American Railway Engineering and Maintenance of Way Association Letter Ballot

Transcription

1 American Railway Engineering and Maintenance of Way Association Letter Ballot 1. Committee and Subcommittee: Committee 12, Subcommittee B 2. Letter Ballot Number: Assignment: General updates and revisions to Manual Chapter Ballot Item: Part 3, Sections 3.1 and Rationale: The original text for Chapter 12 was created during the late 1980 s and early 1990 s. Much of the information and recommended practices in the Chapter had become outdated and superseded by technological developments, research and lessons learned through operation of numerous transit systems constructed over the past 30 years. The committee conducted a thorough review of the Chapter material and developed proposed recommendations for revisions on various sections.

2 Corridor Planning Considerations AREMA Manual for Railway Engineering

3 Rail Transit Part 3 Track and Roadway Considerations TABLE OF CONTENTS Section/Article Description Page 3.1 General Information System Design Criteria General (2006) Safety/Security (2008) Mixed Passenger Transit and Freight (2008) Speeds (2008) Superelevation Deficiency (2008) Passenger Comfort (2008) Vehicle/Track Interaction (2008) Propulsion System (2008) Signal Systems (2008) Environmental (2008) Reliability (2008) Regulatory Requirements (2008) Flange Bearing Wheels (2008) Clearances General (2006) Regulatory Requirements (2006) Passenger Operations (2006) Freight Operations (2006) Fixed Objects (2006) Movable Objects (2006) Right-of-Way Design Criteria and Considerations General (2006) At Grade Crossings (2006) Drainage (2007) Vegetation Control (2006) Environmental (2006) Third Party Occupancy (2007) References, Vol. 92, 1991, p. 65; Vol. 94, 1994, p. 131; Vol. 97, p AREMA Manual for Railway Engineering

4 Track and Roadway Considerations TABLE OF CONTENTS (CONT) Section/Article Description Page 3.5 Track and Roadway General (2006) Regulatory Requirements (2006) Maintenance Philosophy (2006) Safety/Security (2006) Gage (2006) Track Structure (2006) Horizontal Geometry (2006) Vertical Geometry (2006) Signal Considerations (2006) Grounding/Stray Current (2006) Turnouts and Special Trackwork (2006) Special Trackwork Components (2006) Design Considerations for Future Expansion Scope (2010) Introduction (2010) General Approach (2010) Specific Points to be Considered (2010) Conclusion (2010) LIST OF FIGURES Figure Description Page Third-rail Territory LIST OF TABLES Table Description Page Interface Rankings SECTION 3.1 GENERAL INFORMATION The purpose of Part 3 of Chapter 12 is to delineate recommended track and roadway design considerations for heavy and light rail transit systems, particularly those considerations that differ from other types of passenger and freight operations. Many of the engineering considerations for rail transit are the same as for other types of rail operations that are described in other chapters of this Manual. In such cases, this Chapter will reference the other chapters. Other organizations with an interest in transit track design, primarily the American Public Transit Association (APTA) and the Transportation Research Board (TRB), have published design and maintenance information that applies to heavy and light rail transit track design. These publications support the recommendations of this Chapter and will be referenced herein where appropriate. AREMA Manual for Railway Engineering

