TCRP Report 57: Track Design Handbook for Light Rail Transit (Part C)

Chapter 5-Track Components and Materials

Table of Contents

5.1 INTRODUCTION 5-1

5.2 TEE RAIL AND GIRDER GROOVE RAIL 5-I 52.1 Introduction 5-l 52.2 Tee Rail 5-2 5.2.2.1 Rail Section - 115 RE or 124 BC 5-2 5.2.2.1 .l AREMA Rail Sections 5-2 5.2.2.1.2 124 BC Rail Section 5-3 5.2.2.2 Rail Strength-Standard/High-Strength Tee Rail 5-3 5.2.2.2.1 Rail Metallurgyr31 5-5 5.2.2.3 Precurving of Tee Rail 5-5 5.2.2.4 Procurement of Rail 5-6 5.2.3 Girder Groove Rail, “Rillenschiene”, and Girder Guard Rail 5-6 5.2.3.1 Girder Rail Sections 5-6 5.2.3.2 Rail Strength - Girder Rail 5-6 5.2.3.3 Precurving of Girder Rail 5-9 5.2.3.4 Procurement of Girder Rail 5-l 0 5.2.4 Rail Wear 5-10 5.2.5 Wear-Resistant Rail 5-11 5.251 Riflex Welding 5-11

5.3 RESTRAINING RAIL DESIGNS FOR GUARDED TRACK 5-12 5.3.1 Girder Guard Rail for Embedded Track 5-12 5.3.2 Tee Rail for Guarded Ballasted and Direct Fixation Track 5-13 5.3.2.1 Vertically Mounted Restraining Rails 5-l 3 5.3.2.2 Horizontally Mounted Restraining Rails 5-14 5.3.2.3 Strap Guard Rail 5-14 5.3.2.4 UIC33 (U69) Restraining Rail 5-l 5 5.3.3 Restraining Rail Recommendations 5-l 5 5.3.4 Restraining Rail Thermal Expansion and Contraction 5-16

5.4 FASTENINGS AND FASTENERS 5-16 5.4.1 Insulated Fastenings and Fasteners 5-16 5.4.1 .I Isolation at the Rail Base 5-l 7 5.4.1.2 Isolation at the Fastening or Fastener Base 5-l 7 5.4.2 Fastenings for Timber and Concrete Crossties for Ballasted Track 5-18 5.4.3 Fasteners for Direct Fixation Track 5-18 5.4.3.1 Fastener Design Consideration 5-20 5.4.3.1.1 Vertical Static Stiffness 5-20 5.4.3.1.2 Ratio of Dynamic to Static Stiffness (Vertical) 5-20 5.4.3.1.3 Lateral Restraint 5-20 5.4.3.1.4 Lateral Stiffness at the Rail Head 5-20

5-i Light Rail Track Design Handbook

5.5 CROSSTIES AND SWITCH TIES 5-21 5.5 1 Timber Crossties 5-21 5.52 Concrete Crossties 5-22 5.5.2.1 Concrete Crosstie Design 5-22 5.5.2.2 Concrete Crosstie Testing 5-23 5.5.3 Switch Ties-Timber and Concrete 5-23 5.5.3.1 Timber Switch Ties 5-23 5.5.3.2 Concrete Switch Ties 5-23

5.6 TRACK (RAIL) JOINTS 5-24 5.6.1 Welded Joints 5-24 5.6.1.1 Pressure Electric Flash Butt Weld 5-24 5.6.1.2 Thermite Weld 5-25 5.6.2 Insulated and Non-Insulated Joints 5-25 5.6.2.1 Non-glued Insulated Joints 5-25 5.6.2.2 Glued Bolted Insulated Joints 5-25 5.6.2.3 Bolted Joints 5-26 5.6.3 Compromise Joints 5-26

5.7 BALLAST AND SUBBALLAST m 5-26 5.7.1 Ballast Materials 5-26 5.7.1.1 Testing Ballast Materials 5-27 5.7.2 Subballast Materials 5-30

5.8 TRACK DERAILS 5-30

5.9 RAIL EXPANSION JOINTS 5-31 5.10 END OF TRACK STOPS 5-31 5.10 1 Warning Signs 5-32 5.10.2 Fixed Non-energy Absorbing Devices 5-33 5.10.3 Fixed Energy Absorbing Devices 5-33 5.10.3.1 Non-resetting fixed devices 5-33 5.10.3.2 besetting Fixed Devices 5-33 5.10.4 Friction (or Sliding) End Stops 5-33 5.11 REFERENCES 5-34

List of Figures

Figure 5.2.1 Typical Rail Sections Tee Rail (lJ69, 115 RE Strap Guard, ZlJ I-60) 5-4 Figure 5.2.2 Typical Rail Section-Girder Groove and Guard Rail Sections 5-7 Figure 5.2.3 Typical Rail Sections-Girder Groove Rail Sections 5-8 Figure 5.3.1 Typical Restraining (Guard) Rail Arrangements (U69 Restraining Rail) 5-14 Figure 5.4.1 Isolation at the Rail Base 5-18

5-ii Track Components and Materials

Figure 5.4.2 Isolation at the Fastening or Fastener Base 5-18 Figure 5.10. I Friction Element Buffer Stop 5-34

List of Tables

Table 5.1 Chemical Composition of the Steels used for European Girder Rails 5-9 Table 5.2 Relationship of Brine11 and Rockwell Hardness Numbers to Tensile Strength S-10 Table 5.3 Ballast Gradations 5-28 Table 5.4 Limiting Values of Testing for Ballast Material 5-29

5iii Track ComDonents and Materials

CHAPTER 5-TRACK COMPONENTS AND MATERIALS

5.1 INTRODUCTION The rail section identification 115 RE refers to:

l 115 = mass (weight) 57.0 kilograms per The track components that form the track meter (114.7 pounds per yard). structure generally include rail, fastenings, l RE = AREMA standard rail section. crossties, and ballast. This chapter includes these and other sundry components and Rail sections and steel composition continue elaborates on their various designs and to evolve and be improved worldwide. The requirements. 115 RE rail section is the primary section used on contemporary light rail track systems Many standard track components and other because it provides a recognized standard track material (OTM) are usable for freight section, as well as a guaranteed continuous railway, commuter railway, and heavy transit supply. The 115 RE rail easily supports light (metro) systems. The information provided in rail vehicle loads and has sufficient end area this chapter pertains to light rail transit to act as a low-resistance negative return systems with overhead catenary or contact conductor in the traction power circuitry. wire distribution that use the running rail as a negative return for the traction power system. The standards for rail lengths have improved from the customary 11 .&meter (39-foot) length to 23.8-, 24.4-, and 25-meter (78, 80 5.2 TEE RAIL AND GIRDER GROOVE RAIL and 82-foot) lengths. European rail mills have recently produced rail in 122-meter (400-foot) 5.2.1 Introduction lengths. This is not a standard in North American rail mills. Rail is the most important-and most expensive-element of the track structure. It Joints between rails have always been the is the point of contact with the vehicle wheel, weak link in the track system. Welding of the the structural beam supporting the vehicle rolled rail lengths into continuous welded rail load, and one location where noise is (CWR) is customary to eliminate joints and to generated. Hundreds of different rail sections improve the performance of rail in track. The have been created since the first strip of iron development of thermite and flash butt was placed on a timber beam. Each new rail welding allows the track to be constructed in section has been developed to satisfy a CWR strings. CWR is the general standard for particular combination of wheel/rail loading. all transit except for locations, such as very Tee rails were developed for ballasted track. sharp precurved track, where jointed rail may When rails were placed in streets, girder rails be more practical to suit specific site were developed to provide the needed conditions and future maintenance flangeway. procedures.

North American tee rail sections have evolved Precurving of rail is a requirement on light rail over the years into the current American systems at locations where the radii of curved Railway Engineering and Maintenance of Way track exceeds the elastic limit of the rail. Association (AREMA) standards-l 15 RE, 132 RE, and 136 RE. Many other rail sections The two prime maintenance issues associated are still in use today. with rail are head wear in curves and rail

5-l corrugation. These issues are discussed at standard rail or high-strength rail length in this section. requirements. The section has more than adequate beam strength to support the wheel Girder rail is needed to support rail in streets on standard crosstie and direct fixation and to form a flangeway for the wheel. The fastener spacing. rail can then have pavement around the rail to allow motor vehicles to share the road with Wheel/rail interface is one of the most trains. Girder groove rail and girder guard rail important issues in the design of the wheel sections are no longer manufactured in North profile and the railhead section. America. The popular girder rail sections in Contemporary light rail transit systems use and available from European provide the opportunity to customize design manufacturers are the Ri 59N, Ri 60N, IC, and maintain an optimal wheel/rail interface Ri52N, Ri53N, NP4a, and 35G sections. due to the single standard for wheels and rail Previous popular sections no longer available include 128 RE--/A, 149 RE-7A and the GGR- Although rail wear and fatigue are 118. There is a limited selection of girder considerations on transit systems, the primary groove rail and girder guard rail in today’s design concerns are: optimizing vehicle market. Few girder rails have the minimal operation, controlling noise and vibration, and transit flangeway widths, which complicates improving ride quality. the issue of railway wheel gauge and track gauge. For additional information on girder A better understanding of and major rail and flangeways refer to Chapter 4 herein. improvements to wheel and rail design and interface issues are evolving. The optimized Girder groove rail installed to improve track wheel/rail interface (OWRI) system considers performance should be welded where both vehicle suspension characteristics and possible. Girder groove rail requires track and rail standards. precurving of rail for nominal radii curved track alignments due to the section. Modifications in the rail head radius will improve the current rail profile of AREMA sections. The current 115 RE rail section 5.2.2 Tee Rail includes a 254-millimeter (1 O-inch) crown head radius. To improve the wheel tread to The standard section for running rail on rail contact zone, a 203-millimeter (8-inch) contemporary light rail systems for the three head radius is recommended. This will types of track structure are generally similar reduce and control the contact band along the unless specifically stated otherwise. rail to a well-defined 12- to 15-millimeter (l/2- to 5/8-inch) width. Several transit agencies have incorporated more radical 5.2.2.1 Rail Section - 115 RE or 124 BC improvements, such as asymmetrical rail grindings for outside and inside rail in track 5.2.2.1.1 AREMA Rail Sections curves, with documented operational Selection of the running rail section must be performed with consideration for economy, improvements in wheel/rail performance. strength, and availability. The current Vehicle performance is based on the primary selection in North America is limited and the and secondary suspension systems that allow simplest solution is to select an off-the-shelf the vehicle to negotiate curves. The wheel 115 RE rail section conforming to AREMA

5-2 Track Components and Materials and rail profiles control how well the vehicle 5.2.2.1.2 124 BC Rail Section truck steers in curves and how much the truck BC Rail, to improve the standard 115 RE rail will hunt on tangent track. The concentrated section and retain the OTM currently in contact zone between the wheel and rail can service opted to change the rail head portion be positioned at the gauge corner on the high of the 115 RE rail section. BC Rail mated the outside rail of curves to improve steering. The 115 RE rail web and base section to the 136 contact zone on the low rail is best located JK rail head section to create the 124 BC toward the field side of the rail head. These section.[‘l The 124 BC rail section provides positions of the contact zones take advantage additional steel in the rail head wear area as of the wheel rolling radius differential and shown in Figure 5.2.1. improved axle steering in conical wheels. The 124 BC rail section improves on rail head Wheel and rail design that produces a radius and provides additional rail life due to conformal contact zone, or wider wear pattern, increased steel in the rail head wear area. A after a short period of service life exacerbates rail section of this size may be especially poor vehicle tracking performance through effective if tee rail is to be used in embedded curved track. It also introduces early wheel track where replacement of worn rail is more hunting and leads to corrugation in the rail labor intensive. head. Conformal contact conditions are produced when the rail head radius is worn to An imbalanced track/vehicle system a flat condition and the wheel is worn to a contributes to excessive wear of both the similar flat or hollow condition. This simulates wheel and rail. A combination of wheel/rail rail head configuration, producing a wear zone vehicle track incompatibilities contribute to across the head of the rail. high lateral over vertical (L/V) ratios, excessive flanging action, and gauge face The current 115 RE rail section consists of a wear of more than 20 degrees on the high crown radius of 254 millimeters (10 inches) rails of sharp curves. Corrective rail section and gauge corner radii of 38.1 and 9.5 design, rail profile grinding, and an effective millimeters (1-X and 318 inches). The rail wheel truing program along with flange- head width is 69.1 millimeters (2-23/32 mounted lubricators will improve rail inches) and the rail height is 168.3 millimeters performance, reduce maintenance, and (6-518 inches) as shown in Figure 5.2.1. increase rail life. [*I Railroads, including BC Rail, have been searching for an improved rail section or The transit industry and freight railroads will profile-one with increased wear life and continue to push for improvements to the performance. Undesirable wear patterns such current standard rail sections such as as gauge corner lip formation and shelling on standardization of the 124 BC section and a the standard 136 RE rail section have compatible wheel profile. For details on the required early gauge corner and field corner wheel profile development refer to Chapter 2. grinding. Dr. J. Kalousek (JK) proposed a 203-millimeter (8-inch) head radius for the 5.2.2.2 Rail Strength-StandardlHigh- standard 136 JK rail section instead of the Strength Tee Rail standard 254-millimeter (1 O-inch) radius to Chemical composition guidelines for running improve the contact location as previously rail are standardized in the AREMA Manual, described.

5-3 9.53 R I24 BC RNL '33isISlS (‘/a” R) of II5 RE me t.4 BASE WH I36 J( HEM f-31.74 R (f/4” R) j-77194 A

(16” R 6” RI

Y-Y NEUTRiQ. !-----AXIS ; 80mm V-Y .lrlllO.l :(3.15o”l h..1 Elf

K: ALL tWKNSlOi4SARE

UIC-33 OR U69 RESTRAINING RAIL 2.1654 5.5118 UIC 608 (Zul-60) 115 RE RAIL AND STRAP GUARD ASSY. Track Components and Materiais

Chapter 4, for both standard rail and high- high-hardness low-carbon bainitic steel offers strength rail. The use of alloy rail is not wear resistance superior to pearlitic steel recommended to obtain the high-strength standards because of the additional As a guideline for transit installations the complexities of welding alloy rail. Current recommendation is to install clean rail steel standard and high-strength rail hardness, with a hardness of: including the head hardening procedure, l 300-320 BHN (standard rail) in tangent obtain the following standards: tracks, except at station stops and severe l Standard Rail: 300 minimum Brinell profile grades greater than 4%. Hardness Number (BHN) l 380-390 BHN in tangent tracks at station . High Strength Rail: 341 to 388 BHN (may stops, severe profile grades greater than be exceeded provided a fully pearlitic 4% , curved track with radii less than 500 microstructure is maintained.) meters (1,640 feet), and all special trackwork components including switch points, stock rails, guard rails, frog rails 5.2.2.2.1 Rail Merallurg~J and rails within the special trackwork The life of the rail can be extended by area. increasing the rail’s resistance to: 0 Wear These hardnesses may prove to be difficult to l Surface fatigue-damage obtain in European girder rail sections. As a . Fatigue defects guideline, the girder groove rail should have a hardness of 300 BHN and greater. Rail steel hardness, cleanliness, and fracture toughness can increase this resistance. The effect of rail hardness in resisting gauge face 5.2.2.3 Precurving of Tee Rail wear is a known fact. increased rail hardness Where the track radius is sharp enough to in combination with minimized sulfide exceed the elastic limit of the rail, the rail must inclusions reduces the likelihood of surface be precurved. These are the general fatigue cracking. This, in turn, reduces guidelines for precurving tee rail: development of subsequent defects such as l Standard Rail head checks, flaking, and shelly spots. Oxide - Precurve rail horizontally for curve inclusion clean steel, combined with good radius below 120 meters (400 feet). fracture toughness, reduces the likelihood of - Precurve rail vertically for curve deep-seated shell formations. Both shelly radius below 300 meters (984 feet). spots and deep-seated shells can initiate l High-Strength Rail transverse defects, which ultimately cause - Precurve rail horizontally for curve broken rails. radius below 100 meters (325 feet). - Precurve rail vertically for curve The current rail standards include increased radius below 230 meters (755 feet). rail hardness and improved rail steel cleanliness, with the pearlitic steels peaking at Precurved rails are often in high wear 390 BHN. Recent research has focused on locations where the rail is replaced more other structures such as bainitic steels. frequently. These locations often have Although bainitic steels of the same hardness standard joints rather than CWR to facilitate as pearlitic steel are not as wear resistant, maintenance.

