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From page 547... ... 10-i Chapter 10 -- Transit Signal Work Table of Contents 10.1 INTRODUCTION 10-1 10.1.1 General 10-1 10.1.2 LRT Operating Environment 10-3 10.1.3 Transit Signal System Design 10-3 10.2 SIGNAL EQUIPMENT 10-4 10.2.1 Switch Machines 10-4 10.2.1.1 General 10-4 10.2.1.2 Trackwork Requirements 10-4 10.2.1.3 Switch Machines 10-5 10.2.1.3.1 Electric Switch Machines 10-5 10.2.1.3.2 Electro-Hydraulic Switch Machines 10-6 10.2.1.3.3 Electro-Pneumatic Switch Machines 10-6 10.2.1.3.4 Hand-Operated Interlocked Switch Machines 10-6 10.2.1.3.5 Yard Switch Machines 10-6 10.2.1.3.6 Embedded Switch Machines 10-7 10.2.2 Impedance Bonds 10-8 10.2.2.1 General 10-8 10.2.2.2 Trackwork Impedance Bond Requirements 10-8 10.2.2.3 Types of Impedance Bonds 10-9 10.2.2.3.1 Audio Frequency 10-9 10.2.2.3.2 Power Frequency 10-9 10.2.3 Loops and Transponders 10-9 10.2.3.1 General 10-9 10.2.3.2 Trackwork Requirements 10-9 10.2.3.3 Types of Loops and Transponders 10-10 10.2.3.3.1 Speed Command 10-10 10.2.3.3.2 Daily Safety Test 10-10 10.2.3.3.3 Train Location/Train-to-Wayside Communication 10-10 10.2.3.3.4 Traffic Interface 10-10 10.2.3.3.5 Continuous Train Control Loop 10-10 10.2.3.3.6 Transponders 10-10 10.2.4 Wheel Detectors/Axle Counters 10-11 10.2.4.1 General 10-11 10.2.4.2 Trackwork Requirements 10-11 10.2.4.3 Types of Wheel Detectors/Axle Counters 10-11 10.2.5 Train Stops 10-11 10.2.5.1 General 10-11 10.2.5.2 Trackwork Requirements 10-11 10.2.5.3 Types of Train Stops 10-12 10.2.5.3.1 Inductive 10-12 10.2.5.3.2 Mechanical (Electric and Pneumatic) Read the entire page →
From page 548... ... Track Design Handbook for Light Rail Transit, Second Edition 10-ii 10.2.6 Switch Circuit Controller/Electric Lock 10-12 10.2.6.1 General 10-12 10.2.6.2 Trackwork Requirements 10-12 10.2.6.3 Types of Switch Circuit Controller/Electric Lock 10-13 10.2.6.3.1 Switch Circuit Controller 10-13 10.2.6.3.2 Electric Lock 10-13 10.2.7 Signals 10-13 10.2.7.1 General 10-13 10.2.7.2 Trackwork Requirements 10-13 10.2.7.3 Types of Signals 10-13 10.2.7.4 Signal Locations 10-14 10.2.8 Bootleg Risers/Junction Boxes 10-14 10.2.8.1 General 10-14 10.2.8.2 Trackwork Requirements 10-14 10.2.8.3 Types of Bootleg Risers/Junction Boxes 10-15 10.2.8.3.1 Junction Boxes 10-15 10.2.8.3.2 Rail Junction Boxes 10-15 10.2.8.3.3 Bootleg Risers 10-15 10.2.9 Switch and Train Stop Heaters/Snow Melters 10-15 10.2.9.1 General 10-15 10.2.9.2 Trackwork Requirements 10-15 10.2.9.3 Types of Switch/Train Stop Snow Melters 10-16 10.2.10 Highway Crossing Warning Systems 10-17 10.2.10.1 General 10-17 10.2.10.2 Trackwork Requirements 10-18 10.2.10.3 Types of Highway Crossing Warning Systems 10-18 10.2.11 Signal and Power Bonding 10-18 10.2.11.1 General 10-18 10.2.11.2 Trackwork Requirements 10-19 10.2.11.3 Types of Signal and Power Bonding 10-19 10.3 EXTERNAL WIRE AND CABLE 10-21 10.3.1 General 10-21 10.3.2 Trackwork Requirements 10-21 10.3.3 Types of External Wire and Cable Installations 10-21 10.3.3.1 Cable Trough 10-21 10.3.3.2 Duct Bank 10-22 10.3.3.3 Conduit 10-23 10.3.3.4 Direct Burial 10-23 10.4 SIGNAL INTERFACE 10-23 10.4.1 Signal/Trackwork Interface 10-23 10.4.2 Signal-Station Interface 10-24 10.4.3 Signal-Turnout/Interlocking Interface 10-24 10.5 CORROSION CONTROL 10-25 Read the entire page →
From page 549... ... Transit Signal Work 10-iii 10.6 SIGNAL TESTS 10-25 10.6.1 Switch Machine Wiring and Adjustment Tests 10-25 10.6.2 Switch Machine Appurtenance Test 10-26 10.6.3 Insulated Joint Test 10-26 10.6.4 Impedance Bonding Resistance Test 10-26 10.6.5 Power and Signal Bonding Test 10-26 10.6.6 Negative Return Bonding Test 10-26 Read the entire page →
From page 550... ... 10-1 CHAPTER 10 -- TRANSIT SIGNAL WORK 10.1 INTRODUCTION The objective of this chapter is to provide trackwork designers, managers, inspectors, and contractors with a basic knowledge of the terminology, requirements, devices, and coordination issues for a rail transit signal system. 10.1.1 General Typically, there are five types of light rail transit guideway configurations to be considered, each with different signaling characteristics: 1) Read the entire page →
