity would mask a running rail break from the signal system by providing an alternate path for signal current around the rail break. Note that, in general, broken rail protection is not an issue in embedded track since the pavement structure will still keep the rail ends aligned. Rail boot is commercially available for strap guard as well as some configurations of vertically mounted tee restraining rail assemblies. Strap guard has several issues that must be carefully considered: • As currently designed and rolled, strap guard mimics the flangeway dimensions of the former ATEA 140ER7B and 152ER9B girder guard rail sections and, as such, is really suitable only for small flanges such as the former ATEA designs. Baltimore shimmed out the strap guard to widen the flangeway to match an AAR wheel profile and gauge, but does not actually employ it as a restraining rail. • Strap guard is presently rolled in maximum lengths of 30 feet [9.14 meters], a limitation of the rolling mill equipment where it is produced. • The depth of the flangeway provided by strap guard is limited by the height of the head of 115 RE rail. For tall wheel flanges, running rail head wear could therefore limit the service life of the strap guard instead of wear on the working face of the guard. The issue could be relieved by using strap guard with 119 RE rail sections, but that would reduce the effective height of the guard. In addition, 119 RE has significantly dropped in popularity and is no longer an AREMA-approved design. Its long-term availability is uncertain. • Strap guard, like many restraining rail designs, must be bolted to the running rail at frequent intervals. The bolt holes and bolt assemblies are potential maintenance issues, although Pittsburgh has not had any significant problems in this regard. • The strap guard requires that the “collar” that results from thermite welding be ground flush with the fishing of the rail. Some thermite weld kit vendors strongly discourage this amount of rail surface weld finish, stating that the rail weld might actually be more prone to failure. No specific data are available to confirm or deny this assertion, and a substantial quantity of rail welds exist in LRT tracks that have been finish ground to that degree without breaks, tending to disprove this theory. Notably, many of the common concerns about thermite welds are based on experience under railroad loadings, and the substantially lighter loads of LRT make thermite weld failure appreciably less likely. • While strap guard is not a proprietary design, it is currently made at only one rolling mill, the Arcelor Mittal facility in Steelton, Pennsylvania, coincidently the same mill and rolling machinery that has produced block rail. The rolls, which belong to the transit agency in Pittsburgh, will not fit on the equipment at any other rolling mill. When they eventually wear out, it is uncertain what the replacement cost and the source of funding will be. This situation is not unlike the former GGR-118 groove rail section, which was produced at

Track Design Handbook for Light Rail Transit, Second Edition 5-30 only one rolling mill in Europe. When restructuring of the European steel industry resulted in the closure of that specific rail mill, GGR-118 suddenly became unavailable. Slight changes in the rolls and/or the rolling procedures for strap guard might permit the flangeway width and guard angle to be customized to match any given combination of wheel profile and curve radius. If the continuing availability issue noted above could be addressed in a comprehensive manner (perhaps through sponsorship of the design by a consortium organization such as APTA or AREMA), it might be possible to produce strap guard in different shapes so as to better suit the needs of LRT systems using large wheel flange profiles. Some practitioners object to the elevation of the strap guard above the plane of the running rails, arguing that it could be both a tripping hazard to pedestrians and an impediment to snow plows. As discussed in Chapter 4, Article 4.3.5.3, elevated restraining rail of any type is generally discouraged in pedestrian areas, but that limitation should not affect restraining rail design in areas where there is no legitimate pedestrian traffic. Snow plow blades are routinely designed to deal with irregular pavement surfaces, including deviations appreciably larger than the height of the strap guard rail. Where track with strap guard is crossed by a designated pedestrian path, it is a simple matter to machine the top of the guard so as to be level with the running rail. 5.3.2.4 33C1 Restraining Rail A different type of restraining rail design becoming popular in North American light rail transit design is the 33C1 section (see Figure 5.3.3) currently rolled in Europe. Prior to its adoption as part of the European Norms, the 33C1 section was referred to as either UIC-33 or U69 in the French and German standards, respectively. The 33C1 section in Europe was developed and has primarily been used as a guardrail for special trackwork frog locations. More recently, 33C1 has also been used for frog guardrails and continuous restraining rails on several North American light rail transit systems. Figure 5.3.3 33C1 restraining rail

Track Components and Materials 5-31 The major advantage of using the 33C1 section as a restraining rail is the capability of independent mounting from the running rail, as shown in Figure 5.3.1. In addition, the 33C1 section’s independent bracket mounting assembly eliminates very nearly all of the negative issues related to field drilling of the running rails to match the restraining rail hole pattern and placement of fasteners and cross ties. Use of the 33C1 section also simplifies thermal stress adjustment of the running rail because it is structurally independent of the restraining rail. To improve on its function as a restraining rail, the 33C1 section is typically raised above the plane of the running rails. In a common design, the working face of the guard is positioned ¾ inch [19 millimeters] above the top of the running rail to intercept an appreciable amount of the back face of the wheel. See Chapter 4, Article 4.3.5.2, for additional discussion on restraining rail height. The independent mounting is provided by a mounting bracket that allows the restraining rail to be bolt mounted adjacent to the running rail, providing the required adjustable flangeway width. Bracket designs have evolved to the use of elastic spring clips to secure the 33C1 section in place, eliminating the need to drill the 33C1 section. The mounting design of the bracket can either be separate from the running rail fastening plate or direct fixation fastener or an integral part of the fastening plate. Even though 33C1 restraining rail isn’t physically attached to the running rail, broken running rail protection can be compromised if the mounting bracket for the 33C1 is on a baseplate shared with the running rail. If this single plate design is used and track circuits are used for broken rail detection, a detail will be required to insulate the restraining rail from the brackets. The structural loadings at the connection between the 33C1 and the bracket are significant and may be beyond the capacity of some insulating materials. While 33C1 is sometimes employed as a frog guard rail in embedded special trackwork, it is not recommended for use as a continuous restraining rail in embedded track as it would be very difficult to insulate the bracket assemblies from the embedding pavement. Other designs of restraining rail, such as vertically mounted tee rail, are much easier to insulate and hence would be better for this purpose. Early installations of 33C1 restraining rail required drilling it for a bolted attachment to the supporting bracket. This drilling needed to be done in the field so as to exactly match the as-built locations of the supporting brackets. Later designs use an elastic rail clip to hold the 33C1 section in the bracket, thereby creating a boltless assembly that does not require drilling. This greatly simplifies and speeds installation. The 33C1 restraining rail assembly provides for flangeway width adjustment by adding shims directly behind the 33C1 restraining rail. This adjustment can be undertaken without disturbing the running rail installation. 33C1 restraining rail is customarily provided from European rolling mills in 15- and 18-meter [49.2- and 59.1-foot] lengths. By special order it can be obtained in lengths to suit North American requirements. The major restriction is handling the lengths on ships when placing the lengths below deck or into shipping containers.

Track Design Handbook for Light Rail Transit, Second Edition 5-32 Special four-bolt joint bar assemblies and insulated joint assemblies are used to join lengths of 33C1 rail. These joints are preferably located between supporting brackets so as to avoid the need for a special bracket. Insulated joints are required in the 33C1 section opposite running rail insulated joints. To allow for minor thermal movement in the 33C1 section, it is recommended that slotted holes be made in the joint bars, excluding the insulated joints. On aerial structure installations, where thermal expansion of the structure must be accommodated, the 33C1 restraining rail mounting bolt holes at each mounting bracket should be slotted to allow the structure with the mounting bracket to move longitudinally. In boltless 33C1 mountings, thermal expansion will typically be handled through ordinary slippage beneath the toe of the elastic rail clip. Because its asymmetrical shape causes it to curl when sprung into alignment, precurving of the 33C1 section is preferred on sharp radius curved track installations. Detailed shop drawings showing the layout of each segment of curved track, each individual restraining rail segment, and each supporting chair is required. 5.3.3 Restraining Rail Recommendations As a guideline, the following restraining rail sections and mounting details are suggested: • Concrete Cross Tie Track—a separate 33C1 mounting is provided by two additional anchor bolt inserts that are cast in the concrete cross tie during production. The bracket installation should be insulated from the cross tie, and the bracket should be designed to clear the running rail fastening system. These restraining rail cross ties will require different molds than those used for standard cross ties. • Timber Cross Tie Track—there are two alternatives: − 33C1 mounted with the running rail on a single fastening plate. A welded assembly or cast steel fastening plate can be used. The single unit fastening plate with a bracket provides improved holding by using the weight of the vehicle to retain the plate bracket position and avoids possible displacement of the restraining rail relative to the running rail as the timber ties age and decay. The 33C1 bracket is designed to clear the running rail fastenings. If required for stray current control, the installation should be insulated at the top surface of the cross ties. If broken rail protection is required, this design requires insulating the 33C1 section from the mounting bracket, a major load transfer connection that could be detrimental to insulating components. − Vertically mounted tee restraining rail bolted to the running rail with the two on a single fastening plate. If required for stray current control, the installation should be insulated from the cross ties. Broken rail protection is not practical with this design. • Direct Fixation Track—a separate 33C1 mounting is provided by two additional anchor bolt inserts cast in the direct fixation concrete plinth during plinth installation. The bracket installation should be insulated from the concrete plinth and the bracket should be designed to clear the direct fixation fastener body and components.

Track Components and Materials 5-33 • Embedded Track—there are three options, listed below in order of preference. In all cases, the assembly should be insulated from the embedding pavement structure unless it is contained within an insulated bathtub. The three options are − A groove rail section with a flangeway of appropriate width and a guard/tram that both has sufficient thickness for the anticipated service and is at an appropriate elevation relative to the running surface. − Strap guard rail, provided the flangeway shape is appropriate for the wheel profile and gauge at the curve radii where guarding is desired. − Vertically mounted tee restraining rail bolted to the running rail, with the flangeway filled to within 2 inches [50 mm] of the top of rail. 5.3.4 Restraining Rail Thermal Expansion and Contraction Restraining rails undergo thermal expansion and contraction just as running rails do. However, they should not be continuously welded because it would be virtually impossible to install them at the same zero thermal stress temperature as the adjacent running rails. It is customary, therefore, to fabricate restraining rail in segments with lengths of 30 and 39 foot (9 and 12 meters) and provide expansion gaps at bolted restraining rail joints. If the restraining rail is bolted to the adjoining running rail (such as with strap guard or vertically mounted tee rail) and the running rail is continuously welded, any connections between the restraining rail and the running rails should allow for some longitudinal movement between the two rails. This can be accomplished by drilling oversized bolt holes in the restraining rail. Restraining rail on aerial structures may require special details when passing over expansion joints in the bridge deck. 5.3.5 Restraining Rail Restrictions The presence of restraining rail of whatever design can complicate some track maintenance activities. Factors that should be considered include the following: • Restraining rail interferes with the ability to orient the grinding stones of production rail grinding equipment so as to achieve optimal contact with the gauge corner of the rail. Special rail grinding equipment (typically using smaller diameter stones) and slower grinding operations will be necessary, resulting in higher rail grinding costs. • In all open trackforms, the restraining rail can interfere with inspection and maintenance of the rail fastening system on the running rail. • In ballasted track, some designs of restraining rail will interfere with ballast tamping operations. All restraining rail designs will trap stones during ballast dumping operations, and manual methods are usually required to remove them. • In embedded trackforms, restraining rails increase the amount of metal on the surface of the pavement. Such steel surfaces can be slippery when wet, and there may be resulting safety issues for motorists and pedestrians.