5-5 Light Rail Track Design Handbook

5.2.2.4 Procurement of Rail l 59: mass (weight) 58.96 kilograms per Procurement of rail should be in accordance meter (118.6 pounds per yard) with AREMA Standard Specification Chapter l N (or -13): 13-millimeter (0.51-inch) 4, Part 2, Section 2.1, which includes specifics gauge corner radius pertaining to transit agency requirements. A recent revision to the Ri59 and Ri60 girder There is no standard rail or girder rail section rails has been to change the radius of the rail for embedded track. The 115 RE rail section head gauge corner from IO to 13 millimeters has been used for embedded track, with the (0.39 to 0.51 inches) and introduce the head bolted Pittsburgh strap-guard, with formed configuration as a 1:40 cant position when the flangeways in either asphalt or concrete, or rail base is level. This rail section has been with the forming of a flangeway in the street. designated Ri59N or Ri59-13. RiGON rail also All of these have been used by various light has a 13-millimeter (0.51-inch) gauge corner rail transit systems. The ideal rail section for radius. These modified rail head sections embedded track would be girder groove rail, match the 115 RE rail head section. The with girder guard rail for the curved sections latest development by an Austrian rail and more pronounced sharper radius curves. manufacturer is the rolling of the RiGON girder groove rail with a 4-millimeter (0.16-inch) raised lip section to provide additional girder 5.2.3 Girder Groove Rail, “Rillenschiene”, guard lip protection. and Girder Guard Rail The new Ri girder rail head profiles match the The most commonly used running rail in 115 RE tee rail section. Wheel compatibility embedded track (if tee rail is not used) is based on head radii and wheel contact zone is girder groove rail for tangent track and girder possible if the wheel profile is designed to suit guard rail for curved track. The selection of both tee rail and girder rail sections. The girder groove rail currently available is limited wheel designer and the track designer must to the European standards: Ri59N, RiGON consider the impacts of wheel/rail Ri52N, Ri53N, NP4a, and 35G as shown in performance resulting from standardized rail Figures 5.2.2 and 5.2.3. To use these narrow sections. For additional information on flange girder rails, the wheel gauge and track wheel/rail conformance refer to Chapter 2. gauge must be compatible with a reduced gauge clearance between wheel and rail to allow for wheel passage. The wheel flange 5.2.3.2 Rail Strength - Girder Rail profile may also be specialized, conforming to The customary European steel manufacturing a transit wheel profile in lieu of the Association practice is to roll standard rail sections in of American Railway (AAR) AAR-IB wheel accordance with current UIC-860 V standards. profile. For additional information on wheel The standard girder rails are produced with profiles and girder rail, refer to Chapter 2. relatively soft rail steel in the normal grade, with a tensile strength (TS) of 685 Newtons per square millimeter (N/mm’) as shown in 5.2.3.1 Girder Rail Sections Table 5.1. Grooved rail is known as “Rillenschiene” in Germany. Current popular German grooved 0 European steel manufacturers also roll rail rail sections are Ri59N and RiGON. The rail sections in a wear-resistant grade with a identification Ri59N refers to: minimum TS of 885 N/mm’. This grade of l Ri: Rillenschiene for groove rail

5-6 180 t .-.-.I.-.-.-.-.-. NEUTRAL AMS .I0

116 (4 9/W) IM (5 7/S’) 40.75 : 75.25 c -I

~ 56 i ,a 34 RI 52-13 GIRDER GROOVE RAIL RI 53-13 GIRDER GROOVE RAIL

NP 4a GIRDER GROOVE RAIL Track Components and Materials

standard steel is available in three classes: A, provide wear resistance treatments consisting B, and C, where: of wear-resistant weld inserts at the gauge

l C = Class is the wear-resistant corner, top of rail, and/or girder rail lip (see

l B = Class is the primary class for girder Section 52.5). rails, which provides a hardness of approximately 266 BHN 5.2.3.3 Precurving of Girder Rail

l A = Class rail is a very soft steel Like tee rail, girder rail must be precurved if the curve radius is sharp enough to exceed A girder rail section to meet North American the elastic limit in the base or guarding face. BHN standards requires a tensile strength of The guideline for precurving girder rails:

1,080 N/mm2 which equates to approximately l Horizontal: precurve girder rail for curve 320 to 340 BHN according to Table 5.2. radii below 200 meters (650 feet).

l Vertical: precurve girder rail for vertical Recent investigations with European steel curve radii below 300 meters (984 feet). manufacturers have indicated that girder rail in this class can be made available in alloy steel Horizontal bending of girder rail will require girder rail. vertical bending to obtain proper configuration due to the asymmetrical shape of the rail. An alternative to the alloy steel is to use the These operations are best performed in roller standard European girder rail steel and straighteners at the mill.

Table 5.1 Chemical Composition of the Steels used for European Girder Rails

Grade with minimum TS of

Wear-resistant grade with minimum T.S. of 885 N/mm2 I 0.4510.65 = 0.4 1.70/2.10 =0.03 =0.03 C Chrome - manganese special 0.65lO.80 = 0.8 0.80/i .30 =0.03 = 0.03 0.80/l .30 grade steel with minimum TS of 1080 N/mm2 (1) C = Carbon Si = Silicon Mn = Maganese P = Phosphorus S = Sulfur Cr = Chromium

5-9 Light Rail Track Design Handbook

Table 5.2 Relationship of Brine11 and Rockwell Hardness Numbers to Tensile Strength

Rockwell Rockwell Suoetficial Brine11 Hardness Hardness Hardness Numbe;, Superficial Number Number Diamond Penetrator Brine11 Tunasten Indentation Standard Car&de 15-N 30-N 45-N Tensile Strength Diameter (mm) Ball Ball B Scale C Scale Scale Scale Scale (Mpa) (N/mm2) 2.50 601 57 3 89.0 75 1 63 5 2262 2.60 555 547 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 2 545 1738 2.90 444 47.1 840 65.8 51.5 1586 3.00 416 415 445 82.8 63.5 48.4 1462 310 388 388 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 78.6 564 39.1 1131 340 321 321 34.3 77.3 54 3 36 4 1055 3.50 302 302 32.1 76 1 522 33.8 1007 3 60 285 285 29.9 75 0 50 3 31.2 952 3 70 269 269 27.6 73 7 48.3 285 897 3.80 255 255 254 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 4.10 217 217 964 710 4.20 207 207 94.6 682

5.2.3.4 Procurement of Girder Rail constant running of the wheels and is further Procurement of girder rail by North American compounded by the additional forces transit agencies requires a special contract generated by braking and traction during specification stating the specifics as to rail deceleration and acceleration, respectively. section, strength, special treatments and In curved track there is added surface wear, potential precurving requirements in specific where wheel slippage and load transfers lengths of rail. The use of European standard occur due to superelevation and changing UIC 860 V as a reference is acceptable, as direction of the vehicle truck. Gauge face rail long as additional special provisions are wear occurs due to the steering function of the included. rail. Steering contact is at the outer rail of a curve, which guides the outside wheel of the As a guideline, the special provisions for lead axle The action commences when the procurement of girder rail should include: the vehicle wheels negotiate the outside rail of the ultimate tensile strength of the rail in particular curve to the point where the wheel flange the Brine11 Hardness Number at the wearing makes contact with the side of the rail head. surfaces, the compatibility of welding, This contact is referred to and measured as precurving requirements, specific length of the “angle of attack.” r4] rails, and the method of corrosive protection during shipping. This attack on the outer rail is not caused by the vehicle’s centrifugal force, but by the 5.2.4 Rail Wear constant change in the vehicle’s direction. The outer rail constantly steers the outer Rail has continually suffered from abrasive leading wheel inwards towards the curve wear due to the steel wheel running on and center. against it. Surface head wear is due to the

5-10 Track Components and Materials

The wheel acts as a cutting edge, or grinding the wear and abrasion (or machining) of steel stone, that actually machines the gauge and the formation of corrugation. r5] corner and face of the running rail. This is caused by several factors, such as the The hardness of rail steel is proportional to its severity of the wheel’s angle of attack to the toughness or its ultimate tensile strength rail, the stiffness of the vehicle truck which (UTS). UTS is used to measure the quality of retards the curving action, and the velocity of the steel. the vehicle. As stated earlier, rail producers in Europe are Another rail wear phenomenom is the not accustomed to supplying non-alloy special formation of metal flow. The wheel/rail groove rail and other rail sections in the range interaction causes the rail and steel surfaces of 1,100 UTS (320 to 340 HBN). To to deform at the point of contact due to the overcome this deficiency in the rail, a special concentrated load. This contact pressure is welding procedure has been used to provide a extreme to the point where the stress is wear-resistant surface to the rail. The special greater than the yield point of the rail steel, welding known as Riflexf6] also features anti- which causes plastic deformation of the squeal characteristics. surrounding steel. This action leads to metal flow accumulation on the surface edges of the 5.2.5.1 Riflex Welding rail head. Metal flow collects at the gauge The Riflex welding procedure includes three corner of rail in tangent track, where the wheel types of rail welding as follows: is seldom in contact with the rail gauge corner l Riflex--corrugation reduction or elimina- or face. This also occurs on the field side of tion and head wear reduction the inside rail of curves, where the rail head l Eteka 5-rail gauge corner and face wear metal flow migrates toward the field side and reduction accumulates as a pronounced lip. l Riflex AQ-anti-screech weld material Corrugation of rail is another rail wear developed to control noise phenomenom that impacts ride quality and The Riflex process includes four steps: noise generation. Corrugation is discussed in 1. A groove is machine cut into the ball or Chapter 9, Noise and Vibration Control. the gauge face of the rail. 2. Using submerged arc welding techniques, 5.2.5 Wear-Resistant Rail an alloy is welded into the groove. Transit systems have historically suffered 3. The rail is ground smooth. from worn rails and the need for premature rail 4. The rail is roller straightened and replacement due to accumulative wear limits ultrasonically inspected. Riflex welding of the rail head and/or gauge face. To combat can also be field applied with rail in place. the wheel machining of the rail gauge face and loss of metal, an abrasion-resistant steel The three types of weld materials used in the is required. Improvements in the chemical Riflex process have different hardnesses. composition and treating process of rail steel The Riflex anti-corrugating material is applied have led to the development of wear-resistant in a very hard state-approximately 600 types of steel. Research has shown that BHN-and develops a final hardness of about pearlitic steel with sufficient hardness retards 700 BHN. The Eteka 5 material is applied to the rail in a fairly soft form, but develops a hardness of 550 to 600 BHN very quickly.

5-11 Light Rail Track Design Handbook

The AQ anti-screech material is applied in a can improve quality and reduce field soft state and develops a hardness of about installation time. 80 BHN. Although the AQ material is soft, it is protected by and designed to wear at the same rate as the surrounding rail. Additional 5.3.1 Girder Guard Rail for Embedded information on Riflex welding is included in Track Chapter 9. Many historic North American girder guard rail Riflex welding applications have had mixed sections were either 140ER7B or 152ER9B success in North America. The carbon and, more recently, 149 RE7A. These content of rail specified in North America has sections were developed specifically for resulted from adverse performance in the embedded street track to provide a substantial welding procedure and long-term restraining rail guard lip or tram on the rail to performance. The use of the Riflex process act as the restraining guard face. In tangent requires a detailed specification procedure track a mating girder groove rail section of that matches the rail steel. similar height with a reduced girder rail lip was available to complete the embedded track installation. 5.3 RESTRAINING RAIL DESIGNS FOR GUARDED TRACK These girder groove rail and girder guard rail sections were developed to suit specific wheel Guarded track in light rail transit design, as profile sections and transit wheel gauge described in Chapter 4, reduces curve wear resulting in a reduced flangeway. The last on sharp curves by restraining the wheels section rolled in North America, the 149 RE- away from the outer rail. The guard (or 7A, was a railroad girder guard rail with a restraining) rail is close to the inside rail of the wider flangeway that was compatible to the curve and contacts the back of the inside AAR wheel and wheel gauge. Earlier wheel flange. The design of guarded or contemporary light rail systems adopted this restraining rail differs, and over the years girder guard rail section as standard to suit the various designs have been used. AAR vehicle wheel gauge. These sections Traditionally, curve guarding on street railway are no longer manufactured or rolled. systems was frequently achieved using a girder guard rail section similar to the rail To fill the availability void in girder groove and sections illustrated in Figure 52.2. Ballasted girder guard rail, European girder groove rail and direct fixation track requiring guarding sections have been used. The most popular used a separate restraining rail mounted European sections are Ri59, Ri60, and GGR- adjacent to the running rail. Exceptions can 118. These sections are all pure transit girder be found, depending on the requirements and rail sections with reduced flangeway widths as circumstances of a particular system. shown on Figure 52.2. The GGR-118 girder groove rail section is no longer available. The following sections discuss the various Other girder groove rail sections rolled in designs for guarded track or restraining rail. Europe that can be considered for transit use Sharp curves with restraining rail are very in North America are the IC, Ri52N, Ri53N, complicated to fabricate and construct in the NP4a, and G35. European girder rails are not field. Prefabricating curves on a shop floor compatible with freight operations. Recently the Ri60 girder groove rail was modified to

5-12 Track Components and Materials increase the girder lip height to introduce a rail” parallel and concentric to the inside section conforming to girder guard rail running rail, with the horizontal distance requirements. between the two rails set at the required flangeway dimension. The dilemma confronting the North American light rail track designers is the lack of a The restraining rail can be fabricated from one suitable girder guard rail section with the of several steel shapes and may or may not increased flangeway width required to provide be physically attached to the running rail. In guarded track in embedded sharp radius versions that are physically bolted to the curved track sections. The European girder running rail, the restraining rail/running rail groove rail sections are adaptable if a transit assembly must be designed as a unit so that wheel gauge is selected for the wheel set. curvature is consistent and bolt holes in both The AAR wheel gauge of 1414 millimeters rails are aligned. (55.6875 inches) is not compatible with these girder rail sections. 5.3.2.1 Vertically Mounted Restraining Rails Alternate design methods have been used in The most common type of restraining rail is a embedded track to overcome the flangeway vertically mounted tee rail as shown in Figure width issue. These designs included the 5.3.1. The restraining rail is fabricated by “Pittsburgh” strap guard with 115 RE rail, the planing away a portion of the base of a use of conventional tee rail restraining rail, standard tee rail, which is then bolted to the and the use of 115 RE rail with a formed running rail at intervals of 600 to 900 flangeway with no restraining rail protection. millimeters (24 to 36 inches). Cast or Unfortunately, none of these design concepts machined steel spacer blocks are placed provides the ultimate rail section, and they between the running rail and the restraining have proven to be adequate at best. rail to provide the desired flangeway. Some designs fabricate the spacer blocks in two As a guideline, a transit wheel profile and pieces and insert shims between them to transit wheel gauge of 1421 millimeters (55.94 adjust the flangeway width so that the inches) are recommended and the modified Ri flangeway can be restored to the design 59N girder groove rail section with a hardened dimension as the guard rail face wears. girder tram lip can be used in sharp radius Although this design feature appears sound, curved track. This combination of transit- few transit systems actually take advantage of related standards provides an adequate this maintenance feature. guarded track system. A wider wheel gauge of 1429 millimeters (56.25 inches) would allow The restraining rail and the running rail webs the use of RiGON girder groove rail with the must be drilled to insert connecting bolts. The proper truck wheel set (axle spacing). bolt hole spacing must be detailed on the shop drawings because the restraining rail is on a slightly larger horizontal radius than the 5.3.2 Tee Rail for Guarded Ballasted and running rail to which it is attached. In addition, Direct Fixation Track the bolt hole spacing will be different on each rail. While this differential is minor between Ballasted and direct fixation track with sharp any pair of bolt holes, it will become significant curves have used various designs to provide when accumulated over the full length of a the required restraint. Guarding is typically rail. provided by mounting a separate “restraining

5-I 3 Light Rail Track Design Handbook

crosstie or rail fastener should be coordinated to ensure that the bolt assembly will not interfere with insertion of the elastic rail clip. The bolt must be able to be tightened without CfflWTioNAL MRTICAL RfSTTWNlNG RAILS requiring removal of the rail clip.

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. STRAP GUARD REJR*ININC RAlL HORIZCNTAL RESTRAJNINGRPJL Restraining rail installed on concrete crossties will require a special restraining rail crosstie with a wider shoulder mounting.

Vertically mounted restraining rails have been

U69 RESTRAINING RAlL used in all the types of track structures. When employed in embedded track, it is necessary Figure 5.3. I Typicai Restraining (Guard) to seal the flangeway to keep out moisture Rail Arrangements and debris. A restraining rail assembly in For curves with radii less than 100 meters embedded track will have multiple paths for (328 feet), combined running and restraining seepage. Even with sealants, it is critical to rails are typically precurved and fabricated provide sub-drainage to keep the track dry. together on a shop floor. For ease of shipment, these precurved segments are 5.3.2.2 Horizontally Mounted Restraining usually 12 meters (39 feet) long or less. For Rails curves with radii greater than 100 meters as Transit systems have used horizontal designs well as through curve spirals, where the where the restraining rail is mounted with the running rail can usually be field sprung (bent) rails Y axis oriented horizontally, as shown on to the desired curve, shop curving of both Figure 53.1. This is a relatively old design running and restraining rails is typically not that is currently used only in older transit performed. To eliminate the need to drill installations. countless holes in the field conditions, only the restraining rail is drilled. The restraining As a guideline, horizontally mounted rail is often the same rail section as the restraining rail is not recommended for light running rail. In cases where the restraining rail transit use although some traditional rail is elevated above the head of the running streetcar systems used it at one time. rail, the restraining rail is fabricated from the Horizontally mounted restraining rail cannot next larger rail section (e.g., 115 RE running be used in embedded track areas. 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 5.3.2.3 Strap Guard Rail fastening plate beneath the restraining rail to A relatively recent restraining rail design uses elevate it. a special rolled section, known as the Pittsburgh strap guard, with 115 RE rail as If elastic rail fastenings are used, the spacing shown in Figure 53.1. The strap guard between the restraining rail bolts and the section can be bolted directly to the web area

5-14 Track Components and Materials of the running rail. The strap guard section used for frog guardrails on several North was developed for the Pittsburgh light rail American light rail transit systems. transit system in the early 1980s based on similar sections that were roiled for ASCE The major advantage of using the U69 section rails in the early 20ti century. This section, as as a restraining rail is the capability of presently designed, accommodates only small independent mounting from the running rail as streetcar-sized wheel flanges. Where it was shown in Figure 53.1. To improve on its used with railroad wheel flanges, it was function as a restraining rail, the U69 section necessary to insert shims between the web of features a raised design The restraining rail the running rail and the strap guard to obtain a face is positioned 20 millimeters (0.7887 wider flangeway. inches) above the top of the running rail, to allow additional contact with the flat vertical One advantage of the strap guard rail is that it face of the back of wheel. does not require special rail fasteners or crossties. The only requirement is a specially The independent mounting is provided by a designed rail clip that can bear on the lower mounting bracket that allows the restraining flange of the guard on the gauge side of the rail to be mounted adjacent to the running rail, assembly. The field-side rail holddown device providing the required flangeway width. The can be the same as that used in single rail mounting bracket design can either be installations, which facilitates adding strap separate from the running rail fastening plate, guards to an existing curve that is direct fixation fastener, or an integral part of experiencing rail wear. the fastening plate.