5 Rail Transit Several facets of rail transit operations, while applicable to other types of rail operations, usually receive a different or greater emphasis in rail transit, thereby resulting in different design considerations from other types of operations. Several of these facets and their rail transit perspective are as follows: Operational Reliability. For rail transit, this means safe, on-time performance and requires track components that are robust and have long service lives that will not require frequent or disruptive maintenance. Components must be susceptible of easy inspection to identify defective elements and plan for their maintenance or replacement in a safe and timely manner that will not interfere with normal operations. Quality of Ride. Passenger comfort of seated and standing patrons should be a significant factor in determining track modulus, spiral lengths, underbalance limits, and other criteria that result in a smooth ride with gradual changes of direction and grade. Headways. Frequency of trains and length of hours of service dictate track designs that are maintainable with minimal track outages and interference with traffic. Homogeneity of Fleet. Transit vehicles on a particular route usually have nearly identical characteristics and are operated in a consistent manner that results in high numbers of uniform stress applications and consistent wear patterns over time. Anticipated load applications and wear patterns should be during the development of design criteriaat an early stage of design and addressed result in design and addressed in design and anticipated maintenance practices that address them.examined at an early stage of design and result in design and maintenance practices that address them. Track Loading. Transit vehicle axle loads are significantly lower, relatively uniform and more numerous compared to freight railroads. Transit track should be designed to withstand both maximum loads and fatigue loading. Urban Environment. Constrained rights of way and close proximity of residential and other sensitive urban facilities require attention to noise and vibration issues. These and other environmental issues, which concern the surrounding community, should be addressed with regard to access and procedures for construction and maintenance. Vehicle Constraints. Transit vehicles are typically designed to negotiate sharper horizontal and vertical curves than other types of railroad vehicles, but the limitations must be identified (or mutually agreed upon between vehicle and track engineers) and applied to alignment geometry criteria and clearance allowances. A healthy dose of conservatism in the application of these criteria during early stages of design is highly recommended to ensure finished construction meets operational and safety goals without variances from the criteria. Electric Traction. Most transit systems use electric traction with either third rail or catenary for power distribution and with the running rails providing the negative return. The effects of stray current and electric power safety must be considered in design of track components. Aesthetics and Cleanliness. Patrons are sensitive to interior and exterior appearance and cleanliness of their transit systems. Safety and security are, to a lesser extent, also impacted by the appearance and cleanliness of the system. Patron support of transit is, in part, determined by these conditions. Track should be designed to facilitate these concepts GENERAL (2006) SECTION 3.2 SYSTEM DESIGN CRITERIA Developing a safe, operationally efficient, and cost-effective transit system includes the participation of experienced trackwork engineers during all phases from planning through design to operations and maintenance. A key product of the systems engineering approach are the criteria that result from the tradeoff of requirements among the engineering disciplines AREMA Manual for Railway Engineering

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7 Rail Transit and other interests as they coordinate and resolve planning and design issues for each type of transit mode and operating scenario. During the planning phase, operations, planning, engineering, real estate, and architecture (OPERA) as well as environmental and safety personnel should work as a team to define feasible transit corridors, modes and operating scenarios that balance the needs of all participants. Among the engineering disciplines, the trackwork engineer should play a significant role. A preliminary trackwork design criteria, along with other disciplines and interests, should be documented and used as the basis for cost analysis of each scenario. This' planning criteria should become the basis for the final design criteria of the selected alternative. During the design phase, the trackwork engineer should continue to work with the other disciplines ncluding the vehicle design group and interests to define trackwork criteria that are compatible with the criteria prepared by the other engineering disciplines and interests. The following sections will present track related information that interacts with the requirements of other disciplines and which should be used as the basis of discussion during the development of a transit project's design criteria SAFETY/SECURITY (2008) The principal means of securing track and right-of-way, facilities and assets right of way from intrusion is fencing.access controlthat falls within the responsibility of the track and roadway designer is fencing. Public and patron safety is achieved with respect to track and right of way by keeping unauthorized people away from tracks and trains by means of barriers, principally fences. Right of way fence types should be coordinated with security personnel to establish the need, type, height, and whether or not more severe measures such as barbed wire or concertina wire topping is needed. Electrical isolation and proper grounding is required for conductive fences on electrified systems. Fence requirements should also be coordinated with the project architect, owner, and the public, to select styles that are aesthetically pleasing, particularly at stations and other locations of high visibility. Access control Gate locations and their control (locks) should be coordinated with all disciplines that will use them for maintenance access including signals, communications and traction power. Gate locations and keys to locks should be coordinated with local fire and police agencies that will require use the gates for emergency access. Emergency egress walkways, tunnel and station ventilation and firefighting equipment must comply with NFPA 130 requirements. For shared use corridors that are fenced, gate access must be coordinated between thewith the railroad and transit agency with procedures established for control of access through a single "dispatcher or controller.." Right of way fences are commonly placed on the property lines. Clearance between tracks and fences or walls should be sufficient to provide a safe refuge from passing trains. A continuous walkway of not less 30 inches width (including allowance for middle ordinate and end overhang) should be provided adjacent to each track. Where continuous clearance cannot be provided, individual safety refuges not more than 50 feet apart should be provided for the length of the reduced clearance. Many jurisdictionsstates have enacted regulations specifying railroad clearances and in some cases for rail transit. These are compiled in AREMA Chapter 28, Clearances, and should be consulted for applicability to any fence or other safety/security barrier being designed for a transit system. Formatted: Not Expanded by / Condensed by Formatted: Not Expanded by / Condensed by Formatted: Not Expanded by / Condensed by Pedestrian safety when crossing tracks is of paramount importance. Overpasses are preferred to underpasses for patron security. If underpasses are used they must be well lit, well-drained and should be considered for CCTV monitoring. Grade crossings should provide adequate unobstructed sight distances between patrons and train operators, be ADA compliant and, be well- lit if night use is expected. Walk/Don t Walk signalization and the installationinstallation of gates, flashing lights and audible ringing bell warning systems should be considered, as should fencing to channel pedestrian traffic and encourage use of to approved crossings. Ample signage should be provided along rights of way and near stations, whether fenced andor unfenced pedestrian crossings, at gates and at grade crossings to warn people of the perils they face near active, particularly electrified, tracks. Additional safety/security guidelines are provided in APTA publications. The latest revisions of these documents should be used: (1) Guidelines for Design of Rapid Transit Facilities, 1981; (2) Handbook for Transit Safety and Security Certification, 2002; (3) Manual on Uniform Traffic Control Devices from the U.S. Department of Transportation, Federal Highway Administration and (4) Transit System Security Program Planning Guide, (2002).: (1) 1981 Guidelines for Design of Rapid Transit Facilities and (2) Transit Security Guidelines Manual AREMA Manual for Railway Engineering