Track Design Handbook for Light Rail Transit, Second Edition 5-34 5.4 RAIL FASTENINGS AND FASTENERS Perhaps the most important elements of the track assembly are the devices that hold the rails to proper alignment and gauge. These items are called rail fasteners and fastenings. While these terms are often used interchangeably, they are actually distinct items. Therefore, before proceeding further, it is appropriate to define those terms as well as two other related terms that will be mentioned in this discussion. 5.4.1 Definitions Four important terms related to track assembly—fastenings, fasteners, elastic, and resilient— are defined below: • Fastenings—the miscellaneous hardware used to secure the rail to an underlying structural base thereby controlling rail uplift, lateral movement, and longitudinal movement. Examples of fastenings are elastic rail clips, rigid rail clips, and, the case of timber tie ballasted track, ordinary track spikes and rail anchors. In the case of elastic and rigid rail clips, the fastenings may also include insulating pads to electrically isolate the rail from grounded items below the base of rail. • Fasteners—plate assemblies that incorporate both the rail fastenings described above and a system to anchor the plate to an underlying base. Depending on the product design, the electrical isolation requirements can be achieved in the rail fastenings (as described above), within the fastener plate, or beneath the fastener plate. • Elastic—an adjective typically applied to a rail fastening device made of spring steel and used to hold a rail into a rail seat on either a rail fastener or a cross tie. Elastic rail clips are often called “spring clips” or simply “rail clips.” • Resilient—an adjective typically applied to a rail fastener assembly that incorporates elastomeric elements used to dampen vibrations that originate at the rail/wheel interface and thereby minimize their transmission to locations outside of the track structure. Because of the large number of rail fastening/fastener designs, the definitions above are somewhat imprecise, but they should suffice for the purposes of the discussion that follows. It is perhaps notable that one common railway engineering reference source reversed the definitions of “elastic” and “resilient” above. 5.4.2 An Introduction to Common Designs Common rail fastener assemblies include the following: • Conventional rolled steel tie plates with shoulders, punched with square holes to accept a series of cut spikes to secure the tie plate to a timber cross tie and to hold the rail in the rail seat area of the tie plate. These assemblies do not include any specific electrical isolation measures. • Rolled, forged, or fabricated steel tie plates with shoulders that accept an elastic rail fastening and are drilled, punched, or otherwise machined to accept hold-down spikes (typically screw spikes) for attachment of the plate to a timber cross tie. These

Track Components and Materials 5-35 assemblies can incorporate electrical isolation measures either at the base of rail or between the plate and the cross tie. Modifications of this rail fastener assembly are sometimes used on concrete cross ties within special trackwork. • Manufactured plates that include an integral elastomeric pad beneath the plate that provides both electrical isolation and acoustic attenuation. The elastomeric pad may or may not be bonded to the plate during molding. If the pad is bonded to the plate, it is usually also bonded to a second plate positioned beneath the elastomeric pad. If bonded to both plates, the pad itself is typically not a premolded unit but is instead formed by injecting the molten elastomeric compound between the plates in a mold. The rail fastening assembly can be either a rigid clip held in place with a bolt assembly or an elastic clip. Two or more threaded bolts are used to anchor the plate assembly to female anchor inserts in an underlying reinforced concrete base. The overall assembly is commonly named a “direct fixation rail fastener.” As in the case of the definitions above, rail fasteners come in a wide array of designs, many of which cannot be neatly categorized. In many cases, individual components or whole assemblies may be the proprietary products of one manufacturer. Many, if not most, rail fasteners incorporate subassemblies from multiple manufacturers. 5.4.3 Insulated Fastenings and Fasteners As noted previously, the rails are the negative return path for the traction power current to the traction power substation (TPSS). The negative return current must, to the maximum degree possible, be confined to the rail so as to control stray current leakage, which causes corrosion not only of transit tracks and structures but also nearby underground utilities and structures. For additional information on stray current protection, refer to Chapter 8. Conventional ballasted track often relies on timber ties to insulate rails from the ground. Timber ties can actually provide a reasonably good level of rail-to-earth resistance provided the entire track structure, including the ballast, is and remains clean and dry. Maintaining those conditions, particularly in the vicinity of highway grade crossings, is particularly difficult. Therefore, although wood is considered a non-conductive material, timber cross ties will generally not provide sufficient insulation to totally isolate the track from ground over the long term. For this reason, special designs of rail fasteners and fastenings are used to isolate the rail from the cross tie. These systems will be described below. Concrete cross ties typically use elastic rail fastening clips. The rail clips are insulated from both the rail base and the shoulders embedded in the concrete cross tie by plastic insulators. The rail is further insulated in the concrete cross tie’s rail seat area by a pad that is used primarily to prevent the rail from abrading the concrete but that also provides electrical isolation. These pads are often dimpled or ridged with shape factors so as to provide resiliency. Direct fixation track typically uses a direct fixation fastener plate system consisting of a fastener body that incorporates elastomeric elements to provide resiliency and electrical isolation, a rail fastening system to hold the rail to the fastener body’s rail seat area, and an anchorage assembly to secure the fastener body to a substrate—usually a concrete slab. The rail fastening system is

Track Design Handbook for Light Rail Transit, Second Edition 5-36 typically elastic rail clips, although rigid clips held in place by a bolt assembly have been used. The anchorage assembly typically consists of two or more bolts that pass through the fastener body and are then threaded into female anchor inserts embedded in the underlying track slab or plinth. Direct fixation rail fasteners will occasionally be used on timber or concrete cross ties where additional acoustic attenuation is desired. They have also occasionally been used in specialized embedded track installations, but this is uncommon. Most embedded track systems do not include rail fasteners, but most do include some sort of rail fastenings, most often to attach booted rail to an embedded steel (or plastic) cross tie or a steel leveling beam. 5.4.3.1 Isolation at the Rail Base To provide electrical isolation in open track forms, the rail must be isolated from the surrounding track components. The simplest and most reliable location for this isolation is at the surfaces of the rail. Insulators are placed between the base of the rail and the underlying mounting surface and also between the base of rail and the rail clip assemblies, as shown in Figure 5.4.1. 5.4.3.2 Isolation at the Fastener Base To provide electrical isolation of the fastener from the surrounding track components, the insulating barrier must be installed at the base of the fastener plate or mounting surface. The insulating barrier consists of an insulated base fastener pad and insulating flanged bushings (also known as thimble collars) surrounding the anchoring screws or bolts, as shown in Figure 5.4.2. 5.4.4 Elastic Rail Clips Elastic (spring) clips come in many designs, almost all of them proprietary. Examples are various designs of clips made by Pandrol (e.g., the “e-clip,” the “Fast Clip,” and the original PR-series clips), the McKay/Safelock clip, and clips made by Vossloh, to name only a few. All of these clips have merits, and the selection of one versus the other is largely a matter of personal choice. In general, it is preferable to minimize the number of rail clip styles on a transit property so as to simplify maintenance inventory. Some designs of rail clips are installed by inserting them into a shoulder in a direction parallel to the rail while others are installed perpendicular to the rail. In rare instances, one make and model of clip might therefore be preferable to another based on physical space constraints, as often occurs within special trackwork. The toe loads applied by spring clips can be varied, usually through modification of the shoulders into which they are inserted. As manufactured items, the actual toe load applied to the rail base is subject to some tolerances and will vary at installation. A spring clip’s toe load will also slacken off due to creep with years of service and/or multiple removals and reapplications. There are also various designs of rail clips that apply reduced or even zero toe load so as to allow controlled longitudinal movement of the rail. In some cases, these special clips are visually nearly identical to the standard clip and care must be taken to ensure the correct model of clip is installed at a given location.

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Track Design Handbook for Light Rail Transit, Second Edition 5-38 extracted from the rail fastener shoulders because exfoliated rust had filled the small void space around the shank of the rail clips, trapping them in place. Because of such problems, it is strongly recommended that if spring clips are proposed for use in such a hostile environment, consideration should be given to specifying that the clips have a robust and proven protective coating. One clip manufacturer has achieved a measure of success in a very corrosive environment with a zinc silicate coating topped by a second coating of paraffin wax. Some designs of elastic rail clips were formerly proprietary products and thus available from only one source; however, now these designs are either in the public domain or are made by multiple vendors under license. For example, the “e-clip,” which was originally the proprietary product of a firm in the United Kingdom, is now offered by many manufacturers worldwide. Caution is required when procuring such items because, while they may be dimensionally identical to the original product, their material composition and the quality procedures under which they are manufactured could be appreciably different. 5.4.5 Fastenings for Timber and Concrete Cross Ties for Ballasted Track The original rail fastening system for track constructed on timber cross ties in the traditional manner included rolled steel tie plates, cut spikes, and rail anchors. The latter devices clamp to the base of the rails, bear against the sides of the cross ties, and are provided to restrain the rail from longitudinal movement. Since the rail anchors project down well below the elevation of both the rail and the tie plate, it is inevitable that they will be in contact with the ballast. Unless the ballast is absolutely clean and dry, this creates a direct path for stray currents from the rail to ground. Insulating these rail anchors is virtually impossible since any conceivable coating system would be subject to abrasion damage, allowing current leakage. For this reason alone, conventional rail anchors are not recommended for LRT use. Elastic spring clip rail fastening systems, which have no projection down into the ballast section (and also provide superior longitudinal restraint for continuously welded rail) are recommended for any LRT timber tie ballasted track. Main line transit track with timber cross ties must utilize an insulation method similar to that shown in Figure 5.4.2, with screw spikes used to secure the tie plate. For simplicity, Figure 5.4.2 illustrates rail with no rail cant; if cant is required, rolled plates manufactured with the desired cant can be used. In special circumstances, where an off-the-shelf rolled plate will not work, the rail seat area of the plate can be milled to provide the desired cant. Special trackwork installations, whether on timber or concrete cross ties, usually require a plate insulation system similar to that shown in Figure 5.4.2. Such designs have a proven service record. An alternative method of anchoring large plates to concrete switch ties embeds a shoulder in the tie that either projects through a large hole in the plate or is adjacent to the end of the plate. Insulators and an elastic rail clip are then used to secure the plate to the shoulder and the tie, as shown in Figure 5.4.3.

Track Components and Materials 5-39 (Photo courtesy of Bay Area Rapid Transit) Figure 5.4.3 Threadless plate fastenings on concrete switch ties The elastomer pad in direct fixation rail fasteners has been manufactured from natural rubber, synthetic elastomers, and polyurethane products. These materials have been formulated to provide both high- and low-spring rates for the track as well as sufficient electrical isolation. The resilient elastomeric components come in widely varying configurations, grades, and spring rates. Early designs of direct fixation fasteners often specified an anchorage system consisting of an embedded stud bolt projecting up out of the concrete invert and through the rail fastener body, capped by spring washers and nuts. While this simplified some steps during construction, it complicated other construction activities as well as maintenance. For example, to remove or change out a rail fastener, the rail had to be lifted very high to allow the fastener to clear the projecting stud bolt height. To shim the fastener to adjust the rail height, slotted shims were designed with slots for easy installation around the projecting bolts, but such shims were worked out from beneath the fastener under traffic, resulting in a loose fastener installation. For these reasons, stud bolts are not recommended. The preferred design for anchoring direct fixation rail fasteners to the underlying concrete slab or plinth consists of bolting through the rail fastener base plate to embedded female anchor inserts. With female anchor inserts, the shim need only include holes matching the pattern of the

Track Design Handbook for Light Rail Transit, Second Edition 5-40 fastener’s anchor inserts. Shimming of the fastener requires only removing the anchor bolts and lifting the rail and fastener body a small amount more than the desired shim thickness. Early direct fixation fastener designs incorporated anchor bolt assemblies that passed through both the top and bottom plates of the fastener body. Modern designs configure the body so that the anchor bolts pass only through the bottom plate. This approach eliminates bending moments in the anchor bolts due to lateral forces applied to the rails by the wheels, but requires that the fastener body incorporate other measures to keep the top plate aligned with the bottom plate. Most direct fixation rail fasteners include some degree of lateral adjustment capability in the anchor assemblies. This is provided for the purpose of adjusting gauge to within tolerances during construction and corrective maintenance. The adjustment capability obviously adds some cost to the fastener assembly and is also a potential weak spot in the design. Moreover, if the top-down construction method is used (see Chapters 4 and 13 for further discussion of top-down construction), it is entirely practical to build the track without needing to rely on lateral adjustment. It has also been rather uncommon for any transit agency maintenance organization to subsequently use this lateral adjustment for any purpose. For these reasons, some transit agencies have opted for direct fixation rail fastener designs that provide no lateral adjustment at either the anchor bolt or anywhere else in the fastener. One transit agency reasons that lateral adjustment capacity merely gives the constructor an excuse for doing shoddy work, knowing such work can be “corrected” through the use of lateral adjustment. Omitting the lateral adjustment feature forces the contractor to “do it right the first time,” resulting in an arguably superior end product. Nearly all of these direct fixation rail fastener designs are proprietary products of a single manufacturer. For all practical purposes, there are no “standard” designs in the public domain. As a result, for any project that is being constructed with public funding, it is typically necessary for the track designer to first make certain decisions about the general form of the direct fixation track and then prepare specifications that specify the required performance characteristics (but not the details) of the direct fixation rail fasteners. In the case of small procurements for short lengths of direct fixation track, it is sometimes possible to specify a fastener by make and model number “or equal”; however, the product procured may not be tuned to the noise and vibration attenuation needs of the project. 5.4.6 Fasteners for Direct Fixation Track 5.4.6.1 Fastener Design Consideration TCRP Project D-5 and TCRP Project D-7, Task 11, performed extensive investigations into direct fixation track systems. Those investigations resulted in TCRP Report 71: Track-Related Research—Volume 6: Direct-Fixation Track Design Specifications, Research, and Related Material, a comprehensive two-part treatise on direct fixation track that includes CRP-CD-61 with useful software applications for design of direct fixation track systems. This Handbook will not attempt to duplicate the contents of TCRP Report 71, Volume 6. However, as a primer to the topic, the following discussions of some of the principal mechanical characteristics of direct fixation rail fasteners are offered. Readers of this Handbook are strongly encouraged to obtain copies of TCRP Report 71, Volume 6, prior to undertaking direct fixation track design.