The main disadvantage of the strap guard is that a large number of holes must be drilled in 5.3.3 Restraining Rail Recommendations both the strap guard and the running rail and a large number of threaded fastenings must be As a guideline the following mountings are maintained. recommended: Concrete Crosstie Track-a separate U69 As a guideline, the strap guard rail assembly mounting is provided by two additional should be used only as a last resort for either anchor bolt inserts that are cast in the girder rail or girder guard rail light rail transit concrete crosstie during tie production. installations. The installation should be insulated and the bracket designed to clear the running rail fastening. 5.3.2.4 UK33 (U69) Restraining Rail Direct Fixation Track-a separate U69 A new restraining rail design for use in North mounting is provided by two additional American light rail transit system is the anchor bolt inserts cast in the direct popular UIC33 section from Europe. The UIC fixation concrete plinth during plinth 33 section is also referred to as the U69 or installation. The installation should be RL-160 section. For standardization, insulated and the bracket designed to hereinafter the section will be referred to as clear the direct fixation fastener the U69 restraining rail section. The U69 components. section in Europe has primarily been used as a guardrail for special trackwork frog Timber Crosstie Track-joint U69 locations. The U69 section has also been mounting with the running rail fastening plate. A welded assembly or cast steel

5-l 5 Light Rail Track Design Handbook

fastening plate can be used. The single 12-meter (30- and 39-foot)-long segments and unit fastening plate with a bracket provide expansion gaps at bolted restraining provides improved holding by using the rail joints. If the adjoining running rail is weight of the vehicle to retain the plate continuously welded, any connections bracket position. The installation should between the restraining rail and the running be insulated, and the bracket designed to rails should allow for some longitudinal clear the running rail fastenings. movement between the two rails. This can be accomplished by drilling oversized bolt holes. The U69 restraining rail assembly provides for flangeway width adjustment by adding shims directly behind the U69 restraining rail. This 5.4 FASTENINGS AND FASTENERS adjustment can be undertaken without disturbing the running rail installation. The fastening is the device that holds the rail in place on either a tie plate, direct fixation The U69 restraining rail can be provided in 15 fastener, or concrete crosstie. While the and 18-meter (49- and 59-foot) lengths. original spike was used to provide lateral Special four bolt joint bar assemblies are used support, new elastic fasteners also restrain to join these lengths. To allow for minor longitudinal forces in CWR. thermal expansion in the U69 section, it is recommended that slotted holes be made in Track designers are continuously striving to the joint bars. improve rail fastenings and fasteners. Current popular fastenings include:

On aerial structure installations where thermal l Conventional rolled tie plates with cut expansion of the structure must be spikes, used on timber ties (no insulation). accommodated, the U69 restraining rail l Rolled formed shoulder tie plates with mounting bolt holes at each mounting bracket elastic rail fastenings and cut or screw should be slotted to allow the structure to plate holddown spikes, used on timber move longitudinally. ties (with or without insulation).

On sharp radius curved track installations, the l Plates with rigid crane rail clips, used in precurving of the U69 section is preferred in embedded and direct fixation track. lieu of springing (bending) the U69 restraining l Insulated elastomer direct fixation rail into position. Design and shop drawing fasteners used on direct fixation track and layout of the curved track to conform to the occasionally in embedded track. various installations is required.

5.4.1 Insulated Fastenings and Fasteners 5.3.4 Restraining Rail Thermal Expansion and Contraction The light rail vehicle draws power from the overhead catenary wire and returns it through Restraining rails undergo thermal adjustment the running rails to the power substation. The as do running rails. They should not be use of the running rails as an electrical continuously welded because it would be conductor is one of the main differences virtually impossible to install them at the same between freight railroads and light rail transit zero thermal stress temperature as the systems. The negative return current must be adjacent running rails. It is customary, controlled at the rail to retard or reduce stray therefore, to fabricate restraining rail in 9- and

5-16 Track ComDonents and Materials current leakage, which causes corrosion of transit track structures, utilities, and nearby structures. For additional information on stray Eusnc FASTENING current protection refer to Chapter 8.

The rail fasteners and fastenings are used to insulate the rail from the ground Ballasted track often relies on timber ties to insulate rails from the ground. Although wood is l- MOUNTINGSURFACE considered a non-conducting material, the timber crosstie does not provide total Figure 5.4.1 Isolation at the Rail Base insulation for the negative return running rail. Additional insulation may be provided to fastening pad and insulating thimble-collars further isolate the rail and/or fastening plate for the anchoring screws or bolts, as shown in from the timber crossties where stray current Figure 5.4.2. corrosion is an issue.

On concrete and steel ties, elastic clip 5.4.2 Fastenings for Timber and Concrete fastenings are used. The clips are insulated Crossties for Ballasted Track from the rail by plastic insulators and the rail is placed on an insulating pad. Insulated track The current standard for light rail transit fastenings or fasteners are needed to attach ballasted track is to use either timber or rails in ballasted, direct fixation and embedded concrete crossties. For additional information track. However, track fastenings may be on ballasted track refer to Chapter 4. omitted in embedded track designs where the rails are supported by embedment materials. Traditionally, track constructed with timber crossties, CWR, and cut spikes also included rail anchors to restrain the rail from 5.4.1.1 Isolation at the Rail Base movement. This style of track installation has To provide electrical isolation of the rail from been economically replaced with elastic the surrounding track components, the spring clips to hold the rail to the tie plate. insulating barrier must be installed at the base The elastic clip now provides the longitudinal of the rail or mounting surface. The insulating restraint as well as holding the rail down. barrier consists of a rail base pad and These clips eliminate rail anchors that insulators for the edges of the rail base. The protrude into the ballast and are virtually rail base may be fully insulated from the impossible to insulate to provide stray current mounting surface, as shown in Figure 5.4.1. protection.

The trend in design of main line LRT track 5.4.1.2 Isolation at the Fastening or appears to be toward the use of concrete Fastener Base crossties. Concrete crossties provide superior To provide electrical isolation of the fastening gauge, line, and surface retention over timber from the surrounding track components, the crossties and the simple fastening method of insulating barrier must be installed at the base elastic clips holds the rails and electrically of fastening or mounting surface. The isolates them from the ground as shown in insulating barrier consists of an insulated base Figure 5.4.1. Main line transit track with

5-17 Light Rail Track Design Handbook

For additional information on direct fixation track design, refer to Chapter 4.

Although rails can be attached to concrete decks as shown in Figure 54.1, the common practice in direct fixation track is to use a bonded (or unbonded) direct fixation (DF) ENLARGED‘JEW fastener plate as shown in Figure 5.4.2.

The terms fastening and direct fixation FASTENING PAD fastener refer to two distinct track components. Fastenings are the individual components, or series of components, mounted separately to hold the rail tight in MOUNTING SURFACE place, such as on a concrete crosstie with no Figure 5.4.2 Isolation at the Fastening or plate. Direct fixation fasteners consist of a Fastener Base vulcanized/bonded steel plate and elastomer pad or a steel plate mounted on an unbonded timber crossties must consider the insulation elastomer pad. The direct fixation fastener method shown in Figure 5.4.2 with screw plate often provides lateral rail adjustment in spikes used to secure the tie plate. the anchor bolt area. Economically, concrete and timber crossties with insulated tie plates are approximately All modern heavy rail transit systems, starting equal in cost for large-volume procurements. with Toronto in 1964 and BART in 1968, have This may change depending on the availability used resilient DF fasteners in subway track of timber. and aerial track. DF fasteners have been redesigned and improved to the point where Special trackwork installations on timber and there are numerous styles from which to concrete switch ties must consider the choose. insulating method shown in Figure 54.2. This is similar to main line timber crosstie One of the earliest DF fastener designs is the installations, which use larger special Toronto Transit Commission’s (TX) trackwork fastening plates at the switch and unbonded fastener with a natural rubber pad. frog areas. Insulated plates, screwed to the Later designs included vulcanize bonded timber or concrete crosstie insert with an fasteners with rolled steel top and bottom elastic spring clip for rail support, have a plates. More recently, fasteners with either proven service record. rolled steel, cast top plates, or cast bases are being used. Fasteners with a soft elastomer material are available to provide an extra 5.4.3 Fasteners for Direct Fixation Track measure of groundborne noise reduction.

Direct fixation track is most often constructed DF fastener designs have used various on: fastenings including bolted rail connections, l Concrete slab track at-grade rigid clips and spring wedges, and elastic l Concrete invert in tunnels spring clips with variable toe loads. The l Concrete deck on aerial structures elastomer pad has been manufactured with

5-I 8 Track Components and Materials synthetic elastomers, natural rubber the base plate to the concrete invert or elastomers, and polyurethane materials. crosstie, without passing through the top These materials have been formulated to plate. This approach eliminates lateral provide both high- and low-spring rates for the bending moments, which would otherwise be track. Fasteners are held to the invert with applied to the anchor bolts due to lateral rail anchor bolts consisting of embedded studs forces with spring washers and nuts or female anchor inserts with spring washers and bolts. Some of the earlier designs were inadequate 5.4.3.1 Fastener Design Consideration because of problems in design, material, The principal design parameters for direct installation, or overloading, fixation fasteners are discussed in the following paragraphs: Resilient DF fasteners have long been used by U.S. transit systems. These fasteners 5.4.3.1.1 Vertical Static Stiffness provide a moderate degree of vibration Vertical static stiffness is often called spring isolation, require less maintenance, and rate, and represents the slope of the load produce better rail alignment than ballasted versus deflection over a prescribed range of track. The typical static stiffness of DF 5,000 to 55,000 N (1,000 to 12,000 pounds). fasteners used by various U.S. systems is on Current light rail track designs include a static the order of 20 to 50 MN/m (112,000 to stiffness of about 18 to 21 MN/m (100,000 to 280,000 pounds per inch), with spacing 120,000 pounds per inch), which, with a 760- ranging from about 760 to 900 millimeters (2.5 millimeter (30-inch) fastener spacing, gives a to 3 feet). Recent concerns over the control of rail support modulus of about 26 MN/m* (3,700 rail corrugation and the desirability of pounds per square inch). One feature of low approximating the stiffness of ballast and stiffness fasteners is that they distribute rail crosstie track have modified the design of DF static deflection over a larger number of fasteners such that the stiffness is on the fasteners, making the rail appear more order of 19 MN/m (106,000 pounds per inch). uniformly supported. Low rail support These fasteners incorporate elastomer stiffness reduces the pinned-pinned mode bonded between a cast iron or steel top plate resonance frequency due to discrete rail and stamped steel base. A snubber is supports, as well as the rail-on-fastener installed between the top and bottom plates, vertical resonance frequency. Static stiffness beneath the rail seat, to limit lateral motion of in the 18 to 21 NM/m range provides the top plate. Lateral rail head stiffness is on reasonable control of track deflection in the the order of 5 MN/m (30,000 pounds per inch). vertical direction without unduly compromising Fasteners have been supplied with vertical lateral stiffness. stiffness on the order of 20 MN/m, but with very low lateral stiffness on the order of 1.75 5.4.3.1.2 Ratio of Dynamic to Static MN/m (9,800 pounds per inch), due to lack of Stiffness (Vertical) a snubber or other lateral restraint. These The ratio of vertical dynamic to static stiffness differences in lateral stiffness reflect is a very important quantity that describes the differences in design philosophy. quality of the elastomer. A low ratio is Fastener designs that control structure- desirable to maintain a high degree of vibration isolation. A desirable upper limit on radiated noise often feature an anchoring the ratio is 1.4, which is easily obtained with system with anchor bolts that directly attach

5-19 Light Rail Track Design Handbook fasteners manufactured with a natural rubber of overcoming this potential conflict is to move elastomer or a rubber derivative. Ratios of 1.3 most of the elastomer to the ends of the are not uncommon with natural rubber fastener, away from the rail center, thus elastomer in shear designs. As a rule, maximizing the reaction moment to elastomers capable of meeting the limit of 1.4 overturning forces. A snubber should not be must be of high quality and generally exhibit installed at the center of the fastener. If a low creep. snubber is required, it should be located towards the lateral ends of the fastener to minimize rotation of the rail by forcing the rail 5.4.3.1.3 Lateral Restraint to rotate about a point located towards the Lateral restraint is the ability of the fastener to field side of the rail in response to gauge face horizontally restrain the rail. High lateral forces. restraint is often incompatible with vibration isolation design requirements. Therefore, fasteners that provide adequate stiffness to 5.5 CROSSTIES AND SWITCH TIES guarantee both an adequate degree of horizontal position control as well as vibration Ballasted track requires crossties to support isolation are desirable. Snubbers are the rail. Chapter 4 discusses crossties in the protruding portions of metal plate that design of ballasted track. Crossties are used penetrate the adjoining plate to act as a limit mainly for ballasted track, although they are flange in controlling lateral displacement. The occasionally used in both direct fixation guiding design principle is to provide a three encased track, where a crosstie or sections degree-of-freedom isolator. Hard snubbers thereof are encased in a concrete track are undesirable in fasteners, because they structure, and in embedded track, where the limit vibration isolation only in the vertical crosstie is embedded with the track structure direction. Crossties are generally made of three specific materials: timber, concrete or steel. There 5.4.3.1.4 Lateral Stiffness at the Rail Head has been some experimenting with composite Lateral stiffness is measured at the rail head crossties consisting of epoxy composites and and includes the effect of fastener top-plate plastics. These composite ties have seen rotation. Light rail track design must maintain little service and are not discussed further rail head position within tight tolerances on herein. both curves and tangent track. This is potentially in conflict with the requirement for The development of pre-stressed precast horizontal vibration isolation. The lateral concrete at reasonable prices has led to the deflection of the top plate of typical sandwich current concrete crosstie design, which fasteners is limited by the snubbers and to a features encased rail shoulders and sundry lesser extent by the elastomer in shear. If the inserts for the application of trackwork snubber is located beneath the rail, a low components. The concrete crosstie designs fastener with low vertical stiffness will have have been refined to suit light rail transit use. low rotational stiffness and thus poor rail head A recent innovation is the design of the control. This conflict has been overcome by serrated side (scalloped) concrete crossties one European design, which incorporates that improve lateral stability. elastomer in shear with a large lateral dimension to resist overturning. Another way Light rail transit systems use both timber and concrete crossties. The predominant

5-20 Track Components and Materials standard appears to be concrete crossties for inches) long. Transit systems with a wider the main line track, with timber ties for track gauge require a longer timber crosstie. maintenance facility and yard tracks. Special trackwork installations for both main line and Timber crossties are generally required to yard track use timber ties, although concrete conform with the current specifications of the ties have been considered and recently AREMA Manual, Chapter 30 (formerly 3) Ties implemented on a transit system. and Wood Preservation.

As a guideline, timber crossties for light rail 55.1 Timber Crossties transit use should be hardwood-preferably oak-and generally 180 x 230 millimeters (7x9 The timber currently used in crossties inch) wide x 2.6 meters (8 feet, 6 inches) long. includes selected hardwoods, with tropical Tie length may vary depending on the track species also being considered. The reduced gauge selected. The 7-inch tie depth is availability of this timber has driven up the referred to as a 7-inch grade crosstie. (The cost of ties, as has the environmental aspects metric system has not been used to classify of treating the wood. For new light rail transit tie sizes). systems constructed in early 198Os, timber ties (wood is a non-conductor) provided When using timber crossties conforming to sufficient electrical isolation. Today, many AREMA recommendations, the type of wood, believe that additional insulation is required in tie size, anti-splitting device, wood locations where stray current corrosion is an preservative treatment, and machining should issue. Recent timber tie fastening designs be specified in the procurement contract. include a tie plate that adds a layer of insulation between the bottom of the tie plate and the top of the tie. 55.2 Concrete Crossties

The requirement for an insulated tie plate to Concrete crossties are becoming more be mounted on the timber tie dictates the common in light rail transit designs as life general width of the tie. Standard tie plate cycle costing makes them competitive with widths range from l&O to 190 millimeters (7 timber crossties. The most common concrete to7-% inches), with an insulated tie pad crosstie is the monoblock tie with embedded protruding a minimum of 12 millimeters (l/2 cast steel shoulders and pre-tensioned wires. inch) on all sides of the tie plate results in a The rail fastening system consists of an minimum width of 204 millimeters (8 inches). elastic clip with insulating rail seat pad and A 230-millimeter (g-inch) wide timber tie clip insulators, as shown in Figure 5.4.1. provides sufficient surface to support the total In addition to the conventional crosstie that insulator pad with no overhang beyond the holds the two running rails, a special crosstie edge of tie. Skewed tie plates at special is needed to hold the restraining rail in trackwork locations must consider the guarded track at sharp curves. The size of overhang issue in relation to degree of the the two ties is similar. The configuration of skew angle. the restraining rail crosstie provides a The length of crosstie relates to the standard relatively level surface between the rails to track gauge of 1435 millimeters (56-X inches) support the specific design of the restraining and is generally 2590 millimeters (8 feet 6 rail assembly.