8 Track and Roadway Considerations Fencing for LRT Systems Light rail systems and streetcar systems include many areas that are not fenced such as street running segments and grade crossings. Fencing to control or channelize access around hazardous areas is recommended. Fencing near stations and grade crossings should channelize pedestrians to overpasses, underpasses or signalized crosswalks. Aesthetics must also be considered in the case of cityscapes. Painted concrete bollards, pronounced raised painted curbs are also attractive deterrents to vehicle traffic as well as visual deterrents to pedestrians.to use over (or under) passes or crosswalks. Fencing near playgrounds and other areas frequented by children, especially if their likely route to these areas would involve crossing the LRT tracks should be fenced and a safe means of crossing provided at the most convenient feasible location. Yards and multiple track locations where trains are AREMA Manual for Railway Engineering

9 Rail Transit standing on one or more tracks that could obscure pedestrian vision of approaching trains should be fenced. Fencing between tracks may be suitable in lieu of fencing one or both sides of a corridor to control pedestrians crossing the right of way, particularly at stations Fencing for Heavy Rail Systems Heavy rail transit systems should prohibit all access to their rights of way. Access to the right of way should be controlled by locked gates. Unless grade separation is provided by elevated structure, tunnel or walls over 6 feet in height, the right of way should be fenced. Chain link fence at least 6 feet high should be used as the basic security fence with other types of fence that provide similar or greater protection from intrusion used where appropriate. Consideration should be given to installing intrusion detection on all fencing. Where highway vehicles operate near transit rights of way, appropriate barriers to prevent accidental or intended prevent their intrusion into the right of way should be provided. A New Jersey style barrier is recommended for areas where highway vehicles operate parallel with to transit tracks. The height of the barrier should be based on the type of traffic. Barriers 5 feet high have been used on roads with high speed truck traffic. The barrier should not be less than 3 feet high. The barrier should be topped with a 6 foot high chain link fence equipped with an intrusion detection system that automatically and instantaneously notifies both train control and transit agency security forces of any intrusion may be investigated MIXED PASSENGER TRANSIT AND FREIGHT (2008) Transit vehicles (heavy and light rail) with few exceptions are not designed to meet FRA vehicle design parameters, particularly with respect to crashworthiness. This fact along with disparities of speeds and operating schedules make mixed traffic operations difficult if not impossible to implement in a manner that is considered to be safe and reliable in light of FRA regulations. Therefore, in the United States, joint use of the track by both freight and transit requires separation of the two operations by time. Typically, joint use track is used by transit services through most of during the day and freight service while at night during the hours when transit operations are shut down. This is known as temporal separation and FRA regulations apply apply to freight operations.. If a track will be joint use, its design must be coordinated with all users. Freight operations often require clearances greater than transit operations. Rail weight, tie size and spacing, ballast depth, turnout sizes and other track design elements such as maximum superelevation and superelevation deficiency must satisfy the needs of all users and comply with FRA Track Safety Standards. The limits of joint use should be identified and joint use criteria applied only to the portion of the track system requiring it. Minimum radii for curves and maximum grades may be limited by the freight operation. Because freight wheel loads generally are heavier than transit loads, the freight wheel loads will generally govern track component criteria for joint use track. Joint use track requires careful coordination of track gage, wheel gages, and types of wheels that will use the track and special trackwork. Track designs suitable for narrow tread light rail vehicle wheels may not be compatible with freight equipment having wide tread AAR wheels, especially where self guarded frogs or raised guard rails are contemplated. Transit wheel profiles are also more sensitive to adverse rail wear and a good match between rail head and transit wheel profiles is required. Depending on the wear of the railhead by the freight operation, remedial grinding may be required more often to maintain transit vehicle wheel life and vehicle ride quality. Transit vehicle wheel profiling may also be required more frequently. Differences in wheel mounting gages, particularly back to back distance of the wheels, can have a significant effect on the flangeways used in guard rails and frogs. The smaller wheel diameters and variations in flange heights typically used on transit equipment will result in a smaller wheel flange footprint which has a decided effect on switch designs and on the requisite flangeway for check rails/restraining rails if used SPEEDS (2008) Track designs should be coordinated with operations, vehicle and signal designs to establish speed goals for the alignment that are compatible with operating run time objectives, vehicle acceleration and deceleration capabilities, and, where applicable, train control speed limitations. Operations modeling is recommended to verify acceptable levels of service. In an ideal world, with no site constraints, curves would be designed for vehicle maximum speeds and signal speed increments or AREMA Manual for Railway Engineering