Track Components and Materials 5-41 5.4.6.1.1 Vertical Static Stiffness Vertical static stiffness is often called spring rate, and represents the slope of the load versus deflection over a prescribed range of 1,000 to 12,000 pounds (5,000 to 55,000 N). Current light rail track designs include a static stiffness of about 100,000 to 120,000 pounds per inch [18 to 21 MN/m], which, with a 30-inch [760-millimeter] fastener spacing, gives a rail support modulus of about 3,700 pounds per square inch [26 MN/m2]. One feature of low-stiffness fasteners is that they distribute rail static deflection over a larger number of fasteners, making the rail appear more uniformly supported. Low rail support stiffness reduces the pinned-pinned mode resonance frequency due to discrete rail supports, as well as the rail-on-fastener vertical resonance frequency. Static stiffness in the 100,000 to 120,000 pounds per inch [18 to 21 NM/m] range provides reasonable control of track deflection in the vertical direction without unduly compromising lateral stiffness. Noise and vibration experts in the field have additional thoughts on controlling the pinned-pinned mode resonance by varying the fastener spacings. For additional information on this subject, refer to Chapter 9, Article 9.2.1.2.2. The typical static stiffness of direct fixation fasteners used by various U.S. systems is on the order of 112,000 to 280,000 pounds per inch [20 to 50 MN/m], with spacing ranging from about 24 to 30 inches [610 to 762 millimeters]. At least one U.S. rail transit property uses a 36-inch [910-mm] fastener spacing; however, as is explained in Chapter 9 of this Handbook, wide spacings can have undesirable harmonic characteristics, potentially exacerbating the tendency to develop rail corrugations. So as to both deter corrugation growth and better approximate the stiffness of ballasted track, softer fasteners have been developed with an elastomer stiffness on the order of 106,000 pounds per inch [18.6 kN/m]. These fasteners incorporate elastomer bonded between a ductile iron or steel top plate and stamped steel base plate. A snubber is installed between the top and bottom plates, beneath the rail seat, to limit lateral motion of the top plate. Lateral rail head stiffness is on the order of 30,000 pounds per inch [5 MN/m]. Fasteners have been supplied with vertical stiffness on the order of 110,000 pounds per inch [19 MN/m], but with very low lateral stiffness, on the order of 9,800 pounds per inch [1.75 MN/m], due to lack of a snubber or other lateral restraint. These differences in lateral stiffness reflect differences in design philosophy concerning maximum allowable gauge widening under load and consequent sharing of lateral load between fasteners in curved track. 5.4.6.1.2 Ratio of Dynamic to Static Stiffness (Vertical) The ratio of vertical dynamic to static stiffness is a very important quantity that describes the quality of the elastomer. A low ratio is desirable to maintain a high degree of vibration isolation. A desirable upper limit on the ratio is 1.4, which is easily obtained with fasteners manufactured with a natural rubber elastomer or a rubber derivative. Ratios of 1.3 are not uncommon with natural rubber elastomer in shear designs. As a rule, elastomers capable of meeting the limit of 1.4 must be of high quality and generally exhibit low creep. 5.4.6.1.3 Lateral Restraint Lateral restraint is the ability of the fastener to horizontally restrain the rail. High lateral restraint is often incompatible with vibration isolation design requirements. Therefore, fasteners that provide adequate stiffness to guarantee both an adequate degree of horizontal position control as well as vibration isolation are desirable. Snubbers are protruding portions of metal plate that penetrate the adjoining plate to act as a limit flange in controlling lateral displacement. Some

Track Design Handbook for Light Rail Transit, Second Edition 5-42 fasteners use an upsweep curved bottom plate design to restrain or act as the limiting flange. The guiding design principle is to provide a three degree-of-freedom isolator. Hard snubbers are undesirable in fasteners, because they limit vibration isolation only in the vertical direction. 5.4.6.1.4 Lateral Stiffness at the Rail Head Lateral stiffness is measured at the rail head and includes the effect of fastener top-plate rotation. For track to stay in gauge, the rail fasteners must maintain rail head position within tolerances on both curves and tangent track. This goal is potentially in conflict with the requirement for horizontal vibration isolation. The lateral deflection of the top plate of typical sandwich fasteners is limited by either the snubbers or the configuration of the bottom plate and to a lesser extent by the elastomer in shear. If the snubber is located beneath the rail, a low fastener with low vertical stiffness will have low rotational stiffness and thus poor rail head control. This conflict has been overcome by one European design, which incorporates elastomer in shear with a large lateral dimension to resist overturning. Another way of overcoming this potential conflict is to move most of the elastomer to the ends of the fastener, away from the rail center, thus maximizing the reaction moment to overturning forces. If a snubber is located towards the lateral ends of the fastener, it will minimize rotation of the rail by forcing the rail to rotate about a point located towards the field side of the rail in response to gauge face forces. Designers should not confuse the amount of rail head deflection that occurs during laboratory testing with actual gauge widening under load in service. Typical laboratory testing occurs with only one or two rail fasteners beneath a test rail. Track in service does not see loading of a single fastener. Instead, the rail spreads the load so as to be shared by three, four or even more fasteners. A fastener that is laterally soft will result in more load sharing between fasteners, reducing the load experienced by each, and yet still result in acceptable track gauge control. The torsional stiffness of the rail also is a factor in gauge control. 5.4.6.2 Shims beneath Direct Fixation Rail Fasteners The construction of the concrete plinths or grout pads for support of direct fixation rail fasteners is, like all concrete work, subject to some construction tolerances. Particularly in the case of “bottom-up” construction of direct fixation track, it can be difficult to get the plinth concrete at precisely the correct elevation. If the bearing surfaces beneath the rail fasteners are not at a uniform distance below the top-of-rail profile, some fasteners may be stretched vertically while others are in compression, hence taking a disproportionate amount of the vertical loading. So as to avoid this condition, shims are usually selectively inserted beneath the direct fixation rail fastener body. A typical criterion is that if a taper gauge shows a gap of 1/16 inch [1.5 mm] or more between the base of the unclipped rail and the top plate of the rail fastener, the fastener should be shimmed. Shims have been made from a variety of materials, but galvanized steel and high density polyethelene (HDPE) are the most common. Shims are typically made so as to project ¼ to ½ inch [6 to 12 mm] beyond the footprint of the rail fastener body. The HDPE shims will, in theory, provide an additional electrical barrier between the rail fastener and ground and, if they project beyond the footprint of the fastener bottom plate, will increase the surface leakage distance, at least when clean. The shim obviously must have holes to allow the anchor bolts to pass through. Some contractors propose shims with slotted holes that extend out to the edges of the shim, thereby making it possible to insert the shim without fully removing the anchor bolts. However,

Track Components and Materials 5-43 experience has shown that slotted shims can shift out of position during service, and they are therefore not recommended. Shims are typically provided in a variety of thicknesses, and the contractor will stack shims of one or more thicknesses to achieve the requisite shimmed height. However, both the number of shims and the total shimmed height beneath any rail fastener should be limited. There are two reasons for this: • The fastener is most stable if it is placed directly on the concrete plinth with no shims. Each shim introduces an intermediate shear plane where slippage could occur. • Excessively shimming the fastener can alter the way in which the anchor bolts are loaded, including the amount of thread engagement and the moment loading seen at the root of the threads at the plinth surface. For these reasons, it is recommended that not more than three shims be inserted under any direct fixation rail fastener and that the total shimmed height be not more than about ⅜ inch [9.5 mm]. Higher shimmed heights have been used, particularly on “plinthless” design direct fixation aerial structures, but any such installations should be carefully analyzed. Extremely thin shims are subject to failure. For this reason, many designs specify that every rail fastener should have a shim of the minimum acceptable thickness—usually ⅛ inch [3 mm]. Then, if additional shimming is required, that shim is removed and a shim or shims of the required total thickness are inserted. See Chapter 13, Article 13.3.2, for additional discussion on shims in direct fixation track. 5.4.7 Fasteners and Fastenings for Embedded Track Embedded tracks typically do not use a rail fastener as the term is defined above. Some embedded tracks—those where the rail is “floating” in a trough filled with an elastomeric grout— use no rail fastenings at all. More common is the use of a some sort of clip to hold a booted rail to either a steel tie/leveling beam or an individual plate fastener. Booted rail in embedded track can use a non-insulated rail assembly; however, a protective insulator is typically employed beneath the clip to spread the hold-down load and avoid damage to the rail boot. Elastic rail clip assemblies very similar to those used on concrete cross ties are a common choice. The use of an elastic spring clip in embedded track is usually based on an expectation that it will eventually be necessary to change out rails—either on a spot basis or out- of-face—at some time prior to when the embedding pavement structure is life expired. Elastic rail clips greatly facilitate rail change out in ordinary open ballasted track, and it is therefore presumed that similar benefits would ensue from using them in embedded track as well. So as to ensure that the elastic clips remain limber and are not encased in the concrete pavement, they are usually covered with a plastic cap commonly called a “batter’s helmet.” Figure 5.4.4 illustrates a typical installation of this type. Items to note include the heavy duty pad beneath the toe of the elastic clip, so as to protect the rail boot from abrasion, the helmet ready

Track Design Handbook for Light Rail Transit, Second Edition 5-44 for installation, and the jacking screws on the end of the leveling beam. (The track has not yet been elevated to final grade in this view.) Figure 5.4.4 Elastic rail clip assembly for embedded track Potential problems with use of elastic clips in embedded track include the following: Since the elastic clip is installed by hammering it into a shoulder, there is the possibility of a misaimed hammer swing damaging the rail boot. If the damage is not noted and immediately patched, a stray current leak might result. The intentional void beneath the helmet and around the elastic rail clip is not watertight. There is a reasonably good chance that it will periodically be at least partially filled with water, beginning with bleed water from the fresh embedding concrete and later including surface water that leaks through small cracks in the pavement surface. This moisture could initiate corrosion and result in clip failure. (Note also the discussion in Article 5.4.4 on how elastic clips can be subject to brittle fracture when in a corrosive environment.) Since there is no way to inspect, much less easily replace, the clips once the pavement concrete has been poured, loss of rail anchorage might not be apparent until successive failures of adjacent clips have left the rail sufficiently loose to visibly move under traffic. Because of these issues, many designers choose to use a rigid clamp style clip to hold the booted rail to the steel leveling beam. Such clips can be obtained either as steel fabrications, steel or iron castings, or in molded plastic. Hold-down clips should have a smooth finish with rounded edges and corners so as to avoid damage to the boot. All the edges and corners should have ample radii as the clips may rotate slightly when mounting bolts are torqued. If the embedding material includes a substantial amount of reinforcing steel above the base of rail elevation, the pavement itself will serve to hold the rails to alignment and gauge. Under such circumstances, the rail hold-down clips and leveling beams effectively have only one function—to hold the booted rail in place until the embedment concrete is installed. Under such

