Track Design Handbook for Light Rail Transit, Second Edition (2012) / Chapter Skim
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Pages 588-601
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12-i Chapter 12 -- LRT Track in Mixed Traffic Table of Contents 12.1 INTRODUCTION 12-1 12.2 TRACK POSITION WITHIN LANES 12-1 12.2.1 Vehicle Width 12-2 12.2.2 Transverse Position within Lanes 12-2 12.2.3 Adjacent Parking Lanes 12-2 12.3 ON-STREET STATION/STOP PLATFORMS 12-2 12.3.1 Alternative Configurations 12-3 12.3.2 Motorist Perceptions 12-4 12.3.3 Tracks Adjacent to Median Platforms 12-4 12.3.4 Conclusions 12-5 12.4 MINIMUM CURVE RADIUS 12-5 12.4.1 Light Rail Vehicle Limitations 12-5 12.4.2 Vehicles for Small Radius Turns 12-5 12.4.3 Overhead Contact Wire Considerations 12-6 12.5 TURNING MOVEMENTS 12-6 12.5.1 Preferred Configuration 12-6 12.5.2 LRT-Only Traffic Signals 12-6 12.6 CLEARANCE ENVELOPE AND SWEPT PATH IN CURVES 12-7 12.6.1 Difference from Rubber-Tired Traffic 12-7 12.6.2 LRV Tail Swing 12-7 12.7 STREET DRAINAGE, CROSS SLOPES, AND SUPERELEVATION 12-8 12.7.1 Flangeway Drains 12-8 12.7.2 Roadway Crown and Track Cross Slope 12-9 12.7.2.1 Codes and Jurisdictional Issues 12-9 12.7.2.2 Streets with Parabolic Crowns 12-9 12.7.2.3 Special Trackwork Cross Slope 12-10 12.8 PAVEMENT DESIGN FOR IN-STREET TRACKAGE -- SEAM LOCATIONS 12-10 12.9 SPECIAL TRACKWORK IN STREETS 12-11 12.9.1 Switch Hardware 12-11 12.9.2 Switch Location 12-11 12.9.2.1 Hazard Issues 12-11 12.9.2.2 Pedestrian Crosswalk Locations 12-12 12.9.2.3 Advance Switch Positions 12-12 List of Figures Figure 12.6.1 Custom signage for tight clearance zones 12-8 Figure 12.9.1 Advance switch 12-13
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From page 589... ...
12-1 CHAPTER 12 -- LRT TRACK IN MIXED TRAFFIC 12.1 INTRODUCTION While it is highly desirable that light rail transit lines have an exclusive or semi-exclusive guideway, there frequently are circumstances where the only practical or affordable alignment is to place the tracks within a public roadway in a mixed traffic environment. This is, of course, the sort of guideway configuration used by traditional streetcar lines since the 19th century.
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From page 590... ...
Track Design Handbook for Light Rail Transit, Second Edition 12-2 12.2.1 Vehicle Width There is no standard streetcar or LRV body width, but it will always be less, usually by about 2 feet [0.61 meters] , than the width of any lane in which a track is laid.
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From page 591... ...
LRT Track in Mixed Traffic 12-3 compounding factor is that the typical platform edge (presuming a low-floor LRV) is 10 to 13 inches [0.25 to 0.33 m]
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From page 592... ...
Track Design Handbook for Light Rail Transit, Second Edition 12-4 also be subject to misuse. Another issue with a passenger stop request button is where it should be placed so it can be readily found by the visually impaired.
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From page 593... ...
LRT Track in Mixed Traffic 12-5 12.3.4 Conclusions The appropriate relationship of station platforms, lanes, and track location/alignment will not be the same on every project. Different solutions might be more appropriate for heavily trafficked boulevards versus quiet side streets, although there is something to be said for a uniform approach within any particular city.
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From page 594... ...
Track Design Handbook for Light Rail Transit, Second Edition 12-6 invited to propose on an order for a 204-vehicle fleet of new, 100% low-floor streetcars, designs compatible with the existing track geometry were forthcoming. Less recently, but still within the modern light rail era, a fleet of 112 rigid-body, high-floor LRVs was manufactured for operation on Philadelphia's streetcar lines, where the minimum curve centerline radius is 35.59 feet [10.85 meters]
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From page 595... ...
LRT Track in Mixed Traffic 12-7 12.6 CLEARANCE ENVELOPE AND SWEPT PATH IN CURVES As explained in Chapters 2 and 3, on a curved alignment the dynamic envelope of a rail car is widened. The outside corners at the ends of the body move farther from the track centerline on the outside of the curve while the center of the body (or each carbody segment, if there are more than one)
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Track Design Handbook for Light Rail Transit, Second Edition 12-8 signage, such as that shown in Figure 12.6.1, to give motorists who are considering stopping in a curb lane a clear indication of the potential consequences of parking within this zone. A secondary benefit of physically marking the edge of a dynamic envelope on curves is to provide the rail car operator with a clear indication when a stationary motor vehicle has encroached into the swept path of the LRV.
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From page 597... ...
LRT Track in Mixed Traffic 12-9 12.7.2 Roadway Crown and Track Cross Slope The roadway crown, which is an essential element of the storm water drainage system of any street or roadway, often means that any tracks embedded in a mixed traffic lane will have something other than zero cross slope between the rails. Typically, the roadway is crowned on a 2% cross slope, resulting in about 1 1/8 inch [29 mm]
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From page 598... ...
Track Design Handbook for Light Rail Transit, Second Edition 12-10 occupied, but also the adjacent curb and sidewalk on one side and the through traffic lane on the opposite side. This can become particularly problematic in urban areas where buildings and doorway thresholds directly abut the rear edge of the sidewalk, making it difficult or perhaps even impossible to raise the grade of the sidewalk.
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LRT Track in Mixed Traffic 12-11 • The two edges of the actual lane, presumably delineated by pavement markings such as traffic paint. • The two edges of the track slab.
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Track Design Handbook for Light Rail Transit, Second Edition 12-12 potential hazards. The risk that the "hole" on the walking surface might cause pedestrians to trip is obvious.
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From page 601... ...
LRT Track in Mixed Traffic 12-13 Figure 12.9.1 Advance switch
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