10 Track and Roadway Considerations slightly above to maximize operating efficiency. However,Since because transit alignments are often superimposed on existing civil infrastructure, it is often the case that suboptimal curve radii must be used to avoid unaffordable demolition or site work. By example, An operations and vehicle performance coordination example is that, by taking vehicle acceleration/deceleration capabilities into account,an operations and vehicle performance coordination example is that, by taking vehicle acceleration/deceleration capabilities into account, a sharp curve located near a station will have less impact on overall run time than if located midway between stations. An example of coordination with the signals design coordination is in the case of a signal design that sets specific speed increments. AAthat a curve designed for 42 mph curve will be operated at 35 mph if that is the next lowest standard speed increment below the curve s civil design speed and the next increment is higher than the curve speed.. Such curves should be designed for the maximum authorized speed to be enforced by the signal system, not a nonstandard speed: in this example 35 mphan example of coordination with the signals design is in the case of a signal AREMA Manual for Railway Engineering

11 Rail Transit design that sets specific speed increments. A 40 mph curve will be operated at 30 mph if that is the next lowest speed increment below the curve design speed and the next increment is higher than the curve speed. Use of nonstandard speeds and explanatory signage should be avoided. Ideally, vehicle operating characteristics and train control parameters should be established in conjunction with the alignment and not before SUPERELEVATION DEFICIENCY (2008) Superelevation deficiency (unbalanced superelevation) affects ride comfort and may affect rail wear. Since ride quality involves the interaction between track and vehicle, Vvehicle designers should be consulted on maximum allowable superelevation, superelevation transitions (spiral length) and superelevation deficiency. Operations should be consulted to identify operating speeds for both normal and abnormal conditions so that a superelevation deficiency can be selected that best fits the range of operating speeds anticipated. Higher superelevation deficiency may sometimes be used to lower actual superelevation near at -grade crossings without reducing train speed thereby providing a smoother grade crossing, particularly for multiple track grade crossings. A detailed discussion of superelevation that is applicable to both heavy and light rail transit track design including options for combining actual and unbalanced superelevation for various situations is given in Chapter 3 of TCRP Publication No , Track Design Handbook for Light Rail Transit PASSENGER COMFORT (2008) Track designers should coordinate with operations and vehicle designers to reach agreement on alignment elements including spiral length, superelevation, superelevation deficiency and special trackwork design and components that will provide a comfortable ride, particularly for systems anticipating large numbers of standees and for all systems at station approaches where passengers often stand to move toward exit doors before the train has stopped at the platform. Where pedestrians cross tracks, which is often the case at light rail system stations, the pedestrian grade crossing design should be coordinated with architects to select a crossing type that provides a safe comfortable walkway and with operations to locate it where it will not be blocked by standing trains or unsafe because of sudden train movements. Pedestrian grade crossings must be designed to comply with current ADA regulations VEHICLE/TRACK INTERACTION (2008) Transit track design must be selected in conjunction with the selected transit vehicle and the vehicle wheel design to form a compatible system. For rapid transit systems using standard two-truck vehicles, the use of freight railway standards may be entirely appropriate for such items as track gage, check gage, wheel gage and wheel profile. Railway standards are essential for transit system track design when sharing track with freight railways. Where tracks will not be used jointly with freight operations, use of other wheel profiles may be advantageous for improved ride quality and reduced noise. The selection of vehicle parameters, especially wheel profile and wheel gage, must be coordinated between vehicle designer and track engineer for corresponding track parameters, especially rail profile, track gage, flangeway width and depth, and wheel tread overhang in paved track. Adjustments to standard AAR compliant wheelsets and car configurations may require adjustments to standard FRA compliant track and components. This may complicate construction and maintenance which may increase costs Standards Different track and wheel standards may be appropriate for Light Rail Vehicles (LRVs) because of Lighter axle loads. Articulated vehicles. Smaller wheel diameters AREMA Manual for Railway Engineering