Track Components and Materials 5-45 circumstances, the use of plastic rail clips can reasonably be considered. However, should the embedment material be of a nature to not securely restrain the booted rail (as in the case of turf track), then the rail hold-down clip design must be sufficiently robust to hold the rail in alignment without any other supports. The use of plastic rail clips is not recommended under such circumstances. As a guideline, steel rail clips are recommended for any installation where the rail fastening assembly can be expected to take some measurable amount of either lateral load or uplift/rollover load. Plastic clips can be used in circumstances where rail loadings are light or when the reinforcing steel in the embedding concrete is sufficiently robust that the concrete pavement acts as a supplemental, if not the primary, means of holding the rails in position. 5.5 CROSS TIES AND SWITCH TIES Ballasted track requires cross ties to support the rail. Chapter 4 discusses cross ties in the design of ballasted track. Cross ties are used mainly for ballasted track, although they are occasionally used in direct fixation encased track, where a cross tie or sections thereof are partially encased in a concrete track structure, and in embedded track, where the cross tie is fully encased in the track structure. Cross ties are generally made of three materials: timber, concrete, and steel. In addition, cross ties made of plastic and composites of plastics and other materials are now available. Several designs of plastic and composite material cross ties are on the market, but all are proprietary products and none have seen wide acceptance. Handbook users who are interested in such materials should consult industry trade magazines and vendors for current information. Light rail transit systems use both timber and concrete cross ties in ballasted track. However, current designs of prestressed precast concrete cross ties, which feature embedded shoulders for rail clip assemblies plus sundry inserts for the application of trackwork components, are available at first cost prices that are very competitive with insulated timber ties. When life cycle costs are considered, concrete ties are nearly always a better choice and have therefore become the preferred product on most rail transit systems. 5.5.1 Timber Cross Ties The timber species currently used in cross ties varies somewhat by geography, but includes selected hardwoods with occasional consideration of tropical hardwood species. The expense associated with cross tie replacement (including the intangible costs associated with disruption of revenue transit operations) makes it highly desirable to use high-quality timber ties during initial construction. Species of timber commonly used in freight railroad track construction in the region of the project are generally satisfactory. As a guideline, timber cross ties for light rail transit use should be hardwood—preferably oak in the eastern United States and Douglas fir in the western United States. There are risks and rewards associated with the use of tropical hardwoods (e.g., Azobe). Designers must research the topic thoroughly. It is very important to specify such exotic woods

Track Design Handbook for Light Rail Transit, Second Edition 5-46 by their botanical name. The use of a common name can result in obtaining an inferior material. For example, there are several species of Azobe with wildly different performance characteristics. The problem is that they are virtually indistinguishable from each other after the bark has been removed. On-site inspection at the sawmill is therefore essential. Certain grades of Azobe have been known to develop a fungus and decay after only a short period of time under certain track conditions. All things considered, the use of either high-quality domestic timber or concrete cross ties may be preferable to the use of imported hardwoods. The requirement for an insulated tie plate to be mounted on a timber cross tie dictates the general width of the cross tie. Standard tie plate widths range from 7 to 7 ½ inches [180 to 190 millimeters]. An insulated tie pad protrudes a minimum of a ½ inch [12 millimeters] on all sides of the tie plate, which results in a minimum tie width of 8 inches [204 millimeters]. A 9-inch- [230- millimeter-] wide timber tie provides sufficient surface to support the total insulator pad with no overhang beyond the edge of the tie. Skewed tie plates at special trackwork locations should be used with consideration of the overhang issue in relation to degree of the skew angle. To overcome the skew position, specially fabricated tie plates with angled shoulders are usually required. Very often, each such plate will need to be custom made for only one location due to turnout angle and plates being right and left handed in specialwork. Timber ties should generally be 7 x 9 inches [180 x 230 millimeters] in cross section. Per AREMA specification, the 7-inch tie depth is referred to as a “7-inch grade” cross tie. There is no equivalent metric name, as the S.I. system is not used to classify and name tie sizes. Notably, timber ties overseas (where they are usually called “sleepers”) are typically sawn to radically different dimensions than timber ties in North America. In the United Kingdom and other parts of the world influenced by British practice, a typical sleeper will be roughly 125 x 250 millimeters [about 5 x 10 inches] in cross section. Customary lengths of cross ties stem from standard track gauge of 56.5 inches [1435 millimeters] and are generally 8 feet 6 inches [2.59 meters]. Cross tie length is generally set by considering the contact pressure between the bottom surface of the cross tie and the ballast under railroad loading. Under transit loading, the cross ties can generally be shorter and less wide, but other reasons make it more practical to conform to the railroad dimensions. For the same reasons, it is generally unnecessary to use longer cross ties for plain track on broad gauge systems. Broad gauge systems do require longer switch ties. Timber cross ties are generally manufactured to conform to the current specifications of the AREMA Manual for Railway Engineering, Chapter 30—Ties, Part 3—Solid Sawn Timber Ties. AREMA defers to another professional trade group, the American Wood Preservers Association (AWPA) for many issues regarding preservative treatment of timber ties. When using timber cross ties conforming to AREMA recommendations, the type of wood, tie size, anti-splitting device, incising, wood preservative treatment, and machining should be specified in the procurement contract. Regardless of species or preservative treatment methods, timber cross ties will eventually require replacement. In LRT service, the usual failure mode for timber ties is decay rather than mechanical wear. If the guideway configuration does not facilitate the replacement of individual cross ties, this future maintenance activity will be very costly. For example, if timber cross ties

Track Components and Materials 5-47 are used in a curbed ballast section such as that shown in Chapter 4, Figure 4.5.5, it may not be possible to change out individual defective ties, particularly if the track center dimension is less than about 13 feet [4.0 meters]. Under such tight conditions, maintenance forces would need to change out clusters of ties (whether defective or not) by removing ballast, rotating the ties 90 degrees, and lifting them out from the gauge area of the track. Alternatively, the rail could be set aside, allowing full access to all ties albeit only by taking the track out of service for an extended period. Either operation would be costly. Because of such circumstances, timber cross ties are not recommended for curbed ballast sections. Either concrete cross ties or an entirely different trackform should be considered for such areas. For light rail transit systems constructed in the early 1980s, timber cross ties alone were believed to provide sufficient electrical isolation. Current standards require a layer of insulation between the bottom of the tie plate and the top of the tie plus insulating thimbles between the lag screw and the tie plate, as shown in Figure 5.4.2. The environmental aspects of treating the wood and ultimately disposing of old cross ties after their service life has expired has raised their life cycle costs. While the preservatives used to treat timber cross ties do not result in their being classified as hazardous waste, they do need to be disposed of in a controlled manner. This is usually in a licensed landfill, although many are burned as fuel at cogeneration facilities. 5.5.2 Concrete Cross Ties Concrete cross ties have become very common in light rail transit designs as even first cost makes them competitive with timber cross ties with insulated tie plates. Life cycle costing of concrete versus timber ties makes the case for concrete even more compelling. The most common concrete cross tie is the pretensioned monoblock tie with embedded cast steel shoulders for an elastic rail clip assembly. The rail fastening system includes insulating rail seat pad and combination clip and shoulder insulators, as shown in Figure 5.4.1. The typical plan view dimensions at the base of the concrete ties for rail transit are 10 inches [255 millimeters] wide and 8 feet 3 inches [2515 millimeters] long. Vertically, the center of the tie is typically tapered with a 7-½-inch [190-millimeter] height at the rail seat and a 6-½-inch [165- millimeter] height at the center of the tie. In addition to conventional cross ties that hold only the two running rails, special cross tie designs are available to hold restraining rail in guarded track and emergency guard rails. The overall size of the various types of cross ties is similar except that the height at the center of the tie will increase to support the supplemental assemblies at the appropriate elevation. The configuration of the restraining rail and emergency guardrail cross ties provides a relatively level surface between the running rails. The length of concrete cross ties may vary among transit systems; however, 8 feet 3 inches [2515 millimeters] appears to be the most common length for standard track gauge. Extra length cross ties are recommended for supporting the field side panels of modular at-grade highway crossing systems. Additional width in the field side crossing panels has been demonstrated to

Track Design Handbook for Light Rail Transit, Second Edition 5-48 provide better panel stability. Extra long cross ties can also be considered for transition zones between ballasted track and stiffer trackforms, as shown in Chapter 4, Figure 4.4.1. The concrete cross tie design for light rail transit track is based on the light rail vehicle weight, anticipated loads, and vehicle operating velocity. It is generally a less robust version of the railroad concrete cross tie with less reinforcement (and sometimes a reduced cross section). Designs of concrete ties for transit application are tested for positive and negative rail seat bending and tie center bending using the procedures specified in AREMA’s Manual for Railway Engineering, Chapter 30. Compared to concrete cross ties for railroad service, the only differences in the design and testing regimen are the vehicle loadings, cross tie spacing, and speeds that are factored into the AREMA equations. Concrete cross ties for transit use are generally specified in accordance with AREMA Chapter 30, the only difference being the vehicle loadings, cross tie spacing, and speeds that are factored into the AREMA design equations. 5.5.2.1 Concrete Cross Tie Design The design of concrete cross ties for light rail transit track is based on performance specifications that consider the following: • Tie spacing. • Tie size. • Rail section. • Rail fastening system. • Wheel loads. • Impact factor. 5.5.2.2 Concrete Cross Tie Testing Prior to acceptance of the concrete cross tie design, the manufactured cross tie should be tested for compliance with specifications and the determined calculated load limits. The tests should be conducted in accordance with the procedures outlined in the AREMA Manual for Railway Engineering, Chapter 30. 5.5.3 Switch Ties—Timber and Concrete Switch ties for LRT special trackwork installations include both timber and concrete. 5.5.3.1 Timber Switch Ties While economics are shifting in the direction of concrete switch ties for standardized installations, hardwood timber switch ties can still be an economical choice for unique special trackwork layouts. With the exception of length and related parameters, such as straightness, the requirements for timber switch ties for LRT use are generally as discussed above for standard length timber cross ties. Timber switch ties are typically provided in lengths ranging from 9 feet [2.75 meters] to 17 feet [5.20 meters]. Timbers as long as 23 feet [7 meters] are occasionally used on crossover and double crossover tracks. The headblock ties beneath switch machines are often specified to be 9 inches [230 millimeters] thick. This allows the tie to be dapped, thereby allowing a lowered switch machine mounting,

Track Components and Materials 5-49 reducing the projection of the switch machine above top-of-rail elevation. This low profile is generally necessary only on heavy rail transit systems where additional clearance is desired because of the third rail shoes on the transit vehicle. That dimensional constraint in turn led to specialized designs of switch machines and rods for transit use. As is often the case, details developed for one mode of railway are carried over into other modes so as to take advantage of off-the-shelf hardware, hence the use of dapped switch ties on many LRT projects. Similar to main line timber cross ties, the spatial requirements for insulated rail fastener plates often dictates the width of the tie. A 9-inch- [230-millimeter-] wide timber switch tie usually provides adequate surface to support the entire insulator pad with no overhang beyond the edge of the tie. Customized plate designs are usually needed so that the plate can be mounted parallel to, and entirely on, the tie surface. Neither the plates nor the underlying insulating pads should project beyond the edges of tie. Timber switch tie sets for turnouts generally conform to AREMA Plan basic number 912. However, due to the lower transit wheel loads, it is actually possible to increase the spacing of the timber switch ties in the closure rail area. As a practical matter, timber switch tie spacings should not exceed 24 inches [610 mm]. The switch and frog areas should generally remain at the AREMA spacing. When setting switch tie locations, consideration should be given to any thermite field weld locations so that welds are suspended between ties. Timber switch ties, like timber cross ties, should be specified in accordance with current specifications of the AREMA Manual for Railway Engineering, Chapter 30—Ties, Part 3—Solid Sawn Timber Ties. The type of wood, tie size, anti-splitting device, wood preservative treatment, and machining should be specified in the procurement contract. As mentioned previously, designers are cautioned concerning specification of tropical hardwoods. For additional information on timber tie special trackwork, refer to Chapter 6. 5.5.3.2 Concrete Switch Ties Concrete switch ties are gaining wider acceptance in rail transit than was the case when the first edition of this Handbook was published. Concrete switch ties are developed to match the geometry of specific turnouts and spacing of the ties within those turnouts. Up through about the year 2000, most concrete switch tie designs in North America were designed to meet the needs of freight and passenger railroad companies and came about through the joint effort of the railroads and the concrete tie manufacturers through various technical committees. These freight and passenger/commuter railroad turnout designs were primarily for the larger turnouts (No. 15 and above) used for higher main line speeds. Relatively few switch tie design details originated on transit projects. That situation is changing as more transit agencies opt to use concrete switch ties, and designs are now available for several sizes of turnouts, crossovers, and double crossovers—including turnouts as sharp as a No. 5. If concrete switch ties are being considered for a project, particularly a small project that needs only a few turnouts of each size and hand, careful consideration of designs that have already been engineered and fabricated can save money.