5-21 Light Rail Track Design Handbook

The standard size of light rail transit concrete the determined calculated load limits. The crossties is generally 255 millimeters (10 tests should be conducted in accordance with inches) wide and 2515 millimeters (99 inches) the procedures outlined in the AREMA long at the base of tie. The tie is tapered to a Manual, Chapter 30. 190-millimeter (7.5-inch) height at the rail seat and a 165-millimeter (6.5-inch) height at the center of the tie. The height at the center of 5.5.3 Switch Ties-Timber and Concrete the tie will increase to suit the restraining rail Special trackwork switch ties for light rail design. The length of concrete crossties may transit system installations have been vary between transit systems; however, 2515 primarily timber based on conventional millimeters (8 feet 3 inches) appears to be the railroad standards most common length for standard track gauge. Concrete switch ties have been developed by the railroad industry to meet heavy haul freight The concrete crosstie design for light rail maintenance requirements. History has transit track is based on the light rail vehicle shown that high engineering design and weight, anticipated loads and vehicle fabrication costs contributed to the limited use operating velocity. It is generally a smaller of concrete switch tie sets, with timber being version of the concrete railroad crosstie with more economical. less reinforcement and a reduced cross section sufficient to meet the positive and The transit industry’s minimal use of concrete negative rail seat and tie center bending test switch ties has been primarily on commuter requirements. Specifications for concrete railroad lines utilizing large-size turnouts and crossties in light rail transit track differ from high-speed turnouts. standard railroad track crosstie specifications due to the different vehicle loads and resultant Various turnout standards exist among light forces on the crossties. The concrete railroad rail transit agencies; therefore various crosstie is a sturdier tie in conformance with concrete tie geometric layouts and designs the specifications of AREMA Manual, Chapter would be required to meet all requirements. 30. Standardization and simplicity in tie design is required to provide the light rail transit industry with a uniform standard concrete switch tie set 5.5.2.1 Concrete Crosstie Design for the various turnout sizes. The design of concrete crossties for light rail transit track is based on performance specifications that consider: 5.5.3.1 Timber Switch Ties l Tie spacing Timber hardwood switch ties is the standard l Tie size for light rail transit special trackwork turnouts l Wheel loads and crossovers. In locations where stray 0 Impact factor current corrosion is an issue, added insulation is needed. 5.5.2.2 Concrete Crosstie Testing Similar to main line timber crossties, the Prior to acceptance of the concrete crosstie requirement for an insulated switch tie plate to design, the manufactured crosstie should be be mounted on the tie dictates the general tested for compliance with specifications and width of the tie. A 230-millimeter (g-inch) wide

5-22 Track Cumponen ts and Materials timber switch tie provides adequate surface to required, such as the closure curve zone support the entire insulator pad with no between the heel of switch and toe of frog, will overhang beyond the edge of the tie. Special require an alternate rail mounting method. trackwork plates or fastenings are subjected to skewing of the plates to provide a The standard conventional embedded perpendicular mounting at the rail base. shoulder and elastic clip, with proper Otherwise, special provisions within the plate insulation, may be used at locations on the design must allow the plate to mount parallel switch tie where clearance allows the four to, and entirely on, the tie surface. Skewed rails to be mounted individually. The height plates or insulation should not project beyond differentials between switch, frog and guard the edge of tie. rail plates and the standard conventional rail installation must be considered in the design. Timber switch ties should be supplied in Generally the single rail locations have a built- accordance with current recommendations, of up concrete base to match the plated top of the AREMA Manual, Chapter 30. rail height.

As a guideline, timber switch ties for light rail Standards for concrete switch ties should be transit use should be hardwood-preferably developed for various turnout and crossover oak-and generally 180 x 230 millimeters (7 x arrangements in light rail transit track. 9 inches) wide and of a suitable length for the Standardization will allow for more economical turnout installation. The switch tie sets engineering and manufacturing and increased generally conform to AREMA Standard Plan use of concrete switch ties, which are more No. 912. compatible with concrete main line crossties.

When using timber switch ties conforming to As a guideline, concrete switch ties for light AREMA Manual recommendations, the type of rail transit use should be approximately 255 wood, tie size, anti-splitting device, wood millimeters (10 inches) wide at the top of tie, preservative treatment, and machining should 285 millimeters (11.25 inches) wide at the be specified in the procurement contract. base of the tie, and 240 millimeters (9.5 inches) high throughout. The length should be sufficient to suit the turnout geometry and 5.5.3.2 Concrete Switch Ties provide sufficient shoulder length. The Current concrete switch tie designs have fastenings and switch, frog, guardrail, and generally been a joint effort between the turnout plates should be insulated to retard transit authorities and the concrete tie stray current leakage. The concrete switch manufacturers through various technical ties should comply with the appropriate committees. The turnout design provides the specifications for concrete ties, as outlined in geometric layout establishing the tie spacing AREMA Manual, Chapter 30. and the corresponding tie lengths. The spacing for concrete ties must deviate from AREMA standards for timber switch ties due 5.6 TRACK (RAIL) JOINTS to the increased width of the concrete switch tie. Threaded anchor inserts in the tie are a Rail joints are the weakest component in the requirement for standard switch plates, frog track structure, and are unavoidable on any plates and guard rail plates. Areas of the track structure. To connect the short lengths turnout layout where single rail installation is of rolled rail, a rail joint is required. There are various types of rail joints grouped as follows:

5-23 Light Rail Track Design Handbook

1. Welded Joints length to facilitate transport of the rail to the - Pressure electric flash butt weld site. - Thermite (kit) weld 2. Insulated joints Electric flash butt welding is defined as a - Standard non glued bolted insulated forged weld where an electrical charge is joint passed between the rails until the steel is + 4-Hole plastic. The rails are then forced together to + 6-Hole the point at which the steel refuses further - Glued Bolted Insulated joint plastic deformation. + 4-Hole + g-Hole 5.6.1.2 Thermite Weld 3. Bolted Joints Thermite welds are produced with molten - Standard (Non Glued) Bolted Joint steel, cast from a crucible, and poured into the + 4-Hole gap between two rails. The molten steel is + 6-Hole produced with a chemical “exothermic” - Glued Bolted Joint reaction between aluminum and iron oxides. + 4-Hole Additives in the mix create the other + 6-Hole components needed to make the steel. 5.6.1 Welded Joints Thermite welding requires preheating the rail ends in order to create a good bond between Welded rail joints forming continuous welded the old and new steel. It is important that the rail out of many short lengths of the rail has resultant steel plug has the same hardness as been standard in the railroad industry for over the parent rail steel. Manufacturers can 40 years. Elimination of bolted rail joints has produce welds with different hardnesses to improved the track structure and reduced the ensure compatibility. excessive maintenance required at bolted rail joints. Rail welding in North America is CWR rail strings are generally joined or generally accomplished using either the welded together by the thermite weld process. pressure electric flash butt weld or the Portable flash butt welding is an alternative to thermite weld method.. CWR strings allow the the thermite weld process. A flash butt DC current to be carried efficiently through the welding head is transported to the installation rails. site to join the CWR strings. Either weld method is acceptable. 5.6.1.1 Pressure Electric Flash Butt Weld Most rail strings are welded together by the Welding rail eliminates bolted joints and most pressure welding process (flash butt welding) of the associated joint maintenance. in a welding plant operation. The rolled rail However, CWR creates other issues, such as sticks are welded continuously in various structural interaction on bridges which must predetermined rail lengths capable of being be addressed by the designer (refer to transported to the track laying location by Chapter 7). special rail trains. CWR lengths are nominally 439 meters (1440 feet). Rail strings used in light rail transit construction are often half this

5-24 Track ComDonents and Materials

5.62 Insulated and Non-Insulated Joints washers and heavy square nuts. While joint bar standards vary, there are two general Although bolted rail joints are the weakest standards: the 4-hole joint bar and the 6-hole points in the track structure, some bolted joint bar. joints are required. These include insulated rail joints that provide the necessary signal At one time, various railroads had different rail sections for track operations to detect vehicle drilling spacing for the bolt holes; however, locations, tripping signal circuits, clearance over the years, rail drilling spacing was points, and other specific detection networks. standardized, as documented in the AREMA An insulated joint separates the ends of the Manual. The hole spacing recommended in rails to break the signal continuity by use of an AREMA should be followed for jointed rails. insulated end post.

Both non-glued and epoxy glued rail joints 5.6.3 Compromise Joints have become standard for various conditions. Compromise joint bars are required to join two dissimilar rail sections. The compromise joint 5.6.2.1 Non-glued Insulated Joints bars are machined or forged to the shape Standard bolted insulated joints (non-glued) necessary to join the two dissimilar rails. The consist of two coated insulated joint bars, shape allows both rails to align at the top of thimbles and end post bolted similar to a rail and the gauge face of both rails. regular track joint. Standard bolted insulation Compromise joint bars, due to design shape, joints are recommended for use only in bolted are right- and left-hand installations. The jointed track, to provide electrical circuit hand designation is defined by the location of isolation. the larger rail as seen from the center of the track. To overcome the use of bolted compromise joints in main line track, welding 5.6.2.2 Glued Bolted Insulated Joints of the two dissimilar sections is considered Standard glued insulated joints are similar to when the sections are almost identical. non-glued joints, except the joint bars are Thermite weld kits are manufactured for this shaped to fit the rail fishing to allow the bars to situation. A recent design in tee rail-to-girder be glued to the web of the rail. The glued rail joints is the use of a compromise rail joints provide a longitudinal connection at the block, in which the rail sections of each rail rail ends to withstand a rail joint pull-apart in are machined at each end of a block of steel CWR. The glued insulated joints carry the and a common top of rail and gauge line is CWR forces through the adjoining insulated developed in the machining process. The bars, and do not rely on the shear forces on compromise block is then welded into the the joint bolts. track providing a boltless connection.

5.6.2.3 Bolted Joints 5.7 BALLAST AND SUBBALLAST m In light rail transit systems, jointed track is used only for very sharp curves with Ballast, the material used to support the ties restraining rail, maintenance yard facilities, or and rail, is an important component in the secondary non-revenue track. Rail joints track structure. It is the integral part of the consist of two joint bars on each side of the track structure in the roadbed and the quality rail and a series of track bolts with spring lock

5-25 Light Rail Track Design Handbook of the ballast material has a direct relationship - Granite to the track support system. - Traprock - Quartzite: granoblastic metamorphic Light rail transit vehicles often exceed 45,500 rock consisting of quartz and formed kilograms (100,000 pounds) placing increased by recrystallization of sandstone or importance on the track structure, particularly chert by metamorphism. the ballast quality and quantity. Superior - Carbonate: sedimentary rock ballast materials improve the track structure consisting of carbonate materials performance and are an economical method such as limestone and dolomite. of increasing the track strength and the modulus of elasticity Ballast size or gradation is important to match the type of crosstie to be used. The gradation The importance of the quality and type of of the ballast determines the sieve size to be ballast material, along with standard test used in the process of ballast grading. methods for evaluating the ballast material, cannot be overstated. Table 5.3 lists the recommended gradations for light rail transit use with concrete and The quality of the ballast will be determined by timber crossties. the choice of rock and the eventual testing of the rock, followed by observing the No. 5 ballast has been used for yard performance in the track structure. The applications with timber crossties to provide physical and chemical properties of the ballast an easier walking surface. The smaller rock or stone can be determined by many gradation may lead to earlier fouling of the material tests and performance evaluations. ballast and eventual lack of drainage. No. 5 However, the true test of ballast performance ballast is only recommended when the yard is to observe it in the real-life track structure. area is honeycombed with an underlying drainage system and substantial surface drainage channels. Yard personnel, walking 57.1 Ballast Materials within the yard area to service vehicles, will most probably be provided with a paved Ballast should be a hard, dense mineral surface walkway. aggregate with a specific configuration of many fractured faces, angular structure with 57.1 .I Testing Ballast Materials sharp edges, and with the minimum of Ballast material should be tested for quality elongation. through a series of tests undertaken by a certified testing laboratory. The tests should As a guideline, ballast material for light rail include: transit use shall be as follows: 1. ASTM C88: Soundness of Aggregates by l With Concrete Crossties use of Sodium Sulfate (NaSOJ. The - Granite: a plutonic rock with an even sodium sulfate soundness test is texture consisting of feldspar and conducted with the test sample saturated quartz. with a solution of sodium sulfate. This - Traprock: a dark-colored fine grain test will appraise the soundness of the non-granitic hypabyssal or extrusive aggregate. Materials that do not meet rock. applicable test limits can be expected to

l With Timber Crossties

5-26 Track ComDonents and Materials

Table 5.3 Ballast Gradations

Percent Passing

Size No Nominal Size Square 76 (3”) 64 (2%“) 51 (2”) 38 (1%) 25 (1”) 19 (?A”) 13 (‘x”) 10(3/8”) No

Opening 4

Concrete Crossties 24 w-19(2%"-%") 100 90-100 2560 O-IO O-5

3 5%25(2" -1") 100 95-100 35-70 o-15 - o-5

Timber Crossties 4A 51-19 (2" -T) 100 90-100 60-90 IO-35 O-IO o-3

4 38-19 (iv-v) 100 90-100 20-55 o-15 o-5

deteriorate rapidly from weathering and Aggregates. The test for friable materials freezing and thawing. identifies materials that are soft and poorly bonded and results in separate 1. ASTM Cl 17: Tesf Method for Material particles being detached from the mass. Finer than 75 micro-inch (No. 200 Sieve) The test can identify materials that will in Aggregates by Washing (including Dust deteriorate rapidly. Clay in the ballast and Fracture). The concentration of fine material is determined by the same test material below the 200 sieve in the ballast method. Excessive clay can restrict material is determined by this ASTM test. drainage and will promote the growth of Excessive fines are produced in some vegetation in the ballast section. types of crushing and processing bperations and could restrict drainage and 4. ASTM C535: Test Method for foul the ballast section. Resistance to Degradation of Large- Size Coarse Aggregate by Abrasion 2. ASTM C127: Specific Gravity and and Impact in the Los Angeles Absorption. Specific gravity and Machine. The Los Angeles abrasion absorption are measured by this test test is a factor in determining the wear method. Specific gravity in the Imperial characteristics of ballast material. (English) measurement system relates to The larger ballast gradations should weight and in the metric system to be tested in accordance with ASTM density. A higher specific gravity C535, while ASTM C 131 is the wear indicates a heavier material. A stable test for smaller gradations. Excessive ballast material should possess the abrasion of an aggregate will result in density properties shown in Table 5.4 to reduction of particle size, fouling, provide suitable weight and mass to decreased drainage, and loss of provide support and alignment to the track supporting strength of the ballast structure. Absorption measures the ability section. The Los Angeles abrasion of the material to absorb water. test can, however, produce laboratory Excessive absorption can result in rapid test results that are not indicative of deterioration during wetting and drying the field performance of ballast and freezing and thawing cycles. materials.

3. ASTM C142: Test Method for Clay Lumps and Friable Particles in

5-27 LightRailTrackDesign Handbook

Table 5.4 Limiting Values of Testing for Ballast Material

Ballast Material Property Granite Traprock Quartzite Limestone Dolomitic Blast Steel ASTM Limestone Furnace Furnace Test Slag Slag Percent Material 1 .O% 1 .O% 1 .O% 1 .O% 1 0% 1 .O% 1 .O% Cl17 Passing No. 200 Sieve (maximum) Bulk Specific Gravity 2.60 2.60 2.60 2.60 2.65 2.30 2.90 Cl27 (minimum) Absorption Percent 1.0 1.0 1.0 2.0 2.0 5.0 2.0 Cl27 (maximum) Clay Lumps and 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% Cl42 Friable Particles (maximum) Degradation 35% 25% 30% 30% 30% 40% 30% c535 (maximum) Soundness (Sodium 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% C88 Sulfate) 5 Cycles (maximum) Flat and/or Elongated 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% D4791 Particles (maximum)

I. ASTM D4791: Test Method for F/at and resulting in a higher crushing degradation load Elongated Particles. The test for flat and on the ballast particles. The selection of elongated particles uses one of three material for ballasted concrete crosstie track dimension ratios. Track stability is is more restrictive and must be limited to enhanced by eliminating flat or elongated granites and traprock. The selection of particles that exceed 5% of ballast weight. materials for ballast for timber crosstie track Flat or elongated particles are defined as can include all the materials listed in particles that have a width to thickness or Table 5.4. length to width ratio greater than 3. Other test procedures exist for testing Table 5.4 lists the recommended limiting potential ballast materials, such as the values for the ballast material tests. The Petrographic Analysis and the Ballast Box ballast guidelines for timber and concrete Test performed at the University of crosstie applications are based on Massachusetts campus. The services of a experiences with concrete crosstie ballasted qualified certified specialist and testing track. The concrete crosstie load laboratory in the field of geological materials is characteristics are quite different from the recommended to further refine the material timber crosstie loadings on ballasted track. selection process and verify the suitability of a The concrete crosstie is heavier and less quarry for potentially supplying ballast. flexible in absorbing impact loads, thus transmitting a greater load to the ballast

5-28 Track Components and Materials

5.7.2 Subballast Materials l The prevailing track grade of the connecting track is descending toward the main line. The secondary track is used Subballast material can be classified as for the storage of unattended (parked) crushed stone natural or crushed gravel and vehicles. sands or a mixture of these materials.Subballast should be a granular l The secondary track is a storage track for base material placed over the top of the entire track maintenance vehicles only. embankment or roadbed. It is graded and l The connecting track is a railroad compacted to prevent penetration of the industrial siding or at-grade crossing ballast. Subballast material that is impervious track. should divert most of the water falling on the track to the side ditches to prevent saturation Derails are placed at the clearance point of the subgrade. Subballast material that is (centers to be determined) of all railroad impervious requires a layer of sand to be industrial tracks that connect to either an LRT placed between the subballast and the joint use track or to a railroad main track. subgrade to release the capillary water or Derails are also used at other track locations seepage of water below the subballast. A where they would be likely to prevent or layer of non-woven geotextile will accomplish minimize injury to passengers and personnel this as well. and/or damage to equipment.