12 Track and Roadway Considerations Narrower wheel treads. AREMA Manual for Railway Engineering

13 Rail Transit Gage Different (generally shorter) vehicle wheelbases. Sharper curves. Use of girder rail. Use of in-street (embedded) track. The short distance between trucks found on many articulated LRVs can make these vehicles susceptible to hunting. The difference between track gage and wheel gage should therefore be carefully selected to control hunting. Trade-offs are involved when selecting track and wheel standards. Widening the wheel gage to reduce the wheel gage/track gage difference may provide a superior ride at higher speeds, but may also result in increased wear for wheels, and rails, special trackwork and other track components wear Wheel Tread Wheel tread profile must be compatible with the selected rail section, rail head profile and rail cant in order to control hunting, reduce wear, and permit some degree of self-steering on large radius curves. For street track, consideration should be given in both wheel and track design to avoid contact between the wheel and pavement Canted Rail Cant (not to be confused with superelevation) is the rotation of the rail head toward the center of track to move the rail-wheel contact point away from the gage corners of both the rail and the wheel tread. Canted rail is used in freight railway track to align more closely the rail web with the resultant of lateral and vertical wheel loads. This is not strictly necessary for rail transit systems where wheel loads are as little as one-third those of freight railways but locating the contact point near the center of the rail head may result in reduced wheel tread wear, improve curve steering, reduce rail gage corner defects and other advantages. Cant is usually specified as 1:40 or in some cases 1:20. Canted rail is used in freight railway track to align more closely the rail web with the resultant of lateral and vertical wheel loads. This is not strictly necessary for rail transit systems where wheel loads are as little as one-third those of freight railways. Vertical (uncanted) rail is common on European transit systems. Nevertheless, canted rail should still be considered for transit track in order to permit the use of standard freight railway tie plates and hardware, where possible. Changes in rail cant will alter the wheel/rail profile contact geometry. Wheel machining and/or rail grinding policies can obtain restoration of the desired wheel/rail contact geometry Rail Profile AREMA recommended rail sections, as contained in Chapter 4, Rail, are suitable for use in transit systems. The rail head profile may be adjusted by grinding to optimize the rail/wheel interface for specific applications. See Part 8 of this chapter for additional information on rail profiles and their suitability for transit applications Flangeways Narrowing of frog flangeways should be considered in certain circumstances. Transit vehicle wheels may have a tread width narrower than freight railway wheels causing "wheel drop" at frogs and diamond crossings because the flangeway width is designed for wider freight railway wheels. A reduced frog flangeway width will improve the transit vehicle ride through frogs and crossings. This may, however, preclude the use of outside track maintenance machinery. Flange bearing, spring, jump or movable point frogs may be advantageous in some circumstances AREMA Manual for Railway Engineering