Track Design Handbook for Light Rail Transit, Second Edition 5-50 Concrete switch ties for light rail transit use should be approximately 10 inches [255 millimeters] wide at the top of the tie, 11 ¼ inches [285 millimeters] wide at the base of the tie, and 9 ½ inches [240 millimeters] high throughout. The standard embedded shoulder and elastic clip used on ordinary concrete cross ties may be used at some locations on switch ties where clearances allow the four rails to be mounted individually. Placement tolerances for the embedded shoulders are critical. The height differentials between switch, frog, and guard rail plates and the standard conventional rail installation must be considered in the cross tie design. Generally, the single rail locations have the rail seat area formed higher than the remainder of the tie so as to match the base of rail elevations in the plated areas. Threaded anchor inserts in the tie are often used to secure switch plates, frog plates, and guard rail plates, although designs that employ embedded shoulders to permit plates to be anchored using threadless elastic rail clips have become available since 2000; see Figure 5.4.3. Areas of the turnout layout where single rail installation is required, such as the closure curve zone between the heel of the switch and the toe of frog, will require an alternate rail mounting method. Some projects have specified cast-in shoulders for all special trackwork components including plated areas and conventional rail installations, thereby making many of the switch ties in the layout absolutely unique. Concrete switch tie sets for transit use will deviate from AREMA Standard Plan No. 912, due to the lower transit wheel loads and the increased spacing required to permit tamping around wider concrete switch ties. The spacing should not exceed 24 inches [61 cm] in the switch and frog areas and 30 inches [76 cm] in the closure curve area. In the switch and frog area, the tie spacing must provide working space for thermite field welds between ties. As of this writing, there are not yet any universally accepted standards for concrete switch tie sets, and AREMA has not included any recommended concrete switch tie layouts in the Portfolio of Trackwork Plans. Instead, the tie lengths and spacings for various turnout and crossover arrangements in light rail transit track are developed by the individual projects, usually as part of the fabricator’s shop drawings. See Chapter 6, Figures 6.91 through 6.9.3 for illustrations of suggested layouts for concrete switch tie turnouts. Standardization would allow for more economical engineering and manufacturing and increased use of concrete switch ties. The concrete switch tie length should be sufficient to suit the turnout geometry and provide sufficient shoulder length. The fastenings and switch, frog, guardrail, and turnout plates should be insulated to retard stray current leakage. The concrete switch ties should comply with the appropriate specifications for concrete ties as outlined in the AREMA Manual for Railway Engineering, Chapter 30. For additional information on special trackwork concrete switch tie designs, refer to Chapter 6 of this Handbook. 5.6 JOINING RAIL Rail joints are the weakest component in the track structure and are generally unavoidable on any track structure. To connect the short length (sticks) of rolled rail, a rail joint is required. There are various types of rail joints grouped as follows: 1. Welded Joints − Electric pressure flash butt weld

Track Components and Materials 5-51 − Thermite (kit) weld Other types of welded joints (e.g., gas pressure welding and cast welds) have been used in the past, but have been superseded by the technologies noted above. See Article 5.6.1 of this chapter and Chapter 13 for additional discussion of rail welding processes. 2. Insulated Joints − Non-glued bolted insulated joint—the poly-encapsulated design has superseded virtually all previous designs of non-glued insulated joints. The poly-encapsulated design is available from several vendors, and there is no reason to consider obsolete designs. − Glued (“bonded”) and bolted insulated joint—glued joints are recommended for use in continuously welded rail. 3. Non-Insulated Bolted Joints − Standard bolted joint (Non-glued)—these are the ordinary bolted joints such as those that appear in the AREMA Manual for Railway Engineering. − Glued bolted joint—glued bolted joints are uncommon, but are sometimes used in locations where a permanent and robust connection is desired between two rails but it is not practical to install a thermite weld. This design requires a special joint bar that matches the contours of the full height of the rail web. − Pin-bolted joints—some railways have used high-strength pin bolts (also known as “Huck bolts”) to fasten ordinary bolted joints together, typically with a zero joint gap so as to produce “continuous bolted rail.” Keeping these joints tight can be problematic; there is no way to further tighten them because the fishing surfaces of the joint bars and rail webs wear into each other. The resulting loose joint can flex and, because the rail ends are tightly butted to each other, rail end chipping can result. This detail is not recommended unless it is also glued, as described above. 5.6.1 Welded Joints Welded rail joints, forming continuous welded rail (strings) out of many short lengths (sticks) of the rail, have been standard for main tracks in the railroad industry for decades. Elimination of bolted rail joints has improved the track structure and reduced the excessive maintenance required at bolted rail joints. CWR strings with no bolted joints provide three specific improvements: • Elimination of bolted joint connections and their associated mechanical problems and high maintenance costs. • Elimination of the electrical bonding cables that are needed at bolted joints for signaling circuits and traction power return circuits. • Reduction of the resistivity of the rail to the lowest possible level so that traction power return current is carried with the least probability of stray currents.

Track Design Handbook for Light Rail Transit, Second Edition 5-52 Rail welding in North America is generally accomplished using either the electric pressure flash butt weld or the thermite weld method. 5.6.1.1 Electric Pressure Flash Butt Weld Most rail strings are welded together by the electric pressure welding process (commonly called “flash butt welding”). Electric flash butt welding is a forged weld created by placing an electrical charge between the slightly separated ends of the rails until the steel is plastic. The rails are then forced together to the point at which the steel refuses further plastic deformation. There are three types of flash butt welding plants, although the basic welding equipment is the same in each case: • Fixed welding plants are permanent installations where the rail is usually brought in and shipped out on railroad cars. Such facilities are sometimes located at or near the rolling mill where the steel rails are manufactured. • Portable welding plants are modular units that can be brought to a project site. They typically contain most of the same equipment as the permanent plant. • Portable welders are units typically contained within a hy-rail-equipped truck. These are usually used for making welds in track on a spot basis such as when making final closures between CWR strings; however, some contractors are now using them to fabricate strings at small project sites that can’t accommodate a portable plant. On most rail transit projects portable welding plants are used to produce strings of continuously welded rail (CWR). Because flash butt welding forges two rail ends together under pressure, the resulting welded rail is shorter than the sum of the two individual rails from which it is made. The amount of length lost will vary by many factors, but is generally about 1 to 1 ¼ inches [25 to 32 mm] per weld. This is one reason why flash butt welding is generally impractical within special trackwork units. The individual rolled stick rails are welded in various predetermined lengths of CWR. When CWR strings are welded for railroad service, the nominal lengths are normally 1,440 feet [439 meters], a length that has proven convenient for transport in railroad use. In rail transit work, the actual lengths of the CWR strings are usually dictated by the project’s construction work plan, giving due consideration to the following: • The space constraints of the welding location and any intermediate rail string storage locations. • The method of transporting the CWR from the welding location (or to and from an intermediate storage location) to the installation location. CWR trains such as those used by freight railroads are uncommon in rail transit construction. In many cases of LRT construction, particularly when storage space is at a premium, the welding plant will be moved multiple times during a project, and CWR strings may only need to be moved relatively short distances using portable rollers or mini-CWR trains. • The characteristics of the installation location. In urban areas, maintenance of highway traffic requirements will often limit work areas to the length of a city block. Hence, the

Track Components and Materials 5-53 CWR strings might be both very short and fabricated in a variety of lengths to suit the field conditions. During the electric flash butt welding process, heat-affected zones (HAZ) develop in the original rail steel on both sides of the weld immediately adjacent to the upset weld metal created during the forging. The surface hardness in the HAZ is somewhat less than either the original rail steel or the center of the weld. Under traffic, the HAZ can become dipped and battered, a condition often referred to as “mushrooming.” This condition is particularly common under freight railroad loadings, but similar issues can develop in transit track, albeit at a slower growth rate. Immediate air cooling of the HAZ can increase the rail hardness and reduce the length of the HAZ; however, air cooling of the HAZ is not a standard practice as of this writing. As with many things, the track designer should not assume that rail welding contractors will automatically take certain actions. If an action is not specified in the contract, there is a significant chance it will not occur. 5.6.1.2 Exothermic (“Thermite”) Rail Welding Thermite welds are produced with molten steel cast from a crucible and poured into a specified gap between two rails. The molten steel is produced by an “exothermic” chemical reaction between aluminum and iron oxides. Additives in the mix create the other components needed to make the steel. Thermite welding requires preheating the rail ends in order to create a good bond between the rail steel and new steel produced in the thermite crucible. It is desirable that the resultant steel weld material have approximately the same hardness as the parent rail steel. Manufacturers can produce welds with different hardnesses to provide compatibility with different grades of rail steel; however, this is difficult to achieve in practice. Similar to the electric pressure flash butt weld process, the thermite weld process also generates HAZ in the original rail steel. At least one thermite weld kit manufacturer has developed a post- weld heat treatment process that reduces this problem, but it has seen little acceptance in North America. Battered thermite welds (typically in the HAZ adjacent to the weld) are a significant problem in rigid trackforms—particularly in embedded track, which can begin to sound like jointed rail in a distressingly short time after construction. Attempts to repair this condition through surface welding are generally unsuccessful, in part because the heat of welding can damage or destroy the rail insulation system (e.g., rail boot). One industry observer believes that many of the problems with battered thermite welds stem from the “slow bend test” mandated by AREMA. The slow bend test mandates that the weld straddling two rigid supports must be able to deflect over 1 inch [25 mm] without rupture. The apparent intent is to mimic a condition in ballasted track where the cross tie or ties beneath a rail weld have completely failed. So as to meet the slow bend test, the welding kit manufacturers need to make the weld very ductile, and much of this ductility apparently occurs in the HAZ and not the weld metal. The aforementioned industry observer notes that rail deflections on the order of those mandated by the slow bend test are virtually impossible in embedded track and that better welds might be possible if there was a modified slow bend test procedure specifically for embedded rails. European Norm EN-14370-1 might be a model for such a testing regimen. As of 2010, this issue was under consideration by AREMA Committees 4 and 12; readers should consult the current edition of the AREMA Manual for Railway Engineering and recent industry publications for the current status of this topic.

Track Design Handbook for Light Rail Transit, Second Edition 5-54 Prefabricated CWR rail strings are generally joined or welded together by the thermite weld process; however, many transit agencies, whenever practical, require use of a portable electric flash butt welder to join rail strings in order to eliminate thermite welds. For additional information on electric flash butt and thermite welding during construction refer to Chapter 13. Welding rail eliminates bolted joints and most of the associated joint maintenance. However, CWR creates other issues, such as thermal structural interaction on bridges, which must be addressed by the designer (refer to Chapter 7). 5.6.2 Insulated and Non-Insulated Bolted Rail Joints Bolted rail joints consist of two joint bars—one on each side of the rails—that splice the abutting rail ends. They are fastened with a series of track bolts (usually six). Both non-glued and epoxy- glued rail joints are required for various conditions. While all contemporary standards call for bolted joints to have six bolts, four-bolt joints used to be common. While four-bolt joints are usually strong enough for light rail vehicle loadings, they are not recommended because the loss of only one bolt in a four-hole joint means almost certain failure of a second bolt, particularly in CWR. For this reason, having only one functional bolt in one end of a joint constitutes a Class 1 defect under 49 CFR 213—the FRA Track Safety Standards. While 49 CFR 213 is generally not applicable to rail transit, it appears that as of this writing (2010) similar federal requirements may apply to rail transit in the near future. At one time, various railroads had different rail drilling spacing for bolt holes; however, over the years, rail drilling spacing was standardized, as documented in the AREMA Manual for Railway Engineering. The hole spacing recommended in AREMA should be followed for jointed tee rails of North American design. European standards for rail drilling spacings can be appreciably different. Regardless of rail section, non-standard drilling patterns are discouraged since they complicate maintenance. Although bolted rail joints are the weakest points in the track structure, some bolted joints are required. Most bolted joints in modern LRT main tracks will be insulated rail joints. These provide and define the signal circuit limits/sections, detect vehicle locations, define clearance points, and provide related functions. An insulated joint separates the ends of the rails to break the signal continuity by use of an insulated end post and insulation between the rails and both the joint bars and the bolt assemblies. Insulated joints are also used to isolate traction power return current paths as part of the effort to control stray current. 5.6.2.1 Non-Glued Insulated Rail Joints These are suitable for bolted rail track and within special trackwork layouts. Bolted insulated joints (non-glued) consist of two polyethylene-coated joint bars, bolt thimbles, and an insulated end post all held together by bolt assemblies. Because these joint assemblies cannot routinely accept high tensile forces in continuously welded rail, they are recommended for use only in bolted jointed rail track.