From page 551... ... Track Design Handbook for Light Rail Transit, Second Edition 10-2 into segments called blocks. Signals keep two trains from occupying the same block at the same time and generally keep an empty block between trains that are travelling at the posted or indicated speed. Read the entire page →
From page 552... ... Transit Signal Work 10-3 10.1.2 LRT Operating Environment Design differences in light rail systems are primarily related to their operating environments. Since the latter can vary over a large range, the appropriate level of signal automation varies by transit agency, their operating requirements for speed and headways, and the configuration and alignment of the track system components, including special trackwork. Read the entire page →
From page 553... ... Track Design Handbook for Light Rail Transit, Second Edition 10-4 10.2 SIGNAL EQUIPMENT 10.2.1 Switch Machines 10.2.1.1 General Track switches can be operated by hand or by power. When time and convenience are important, automated switch machines are advantageous. Read the entire page →
From page 554... ... Transit Signal Work 10-5 10.2.1.3 Switch Machines Track switches need some sort of mechanical device to change the orientation of the switch from the straight movement to the diverging movement and back and to also hold the switch points in the desired orientation. There are two broad categories of such devices: • Switch stands, which are manually operated devices with no direct connection to the train control system. Read the entire page →
From page 555... ... Track Design Handbook for Light Rail Transit, Second Edition 10-6 Switch machines are usually specified to meet the requirements of the AREMA Communications & Signaling Manual, Part 12.2.5, Load Curve Figure 1451-1 and thereby provide ample thrust to operate the heaviest of switches. Electric switch machines are normally provided with one throw rod, one lock rod, and one point detector rod connected to the rails. Read the entire page →
From page 556... ... Transit Signal Work 10-7 mm] for tee rail and 2.4 inches [60 mm] Read the entire page →
From page 557... ... Track Design Handbook for Light Rail Transit, Second Edition 10-8 lubrication. An access/cleanout box is often installed on the field side of the switch casting to provide access to connecting rod adjusting nuts if they extend beyond the switch. Read the entire page →
From page 558... ... Transit Signal Work 10-9 10.2.2.3 Types of Impedance Bonds 10.2.2.3.1 Audio Frequency Audio frequency impedance bonds are designed to terminate each end of audio frequency track circuits in transit installations. They provide the following: • Low resistance for equalizing propulsion current in the rails • Means of cross bonding between tracks to reduce electrical resistance along the negative return path • Connection for traction power negative return • Means of coupling the track circuit transmitter and receiver to the rails • Means of coupling cab signal energy to the rails • Means of inhibiting the transmission of other frequencies along the rail 10.2.2.3.2 Power Frequency Power frequency impedance bonds are designed for use in AC or DC propulsion systems that use insulated joints to isolate track circuit signaling current from signaling currents of adjacent circuits, but permit propulsion current to flow around the joints to or from adjacent track circuits. Read the entire page →
From page 559... ... Track Design Handbook for Light Rail Transit, Second Edition 10-10 • Cable and conduit location for signal equipment • Block-out area for loop or transponder and junction box 10.2.3.3 Types of Loops and Transponders 10.2.3.3.1 Speed Command Speed command loops are used to provide a means for coupling cab signal energy to the rails. Typically, speed command inductive loops are installed with or without rubber hoses within the turnout diverging track. Read the entire page →
From page 560... ... Transit Signal Work 10-11 10.2.4 Wheel Detectors/Axle Counters 10.2.4.1 General Wheel detectors and axle counters are used to detect trains without relying on a track circuit. Since they do not require insulated joints, they cause less interference with traction return current than detection devices that depend on electrical signals in the rails. Read the entire page →