The subballast layer must be of sufficient Derails are located so as to derail equipment shear strength to support and transfer the load in the direction away from the main track. from the ballast to the subgrade. Derails are available in various designs: sliding block derail, hinged block derail, and 5.8 TRACK DERAILS switch point derail. Derails are generally designed to derail the vehicle in a single Track derails are operating protective devices direction either to the right or left side of the designed to stop (derail) unauthorized track. vehicles from entering a specific track zone. Generally the track zone is the operating The sliding and hinged block derails consist of segment of the main line. The protection is essentially two parts: the steel housing and placed at all strategic track locations where the derailing guide block. The sliding derail is secondary non-main line operating side generally operated with a connecting switch tracks,such as pocket tracks, storage or stand. The hinged derail is operated manually maintenance tracks, and, in some instances, by lifting the derailing block out of the way or yard lead entry tracks connect to the main off the rail head. line. Derails are occasionally used to prevent vehicle or equipment movement onto portions The switch point derail is exactly as of track where vehicles, work crews, or described, a complete switch point (or two equipment are utilizing the designated track points) placed in the track to derail when the space. switch point is open.

Derails should be considered at track As a guideline, the type of derail to be used connections to the main line where: depends upon the site-specific conditions and type of protection to be provided. Main line

5-29 Light Rail Track Design Handbook track exposed to the intrusion of heavily expansion joint is fixed and connected to a loaded cars, multiple car trains, physical track rigid no-movement portion of rail. The other conditions that permit the intruding cars to end consists of the expandable moveable rail gain momentum in advance of the derail, and which is allowed to slide in and out of a tight curvature on the siding track lead to the designed guideway. The expansion joint occasional failure of block derails. The switch simulates a switch point and stock rail type of point derail provides the greatest assurance installation with the expansion rail being the that all wheels of the vehicle will be derailed. curved stock rail.

Expansion joints in the track system present 5.9 RAIL EXPANSION JOINTS problems, from both a track maintenance and an environmental perspective. Due to the Continuously welded rail in long strings does discontinuous running rail surface and the not expand or contract with changes in special trackwork sliding rail joint component, temperature, unless there is a break in the extra maintenance is required to maintain the rail. This type of installation introduces high joint and adjacent rails and to monitor the thermal stress in the rail as the temperature position of the loose rail end to ensure that changes. sufficient space is available for further expansion. The specific design of the In certain structures, the interaction between expansion joint within the discontinuous the CWR and the structure makes it desirable running rail surface introduces additional to limit rail stresses from thermal forces. This noise and vibration. can be accomplished by allowing the rail to move freely within defined zones. A As a guideline, rail expansion joints in combination of low-restraint track fasteners ballasted track or direct fixation track are only and rail expansion joints allows this recommended for long bridges or aerial movement to take place safely. The use of structures. They are also needed at the fixed low-restraint fasteners at structural expansion span approach to a movable bridge. joints allows the structure to “breathe” without overstressing the rails. The rails must also be Exceptions to this guideline include embedded anchored between expansion zones with high- track on an aerial structure, wherein the rail is restraint fasteners, in order to transfer an integral part of the deck structure and the acceleration and braking forces into the design does not allow the structure to move structure. independently from the rail. In this situation, an embedded expansion rail joint at the In high-restraint areas, a conventional direct expansion end of the structure is a definite fixation fastener is utilized, and the structure is requirement. For this reason, the use of designed to accept the thermal stress loads embedded track on an aerial structure is not generated by movement of the structure. The recommended and should be avoided in the expansion or contraction of low-restraint rail initial planning phase when considering the emanates from the high-restraint zone and is types of transit operation modes. bounded on the other end by a rail expansion joint. 5.10 END OF TRACK STOPS Rail expansion joints are designed to allow for a specific length of thermal rail expansion and As important as the tangent and curved track contraction to occur. One end of the is throughout the transit system, the end of

5-30 Track Components and Materials track cannot be overlooked. There is a third parties, and surrounding structures. requirement to protect the passengers and Each agency’s requirements are studied pedestrians (on and off the vehicles), the individually and are site specific operators, the vehicles, the track and surrounding structures. Bumping posts, Assuming the 0.39 deceleration rate is stops, and retarders are used to prevent an selected, the next decision is to determine the accidental overrun vehicle derailment at the type of end stop capable of providing this end of track. The capabilities of the track deceleration rate. stops are limited to halting the vehicle entirely with minimal damage to the vehicle and To absorb 1,998 kJ of kinetic energy at a stopping the vehicle with the minimum of deceleration rate of 0.3 g, the distance impact to the passengers on board. traveled after initial impact would have to be 3.39 meters (11.12 feet) calculated in the The end stop is the point of impact, the following manner location where kinetic energy has to be 2 dissipated. The kinetic energy is determined Distance = Vat+% considering the mass or weight of the vehicle 2 or vehicles (train) and the velocity of the V= velocity of train in m/set vehicle or train. The kinetic energy (KE) can t= time to stop in seconds be calculated using the following formula: d= deceleration rate(-x l 9.81 m/set*) x = deceleration negative rate (selected) MxV* KE=- 4.47 2 t=L d* 0.3 x 9.81 mlsec’ 200,OOOkgx (4.47)* = = 1 52 seconds 2 dot2 = 1,998,09OJ or 1,998kJ From Above Distance = V l t + - 2 where : M = mass of the vehicle or train 44.47*,.52)+ = 200 Tonnes (1 Tonne = 1000 kg) (-o.~y4*w2

V =velocity of vehicle or train = 3.39 meters (ll.l*feet) 4.47 meter/seccnd (10 MPH) The standards for end stops consist of the To safely absorb this amount of energy with following: little damage to the vehicle (train) or injury to 0 Warning Signs passengers or the operator requires an l Fixed Non-Energy Absorbing Devices elaborate end stop with extensive capacity. l Fixed Energy Absorbing Devices

l Friction Energy Absorbing Devices To absorb this amount of energy without causing severe injury to operator or passengers, an acceptable deceleration rate 5.10.1 Warning Signs must be selected. The transit agency should select the rate of deceleration; a rate of 0.3 g Ideal conditions, alert operators, no is an acceptable deceleration. The mechanical vehicle or signal failures, and a establishment of a deceleration rate will well-illuminated warning sign should be consider the likelihood of injury to passengers adequate for the train operator to bring the and operators and damage to the vehicles, vehicle or train to a safe controlled stop.

5-31 Light Rail Track Design Handbook

510.2 Fixed Non-energy Absorbing withstand the forces at impact. As noted Devices above, the displacement distance of the stop at impact governs the magnitude of g force- Most fixed non-energy absorbing end stops the longer the distance the lower the g force (bumping posts) do no more than delineate The anchoring stability of the end stop to the the end of track. The end stops appear sturdy substrata governs the amount of energy that since they are bolted to the rail, however, they can be absorbed by the stroke of the shock have little ability to absorb anything but a very absorber. minimal amount of kinetic energy. impact often results in breaking of the rail, potential derailment, and damage to the vehicle. 5.10.4 Friction (or Sliding) End Stops

A positive fixed non-energy stop will halt Friction type end stops absorb the kinetic heavy vehicles or trains exists at the expense energy of stopping a vehicle or train by sliding of vehicle damage and personnel injury. along the end of track (see Figure 5.10.1). These stops consist of a solid concrete and This sliding action converts the energy to steel barriers generally located at end of friction heat at the rail surface. The friction tracks in the older railroad stations. end stops consist of two types: l Units that are clamped to the rail

l Units that are mounted on skids that slide 5.10.3 Fixed Energy Absorbing Devices with the weight of vehicle upon them, dissipating the energy between the Fixed energy absorbing devices can be either wooden skids and the concrete base of non-resetting or resetting. track structure.

Friction end stops have the highest energy 5.10.3.1 Non-resetting fixed devices absorption of all regularly installed structures. Non-resetting fixed devices (bumping posts) Friction stops can be designed to cover a wide include sand traps, ballast mounds and timber range of energy absorption situations from tie stops. These devices dissipate the kinetic single vehicle to multi-vehicle trains of various energy upon vehicle impact. Sand traps and mass. The combination of resetting shock ballast mounds are effective in stopping large absorbers and friction end stops can allow a loads or trains; however, derailment of the friction end stop to accept light impacts initial vehicle is inevitable. Under severe cold without negotiating the friction end stop while weather conditions the sand and ballast can providing the higher friction end stop freeze, reducing the cushioning effect and protection for ultimate situations. possibly causing additional vehicle damage. The barrier would have to be rebuilt after Transit conditions have potential use for the experiencing an impact. various end of track stops, as follows:

l Main Line End of Track (Ballasted-Direct 5.10.3.2 Resetting Fixed Devices Fixation): friction/sliding end stop with Resetting fixed devices are self-resetting and resetting shock absorber, if track sliding contain an energy-absorbing feature, such as distance available. a hydraulic, elastomeric, or spring shock absorber. Resetting stops are limited in amount of energy the shock absorber can dissipate and the stop structure’s capability to

5-32 Track Components and Materials

6A

GUIDE FRICTION CLAW ELEMENT MOUNTING DEVICE

SECTKH A scam B GAUGE 1435 GUIDE CLAW FRICTION ELEMENT c (4’-8 l/2”) FRONT MEW

Figure 510.1 Friction Element Buffer Stop i8J

5-33 Light Rail Track Design Manual

Main Line End of Track (Embedded): PI The Rail Wheel Interface: Refining Same as above, if conditions warrant, or a profiles to transit applications, Joe resetting track stop anchored to the Kalousek & Eric Mogel, Railway Track substrata. & Structures - Sept 1997. Main Line End of Track (Aerial-Direct Managing Rail Resources, Joe Fixation): friction/sliding end stop with [31 Kalousek & Eric Magel, American resetting shock absorber; track distance Railway Engineering Association, must be provided. Volume 98 Bulletin 760, May 1997. Yard Tracks (Maintenance Tracks): fixed non-energy absorbing devices, bumping [41 Performance of High Strength Rails in posts anchored to the track Track-Curico/Marich/Nisich, Rail Research Papers, Vol. 1 - BHP Steel. Storage Tracks: resetting fixed devices anchored to the track. Fl Development of Improved Rail and Maintenance Shop Tracks: Fixed Wheel Materials - Marich, BHP Resetting Energy Absorbing Device Melbourne Research, Vol. 1. anchored to the structure floor. (Non- movable). PI Riflex comes to America, Modem Railroads, July 1985. 5.11 REFERENCES [71 AREA Manual, Chapter 1, Roadway Ill Reducing Rail costs Through and Ballast, Part 2 Ballast, 1996. Innovative Methods, Norm Harper BC Rail Railway Track and Structures July PI H. J. Skelton, Illustration. 1993.

5-34 Chapter (i-special Trackwork

Table of Contents

6.1 INTRODUCTION 6-1

6.2 DEFINITION OF SPECIAL TRACKWORK 6-1 6.2.1 Basic Special Trackwork Principles 6-2

6.3 LOCATION OF TURNOUTS AND CROSSOVERS 6-7 6.3.1 Horizontal Track Geometry Restrictions 6-9 6.3.1 .I Adjacent Horizontal Track Geometry in the Vicinity of a Switch 6-9 6.3.1.2 Turnouts on Curves 6-9 6.3.1.3 Track Crossings on Curves 6-l 0 6.3.1 4 Superelevation in Special Trackwork 6-l 0 6.3.2 Vertical Track Geometry Restrictions 6-10 6.3.3 Track Design Restrictions on Location of Special Trackwork 6-l 1 6.3.4 Interdisciplinary Restrictions on Location of Special Trackwork 6-l 1 6.3.4.1 Overhead Contact System Interface 6-l 1 6.3.4.2 Train Control/Signaling Interface 6-12 6.3.5 Miscellaneous Restrictions on Location of Special Trackwork 6-12 6.351 Construction Restrictions 6-12 6.3.5.2 Clearance Restrictions 6-12 6.353 High Volume of Diverging Movements 6-12 6.3.5.4 Track Stiffness 6-13 6.3.5.5 Noise and Vibration Issues ’ 6-l 3

6.4 TURNOUT SIZE SELECTION 6-13 6.4.1 Diverging Speed Criteria 6-l 9 6.4.2 Turnout Size Selection Guidelines 6-19 6.4.3 Sharp Frog Angle/Tight Radius Turnouts 6-20 6.4.4 Equilateral Turnouts 6-20 6.45 Curved Frog 6-21 6.4.6 Slip Switches and Lapped Turnouts 6-21 6.4.7 Track Crossings 6-21

6.5 SWITCH DESIGN 6-22 6.51 Conventional Tee Rail Split Switches 6-22 6.5.2 Tangential Geometry Switches 6-22 6.5.3 Uniform and Graduated Risers 6-24 6.5.4 Switches for Embedded Track 6-25 654.1 North American Tongue Switch Designs 6-26 6.5.4.2 European Tongue Switch Designs 6-28 6.5.4.3 Switch Tongue Operation and Control 6-28

6-i Light Rail Track Design Handbook

6.5.4.4 Embedded Switch Drainage 6-29 6.545 Design Guidelines for Embedded Switches 6-29 6.55 Fully Guarded Tee Rail Switch Designs 6-30 6.5.6 Switch Point Detail 6-31

6.6 FROGS 6-32 6.6.1 Frog Design 6-32 6.6.2 Frog Design Modifications 6-33 6.6.3 Flange-Bearing Frogs 6-34 6.6.3.1 Flangeway Depth 6-34 6.6.3.2 Flangeway Ramping 6-34 6.6.3.3 Flange-Bearing Frog Construction 6-35 6.6.3.4 Speed Considerations at Flange-Bearing Frogs 6-35 6.6.3.5 Wheel Flange Interface 6-35 6.6.4 Spring and Movable Point Frogs 6-36 6.6.5 Lift Over (“Jump”) Frogs 6-36 6.6.6 Frog Running Surface Hardness 6-36

6.7 FROG GUARD RAILS 6-36 6.8 WHEEL TREAD CLEARANCE 6-39

6.9 SWITCH TIES 6-39

6.10 RESTRAINING RAIL FOR GUARDED TRACK 6-40

6.11 PRECURVINGISHOP CURVING OF RAIL 6-40 6.11 .l Shop Curving Rail Horizontally 6-40 6.11.2 Shop Curving Rail Vertically for Special Trackwork 6-40 6.12 PROPRIETARY SPECIAL TRACKWORK DESIGNS AND LIMITED SOURCES OF SUPPLY 6-44

6.13 SHOP ASSEMBLY 6-44

6.14 REFERENCES 6-U

List of Figures

Figure 6.2.1 Turnout Layout 63 Figure 6.2.2 Single Crossover Track-Two Turnouts 6-6 Figure 6.2.3 Double Crossover Track-Four Turnouts and Crossing 6-6 Figure 6.2.4 Single-Track and Double-Track Crossings 6-7 Figure 6.2.5 Single Slip Switch 6-8 Figure 6.2.6 Double Switch Lap Turnout-Three Frogs 6-8

Figure 6.2.7 Full Grand Union 6-8 Figure 6.2.8 Half Grand Union 6-9

6-ii Special Trackwork

Figure 6.4.1 Turnout and Crossover Data and Arrangement 6-15

Figure 6.4.2 Number 6 Turnout-Ballasted Timber Ties with 13’ Curved Switch Points 6-16

Figure 6.4.3 Number 8 Turnout-Ballasted Timber Ties with 19’-6” Curved Switch Points 6-l 7

Figure 6.4.4 Number 10 Turnout-Ballasted Timber Ties with 19’-6” Curved Switch Points 6-18

Figure 6.4.5 Typical Curved Frog Turnout 6-23

Figure 6.5.1 2~1-60 Rail Section for Switch Point 6-24

Figure 6.5.2 Tongue Switch and Mate-Non-embedded 149 RE 7A Rail 6-26 Figure 6.5.3 ATEA 75’ Radius Solid Manganese Tongue Switch 6-27

Figure 6.5.4 European Fabricated Steel Double Tongue Switch 6-28

Figure 6.5.5 Embedded Tee Rail Switch-Equilateral Turnout, Steel Cover Plates, Epoxy Filler 6-29

Figure 6.5.6 Fully Guarded House Top Switch 6-30

Figure 6.5.7 Fully Guarded Turnout-l 15 RE Rail Switch with House Top and Double Point Guarding 6-31

Figure 6.5.8 Switch Point and Stock Rail Details 6-32

Figure 6.6.1 Monoblock Frog Details 6-33

Figure 6.6.2 Plan View at Frog Area with 45-mm Flangeway 6-33

Figure 6.6.3 Section at 15-mm Frog Point 6-34 Figure 6.6.4 Section at 15mm Frog Point, Flange Bearing 6-34

Figure 6.6.5 Lift Over Frog Design 637

Figure 6.9.1 No. 8 Turnout-Ballasted Concrete Ties with 5944 Curved Switch 6-42

Figure 6.9.2 No. 10 Turnout-Ballasted Concrete Ties with 5944 Curved Switch 6-43

6-iii CHAPTER 6-SPECIAL TRACKWORK

6.1 INTRODUCTION Light rail systems that are located in urban streets, particularly those that are located in Light rail vehicles, like all steel flange wheeled Central Business Districts with narrow rights- railway equipment, need to be able to transfer of-way, often have sharp curves. This from one track to another or to cross other constraint often requires light rail special tracks. The fabricated track systems needed trackwork to be designed for a specific to support and steer the car at these locations location, with unique parts. are collectively called special trackwork. It is presumed that most readers of this chapter are generally familiar with the layout and use 6.2 DEFINITION OF SPECIAL of common special trackwork terms. Readers TRACKWORK who are new to the topic can find a brief primer on basic concepts and terminology in Special trackwork is customarily defined as Section 6.2.1. “all rails, track structures and fittings, other than plain unguarded track, that is neither Readers with a background in railway track curved nor fabricated before laying.” ~1 Hence, design will note pronounced differences any track can be considered special trackwork between requirements for special trackwork that is built in whole or part using rails that are for light rail transit (LRT) systems and those machined, bent, or otherwise modified from for other types of railways. In general, their as-rolled condition. This includes any designers can expect to find that special additional track components that may take the trackwork design requirements on a light rail place of rails in supporting and guiding the system will be more numerous and more wheels, as well as miscellaneous components complex than those encountered on other that may be attached to the rails to fulfill the types of railways. In addition, sources of functions required. The term is often supply will be more limited than they may be contracted and called simply “specialwork.” used to. In general, the following items are customarily Most turnouts that are available for tangent included in special trackwork: track are standardized for simplified l Turnouts and crossovers, including manufacture and installation, both of original switches, frogs, guard rails, stock rails equipment and replacements for worn and closure rails; rail fastening components. These turnouts are intended for assemblies unique to turnouts; and installation in tangent track, without any miscellaneous components associated vertical curvature. One of the most common with turnouts, including switch rods and design deficiencies is the placement of gauge plates. Crossover tracks, double turnouts within horizontal or vertical curves. crossovers, and single and double slip Construction and maintenance of curved track switches are included in this category. is difficult and expensive. Superimposed l Track crossings that permit one track to special trackwork only exacerbates those cross another at grade. Such crossings problems. It is recommended that can be designed as a rigid block or can standardized trackwork be used on flat include movable center points. By tangent track whenever possible.