14 Steerable Axles Track and Roadway Considerations Vehicular trucks developed with steerable axles provide flexibility for the wheel sets to take up radial positions in negotiating track curvature. This provides improved stability at high speeds and reduces both wheel/rail forces and wheel/rail wear. Commented [JLK1]: Not a subset of Flange Beadring Frogs. Moved from Formatted: Font: Bold Formatted: Font: Bold Track design should be coordinated with vehicle design to consider any special requirements of transit vehicles with steerable axles, independent rotating wheels, cylindrical wheel treads and other considerations. It should be noted that most self-steering trucks rely on top of rail friction to provide steering forces. Thus, improper use or application of rail lubrication can limit the effectiveness of such designs Lubrication Lubrication of the wheel/rail flange contact surface should be considered in the design of any transit system. Both on board and wayside lubrication may be feasible depending on the geometric characteristics of the transit system. For relatively short transit trains, on board lubricators can provide a clean, compact, unobtrusive, all-weather lubrication system. Wayside lubricators allow lubrication to be controlled over relatively short distances and/or on a curve-specific basis, but they require on-track access and adjustment. Placement of wayside lubricators should consider track gradient and roadway access for filling and maintaining the equipment without interrupting train service. Commented [JLK2]: Not a subset of Flange Bearing Frogs. Moved from Formatted: Font: Bold Formatted: Font: Bold Formatted: Font: Bold Formatted: Font: Bold Care must be exercised in using lubricators where the rail is used as the negative return in an electrically operated transit system, or where signal systems use track circuits, as the types and amounts of lubricants or friction modifiers used may have an adverse effect on electrical conductivity. Movable-point frogs may be the solution in some circumstances PROPULSION SYSTEM (2008) Electrical traction power systems are typically 500 to 1000 volts DC and may be dangerous if touched by workers, patrons or trespassers. Overhead contact systems, also call OCS or catenary, consist of overhead wires for traction power transmission and raise conductors out of reach of many activities. These systems are typically more expensive than third rail systems, but do not require isolated rights-of-way. OCS systems support grade crossings and provide an additional level of electrical isolation for a patron who may fall on the track and for trespassers who may accidentally or deliberatelyon purpose engage the third rail. Track designers should coordinate with traction power designers on the track requirements for the use of the running rail as the traction power negative return. Rail weight and chemical composition determine its capacity for carrying return current. Special trackwork and insulated joints must provide continuous paths for return current which require bond cables and impedance bonds to electrically bridge bolted joints and insulated joints respectively. AREMA Manual for Railway Engineering

15 Rail Transit Third rail systems are usually part of track design and must be coordinated with traction power design as to location of third rail gaps, methods of mounting and details of components including type of conductor rail, ramps, insulators, anchors, and expansion joints. Third rails should be located away from platform edges, emergency egress pathways, drainage paths and should consider the required clearances of possible maintenance equipment and material storage areas. and emergency egress pathways. Track design must also be coordinated with vehicle design to properly place the third rail to interface with the vehicle electrical pickups. Impedance bond design includes selecting sizes and mounting systems that are compatible with the track including wayside mounting. The design of grease lubrication and friction modifier systems to control noise and rail wear should be coordinated with vehicle, signals, and traction power designers to assess the potential for loss of traction or loss of conductivity where grease lubricants are used. Research indicates that friction modifiers do not cause loss of traction or conductivity. Lubrication and friction modification are very cost effective at reducing wear and noise; it is recommended that their use be incorporated into designs where appropriate and that the coordination effort focus on ensuring proper selection of lubricants and friction modifiers, application systems, and maintenance of these systems rather than their exclusion from consideration. Electrification has high initial capital cost but has a lower operating cost and life-cycle costs. Some systems utilize bus rapid transit or rail mounted diesel multiple units (DMUs) that do not require electrical traction power systems. Since these options can provide an alternative with lower initial costs, they can be an attractive option for initiating service or providing service on corridors whose density does not justify electrification. On new systems that will not be electrified, it is recommended that provision for future electrification be considered in the initial design since it is likely that electrification may be considered in the future Stray Current Electrified rail systems use the running rails as the return path to complete the electrical circuit that runs through the vehicles. Physical or meteorological conditions that allow the running rails to become grounded may cause an alternate electrical path. If that path provides less electrical resistance than the track, the electricity will follow the easier path and becomes stray current. If stray current follows utilities or other facilities it may cause corrosion which can erode pipes, rebar, conduits and other vulnerable metal fittings and cause them to fail prematurely. In transit, a primary cause of stray current is full or partial grounding of the running rails or third rail chairs. Adequate third rail or OCS insulation, proper grounding of electrical substations, and physical isolation of the running rails from ballast, dirt, trash, metal shavings and other contaminants provides the electrical isolation required to minimize stray current. Formatted: Indent: Left: 0.13" Many urban regions have cooperative committees that coordinate between owners of potential stray current generators (transit agencies, heavy industry, power companies, etc.) and infrastructure owners, including vulnerable utilities, to assure adequate stray current monitoring, management and countermeasures. The properties of stray current caused by direct current (DC) and alternating current (AC) traction power can be quite different. Systems that chop DC power into functional AC power on the vehicles may have characteristics of both. These effects should be considered in the design of new rail transit systems and in existing systems undergoing technological upgrade. Refer to AREMA Chapter 33, Electrical Energy Utilization for more detail on electrification and stray current. On new systems that will not be electrified it is recommended that provision for future electrification be considered in the initial design. Electrification has high initial capital cost but has a lower operating cost. Therefore it is probable that for systems that are initially built as diesel operations electrification will be given consideration in the future. Coordinate with AREMA Chapter 33, Electrical Energy Utilization SIGNAL SYSTEMS (2008) Signals (and traction power) require electric isolation of one rail from the otheranother and from ground to obtain signal circuit integrity and prevent stray current corrosion. Track design must be coordinated with signals and traction power design to establish practical, feasible levels of isolation and means of verifying them as part of the track design criteria and specifications. Signal and traction power designs should reflect these levels of isolation and take into account that isolation levels tend to deteriorate with time due to lack of maintenance. Unreasonably high levels of isolation should not be attempted AREMA Manual for Railway Engineering