From page 561... ... Track Design Handbook for Light Rail Transit, Second Edition 10-12 • Location of train stop • Conduit and cable location • Relationship to signals, insulated joints, and impedance bonds • Location of train stop and wheel detectors relative to top of rail 10.2.5.3 Types of Train Stops 10.2.5.3.1 Inductive Inductive train stops are designed with a magnetic system that interacts with carborne vehicle control equipment. Both the vehicle magnet and the track magnet need to be strategically mounted on the vehicle and track, respectively. Read the entire page →
From page 562... ... Transit Signal Work 10-13 10.2.6.3 Types of Switch Circuit Controller/Electric Lock 10.2.6.3.1 Switch Circuit Controller A switch circuit controller is a ruggedly constructed unit commonly used with switches to detect the position of switch point rails. The switch circuit controller has a low clearance profile and is mounted on a single tie. Read the entire page →
From page 563... ... Track Design Handbook for Light Rail Transit, Second Edition 10-14 Embedded signals or indicators are designed to be installed in embedded track. The housing of the embedded signal can require drainage. Read the entire page →
From page 564... ... Transit Signal Work 10-15 • Drainage track junction boxes for embedded track • Block-out requirements • Rail size and type 10.2.8.3 Types of Bootleg Risers/Junction Boxes 10.2.8.3.1 Junction Boxes Pedestal-mounted junction boxes are typically used in ballasted track at switch machines, switch circuit controllers, track circuit locations, etc., as a central termination point for underground cables. A variety of adapter plates allow the junction box to be used with air hose adapters and connectors during testing and when staging the installation of cabling that cannot be completed due to incomplete trackwork construction. Read the entire page →
From page 565... ... Track Design Handbook for Light Rail Transit, Second Edition 10-16 • Conduit and cable location • Junction box(es) location(s) Read the entire page →
From page 566... ... Transit Signal Work 10-17 Other types of snow melting systems include oil, natural gas, or an electric high-pressure heating unit that forces hot air throughout the switch area via ducts and nozzles. An alternate snow blower arrangement uses ambient non-heated air to blow snow clear of the switch point areas. Read the entire page →
From page 567... ... Track Design Handbook for Light Rail Transit, Second Edition 10-18 Crossing warning systems work best, with minimal delays to traffic, when the approach time of trains to the crossing can be accurately predicted. If train speed might vary, or if there is a possibility that the train might even stop on either the approach or departure side of the crossing, vehicular traffic could be significantly delayed for reasons the motorist will not understand. Read the entire page →
From page 568... ... Transit Signal Work 10-19 could produce electromagnetic interference or constitute a shock hazard to track maintenance personnel. It also provides a homogeneous and stable ground plane, as well as a fault current return path. Read the entire page →
From page 569... ... Track Design Handbook for Light Rail Transit, Second Edition 10-20 rails. The conduits carrying the cables will stub up into the box, which then has a lid held in place by corrosion- and tamper-resistant fastenings. Read the entire page →
From page 570... ... Transit Signal Work 10-21 • Mechanical connectors provide a rail connection without the risk of overheating the rail steel during installation. • Rail connection can be easily relocated or temporarily removed without grinding the rail or chopping the connection. Read the entire page →
From page 571... ... Track Design Handbook for Light Rail Transit, Second Edition 10-22 in the crib between two cross ties. Cable trough may be in locations where maintenance trucks might drive over it and hence should be capable of supporting an H-20 highway load at any point. Read the entire page →