6-1 Light Rail Track Design Handbook

definition, slip switches include a track movable rails that flex back and forth and crossing. intercept the wheel flanges to direct them to the appropriate track. In its usual form, l Restraining rail, either bolted to a parallel a switch point rail consists of a plain rail running rail or supported independent of that has been machined and bent into an the running rail. elongated wedge shape that is sharp on l Shop curved rail of any type, including one end. This pointed end is known as rails that are precurved in the horizontal the “point of switch.” The opposite end is plane, the vertical orientation, or both. known as the “heel of switch.” Switches come in various lengths and can be either Turnouts, crossovers, and track crossings will straight or curved. In general, the longer be addressed directly in this chapter. the switch point rail, the more gradual the Information on restraining rail and shop angle of divergence from the main track curved rail can be found in Chapters 4 and 5. and the faster the rail vehicle can travel through it. The switch point rails, together with the stock rails (described below) and 6.2.1 Basic Special Trackwork Principles associated fastenings and mechanisms, The most common form of special trackwork are collectively called the switch. is the turnout, which permits two tracks to l The stock rails are the rails which the merge with each other. A simplified layout of switch point rails lay against when in the a turnout is illustrated in Figure 6.2.1. The closed position. The stock rails are turnout itself consists of several fundamental otherwise ordinary rails that are elements: machined, drilled and bent as required to l The switch point rails (often called either suit the design of the switch point rails. the switch points or the point rails) are the

POINT OF SWlTCH THEORETICAL POINT OF FROG I L THEORETICAL LEAD DISTANCE CURVED SWlTCH POINT RAIL -7 LS \ /- HEEL OF SIMIC)-CLOSURE RAILS

STRAIGHT S POINT RAIL ______-____-____ S’MTCH THROWN MECHANISM-

CURVED STOCK RAI RUNNING RAILS INTERMEDIATE RAILS

Figure 6.2.1 Turnout Layout

6-2 Special Trackwork

l The frog is an assembly placed where straight or main track closure rail is known one rail of a track must cross a rail of as the turnout lead distance. another. Openings called flangeways must be provided through the top surface Additional components that are common on a of the frog so that the flanges on the turnout include: vehicle wheel can pass through. The . Guard Rails are supplemental rails, intersection of the gauge lines of the two placed inboard of the main running rails intersecting rails is known as the that support the railcar wheels. They theoretical point of frog. The theoretical define a narrow flangeway to steer and point of frog would be a razor sharp tip control the path of the flanged wheel. that would quickly wear and fracture in Guard rails are positioned opposite the service. Therefore, the intersecting rails frogs so as to ensure that the wheel are cut back a short distance to a location flange does not strike the point of frog or known as the actual point of frog, where take the “wrong” flangeway. the metal will have enough rigidity to l Heel Blocks are splicing units placed at withstand the effects of service wear. The the heel of the switch that provide a end of the frog closest to the switch rails location for the switch to pivot as well as is known as the toe of frog; the opposite a fixed connection between the end is known as the “heel of frog.” intersecting rails. Typically, both rails passing through a frog are straight, although it is possible for one l A switch operating device. Switch rails or both rails to be curved. Straight frogs can move from one orientation to another are commonly designated by a number by either a hand-operated switch stand or that indicates the ratio of divergence of a mechanically or electro-mechanically one rail to the other. In a Number IO frog, operated switch machine. In both cases, the two rails will diverge at a ratio of one the switch machines are positioned at the unit laterally for every ten units of frog beginning of the turnout opposite the tips length. In a Number 8 frog, the of the switch rails. divergence ratio will be one to eight, etc. Various arrangements of individual turnouts The higher the frog number, the more create various track layouts, thereby acute the angle of divergence and the permitting alternative train operation faster the rail vehicle will be able to travel scenarios: through it. A single crossover (Figure 6.22) consists l The closure rails are the straight or curved of two turnouts positioned in two tracks rails that are positioned in between the that allow the vehicle to go from one track switch and the frog. The length and to another. The two tracks are usually, radius of the closure rails are dictated by but not always, parallel, and the turnouts the angles of the switch and the frog. are usually identical. Combinations of short switches with large A double crossover (Figure 6.2.3) angles and similar frogs will result in a consists of two crossovers of opposite sharp radius curve through the closure rail hand orientation superimposed upon each areas that will limit vehicle speed. The other. In addition to the four turnouts distance between the point of switch and involved, a track crossing (see below) is the point of the frog measured along the needed between the two main tracks. A double crossover is used only when it is

6-3 Light Rail Track Design Handbook

necessary to be able to switch from one then the four frogs will be identical. If the track to another in either direction and angle is not 90°, then the crossing will be there is insufficient space to install two elongated along one diagonal axis called the independent single crossovers of opposite “long diagonal” and the “end frogs” will be hand orientation. different from the “center frogs.”

Another common type of special trackwork is If the angle of the intersecting tracks is less the track crossing. As the name implies, this than that in a Number 6 frog (9’ 31’ 38”) it is specialwork permits two tracks to cross each usually necessary to use a movable point other. Track crossings are often called crossing. Movable point crossings crossing diamonds or simply diamoncfs, due to incorporate movable rails in the two frogs the plan view shape that they have when closest to the center of the crossing. looking diagonally across the tracks (see Depending on the position of these movable Figure 6.2.4). The intersecting angle rails, a flangeway will be provided for one between the two tracks can be 90” or less, but track or the other, but not both simultaneously. crossings under approximately 15” are rarely Movable point frogs are needed on flat-angle encountered. In its simplest form, a track crossings since it is otherwise impossible to crossing is simply four frogs arranged in a ensure that the wheel flange will follow the square or parallelogram. The tracks through a correct flangeway path through the center crossing can be either straight or curved. frogs of the crossing diamond. The movable Straight tracks are preferred since it makes rails in a movable point crossing are called the unit symmetrical, thereby simplifying knuckle rails and are usually operated by the design, fabrication and maintenance. If the same type of equipment used to move crossing angle between straight tracks is 90”, switches.

TURNOUT B

TURNOUT A

Figure 6.2.2 Single Crossover-Two Turnouts r CROSSING (DIAMOND) E TURNOUT C TURNOUT B

TURNOUT D TURNOUT A

Figure 6.2.3 Double Crossover-Four Turnouts and Crossing

6-4 Special Trackwork

SINGLE TRACK DOUBLE TRACK CROSSING (DIAMOND) CROSSING (DIAMONDS)

Figure 62.4 Single-Track and Double-Track Crossings

If it is necessary to be able to switch from one have been used on some modern light rail track to another at a flat-angle crossing and systems when space was extremely limited. space constraints make it impossible to provide separate turnouts outside of the limits Lap turnouts can be used to achieve a more of the diamond, a slip swifch can be installed. compact track layout in constrained locations. A slip switch superimposes two switches and In a lap turnout, as seen in Figure 6.2.6, the curved closure rails on top of an elongated switch rails for a second turnout will be placed track crossing as shown in Figure 6.2.5. A between the switch and the frog of the initial double slip switch provides that same routing turnout. This introduces a third frog where a capability along both sides of a track crossing closure rail of the first turnout crosses a as shown in phantom line on the figure. closure rail of the second.

Combinations of turnouts and track crossings Lap turnouts, movable point crossings, slip are used to produce route junctions. switches, and double slip switches are all very Junctions can range from very simple to very costly to design, fabricate, install, and complex as seen in Figures 6.2.6 to 6.2.8. maintain, A more economical track system is The most complex junctions can occur in the achieved when the special trackwork consists central business districts of urban areas when only of turnouts and simple track crossings. two double-track routes cross one another. Figure 6.2.7 illustrates a “Grand Union,” an 6.3 LOCATION OF TURNOUTS AND extremely complex arrangement that permits CROSSOVERS a vehicle entering a junction from any direction to exit it on any of the other three The ideal location for turnouts, crossings and legs. A junction that resembles a “T crossovers is in flat and straight sections of intersection would require a “half grand union” track. If special trackwork is installed in track (see Figure 6.2.8) to provide the same routing with horizontal curves, superelevation, or flexibility. Such complex junction layouts were common on traditional streetcar systems and

6-5 Light Rail Track Design Handbook

SINGLE SLIP

MOVABLE CENTER END SWITCH POINTS POINTS

__.______-.------_.__-.--- ______------____.______-----0----______.___.-___ ._.-.-.-.-.-.-, __.-.-.-_-.-.-_ --.-.-.-.-. _____.__e -.-----

(PHANTOM INCLUDED)

Figure 6.2.5 Single Slip Switch

TURNOUT A

Figure 6.2.6 Double Switch Lap Turnout-Three Frogs

Figure 6.2.7 Full Grand Union Special Trackwork

Figure 6.2.8 Half Grand Union

vertical curves, the ability of the trackwork to located in advance of the switch, the turnout perform in a satisfactory manner is should be positioned with the point of switch compromised. Trackwork designers should beyond the limits of the restraining rail. work closely with their counterparts who are defining transit operations requirements and Horizontal curves that are located beyond the setting route geometry, so that turnouts and heel of the frog should generally be positioned crossovers are not placed in difficult locations beyond the last long tie of the switch set. and the overall requirements for special Horizontal curves can be placed on the long trackwork are minimized. timbers within 0.5 meters (20 inches) of the heel joint of the frog. However, special switch tie or track concrete layout will be required. If 6.3.1 Horizontal Track Geometry the curve is guarded, and the restraining rail is Restrictions on the frog side of the alignment, the curve should be located so that the restraining rail terminates prior to the heel joint of the frog. If 6.3.1 .I Adjacent Horizontal Track this is not possible, the restraining rail should Geometry in the Vicinity of a be run into the frog and be continuous with the Switch frog wing rail to provide continuous guarding Switch point rails direct vehicle wheelsets in action. an abrupt change of direction, making it highly desirable that wheels be rolling smoothly as they approach the switch. To best ensure that 6.3.1.2 Turnouts on Curves wheel flanges can be smoothly intercepted by Turnouts can be constructed within curved switch point rails, tangent track should be track in difficult alignment conditions. placed immediately in front of the switch. The Railroad operating personnel will state, absolute minimum length of tangent track in however, that turnouts on curves provide a advance of the point of the switch should be poor quality ride. Track maintenance no less than 3 meters (10 feet) and much personnel contend that the curved turnouts greater distances -10 to 15 meters (33 to 50 consume a disproportionate amount of their feet)-are desirable. If a guarded curve is maintenance budgets. Therefore, turnouts

6-7 Light Rail Track Design Handbook

and crossovers should only be located in the main track is located on a curve. The horizontally tangent track, except under the correct amount of superelevation for one hand most unusual and constrained conditions. of the turnout will be incorrect for the other This will ensure that the track geometry and an excessive underbalance or through the special trackwork unit will be as overbalance could result. A particularly uniform as possible, thereby improving wheel dangerous situation occurs with a turnout to tracking and extending the life of both the the outside of the curve, where a severe special trackwork unit and the vehicle that negative superelevation situation could be operates over it. created on the diverging track. In ballasted track, normal deterioration of the track surface A turnout on a curve must be custom could quickly result in the diverging track designed. The design objective should be to becoming operationally unsafe. provide an alignment that is as smooth and uniform as possible. Designers should note When a superelevated curve is required that this turnout geometry will differ beyond the frog of a turnout, the appreciably from ordinary turnouts located superelevation should begin beyond the last along tangent track. Parameters such as long tie of the switch set in a ballasted track turnout lead distance and closure rail offsets turnout. In a direct fixation track turnout, will be distinctly different from those of a superelevation can physically begin earlier, standard lateral turnout with the same frog although typically not within 500 millimeters number. Several good books exist on the (20 inches) of the heel joint of the frog. subject, including Allen’s Railroad Curves & Earthwork. 6.3.2 Vertical Track Geometry Restrictions

6.3.1.3 Track Crossings on Curves Turnouts, crossovers and track crossings Either one or both tracks of a crossing should be located on tangent profile grades (diamond) may be located in horizontally whenever possible. This is because the curved track if required by the selected critical portions of a turnout-the switch and alignment. This is often a requirement at a the frog-are too rigid to conform to a vertical route junction. At such locations, it is typically curve, which will cause the switch points to allowable to have one or both sides of the bind. The area between the switch and the track crossing on a curved alignment. In frog can theoretically be curved vertically, but general, however, curved crossings should be this practice is discouraged since ordinary avoided because they are typically one-of-a- construction tolerances make it difficult to kind units and hence very expensive to confine the curvature to the closure rail area. procure, maintain, and ultimately replace. In Vertical track curvature outside of the turnout addition, the crossing must be flat, without area should also be restricted; the absolute superelevation. This has a detrimental impact minimum distance from the switch and frog on the operation of trains over curved track. will depend on the type of track structure. In the case of ballasted track, for example, it is not practical to introduce any vertical 6.3.1.4 Superelevation in Special curvature until after the last long tie of the Trackwork switch set. Superelevation should not be used within any turnout, crossover, or track crossing, even if

6-8 Special Trackwork

In difficult alignment conditions, vertical required, the track designer should either curvature at or near a turnout location may be detail the tie layout or require the track necessary. If it is not possible to avoid a fabricator to provide a submittal of the vertical curve within a turnout, every effort proposed layout In the latter case, the track should be made to avoid non-standard track designers should be certain ahead of time that components, such as switch point rails or a workable tie layout is possible. It is frogs, that must be shop-fabricated with a absolutely essential that switch ties supporting vertical curve. Generally, special designs can switches are perpendicular to the straight be avoided if the middle ordinate of the track. This is a problem when switches are vertical curve in the length of any switch point placed immediately beyond a frog on the rail or frog is less than 1 millimeter (0.040 curved side of a turnout. inches). Special trackwork in embedded track can be particularly complicated and should be 6.3.3 Track Design Restrictions on minimized. Route intersections within street Location of Special Trackwork intersections can be phenomenally complex and require intricate plans and pre-delivery While special trackwork can be required in assembly on the factory floor. When special ballasted, direct fixation, and embedded track trackwork must be located in embedded track, sections, turnouts are most economical to it should be positioned so that pedestrians are procure, construct and maintain in ballasted not exposed to switch point rails and switch track. Alignment design should minimize operating mechanisms and frogs are not special trackwork requirements in direct positioned in pedestrian paths. Reliable fixation and embedded track environments, signal systems and switch operating because these elements are expensive to mechanisms for embedded track turnouts are procure, construct and maintain. Exceptions also difficult to procure and maintain as noted can be made, for example, when route in Sections 6.3.4.1 and 6.5.4.3. geometry forces a particularly complex special trackwork layout with multiple turnouts and track crossings. It is often particularly difficult 6.3.4 Interdisciplinary Restrictions on to design a satisfactory switch tie layout under Location of Special Trackwork such complex layouts and even more difficult to renew defective switch ties during Special trackwork should be located so as to subsequent maintenance cycles. In such minimize requirements for special Overhead special circumstances, the use of direct Contact System (OCS) and train control/ fixation special trackwork track may be signaling system structures and devices. preferable to a ballasted configuration.