16 Track and Roadway Considerations in the track design. Track designers must coordinate with signal designers on the type and location of insulated joints, especially within special trackwork. Avoid, if possible, locating insulated joints where they weaken the special trackwork track structure or require double rail type joints. Special trackwork design must be coordinated with signal design to accommodate switch machines, switch heaters and other signal hardware. Sight distance for signals must be coordinated with alignment, clearances, catenary poles, walls and fences. Signal locations and clearances from track must be coordinated with track design. Embedded track design requires detailed coordination with signal and traction power designers to ensure all embedded items including signal and power conduits, traffic loops, signal boxes, signal and traction power equipment foundations, and other embedded items within the track area are accounted for before roadway surfaces are placed ENVIRONMENTAL (2008) Transit systems are required to comply with federal, state or provincial and local environmental regulations regarding the process of selecting and designing new alignments and when making major changes in existing operations. Environmental issues that are required by law to be addressed include air quality, noise, vibration, wetland impacts, community impacts and impacts on natural habitats. Where United States federal funds are being sought, the FTA guidelines for environmental analysis are applicable to the environmental analysis and review process. Noise and vibration are the principal environmental issues that have impact on track design and may be mitigated by selection of appropriate technologies incorporated into the track and roadway design. Chapter 9, Noise and Vibration, of TCRP Report AREMA Manual for Railway Engineering

17 Rail Transit No , Track Design Handbook for Light Rail Transit provides FTA and APTA noise and vibration level guidelines and lists many mitigation technologies applicable to track and roadway design of both heavy and light rail transit. Noise and vibration generated by vehicle wheels on rail must be assessed during planning and mitigated as part of the track design where anticipated levels exceed local codes or federal guidelines. The use of ballast mats, sound barriers, softer direct fixation fasteners, floating slabs, lubrication and other means of mitigating noise and ground borne vibration must be addressed from the Environmental Impact Statement (EIS) stage through final design. The track criteria must be developed in conjunction with acoustical consultants to achieve cost effective solutions. Track design should be coordinated with track maintenance planning regarding noise and vibration control because with time, track systems develop rail corrugation and rail defects which generate noise and vibration. Anticipation of these effects by means of a well planned preventive rail grinding program is recommended. Track maintenance operations may generate significant levels of noise and vibration. Such activities include ballast installation, surfacing and tamping, rail grinding, tie replacement, and other maintenance operations that should also be considered when minimizing effects of noise and vibration after revenue service begins. Often these activities occur at night after system shutdown when they are more likely to generate complaints from adjacent neighborhoods. It is wise to coordinate with adjacent neighborhoods to mitigate these impacts and minimize disruption to transit operations and maintenance RELIABILITY (2008) Reliability of track components and designs should be based upon their demonstrated performance under conditions that are representative of the conditions they will face in service. This can be verified based on past history and/or by performance testing. Track components and designs must be reliable under the full range of conditions which they will experience during their service life. They must be suitable for specific although infrequent high loadings such as may occur during maintenance as well as the loads from normal operating conditions. Track components should be designed for easy inspection and with an anticipated failure/deterioration rate that reflects the time lapse that occurs between inspections and discovery of deterioration and time required to plan and execute replacement of deteriorated components. Track components must function under all weather conditions they are expected to encounter with a reasonable measure of conservatism for extreme conditions. It is recommended that track designers coordinate with operations and maintenance personnel, vehicle, signal, and traction power designers to select the parameters and ranges that apply to these considerations Switch Heaters An example of a weather-related consideration is that switches in northern climates should be furnished with switch heaters, and the most reliable type should be employed, depending on the prevailing weather conditions. In some cases, electric heaters are fine, and in others the forced-air blowers work the best. In addition, the decision as to when to turn the heaters on is a reliability factor Continuous Welded Rail Another example of a weather related consideration is the design of continuous welded rail (CWR) track against track buckling and rail pull-apart at the extremes of the expected temperature range. This consideration affects, among other factors, selection of the zero thermal stress temperature for anchoring CWR, rail yield strength, joint pull-apart strength, lateral and longitudinal restraint parameters for fasteners, and ballast shoulder widths Operating Schedule Another example is that tthe operating schedule (timetable) must be coordinated with branch line turnouts and crossover spacing so that trains can meet the schedule reliably under abnormal as well as normal operating conditions. This means testing the schedule through simulations of single tracking during maintenance and around train breakdowns. The schedule should also be verified in the field before publishing it for the public and the employees. Bottlenecks and/or speed restrictions should be investigated to determine if they can be economically mitigated to improve the operating reliability REGULATORY REQUIREMENTS (2008) AREMA Manual for Railway Engineering