Track Components and Materials 5-55 These are the only insulated joints that are practical for field assembly under adverse weather conditions and in locations, such as crossing diamonds, where correct assembly of a glued insulated joint with the pot life of the adhesive would be problematic at best. 5.6.2.2 Glued Bolted Insulated Rail Joints Glued insulated joints, sometimes known as “bonded” insulated joints, are similar to non-glued joints, except that the joint bars are shaped to fit the rail fishing to allow the bars to be glued to the web of the rail. The adhesive in the glued insulated joints provides a continuous shear path for CWR rail stresses to be carried through the joint so that those forces are not carried solely by the track bolts and their insulating thimbles. Proper assembly of glued joints requires skill, good weather conditions, and the ability to keep the rail ends precisely aligned and absolutely stationary during the assembly and curing process. In the absence of these conditions, either electrical or mechanical failure of the insulated joint is very likely. For these reasons, it is recommended that glued joints be assembled in a controlled shop environment whenever possible. The resulting plug rail is then thermite welded into the proper location within the CWR after the rail has been adjusted for zero thermal stress. For additional information on assembly of insulated joints refer to Chapter 13. 5.6.2.3 Bolted Rail Joints Bolted rail joints can be of two designs, non-glued or glued (bonded). In light rail transit systems, non-glued bolted rail joints are typically used only in very sharp curves, maintenance yard facilities, or secondary non-revenue track. Bolted rail has often been used on sharp curves on the premise that doing so will make it easier to replace the rail when it wears out. Arguably, the presence of the bolted joints could cause the rail to wear out faster. It’s also usually not easy to replace a single rail in a sharp curve since gauge face wear on the existing rail could create unacceptable gauge line mismatch with the new rail. The theory that the internal rail stresses would be more easily controlled with bolted joints doesn’t necessarily apply in extremely sharp curves since the joints are more likely to lock up, particularly if the joint bars were not precurved to match the radius. The result is often the same. Very sharply curved track often “breathes,” that is, all or a portion of the track cyclically shifts in and out due to thermal expansion/contraction of the rail. This condition will leave gaps in the ballast section at the ends of the ties. Provided it happens uniformly along the length of the track curve, this is often not a concern, but it can be a major problem if the compressive rail stresses are concentrated in one area, resulting in a “sun kink.” Non-insulated glued rail joints can be used in CWR territory to maximize longitudinal load transfer through the joint bar assembly. Non-insulated glued rail joints are occasionally used in locations where a field-welded joint might be desired, but is not possible. As in the case of bonded insulated joints, a high degree of quality control is necessary during assembly. Non-insulated glued rail joints generally have a zero joint gap with abutting rail ends. Zero gap connections have a tendency to result in chipped rail ends due to rail steel migration across the butted joint. Although bonded, each rail end tends to independently pump vertically, resulting in chipped ends. This condition can require more maintenance than thermite weld mushrooming.

Track Design Handbook for Light Rail Transit, Second Edition 5-56 When non-insulated bolted joints of any design are used in electrified rail transit tracks, it is necessary to bridge them with an electrical cable so that signal and traction power currents can pass through. For additional information on electrical bonding for signal and traction power, refer to Chapters 10 and 11. 5.6.3 Compromise Joints and Compromise Rails Compromise joint bars are the customary method for joining two dissimilar rail sections. The compromise joint bars are machined or forged to the shape necessary to join the two dissimilar rails. The shape allows both rails to align at the top of rail and the gauge face of both rails. Compromise joint bars, due to design shape, are virtually always made for right- and left-hand installations. The hand designation is defined by the location of the larger rail as seen from the center of the track. To avoid abrupt changes in rail stiffness, compromise joints should not be installed between rails of greatly different heights. Generally, the difference in rail height should not exceed about 1 inch [25 mm]. If the difference exceeds that value, a transition rail of intermediate height should be used with two compromise joints. Exceptions can be made if the rails are continuously supported, as occurs in embedded track, or if rail operations occur at a very slow speed, such as within a maintenance shop. Like any bolted rail joint in CWR track, compromise joints are subject to high tensile stresses and possible bolt failure due to high shear stress. The problem is exacerbated by the moment loading of the joint caused by eccentricity of the loading. To overcome these issues, welding of the two dissimilar rail sections can be considered. Special thermite weld kits are available for this situation, and some vendors of flash butt welding services can pressure weld dissimilar rail sections that are not too different in overall cross section. Other options include forged steel compromise rails and compromise rails machined from a block of rail steel. The latter are often used for connections between groove rails and tee rails. Figure 5.6.1 shows a freshly machined central block for a compromise rail between CEN 67R1 groove rail and 115 RE tee rail. The compromise rail includes a central block made of rail steel with segments of each rail section machined at opposite ends. A common top of rail and gauge line are developed during the design and machining process. The central compromise block is then electrically flash butt welded to the two short sections of the matching rails. This compromise rail block with extended rails is then welded into the track, providing a boltless connection. 5.7 BALLAST AND SUBBALLAST Ballast, the material used to support the cross ties and rail, is an important component in the track structure. It is the integral part of the track structure in the roadbed, and the quality of the ballast material has a direct relationship to the track support system.[7]

Track Components and Materials 5-57 Photo courtesy of Voest Alpine Figure 5.6.1 Machined central block for compromise rail Light rail transit vehicles often exceed 100,000 pounds [45,500 kilograms], placing increased importance on the track structure, particularly the ballast quality and quantity. Superior ballast materials improve the track structure performance and are an economical method of increasing the track strength and the track’s modulus of elasticity. The importance of the quality and type of ballast material, along with standard test methods for evaluating the ballast material, cannot be overstated. The quality of the ballast will be determined by the choice of rock and the eventual testing of the rock, followed by observing the performance of the track structure. The physical and chemical properties of the ballast rock or stone can be determined by many material tests and performance evaluations. However, the true test of ballast performance is to observe it in the real-life track structure. 5.7.1 Ballast Ballast should be a hard, dense, mineral aggregate with a specific configuration of many fractured faces, an angular structure with sharp edges, and a minimum of flat and elongated particles. 5.7.1.1 Ballast Materials As a guideline, ballast material for light rail transit use shall be as follows: With Concrete Cross Ties Granite: a plutonic rock with an even texture consisting of feldspar and quartz. Traprock: a dark-colored, fine-grain, non-granitic, hypabyssal or extrusive rock.

Track Design Handbook for Light Rail Transit, Second Edition 5-58 • With Timber Cross Ties − Granite and traprock, as noted above for concrete cross ties. − Quartzite: granoblastic metamorphic rock consisting of quartz and formed by recrystallization of sandstone or chert by metamorphism. − Carbonate: sedimentary rock consisting of carbonate materials such as limestone and dolomite. Carbonate ballast must never be used with concrete cross ties. − Blast furnace slag (commonly used for ballasting secondary tracks on freight railroads). It should never be used on electrified transit lines since the residual metals in the slag can exacerbate any problems with stray currents. 5.7.1.2 Ballast Gradation It is important to match ballast size or gradation to the type of cross tie that will be used. The gradation of the ballast determines the sieve size to be used in the process of ballast grading. Table 5.7.1 lists the recommended ballast gradations for light rail transit use with concrete and timber cross ties. No. 5 ballast has been used for yard applications with timber cross ties to provide an easier walking surface. The smaller gradation may lead to earlier fouling of the ballast and eventual lack of drainage. No. 5 ballast is only recommended when the yard area is honeycombed with an underlying drainage system and substantial surface drainage channels. As an alternative, a thin layer of No. 5 ballast placed over the larger principal ballast stone can provide a safe walking surface. However, for safety and convenience, any areas where a significant number of employees can be expected to be walking, such as where train operators pick up and drop off trains, should be provided with a paved walkway surface. Paved walkways also facilitate snow removal in cold weather climates. Table 5.7.1 Ballast gradations Ballast Size No. Square Opening Î 3” [76] 2½” [64] 2” [51] 1½” [38] 1” [25] ¾” [19] ½” [13] 3/8” [10] #4 [6] Nominal SizeÐ Percent Passing Concrete Cross Ties 24 2½” – ¾” (64-19) 100 90-100 – 25-60 – 0-10 0-5 – – 3 2” – 1” (51-25) – 100 95-100 35-70 0-15 – 0-5 – – Timber Cross Ties 4A 2” – ¾” (51-19) – 100 90-100 60-90 10-35 0-10 – 0-3 – 4 1½” – ¾” (39-19) – – 100 90-100 20-55 0-15 – 0-5 – 5 1’ – 3/8’ (25-10) – – – 100 90-100 40-75 15-35 0-15 0-5

Track Components and Materials 5-59 5.7.1.3 Testing Ballast Materials Ballast material should be tested for quality through a series of tests undertaken by a certified testing laboratory. The tests should include the following: • ASTM C88: Soundness of Aggregates by Use of Sodium Sulfate (NaSO4). The sodium sulfate soundness test is conducted with the test sample saturated with a solution of sodium sulfate. This test will appraise the soundness of the aggregate. Materials that do not meet applicable test limits can be expected to deteriorate rapidly from weathering and freezing and thawing. • ASTM C117: Test Method for Material Finer than 75 microinch (No. 200 Sieve) in Aggregates by Washing (including Dust and Fracture). The concentration of fine material below the 200 sieve in the ballast material is determined by this ASTM test. Excessive fines are produced in some types of crushing and processing operations and could restrict drainage and foul the ballast section. • ASTM C127: Specific Gravity and Absorption. Specific gravity and absorption are measured by this test method. Specific gravity in the Imperial (English) measurement system relates to weight and in the metric system to density. A higher specific gravity indicates a heavier material. A stable ballast material should possess the density properties shown in Table 5.7.2 to have suitable weight and mass to provide support and alignment to the track structure. Absorption measures the ability of the material to absorb water. Excessive absorption can result in rapid deterioration during wetting and drying and freezing and thawing cycles. • ASTM C142: Test Method for Clay Lumps and Friable Particles in Aggregates. The test for friable materials identifies materials that are soft and poorly bonded and thereby lead to separate particles being detached from the mass. The test can identify materials that will deteriorate rapidly. Clay in the ballast material is determined by the same test method. Excessive clay can restrict drainage and will promote the growth of vegetation in the ballast section. • ASTM C535: Test Method for Resistance to Degradation of Large-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine. The Los Angeles abrasion test is a factor in determining the wear characteristics of ballast material. The larger ballast gradations should be tested in accordance with ASTM C535, while ASTM C131 is the wear test for smaller gradations. Excessive abrasion of an aggregate will result in reduction of particle size, fouling, decreased drainage, and loss of supporting strength of the ballast section. The Los Angeles abrasion test can, however, produce laboratory test results that are not indicative of the field performance of ballast materials. • ASTM D4791: Test Method for Flat and Elongated Particles. The test for flat and elongated particles uses one of three dimension ratios. Track stability is enhanced by eliminating flat or elongated particles that exceed 5% of ballast weight. Flat or elongated particles are defined as particles that have a width-to-thickness or length-to-width ratio greater than 3.

Track Design Handbook for Light Rail Transit, Second Edition 5-60 Table 5.7.2 lists the recommended limiting values for the ballast material tests. The ballast guidelines for timber and concrete cross tie applications are based on experiences with concrete cross tie ballasted track. The concrete cross tie load characteristics are quite different from the timber cross tie loadings on ballasted track. The concrete cross tie is heavier and less flexible in absorbing impact loads, thus transmitting a greater load to the ballast, which results in a higher crushing degradation load on the ballast particles. The selection of material for ballasted concrete cross tie track must be limited to granites and traprock. The selection of ballast materials for timber cross tie track can include all the materials listed in Table 5.7.2. Table 5.7.2 Limiting values of testing for ballast material Ballast Material Cross Tie Material Concrete Ties Timber Ties ASTM Test Property Granite Traprock Quartzite Limestone Dolomitic Limestone C117 Percent Material Passing No. 200 Sieve (maximum) 1.0% 1.0% 1.0% 1.0% 1.0% C127 Bulk Specific Gravity (minimum) 2.60 2.60 2.60 2.60 2.65 C127 Absorption Percent (maximum) 1.0% 1.0% 1.0% 2.0% 2.0% C142 Clay Lumps and Friable Particles (maximum) 0.5% 0.5% 0.5% 0.5% 0.5% C535 Degradation (maximum) 35% 25% 30% 30% 30% C88 Soundness (Sodium Sulfate) 5 Cycles (maximum) 5.0% 5.0% 5.0% 5.0% 5.0% D4791 Flat and/or Elongated Particles (maximum) 5.0% 5.0% 5.0% 5.0% 5.0% Other test procedures exist for testing potential ballast materials, such as the Petrographic Analysis and the Ballast Box Test performed at the University of Massachusetts. The services of a qualified certified specialist and testing laboratory in the field of geological materials is recommended to further refine the material selection process and verify the suitability of stone from a particular quarry for potentially supplying ballast. The quality of stone within any particular quarry can vary depending on a number of factors, including the working face of the quarry and the amount of original overburden at that part of the site. In particular, stone excavated from higher elevations on a quarry face should be monitored closely since visual methods may be insufficient to accurately define the line between acceptable and inferior material.