From page 572... ... Transit Signal Work 10-23 10.3.3.3 Conduit Encased or direct burial conduit should be installed as outlined above or as required by the National Electric Code, Article 300-5 and 1110-4(b) Read the entire page →
From page 573... ... Track Design Handbook for Light Rail Transit, Second Edition 10-24 • Grounding • Yard signaling • Grade crossing warning systems • Wayside equipment housings and cases • Corrosion control • Cross tie spacing for signal control equipment, impedance bonds, train stops, and switches • Tie size and length requirements for switch machines and derails • Signal cable connection to rail at special trackwork • Physical connection of switch machines to special trackwork, with adjustment and testing • Loop or transponder mounting on track for train-to-wayside communication • Spaces for cables and conduit passing beneath the rail • Location of guard and restraining rails with respect to insulated rail joints • Horizontal clearance between track and wayside signals and equipment • Vertical clearance between track and signal equipment • Space and drainage for switch machine in direct fixation or embedded track • Provision for installation of snow melters • Location of switch indicators for embedded track • Location of cross bonding and negative return cables • Location of speed limits • Ballast resistance • Foundations for cases, housings, pushbuttons, and signals 10.4.2 Signal-Station Interface The following signal equipment is typically installed at station locations: impedance bonds, inductive loops, bootleg risers, junction boxes, and transponders. If the station is located near an interlocking or highway crossing, there should be sufficient room from the end of the platform to the signal equipment (impedance bonds and signals) Read the entire page →
From page 574... ... Transit Signal Work 10-25 • Cases/signal equipment houses ("bungalows") • Signals • Snow melter systems The design of the track circuit and fouling protection used will determine the location of insulated joints in the special trackwork. Read the entire page →
From page 575... ... Track Design Handbook for Light Rail Transit, Second Edition 62-01 confirm throw rod capability, ensure point closure, and ensure proper nesting of the switch point rail to stock rail. 10.6.2 Switch Machine Appurtenance Test Switch machine appurtenance tests verify the integrity of switch machine layout by taking resistance measurements across the following assemblies: • Center insulation of the front rod • Front rod to switch point • No. Read the entire page →

From page 547...

... 10-i Chapter 10 -- Transit Signal Work Table of Contents 10.1 INTRODUCTION 10-1 10.1.1 General 10-1 10.1.2 LRT Operating Environment 10-3 10.1.3 Transit Signal System Design 10-3 10.2 SIGNAL EQUIPMENT 10-4 10.2.1 Switch Machines 10-4 10.2.1.1 General 10-4 10.2.1.2 Trackwork Requirements 10-4 10.2.1.3 Switch Machines 10-5 10.2.1.3.1 Electric Switch Machines 10-5 10.2.1.3.2 Electro-Hydraulic Switch Machines 10-6 10.2.1.3.3 Electro-Pneumatic Switch Machines 10-6 10.2.1.3.4 Hand-Operated Interlocked Switch Machines 10-6 10.2.1.3.5 Yard Switch Machines 10-6 10.2.1.3.6 Embedded Switch Machines 10-7 10.2.2 Impedance Bonds 10-8 10.2.2.1 General 10-8 10.2.2.2 Trackwork Impedance Bond Requirements 10-8 10.2.2.3 Types of Impedance Bonds 10-9 10.2.2.3.1 Audio Frequency 10-9 10.2.2.3.2 Power Frequency 10-9 10.2.3 Loops and Transponders 10-9 10.2.3.1 General 10-9 10.2.3.2 Trackwork Requirements 10-9 10.2.3.3 Types of Loops and Transponders 10-10 10.2.3.3.1 Speed Command 10-10 10.2.3.3.2 Daily Safety Test 10-10 10.2.3.3.3 Train Location/Train-to-Wayside Communication 10-10 10.2.3.3.4 Traffic Interface 10-10 10.2.3.3.5 Continuous Train Control Loop 10-10 10.2.3.3.6 Transponders 10-10 10.2.4 Wheel Detectors/Axle Counters 10-11 10.2.4.1 General 10-11 10.2.4.2 Trackwork Requirements 10-11 10.2.4.3 Types of Wheel Detectors/Axle Counters 10-11 10.2.5 Train Stops 10-11 10.2.5.1 General 10-11 10.2.5.2 Trackwork Requirements 10-11 10.2.5.3 Types of Train Stops 10-12 10.2.5.3.1 Inductive 10-12 10.2.5.3.2 Mechanical (Electric and Pneumatic)