18 Track and Roadway Considerations Track and roadway design are subject to few direct regulations. Indirectly, there are many federal, state, and local jurisdiction laws and ordnances governing diverse topics including speeds, noise and vibration, grade crossings, ADA requirements at station platforms, street traffic, traffic signals and signage, etc. that may affect track design. Where joint use of tracks with freight operations or intercity passenger operations will occur, FRA regulations apply as well as United States CFR Title 49, Part 213 Track Safety Standards (in Canada, the Rules Respecting Track Safety) and laws in most states that establish minimum clearances for freight operations which may also govern transit operations. AREMA Manual for Railway Engineering

19 Rail Transit National Fire Protection Association (NFPA) 130, Standard for Fixed Guideway Transit and Passenger Rail Systems, details fire protection and life-safety requirements for elevated, surface and underground passenger rail systems. In systems that span multiple states or jurisdictions, it is advantageous if one jurisdiction s regulations are selected to govern the entire system. This standardizes operating rules, enhances safety, simplifies reporting requirements and eliminates the confusion multiple regulations and operating rules may cause FLANGE BEARING WHEELS (2008) Some transit systems use a wheel profile having a flange designed to bear on the bottom of flangeways through frogs of complex trackwork. This concept reduces impacts and noise, and may be considered in the design of a new transit system. Recently jump frogs have become available that raise one rail near the frog, allowing wheels on the diverging route to pass over the rail of the dominant route. This provides a continuous rail on the more heavily traveled route which decreases noise and wear. Such components may have advantages in certain applications, but care must be taken to assure all car, track, signal, traction power and related components are compatible so that the interrelated systems functions as intended. Steerable Axles Some transit systems use a wheel profile having a flat flange to bear on the bottom of flangeways through frogs of complex trackwork. This concept reduces impacts and noise, and may be considered in the design of a new transit system. The use of flange bearing systems is generally associated with the use of narrower wheel treads. Commented [JLK3]: Not a subset of Flange Bearing Frogs. Moved from Steerable Axles Vehicular trucks developed with steerable axles provide flexibility for the wheel sets to take up radial positions in negotiating track curvature. This provides improved stability at high speeds and reduces both wheel/rail forces and wheel/rail wear. Track design should consider any special requirements of transit vehicles with steerable axles. It should be noted that most self-steering trucks rely on top of rail friction to provide steering forces. Thus, improper use or application of rail lubrication can limit the effectiveness of such designs Lubrication Lubrication of the wheel/rail flange contact surface should be considered for the design of any transit system. Both on-board and wayside lubrication are feasible depending on the geometric characteristics of the transit system. For relatively short transit trains, on-board lubricators can provide a clean, compact, unobtrusive, all-weather lubrication system. Wayside lubricators allow lubrication to be controlled over relatively short distances and/or on a curve-specific basis, but they require on-track access and adjustment. Placement of wayside lubricators should consider track gradient. Care must be exercised in using lubricators where the rail is used as the negative return in an electrically operated transit system, or where signal systems using track circuits are involved. 12-G-16 AREMA Manual for Railway Engineering

20 Track and Roadway Considerations AREMA Manual for Railway Engineering 12-G-17