Track Components and Materials 5-61 5.7.2 Subballast Materials Subballast is a granular base material placed and compacted over the top of the entire embankment or roadbed to prevent penetration of the ballast into the subgrade. Common subballast materials include crushed stone, natural or crushed gravel and sands, or a mixture of these materials. The subballast layer must be of sufficient depth and shear strength to support and transfer the load from the ballast to the subgrade. Saturated subgrade soils are the principal reason that ballasted track surface can deteriorate. For this reason, unlike a highway subbase material, track subballast is generally graded to be somewhat impervious and shed water from its surface. Impervious subballast material should divert most of the runoff within the track area to the side ditches to prevent saturation of the subgrade. Use of impervious subballast material sometimes requires the placement of a layer of sand between the subballast and the subgrade to release the capillary water or seepage of water below the subballast. A layer of non-woven geotextile will accomplish this as well. A qualified geotechnical engineer should make this determination based on analysis of the soils that will make up the subgrade. 5.8 HIGHWAY/RAILWAY AT-GRADE CROSSINGS Designs for at-grade crossings of railway track by roadways vary depending on the specific type of track structure involved—ballasted, direct fixation, or embedded track—and the issues associated with their implementation. The design of any crossing must address subbase preparation, drainage, limits of crossing installation, type of crossing materials, flangeway widths, and walkway/street delineation markings. In some cases, transition sections may be appropriate between the relatively stiff track at the crossing and softer adjoining trackforms. Providing a solid subgrade beneath railway/roadway crossings is extremely important due to the double loadings and impact of railway and roadway traffic. A geotechnical engineer should be involved in the design of the subbase with consideration of whether the natural soil materials at the site might require reinforcement or replacement so as to provide a solid base for the crossing. Drainage is as important to road crossings as the subbase. It is imperative that surface runoff be controlled and any penetration in the crossing area be removed before the accumulation of water becomes detrimental to the subbase. Drainage of the area must be carried to the closest storm drainage catch basin or system. Drainage in embedded track must include a transverse track drain on the track profile high side of the road crossing to intersect track surface runoff and flangeway flow. The limits of the crossing materials and adjoining roadway reconstruction must be considered along the track and extending into the intersecting street. The crossing limit along the track should include any existing or required adjacent crosswalks. The track profile grade line usually must be set to conform to the existing roadway conditions and still provide the proper geometrics for transit. The intersecting street profile, contours, and curbline elevations often must be

Track Design Handbook for Light Rail Transit, Second Edition 5-62 modified to adapt to the track crosslevel and to intercept and channel roadway surface drainage away from the track. It generally is not recommended to construct crossings using asphalt except in instances where the roadway traffic is extremely light. Even then, modular flangeway rubber, available from several manufacturers, should be used. A better design for ballasted track utilizes modular crossing panels that span from rail to rail and also extend a little more than 2 feet [60 cm] outside of the rails. Commercially available crossing products include both precast concrete panels and rubber panels. Proper support of the panels on the outside (“field side”) of the rails generally requires extra length cross ties, with 10-foot [300-cm] ties being common. Regardless of the grade crossing product used, the rail should be wrapped in rail boot so as to electrically isolate the rail from the crossing panels and the earth. LRT crossings constructed without rail boot invariably incur extreme electrolytic corrosion of the rails and rail fastenings within only a few years. Occasionally, it might be necessary to provide a highway crossing of a direct fixation track. It generally isn’t possible to use off-the-shelf modular panels designed for ballasted track as they will not provide clearance for the direct fixation rail fasteners. In such cases, a segment of embedded track may be a more appropriate choice. The state of the art in grade crossing surface materials is constantly evolving, and the reader should contact vendors for current product information. Modular grade crossing systems are not watertight, and it is possible for storm water runoff to convey dirt that will penetrate the crossing and compromise the methods of electrically isolating the rail. Rail boot flexure over the edges of the cross ties may eventually lead to tears and resulting electrical leaks. The crossings and their insulation systems may therefore require excessive amounts of maintenance to remain effective. For this reason, some projects have used a segment of embedded track in lieu of other types of crossings. Embedded track provides the required total rail isolation required for stray current control through the crossing area. The flangeway width is important and current ADAAG standards for railroad and flangeway for transit use must be determined during the design. As of 2010, ADAAG requires flangeways for rail transit crossings to be no greater than 2 ½ inches [63.5 mm]. Flangeways for freight railroad crossings are permitted to be no more than 3 inches [76 mm], the same value that is recommended by AREMA. AREMA’s standard is based on the fact that the allowable wear on railroad flanges under AAR rules for interchange freight cars effectively raises the track gauge/wheel gauge freeplay to a value at which the backs of the wheels could contact the crossing surface material in any flangeway less than the 3-inch [76-mm] dimension. Whether this dual standard will persist is unclear, and users of this Handbook are encouraged to verify the current requirements before commencing design. Delineation of the walkways, the traveled roadway, and the restricted entry to the trackway must be designed to suit each road crossing intersection.

Track Components and Materials 5-63 Design of the track and civil engineering elements of highway/railway crossings must be carefully coordinated with the designers of the LRT signal systems and crossing warning systems. See Chapter 10, Article 10.2.10, for additional information. 5.9 TRACK DERAILS Track derails are operating protective devices designed to stop (by derailing) any unauthorized rail vehicles from entering a specific track zone. Generally the track zone is the operating segment of the main line. The protection is placed at all strategic track locations where secondary, non–main line operating side tracks such as pocket tracks, storage or maintenance tracks, and, in some instances, yard lead entry tracks connect to the main line. Derails are occasionally used to prevent vehicle or equipment movement onto portions of track where vehicles, work crews, or equipment are utilizing the designated track space. Derails are placed at the clearance point of all railroad industrial tracks that connect to either an LRT joint use track or to a railroad main track. Derails are also used at other track locations where they would be likely to prevent or minimize injury to passengers and personnel and/or damage to equipment. Derails are located so as to derail equipment in the direction away from the main track. Derails should be considered at track connections to the main line where • The prevailing track grade of the connecting track is descending toward the main line. The secondary track is used for the storage of unattended (parked) vehicles. • The secondary track is a storage track for track maintenance vehicles only. • The connecting track is a railroad industrial siding. • A railroad track crosses the LRT at grade. In the situation of a railroad track crossing the LRT at grade, there would likely be appreciable controversy concerning which railway’s vehicles are to be derailed. Derailing a freight train headed toward an LRT crossing that is already occupied by an LRV loaded with passengers might be just as disastrous as derailing the LRV. However, this may be a moot point; while there are dozens of locations in the United States where rail transit crosses a freight railroad at grade, the liability issues involved have caused the railroads to become increasingly concerned about not permitting any more such crossings. Derails are available in various designs—sliding block derail, hinged block derail, and switch point derail (available in single switch point or double switch point rail designs). Derails are generally designed to derail the vehicle in a single direction either to the right or left side of the track. The sliding and hinged block derails consist of essentially two parts, the steel housing and the derailing guide block. The sliding derail is generally operated with a connecting switch stand. The hinged derail is operated manually by lifting the derailing block out of the way or off the rail head. The switch point derail is exactly as described, a complete switch point (or two points) placed in the track to derail when the switch point is open. As a guideline, the type of derail to be used depends upon the site-specific conditions and type of protection to be provided. Occasionally block derails can fail, particularly when main line track is

Track Design Handbook for Light Rail Transit, Second Edition 5-64 exposed to the intrusion of heavily loaded cars, multiple car trains, track conditions that permit the intruding cars to gain momentum in advance of the derail, and tight curvature on the siding track. The switch point derail provides the greatest insurance that all wheels of the intruding vehicle will be derailed and deflected away from the main track. In addition, switch point derails are readily adaptable to standard power switch machines, which can provide positive indication to the train control system that the derail is or is not in the derailing position. 5.10 RAIL EXPANSION JOINTS Continuously welded rail in long strings does not expand or contract with changes in temperature unless there is a designed opening or break in the rail. A continuous CWR installation introduces high thermal stress into the rail as the temperature approaches the extremes (both cold and hot) for the geographic area. Ordinarily, these stresses can be handled by the track structure. However, there are situations, typically on bridges, where rail expansion joints are installed so as to allow the rails to expand and contract to alleviate a build-up of thermal stresses. 5.10.1 Rail Expansion Joint Theory When the track is carried by an aerial structure or bridge, the superstructure will need and is designed to thermally expand and contract with temperature. If the structure spans or deck are designed with one fixed end and one expansion end per span length, allowing a controlled, limited amount of span expansion and contraction, thermal structural expansion should not be a major concern for the rail installation. This type of installation is generally not a concern in tangent track as the elastic rail clips used in the direct fixation rail fasteners allow sufficient fastening slippage to permit the structure, including the rail fastener assemblies, to expand and contract beneath the fixed length of rail. If the structure is designed with a limited number of joints and expansion/contraction is transferred to only one or two locations, with a sizable accumulation of expansion/contraction at these few points, there will need to be a detailed rail-to-structure interface analysis. For additional information on structure/ rail interaction, refer to Chapter 7. In certain structures, particularly those that carry sharply curved track, the interaction between the CWR and the structure makes it desirable to limit rail stresses from the thermal structural forces. This can be accomplished by allowing the rail to freely move longitudinally within defined zones. A combination of low-restraint track fasteners and rail expansion joints allows this movement to take place safely. The use of low-restraint fasteners at structural expansion joints allows the structure to “breathe” without overstressing the rails. The rails must also be anchored or fixed between expansion zones with either a section of high-restraint fasteners or a specific rail anchor to control overall rail position. The anchoring will also control the transfer of acceleration and braking forces into the structure. Experiences have shown that extremely sharp curves—radii below about 220 feet [67 meters]— will not consistently allow the rail to slip through the fastenings, resulting in forces being transferred directly into the structure. Again, this type of rail/structure interface should be reviewed by referring to Chapter 7.

Track Components and Materials 5-65 5.10.2 Structural Configuration Bridge trackwork that includes rail expansion joints still needs to have the rail anchored at some location. In those high-restraint areas, a conventional direct fixation fastener is utilized, and the structure is designed to accept the thermal stress loads generated by movement of the structure. The expansion or contraction of the rail emanates from the high-restraint zone through a zone of low-restraint rail fasteners and is bounded on the other end by a rail expansion joint. Simple span bridge structures with an arrangement of fixed (“F”) and expansion (“E”) bearings following this general pattern: E span F/F span E/E span F/F span EE span F/F span E can usually be constructed using conventional high-restraint direct fixation fasteners and without any rail expansion joints. In special cases, it might be appropriate to include a short segment of low-restraint rail fasteners straddling the vicinity of each E/E pier. See Chapter 7, Article 7.5, for additional discussion of rail/structure interaction. See Article 7.4.2.3 for detailed discussion of rail expansion joints for embedded track. 5.10.3 Rail Expansion Joint Track Details Rail expansion joints are designed to allow for a specific length of thermal rail expansion and contraction to occur. One end of the expansion joint is fixed and connected to a rigid no- movement portion of rail. The other end consists of the expandable movable rail, which is allowed to slide in and out of a designed guideway. 5.10.3.1 Rail Expansion Joints for Open Trackforms The most common rail expansion joint design for open track functionally resembles a fixed switch point nestled against a stock rail that is free to slide back and forth. Special expansion rail joints have been designed with dual direction rail expansions or double-ended expansion joints. Figure 5.10.1 illustrates a double point rail expansion joint assembly suitable for use in either ballasted or direct fixation track. Expansion rail joints in the track system present problems from both a track maintenance and an environmental perspective. Due to the slightly discontinuous running rail surface and the special trackwork sliding rail joint component, extra maintenance is required to maintain the rail joint and adjacent rails and to monitor the position of the loose rail end to ensure that sufficient space is available for further rail expansion. The specific design of the expansion rail joint within the discontinuous running rail surface introduces additional noise and vibration. Similar to bolted rail joints, sliding rail expansion joints must be electrically bonded. The bond cable must have sufficient slack to accommodate the rail movement and also not present an obstacle to inspection and maintenance of the rail joint. In double rail expansion joints, the main bond cable would extend from one running rail to the other bypassing the central fixed portion of the expansion joint, and smaller bond cables would connect the central unit to the rails on each side. See Chapter 10 for additional information on rail bonding methods.