Yard trackage, which is usually ballasted, 6.3.4.1 Overhead Contact System Interface often requires that successive turnouts be The installation of catenaty is complicated by constructed close to each other. The track the presence of turnouts and crossovers. designer should verify that turnouts are Additional wires, pull off poles, and insulating sufficiently spaced to permit standard switch sections are needed to provide a smooth ride ties to be installed and to permit maintenance for the pantograph. Electrically isolating the personnel to renew individual switch ties. opposite bound main tracks is particularly When special switch tie arrangements are difficult at double crossovers if the adjacent tracks are close together. These conditions

6-9 Light Rail Track Design Handbook should be discussed with the catenary special trackwork unit, including guarded designer to ensure that the catenary can be curved track. This will ensure that one economically constructed. contractor will be responsible for the uniformity of the horizontal and vertical track alignment through the special trackwork unit. 6.3.4.2 Train Control/Signaling Interface Switch machines that comply with North American signal system standards are difficult 6.3.5.2 Clearance Restrictions to obtain for fully guarded open track turnouts Special trackwork should be located with and are not available for tongue switch adequate clearances from trackside embedded track turnouts. The principal obstructions. For example, unless the problem is that proper switch locking is vehicles are equipped with automatic bridge required for automatic routing at design track plates for pedestrian access, tangent track is speed. Many rail transit systems require train required alongside platforms to meet the tight operators to stop, verify switch position, and tolerances required by Americans with then proceed at any turnout that is not Disabilities Act (ADA). If a station platform is equipped with a locking switch device. This located ahead of a point of switch, the causes delays and, for this reason alone, minimum tangent distance between the end of designers are strongly encouraged to avoid the platform and the point of switch should be these types of turnouts. In addition, the track equal to the truck center length of the LRV circuits that are needed to determine track plus the car body end overhang. Refer to occupancy are more difficult to install and Chapter 3 for additional guidance on special maintain in embedded track since the trackwork clearances. embedment material will restrict access to key areas where unintended shunts can cause signals to drop. Accordingly, embedded track 6.3.5.3 High Volume of Diverging switches should be avoided to the maximum Movements degree possible. Track designers should be very cautious whenever the route geometry results in a Insulated rail joints in special trackwork can preponderance of the traffic passing through be especially complicated, particularly if they the curved side of a turnout. High traffic must be located in guarded track or in and volumes through the curved side of a switch around crossing diamonds. The trackwork will result in accelerated wear of the switch designer should coordinate with the signal point and the adjoining stock rail. Whenever designers to verify that a workable insulated possible, turnouts at junctions should be joint layout is possible. In many cases, a oriented to guide the branch with the more workable track plan cannot be properly frequent or heavier traffic over the straight part signaled and the route geometry must be of the switch.. If the traffic is (or will redesigned. eventually be) approximately equal, consideration should be given to an equilateral turnout design as discussed in 6.3.5 Miscellaneous Restrictions on Section 6.4.4. This will reduce maintenance Location of Special Trackwork of the switch points.

6.3.5.1 Construction Restrictions Turnouts at the end of a double-track segment The construction limits of any trackwork should be oriented to guide the facing point contracts should not be located within any

6-10 Special Trackwork movement over the straight side of the hospitals, concert halls, and other sensitive turnout. If this results in an unsatisfactory noise and vibration receptors. If special operating speed for the trailing movement, the trackwork must be located in such areas, designer should consider using either a investigation of possible noise and vibration equilateral turnout design or a turnout with a mitigation measures should be undertaken. flatter divergence angle and curve than might Such investigations should include the ordinarily be provided. Ordinarily, facing point ramifications of repositioning the special diverging movements should be limited to trackwork away from the area of concern. situations where the single-track section is temporary and the double-track section is to be extended. 6.4 TURNOUT SIZE SELECTION

Track designers have a wide array of standard 6.3.5.4 Track Stiffness turnout geometric configurations to choose Ballasted turnouts, crossovers, and crossing from when considering route alignment. While diamonds have a considerably higher track not all transit systems can use the same menu modulus than ordinary ballasted track due to of turnouts and crossovers, the designer can their mass and the frequent interconnections usually achieve an acceptable route alignment between rails. Nevertheless, they are still without resorting to special designs. Using more resilient than either direct fixation or standard, off-the-shelf, and service-proven embedded track layouts. Because of this materials will reduce the probability that future differential, ballasted track turnouts located maintenance will be complicated by the need close to interfaces with stiffer track structures to purchase expensive one-of-a-kind products. will ride poorly and require more frequent This also avoids the situation where essential surfacing, particularly if vehicle speeds are replacement parts may not be available when relatively high. To avoid these circumstances, needed. Figures 6.4.1 to 6.4.4 show main tracks where vehicles operate at speeds standard turnouts and crossovers. Situations greater than 100 kph (62 mph) should not will arise when a non-standard turnout design have specialwork units located within 75 is needed. In such cases, justification should meters (233 feet) of a transition between be documented. This validation should ballasted track and a more rigid track include: the reasons why a particular turnout structure. As a guideline, this distance can be size is required; what alternatives were reduced in areas where modest operating investigated; why standard options were speeds are contemplated. A minimum travel unacceptable; and the ramifications of using a time of 3 to 5 seconds between the special smaller turnout, including its affect on vehicle trackwork unit and a more rigid structure is operations, signaling systems, and OCS recommended. Design exceptions will require systems. Consideratibn should also be given stiffening of the ballasted track or retrofitting of to procurement of a spare assembly along the adjoining track to be more resilient. with the original unit, so as to save the design and tooling costs that would be incurred to purchase the unit at a later date. This 6.3.5.5 Noise and Vibration Issues provides an immediate replacement part if one Even well-designed special trackwork can be is needed. a source of noise and vibration. As such, special trackwork installations are undesirable in the vicinity of residential buildings, schools,

6-l 1 T GEOMETRIC SCHEMATIC - SINGLE OR DOUBLE CROSSOVER w TO Y1‘

CROSSOVER DATA TABLE - BALLASTED OR DIRECT FIXATION TRACK I fUUL lAYOUT DIAGRAM ----- ICKY.%” . r-0’

NO. 6 BALLASTED TURNOm BILL OF MATERIAL I BILL OF MATERIAL TIMBER SWTCH TIES 180 x 230 U’B-,

I.

4.

5 6.

7.

1.

9. Light Rail Track Design Handbook

6.4.1 Diverging Speed Criteria half of the desired speed in miles per hour). Handbook users should keep in mind that Turnout size (by either frog number or radius) operating speed objectives vary among light should be selected to provide the highest rail operations, as well as from one portion of diverging movement speed possible that is an LRT system to another. consistent with adjoining track geometry. A high speed turnout is not needed if the High speed on one system may be low speed adjoining track geometry restricts operating on another. Accordingly, the speed. Similarly, a sharp turnout should recommendations that follow should be generally not be used in a track segment that modified to suit on site-specific requirements. has no restrictions on operating speed. Limits l Route junctions between primary tracks on operating speeds through the curved side should use No. 15 turnouts. A larger of turnouts are typically based on the turnout number turnout should be employed if the geometry and the maximum unbalanced route geometry in proximity to the turnout superelevation criteria adopted for the system. does not restrict higher speed operations. In many cases, the closure rail zone will When sufficient space is not available for impose a greater restriction on operating a No. 15 turnout, or if there are nearby speed than the switch, particularly if tangential speed restrictions-such as station stops switch geometry is not used. There are or roadway crossings-a sharper turnout, typically no operating speed restrictions on such as a No. IO, may be considered. the straight through side of a turnout. l Connections between primary main line tracks and slower speed yard and While larger number/radius turnouts will secondary tracks, including center pocket generally have higher initial costs, they will tracks, should typically use No. 10 incur less wear and tear and can be more turnouts. When design space for a No. 10 economical in the long run. There are turnout is not available, a No. 8 turnout reasonable limits to this rule of course-it may be sufficient. makes little sense, for example, to install a

Number 20 turnout that will never be traversed l Seldom-used crossover tracks that are at more than 40 km/hr (25 mph). In general, provided for emergency and maintenance trackwork designers will find that Number 8, use only should use No. 8 turnouts. 10 and possibly Number 15 turnouts will When sufficient design space for a No. 8 typically be the most economical choices for turnout is not available, a No. 6 turnout main line track on virtually any light rail may be considered. system. l Turnouts within maintenance facilities and storage yards should use either No. 8 or 6.4.2 Turnout Size Selection Guidelines No. 6 turnouts. Main line connections to the maintenance facility and storage yard The following criteria recommend various should use Number 10 turnouts turnout sizes for various track applications. l Turnouts that are located in embedded The typical conditions and operating speed track are often in odd geometric layouts objectives are based on a rule of thumb which and thus must be sized in accordance states that the frog number should be about with the use and function of the turnout. one-third of the desired diverging movement Alternatives to the use of an embedded operating speed in kilometers per hour (one- turnout should always be investigated

6-16 Special Trackwork

6.4.3 Sharp Frog Angle/Tight Radius “cracking the whip,” is a distressingly Turnouts common operating practice on many systems where the LRV operator may Many light rail systems, particularly older docilely enter the turnout at the posted street railway operations, use turnouts that are speed limit but then accelerate. The result sharper than those suggested above. Frogs is that the rear truck enters the curve and as low as number 5 and 4 are not uncommon. travels through the turnout at a much Many difficult alignment conditions may be higher speed than intended. High rail and resolved using turnouts that are curved wheel wear will result and derailments of through both the switch and the frog. Some rear trucks and trucks on rear cars of transit agencies have curved frog turnouts multiple car trains are not uncommon. with radii as sharp as 15 meters. In virtually all cases, these sharp turnouts were required l Maintenance expenses will be higher. due to unique site conditions and the Even if vehicle speed is controlled, either particular requirements of the system. While through the signal system or by strict enforcement of operating rules, sharp such sharp turnouts are not recommended for turnouts will incur more wear than flatter general application, there is nothing inherently turnouts. If the associated maintenance wrong with their use provided that they meet the requirements of the transit operation and expense is preferable to the additional the transit agency understands and accepts first cost of a right-of-way that would permit the use of flatter turnouts, then the limitations that sharp turnouts impose. sharp turnouts may be a prudent choice. Some of the restrictions imposed by sharp turnouts are: If, on the other hand, a life-cycle cost analysis shows that procuring additional l Vehicle fleet must be designed to be able right-of-way that allows flatter turnouts will to negotiate them. This may reduce the number of candidate light rail vehicles that reduce the overall expense, then that course should be pursued. can be considered for the system. l Operations will be slower. Operating personnel must be made aware of the 6.4.4 Equilateral Turnouts speed restrictions that the sharp turnouts impose and systems must be in place to Equilateral turnouts split the frog angle in half limit speeds to the allowable limit. This between both sides of the turnout, thereby can be a significant problem on a system, producing two lateral diverging routes. Both or portion of a system, where vehicle sides of the turnout are curved. Equilateral speed is entirely under the operator’s turnouts are occasionally suggested for the control. Most vehicle storage yard tracks, end of double-track locations and for locations which are the most likely location for where a turnout must be installed on a curve. sharp turnouts, do not have signal The track designer should consider the systems that provide speed control. This following characteristics. makes it highly probable that sharp l A perfectly symmetrical equilateral turnout turnouts will be negotiated at higher-than- will evenly divide not only the frog angle design speeds, leading to excessive wear, but also the switch angle. The division of more frequent maintenance, and an the switch angle will require a custom set increased risk of derailments. A common of stock rails, each with half the normal problem in this regard, known as stock rail bend. This is the preferred arrangement when both hands are used in

6-l 7 Light Rail Track Design Handbook

the facing point direction, such as the The use of an equilateral turnout on a curve diverging turnout at a route junction. usually does not provide satisfactory ride quality and is, therefore, not recommended. l An alternative to customized stock rails is to configure the switch in an ordinary lateral turnout, thereby giving one 6.4.5 Curved Frog movement the straight route through the switch and the other movement the lateral A straight frog is standard for most turnouts, route. The frog does not need to be for both normal and diverging train oriented symmetrically and the optimum movements. This creates a “broken back alignment for each route may be achieved curve” alignment for the diverging movement by rotating it by an amount equal to the that can provide a disagreeable ride quality, switch angle. This switch and frog particularly in lower numbered (sharp radius) orientation would be a preferred turnouts. If a system will have a large number arrangement for an end of double-track of lower numbered turnouts, such as for yard location where extension of the double tracks, and there are approximately equal track is not expected to occur in the near quantities of right-hand and left-hand turnouts, future. it may be beneficial to consider curved frogs that allow a uniform turnout curve. A superior l If the switch angle is to be split equally, curved switch points will need to be yard layout may be possible using curved frog specially designed and fabricated since turnouts, as shown in Figure 6.4.5, without each point must not only have a concave incurring excessive costs. curve on its gauge face, but also a 6.4.6 Slip Switches and Lapped Turnouts concave vertical surface on its back face. Such points are not off-the-shelf items Slip switches and lapped turnouts are often and the transit system will have to procure suggested as a means of concentrating a spare points for future replacement. large number of train movements into a Straight switch points on the other hand, constrained site. Such components are very such as the AREMA 5029-millimeter expensive to procure and maintain and are (16.5foot) design, can be obtained off- seldom justifiable in a life-cycle cost analysis. the-shelf although they still must be They should only be considered in cases matched to custom stock rails. If the where extremely restrictive rights-of-way switch is oriented as in an ordinary lateral leave no other design options. turnout, standard switch point rails can be used. 6.4.7 Track Crossings l The lead distance of the equilateral turnout need not have any direct Whenever possible, track crossings correlation to the customary lead for a (diamonds) should have angles that do not lateral turnout. The closure curves require movable point design. Movable point between the switch and frog can be crossings have high initial costs and require configured to any geometry that is more frequent maintenance and, therefore, suitable to meet the speed objectives of should be used only as a last resort. To the turnout. provide for the use of rigid crossings only, the route geometry engineer will be required to configure the tracks so that crossing tracks

6-18 Special Trackwork

intersect at an angle at least equal to that of a 6.5.1 Conventional Tee Rail Split Switches No. 6 frog (9’31’38”). Some systems have successfully used crossings with flatter Most rail transit systems in North America use angles, but they are not recommended switch point rails that are identical or similar to because of the increased potential of designs used by North American freight derailment at the unguarded center frog railroads. Such switches, known as split points. If a flat-angle movable point crossing switches, generally conform to designs appears to be required at a location such as a promulgated by the American Railway route junction, a detailed investigation of Engineering & Maintenance-of-Way alternatives should be conducted before Association (AREMA). Split switches are trackwork final design commences. These produced by planing and bending a piece of alternatives could include spreading track standard tee rail to a knife edge point on one centers to permit one track to cross the other end. The sharpened point then lays up at a sharper angle or substituting a crossover against a section of standard rail and diverts track in advance of the junction for the the flanged wheel from one track to another. crossing diamond. Simulations may be Split switches are relatively inexpensive to required to determine if the operational produce and provide satisfactory service scenarios resulting from an alternative track under most operating scenarios. plan are acceptable. The maintenance requirements of the baseline movable point Split switch point rails can be either straight or crossing should be included in the analysis, curved. Straight switch point rails can be including the operational restrictions that may used universally within a turnout, but are be enforced during such maintenance. almost always an inferior choice for a diverging route. As a guideline, curved switch point rails are recommended for all transit 6.5 SWITCH DESIGN designs to provide a much smoother transition through a turnout. The switch area is the most critical portion of any turnout. Most turnout maintenance is switch related, requiring both trackwork and 6.5.2 Tangential Geometry Switches signal maintenance. Most derailments occur at and are caused by unmaintained or Conventional North American curved switch neglected switches. As such, they are one of points still require the wheels to make a the most important locations to examine for somewhat abrupt change of direction near the the interaction between the wheel and the rail. point of switch. The actual angle at the point As a guideline, the following sections will rail will vary depending on the length from the discuss the various types of switch designs switch point to the heel of switch, but it that can be used on light rail systems, and will typically ranges between 1 and 3 degrees. provide guidelines to follow in selecting what Depending on the speed of the transit vehicle, design to implement. this change in direction can produce an uncomfortable ride. In addition, a switch point used for diverging movement will frequently incur a much greater amount of wear due to the abrasive impact associated with redirecting the vehicle wheels.

6-19 Light Rail Track Design Handbook

Figure 6.4.5 Typical Curved Frog Turnout

6-20 Special Trackwork

To improve switch performance and service the diverging side of a turnout. A few North life, European track designers developed American manufacturers are now producing “tangential geometry” switches. In a proprietary tangential geometry switch point tangential geometry switch, the switch point rail designs. These may be appropriate for that deflects the diverging movement is not some applications on a light rail transit system only curved but also oriented so that the curve but are not generally warranted. is tangential to the main track The wheel is not required to make an abrupt change of direction; instead it encounters a flatter 6.5.3 Uniform and Graduated Risers circular curve that gradually redirects the Split switch designs, whether using wheel. The lead distance for a tangential conventional AREMA geometry or tangential geometry turnout is typically much longer than alignment, typically elevate the top of the for an ordinary turnout with the same frog switch point rail approximately 6 millimeters number (l/4 inch) above the top of the stock rail. This European tangential geometry switch point prevents false flanges on worn wheels from rails are usually manufactured from special contacting the top of the stock rail and rolled rail sections that are not symmetrical possibly lifting the wheel off the top of the about their vertical axes. These asymmetrical switch rail. To achieve this elevation, special switch point rail sections are also usually riser switch plates are incorporated beneath shorter in height than switch stock rails, the switch rails. This additional elevation can thereby permitting the switch slide plate to be eliminated once the switch rail has anchor the stock rail to resist rollover. The diverged sufficiently from the stock rail such difference in rail configuration and height that false flanges on wheels are no longer a usually requires a shop-forged connection concern. The two design details that achieve between the asymmetrical switch point rail this transition are called uniform risers and and the common tee rail used in the turnout graduated risers. closure curve. The Zu I-60 section (Figure A uniform riser switch maintains the additional 6.5.1) is a typical asymmetrical point rail 6 millimeters of height through the heel block section. Nearly all tangential design switches of the switch and then ramps it out over a also employ a floating.heel design. . distance of 4 to 5 switch ties beyond the heel. At each of these ties, a special rail fastening plate must be installed that provides progressively less riser elevation until the base of the closure rails beyond the switch are in the same plane as the stock rails. Such turnout plates must be specially fabricated and each will fit in only one location within the turnout.