Track Design Handbook for Light Rail Transit, Second Edition 5-66 Figure 5.10.1 Double-ended sliding rail expansion joint As a guideline, rail expansion joints in ballasted track or direct fixation track are only recommended for long bridges or aerial structures. They are also needed at the fixed span approach to a movable bridge. 5.10.3.2 Rail Expansion Joints for Embedded Track Exceptions to the aforementioned guideline include embedded track on an aerial structure, where the rail is an integral part of the deck structure and the design does not allow the structure to move independently from the rail. In this situation, an embedded expansion rail joint at each bridge deck expansion joint of the structure is a requirement. Embedded rail expansion joints must be carefully detailed so that they are free draining; otherwise, they can fill up with dirt and become non-functional. Since rail expansion joints are an inherently weak part of the track structure, it is recommended they be positioned entirely on one span or the other and not actually span the joint in the bridge deck. Embedded rail expansion joints can also become a source of stray current leakage and hence endanger the underlying structure. Electrically bonding around embedded rail expansion joints without creating an unintentional path for stray currents is a challenge. On any bridge with two or more expansion joints along each rail, it is recommended that a separate negative return bond cable run around the full length of the superstructure. Doing this will help protect the

Track Components and Materials 5-67 superstructure from stray current corrosion by limiting the amount of traction power return current carried by the rails on the bridge. While embedded track can be used on an aerial structure, the complications cited above mean that it will require frequent inspection and maintenance. For this reason, the use of embedded track on an aerial structure is not recommended and should be avoided in the initial planning phase when considering the types of trackway. See Chapter 7, Article 7.4.2.3, for additional information on rail expansion joints for embedded track bridges. 5.10.4 Rail Anchorages In conjunction with the use of sliding rail expansion joints, situations arise where it is desirable to fix the rail at a particular location so that all expansion movement occurs predictably in one direction only. Rail anchorages (not to be confused with the rail anchors used in conventional timber tie ballasted track) are devices that are securely clamped to the rail and also anchored to an underlying structure. The design of the rail anchorage should be sufficiently robust to handle the thrust associated with the length of rail to be controlled. Figure 5.10.2 illustrates a rail anchorage for medium duty application. Figure 5.10.2 Rail anchorage

Track Design Handbook for Light Rail Transit, Second Edition 5-68 5.11 END-OF-TRACK BUMPERS AND BUFFERS As important as the tangent and curved track is throughout the transit system, the end of track cannot be overlooked. Bumping posts, friction buffers, and hydraulic buffers are therefore used to prevent an out-of-control vehicle from overrunning the end of the track. The device used should be able to bring the vehicle to a stop with minimal damage and injury to the vehicle and persons on-board. The issues for end-of-track equipment include the following: • Warning signs and signals in advance of the end of track. • The type of end-of-track device used. Options include the following: − Fixed non-energy-absorbing devices (fixed bumpers). − Fixed energy-absorbing devices (hydraulic buffers). − Friction energy-absorbing devices (Friction buffers). • Provision of sufficient space in the civil/architectural design for the end-of-track device. • The match between the striking face of the end-of-track device to points on the vehicle body that are designed to accept the impact forces. Candidate end-of-track devices for various situations include the following: • Main Line End of Track (Ballasted-Direct Fixation): friction/sliding end stop with resetting shock absorber if track sliding distance is available. • Main Line End of Track (Embedded): Same as above, if conditions warrant, or a resetting track stop anchored to the substrata. • Main Line End of Track (Aerial-Direct Fixation): friction/sliding end stop with resetting shock absorber. Track distance must be provided, sometimes requiring that the structure be extended. • Yard Tracks (Maintenance Tracks): fixed non-energy-absorbing devices, such as bumping posts, anchored to the track. • Stub-End Yard Storage Tracks and Main Line Pocket Tracks: resetting fixed devices anchored to the track. • Maintenance Shop Tracks: Fixed resetting energy-absorbing device anchored to the structure floor (non-movable). While fixed bumpers are commonly used in railroad service and occasionally on stub-end tracks in transit yards, they can result in significant damage to the vehicle even when equipped with a spring-mounted striking face. Therefore, the ends of track devices used at the ends of revenue service tracks should generally be of a type that gradually brings the vehicle to a stop over a appreciable distance, The two principal types of buffers in common service dissipate the kinetic energy of the moving train through either friction, hydraulics, or a combination thereof.

Track Components and Materials 5-69 All end-of-track devices take up a certain amount of track length. In particular, sliding friction buffers require a significant length of track beyond the striking face. In addition, there should be a distance of not less than 15 feet (4 meters) between the striking face of any end-of-track device and the desired normal stopping location of the LRV. This length must be accounted for in the initial planning of the project, particularly if the end of track is close to the terminal station platform. The position of the end-of-track device must also be coordinated with the OCS designers, as they frequently wish to place a catenary dead-end pole immediately beyond the end of the rails. The striking face of the bumper/buffer and how it interfaces with the vehicle is an important design feature. Unlike older LRVs, current vehicles generally do not have an exposed anticlimber that can be engaged by a matching striking head. LRVs with “bumpers” that conceal the coupler and are also designed around crash-energy management principles require different striking head configurations and quite possibly more than one head. Practitioners are encouraged to confer with vendors for the most recent information since the state of the art for bumpers and buffers is a dynamic situation. 5.11.1 Warning Signs/Signals With ideal conditions, alert operators, no mechanical vehicle or signal failures, and a well- illuminated warning sign or signal, a train operator should be able to bring the vehicle or train to a safe, controlled stop well short of the end of track. If the track with the end-of-track device is signaled, it will be necessary to coordinate the design of the end-of-track device with the train control system designers. In such cases, it will typically be necessary to insert at least one insulated joint in the rail ahead of the bumper. Two insulated joints will be necessary if the end-of-track device itself is grounded. Hydraulic buffers are often grounded so as to protect the sliding surfaces in the hydraulic pistons from corrosion. The insulated joints are typically positioned beyond the normal, non-emergency stopping location of the rail vehicle. Some friction buffers have insulation incorporated in the attachment points to the rails, eliminating the need for insulated joints. 5.11.2 Fixed Non-Energy-Absorbing Devices Most fixed non-energy-absorbing end stops (bumping posts) do no more than delineate the end of track. The end stops appear sturdy because they are bolted to the rail; however, they have little ability to absorb anything but a very minimal amount of kinetic energy. Impact often results in breaking of the rail, potential derailment, and damage to the vehicle. A positive fixed non-energy stop will halt heavy vehicles or train consists at the expense of vehicle damage and personnel injury. These stops consist of solid concrete and steel barriers generally located at the end of tracks and are generally found in freight yards and older railroad stations. Such devices are not recommended except on freight-only tracks when the railroad’s standards include such units.

Track Design Handbook for Light Rail Transit, Second Edition 07-5 5.11.3 Fixed Energy-Absorbing Devices The end stop is the point of impact, the location where kinetic energy has to be dissipated. The kinetic energy is determined considering the mass or weight of the vehicle or vehicles (train) and the velocity of the vehicle or train. Vendors of buffers have design formulas for calculating the requirements for a particular installation. For example, kinetic energy (KE) can be calculated using the following formula (these design guidelines typically use only S.I. units since the buffer manufacturers are usually overseas businesses): To absorb this amount of energy without causing severe injury to the operator or passengers, an acceptable deceleration rate must be selected. The transit agency should select the rate of deceleration considering the likelihood of injury to passengers and operators and damage to the vehicles, third parties, and surrounding structures. Each agency’s requirements are studied individually and are site specific. As a guideline, a deceleration rate of 0.3 g is generally considered to be acceptable. Assuming the 0.3 g deceleration rate is selected, the next decision is to determine the type of end stop capable of providing this deceleration rate. To absorb 1,998 kJ of kinetic energy (calculated above) at a deceleration rate of 0.3 g, the distance traveled after initial impact would have to be 3.39 meters (11.12 feet), calculated in the following manner: ( ) ( ) ( ) 93.3 sretem 21.11( )teef 2 2 1.523.0 18.9 74.4 25.1 morF evobA ecnatsiD 25.1 sdnoces 23.0 18.9 ces/m 4.47 2d V t deceleration negative rate (selected)x )2deceleration rate (x • 9.81 m/secd t emit ot pots ni sdnoces yticolev fo niart ni .ces/mV 2 Distance = • • × + = × = = = = = = 2d • t = V • t + 2 2d • t = V • t + =

5.11.3 Non-r stops moun inevita cushio rebuil of-trac 5.11.3 Reset hydra energ forces magn the en the sh 5.11.4 Frictio end o surfac .1 Non-Res esetting fixed . These dev ds are effecti ble. Under ning effect a t after experie k unprotecte .2 Resettin ting fixed de ulic, elastom y the shock at impact. itude of g for d stop to the ock absorbe Friction (o n type end s f track (see F e. (Illustration etting Fixed devices (bu ices dissipate ve in stoppin severe cold w nd possibly c ncing an im d for some p g Fixed Devi vices are se eric, or sprin absorber ca As noted abo ce—the long substrate go r. r Sliding) En tops absorb t igure 5.11.1 courtesy of H. J. Figu Devices mping posts the kinetic e g large loads eather cond ausing addit pact. Any de eriod. ces lf-resetting a g shock abs n dissipate a ve, the disp er the distan verns the am d Stops he kinetic en ). This sliding Skelton, Ltd.) re 5.11.1 Fr T 5-71 ) include san nergy upon or trains; ho itions, the sa ional vehicle lay in reconst nd contain a orber. Rese nd the stop lacement dis ce, the lower ount of energ ergy of stopp action conv iction energy rack Comp d traps, balla vehicle impa wever, derail nd and balla damage. Th ructing the d n energy-ab tting stops a structure’s tance of the the g force. y that can b ing a vehicle erts the ener buffer stop onents an st mounds, ct. Sand tra ment of the i st can freeze e barrier wo evice would sorbing featu re limited in capability to stop at impa The anchor e absorbed b or train by sl gy to friction d Material and timber t ps and balla nitial vehicle , reducing th uld have to b leave the end re such as the amount o withstand th ct governs th ing stability o y the stroke o iding along th heat at the ra s ie st is e e - a f e e f f e il

Track Design Handbook for Light Rail Transit, Second Edition 27-5 Friction end stops consist of two types: • Units that are clamped to the rail. • Units that are mounted on skids that slide with the weight of the vehicle upon them, dissipating the energy between the skids and the concrete base of track structure. Friction end stops have the highest energy absorption capacity of all end-of-track devices. Friction stops can be designed to cover a wide range of energy absorption situations from single- vehicle to multi-vehicle trains of various mass. Impacted friction end stops move when struck and typically need to be manually reset after use; however, they are designed so that this can be accomplished with relative ease. Sometimes a friction end stop will be combined with an automatic resetting device, allowing the unit to accept light impacts without moving the friction end stop while providing the higher friction end stop protection for higher speed impacts. 5.12 REFERENCES [1] [Deleted from 2nd Edition] [2] The Rail Wheel Interface: Refining profiles to transit applications, Joe Kalousek & Eric Mogel, Railway Track & Structures, Sept 1997. [Deleted from 2nd Edition] [3] Joe Kalousek & Eric Magel, Managing Rail Resources, American Railway Engineering Association, Volume 98, Bulletin 760, May 1997. [4] Performance of High Strength Rails in Track-Curico/Marich/Nisich, Rail Research Papers, Vol. 1, BHP Steel. [5] Development of Improved Rail and Wheel Materials - Marich, BHP Melbourne Research, Vol. 1. [6] “Riflex Comes to America,” Modern Railroads Magazine, July 1985. [7] AREMA Manual for Railway Engineering, Chapter 1, Roadway and Ballast, Part 2: Ballast.

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TRB’s Transit Cooperative Research Program (TCRP) Report 155: Track Design Handbook for Light Rail Transit, Second Edition provides guidelines and descriptions for the design of various common types of light rail transit (LRT) track.

The track structure types include ballasted track, direct fixation (“ballastless”) track, and embedded track.

The report considers the characteristics and interfaces of vehicle wheels and rail, tracks and wheel gauges, rail sections, alignments, speeds, and track moduli.

The report includes chapters on vehicles, alignment, track structures, track components, special track work, aerial structures/bridges, corrosion control, noise and vibration, signals, traction power, and the integration of LRT track into urban streets.

A PowerPoint presentation describing the entire project is available online.

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