Figure 6.5.1 201-60 Rail Section for Switch A graduated riser switch maintains the Point additional elevation only as long as absolutely necessary and then ramps it out prior to the Tangential geometry turnouts should be heel block of the switch. Two vertical bends considered whenever high speeds or a large are required in the switch rail-one concave number of movements must be made through

6-21 Light Rail Track Design Handbook and the next convex-so that the 6 millimeters impractical. The switch point “throw,” the of riser elevation is eliminated in increments of distance the switch point rail needs to move 2 or 3 millimeters. Special plates are not from one orientation to another, results in an required beyond the switch heel block; most unacceptably large void in the pavement timber tie ballasted track turnouts with surface. This void is dangerous to roadway graduated risers use hook-twin tie plates in vehicles and pedestrians. Voids also tend to that area. collect debris and dirt, which impair switch operations. To deal with these difficulties, As a guideline, uniform risers will usually trackwork designers long ago developed what provide the best and most economical service are known as tongue switches. for turnouts in main track or where insulation is required. Uniformity of maintenance A tongue switch consists of a housing that suggests that switches in yard and secondary incorporates the three rails that converge at tracks on the same transit system should also any switch The switch tongue is usually use uniform risers. Graduated risers should located in a roughly triangular opening in the only be considered for use in maintenance center of the housing . The switch tongue is and storage yard tracks-areas where special typically grooved on its top surface and either plates for stray current isolation are typically pivots or flexes on its heel end. This not required. movement directs the wheel flange to either the straight track or the diverging track. European switch point design does not consider the raised switch point concept. Tongue switches can either be used in pairs Therefore, the selection of either uniform or (a “double-tongue” switch) or a single tongue graduated risers is not a concern. However, switch can be paired with a “mate.” A mate is both raised switch point and level switch point a rigid assembly that has no moving parts but design perform best during operation with the rather only two intersecting flangeways in the regular maintenance of wheel truing. This will top surface. The mate does not steer the eliminate the false flange and secondary wheels, it only provides a path for the wheel batter caused by the false flange. The flange. All guidance must therefore come standards for vehicle wheel maintenance from the companion tongue switch. Traditional plays an important part in the switch point North American street railway operations used design and must be considered when tongue switches and mates almost exclusively contemplating the interface between the until very recently. wheel and switch point. In a street environment, tongue switches are far easier to keep clean than conventional tee 6.5.4 Switches for Embedded Track rail split switches. The mate component, having no moving parts, is especially well Turnouts in embedded track are a signature suited to a street environment; since the characteristic of light rail transit systems. flangeways are no deeper than those in the Whenever the railroad or rail transit track must adjoining track and are thus easy to keep be paved or embedded to permit either clean. rubber-tired vehicles or pedestrians to travel along or across the track area, conventional ballasted track split switches-either conventional or tangential design-are

6-22 Special Trackwork

6.5.4.1 North American Tongue Switch with the point of the tongue recessed into Designs the switch housing. The nearly tangential North American tongue switches are typically geometry results in turnout lead distances constructed of solid manganese steel and are much shorter than straight tongue designed as illustrated in the 980 series of switches. Tongues with radii as short as drawings in the AREMA Potiolio of Trackwork about 15 meters (50 feet) were not Plans Those drawings show both double- uncommon. tongue switches and a tongue switch/mate l The flangeway widths in traditional street While these examples are design. railway tongue switches and mates were conveniently available, a detailed examination narrower than those for railroad service. is required to appreciate the differences Track gauge was also usually unchanged between the AREMA designs and the from tangent track. The AREMA designs, configurations used by traditional street on the other hand, have extremely wide railway operations. Figure 6.5.2 illustrates a flangeways and widened track gauge‘to typical tongue switch designed in accordance accommodate steam locomotives with with the practices of the former American multiple axles and large diameter driving Transit Engineering Association (ATEA). wheels. These factors make railroad These design differences include the tongue switch designs ill-suited for light following: rail vehicles that have narrower wheel treads and almost always have small wheel diameters. The wide flangeways are also hazardous to pedestrians.

Typically, the switch tongue is placed on the inside rail leading to the diverging curve, so that truck steering action is provided by the interaction between the back side of the wheel flange and the tongue This produces reliable Figure 6.52 Tongue Switch and Mate- steering of the truck due to the curve being Non-embedded 149 RE 7A Rail continuously guarded. Some tongue switch designs amplified this guarding by depressing l Traditional street railways (transit the wheel tread level of the diverging systems) in North America typically movement immediately beyond the point of employed tongue switches and mates switch, as shown in Figure 6.5.3. This rather than double-tongue switches which causes the tongue to become an even more were more common for railroad service. effective guard because it is higher than the This was probably due to a desire to wheel tread. reduce the number of moving parts to be maintained, a key factor on large streetcar Switch tongues require frequent maintenance systems that could have hundreds of to keep them clean and tight. Traffic riding on switches in embedded track. top of a rigid tongue tends to loosen and rattle it. For that reason, many properties l Tongue switch and mate designs for positioned tongue switches on the outside of street railway service, as well as modern the curve for turnouts that were used either flexible double-tongue switches, are infrequently or only for converging typically curved throughout their length, movements. With the tongue positioned on

6-23 Light Rail Track Design Handbook the outside of the curve and the mate on the tightening can make the switch difficult to inside, straight through LRV wheel throw. movements do not ride on the tongue, providing a quieter street environment. Note, The ATEA standard tongue switch included a however, that with the mate on the inside of tongue heel design that could be locked down the curve, outside tongue switch turnouts are by lever action. American special trackwork not fully guarded. The deletion of a fabricators produced several other proprietary continuous guard through the critical switch heel designs. These alternative heel designs area can result in derailments under some generally required less maintenance and circumstances. Accordingly, outside tongue performed better in street railway use than the switches were typically not employed on AREMA designs, but may have been ill-suited switches with radii of less than about 30 to the heavy axle load demands of railroad meters (100 feet). service. Manufacturers of these alternative designs are no longer in the transit industry The AREMA switch tongue design pivots on and the patents on their designs may have an integral cylinder that is positioned beneath lapsed, placing them in the public arena. the heel of the tongue. This cylinder is held in place by wedges on either side that are Standard American-designed tongue switches tightened by large diameter bolts. These and mates were typically fabricated from wedges tend to work loose as both they and manganese steel castings, similar to the solid the cylinder wear, causing the tongue to rattle manganese steel frogs. Some alternative and rock which leads to noise and accelerated designs were partially fabricated from either wear. Tightening the wedges will only girder or tee rail sections. Tongue switches temporarily correct the problem and over- and mates have always been expensive items

SNGUE POINT DETPJL

Figure 6.5.3 ATEA 75’ Radius Solid Manganese Tongue Switch

6-24 Special Trackwork

because it is difficult to produce large castings A number of North American light rail to precise tolerances. operators have procured such switches. In- track performance of these installations has varied. Traditional street railway operations 6.5.4.2 European Tongue Switch Designs rate fabricated flexible tongue switches as European light rail manufacturers developed inferior to the robust design of the cast flexible tongue switches in the post-WII era. manganese steel tongue switches and mates, A typical flexible tongue switch is illustrated in particularly with respect to wear. This poor Figure 6.5.4. performance could be due to the use of relatively soft European girder rail steels. Newer LRT operations, on the other hand, have no problems with the European designs, perhaps because they have no basis for comparison. Special surface hardening weld treatments can be incorporated in the design of flexible tongue switches to provide enhanced protection against wear. Refer to Section 5.2.4.

6.5.4.3 Switch Tongue Operation and Control The switch throw of a tongue switch must be extremely short to preserve the switch tongue’s ability to perform as an effective Figure 6.5.4 European Fabricated Steel guard and to keep the open point flangeway Double Tongue Switch as narrow as possible. The ATEA switch throw was only 64 millimeters (2-l/2 inches) Fabricated from rolled and machined rails and long; a steel company designed an even flat steel plate sections, these designs are shorter throw, 57 millimeters (2-l/4 inches). considerably less expensive to manufacture Such small switch throws are completely than the solid manganese steel castings used outside of the adjustment range of any in North American tongue switches and standard railroad power switch machine of mates. The European design also typically North American design. Instead, traditional employs double tongues (no mate) so that North American street railway properties both wheels provide the steering action. employed switch machines that are Some European designs provide a rigid mate essentially a large solenoid. Depending on in lieu of an outside tongue switch, but usually the current flow direction in the solenoid field, only in complex layouts where overlapping the switch will be thrown in one direction or turnouts make it impossible to provide the another. Once thrown, the tongue is held in second tongue. In nearly all cases the place by a spring loaded toggle. The toggle tongues are rigidly fastened at the heel and keeps the tongue in place until the solenoid is flex, rather than pivot as is the case with North activated to throw the switch in the opposite _ American design. direction. It also makes the switch trailable without having to first throw the switch. The most common design, which is stilt in

6-25 Light Rail Track Design Handbook production, was known as a Cheatham switch, Corrosion of threaded fastenings in embedded after its original manufacturer. A major switches can make them impossible to adjust. drawback of the solenoid design is that the All threaded fastenings in embedded switches spring toggle does not lock the switch tongue should be made of corrosion-resistant in place. This makes it possible for a switch materials, such as bronze or stainless steel, to tongue to accidentally throw under a rail car. avoid corrosion problems. Some North American operators have equipped Cheatham switches with point detection relays that verify electronically that 6.5.4.5 Design Guidelines for Embedded the switch tongue has been completely Switches thrown. If pedestrians can be reliably restricted from the location, embedded track switch designs European suppliers have developed more identical to those used on open track turnouts modern switch machines for tongue switches can be considered, as shown in Figure 6.5.5, that do provide point locking. Their design since conventional North American philosophy, however, does not comply with interlocked switch operating mechanisms can conventional North American signal practice. be used. If pedestrians cannot be reliably excluded from the vicinity of an embedded turnout-which is usually the case- 6.5.4.4 Embedded Switch Drainage embedded switches should use either Tongue switches, regardless of design, create traditional North American street railway an opening in the street surface that will tongue switches and mates or European inevitably fill with water and miscellaneous fabricated flexible double-tongue switches. debris that is blown or washed into the switch. AREMA tongue switch and mate and double- A positive drainage system must be installed tongue switch designs should not be used, as that will also permit solid debris to be flushed the flangeway openings are too large for away. The switch design should promote free areas where the general public has access. drainage of any cavity and should also allow access into all cavities to enable cleaning out any solid material that may accumulate. Leaving such materials in place can interfere with the operation of the switch, promote corrosion, and facilitate stray currents. If the design includes cavities that are not essential to operation of the switch, but are likely to cause problems if they become filled with water or debris, the designers should consider filling such areas with a non-conductive material, such as an epoxy grout, prior to installation in track. The maintenance program should include sweeping, vacuuming, Figure 6.5.5 Embedded Tee Rail Switch- flushing, or blowing out embedded switches Equilateral Turnout, Steel Cover Plates, on an as-needed basis, as well as an Epoxy Filler inspection to verifiy that the drainage systems are clear and functional.

6-26 Special Trackwork

6.55 Fully Guarded Tee Rail Switch l The house top guard piece, which is Designs positioned above the straight switch point, protects the critical first 300 to 450 Readers will have noted that tongue switch millimeters (12 to 18 inches) of the and mate turnouts provide a continuous diverging switch point by pulling the wheel restraining rail through the entire turnout. This set away from it. Because the house top includes the critical switch area, where the is rigidly fixed and must allow the passage vehicle trucks must first make a change of of a wheel that is traveling on the straight direction. The preponderance of derailments switch rail, it does not provide any occurs at switches. Providing a guard in the guarding action for lateral moves beyond switch area can be very beneficial, particularly the immediate vicinity of the point of the if the turnout curve immediately beyond the switch. The house top is usually a switch is sharp and protected with a continuation of a conventionally designed restraining rail. Rail transit systems that have restraining rail that is placed in the extremely sharp turnouts in open track often tangent track ahead of the switch point. employ what are variously known as either The “double point” for the straight switch “house top” or “cover guard” switches. These rail provides a continuation of the switch designs are the signature component restraining rail along the curved stock rail of “fully guarded” turnouts. A typical house from the house top to the heel of the top double-point switch is illustrated in switch. This restraining rail is fastened Figures 6.5.6 and Figure 6.5.7. As the name directly to the back face of the switch implies, a fully guarded turnout is one in which point and extends the restraining face the diverging movement through the turnout through the switch area beyond where the includes continuous guarding from ahead of house top provides guarding action. the point of switch through the frog. Note that the spread at the heel of the The switch area provides the unique switch is much larger than in conventional characteristics of a fully guarded turnout, AREMA split switch design. This is including: required so that the connection can be made between the double-point switch

~GUbJXl RAILS ,-ADJUSTABLE RAIL BRACES UNDERCUT CURVED STRAIGHT SWITCH S’IOCK RPU. r POINT R&L

HOUSE TOP OR COVER CUM?0

----.-.-.______m m L*mrol F Dr-wWT Ddll

LUNoER CUT CURVED CAST STEEL TY- STOCK R&L HEEL BLOCKS

Figure 6.5.6 Fully Guarded House Top Switch

6-27 Light Rail Track Design Handbook

A large amount of freeplay between wheel gauge and track gauge is essential for a house top to be an effective guard and to protect an appreciable portion of the curved switch rail. Therefore, house tops are most effective when used with railroad standard wheel gauges. If conventional transit standard wheel gauge is used as the standard on a light rail system, track gauge will need to be widened through the switch area.

Fully guarded turnouts with house top switches are rarely justified and should be Figure 6.5.7 Fully Guarded Turnout- used only as a last resort in cases where 115 RE Rail Switch with House Top and sufficient right-of-way cannot be acquired to Double Point Guarding permit the use of flatter turnouts. and the restraining rail. Some transit 6.5.6 Switch Point Detail agencies have installed house tops without a double point, thereby protecting the point of Very careful attention must be given to the the switch but not the remainder of the cross section of the switch point rail at the diverging switch rail. point of the switch, particularly if the wheel contour is not a standard railroad design. If In order for the double point to act as an the transit system includes a street railway effective restraining rail, the switch throw must wheel profile with a narrow or short wheel be as short as possible. A throw distance no flange (generally less than 25 millimeters (1 greater than 89 mm (3-l/2 inches) is required inch) in either dimension}, there is a real and a shorter throw dimension would be danger that the wheel will either “pick” or ride preferred. The normal throw distance for a up on the switch point. This is a particular powered switch in accordance with standard problem in facing point diverging movements. North American railroad practice is approximately 121 mm (4-314 inches). Most In general, the top of the tip of the switch point conventional North American power switch rail should be at least 8 to 13 millimeters (3/8 machine designs allow for an adjustment of 89 to l/2 inch) above the bottom of the wheel to 140 millimeters (3-l/2 to 5-l/2 inches). If flange and should rise to the full height of the they were set to the smaller dimension, they flange as rapidly as possible. Special would have no adjustment left for wear. attention must be given if the wheel flange, in Hence, a power switch machine for a house either the new or maximum-wear condition, top switch must be custom designed. North has either a flat bottom or a sharp bottom American signal equipment manufacturers corner. Such wheels can readily ride up the can provide machines with short throws; flat surface provided by the second machined however, the locking rod design cannot be as cut in the AREMA 5100 switch point detail. If robust as those provided with ordinary switch the light rail system employs such wheels, it machines. This makes them a high may be necessary to use switch point details maintenance item that requires frequent other than the 4000, 5100, and 6100 designs adjustment.

6-28 Special Trackwork contained in the AREMA Porffolio of accomplished by either grinding or planing Trackwork Plans (see Figure 6.5.8). away a portion of the head of the stock rail for a distance of approximately 300 millimeters (12 inches) ahead of and beyond the point of the switch. This “stock rail tread depression” lowers the relative position of the tip of the wheel flange so that it cannot easily climb on top of the point. The gauge corner radius of the stock rail is reduced to approximately 15 millimeters (about 9/16 inch) through the depressed area. While the stock rails with the AREMA AREMA DETAJL 5100 DFTAJL 6100 depressed tread must be custom fabricated, this technique enables the use of off-the-shelf AREMA 5100 detail switch points. An alternate design where the undercut stock rail and switch point machining of the 5100 point detail actually places the switch point l/4 to 318 inches below the top of the stock rail has recently been implemented to improve gauge point contact. For future transit design of switch points, a 7200 point detail number AREA AREA DFTAIL 1000 DETAIL ZOOQ should be considered. (OBSOLETE1 (OBSOLETE) Trackwork designers on new systems should strongly encourage the adoption of wheel profiles with flange contours that are no less than 25 millimeters (1 inch) high. In addition to the above mentioned problems with switch points, short wheel flanges also concentrate the lateral component of the wheel-to-rail ATEA DETAIL FOR SHALLOW FLANGES loading onto a narrower band than taller (OBSOLETE) flanges. This higher contact pressure leads to accelerated wear on both wheels and rails. Figure 6.5.8 Switch Point and Stock Rail Refer to Chapter 2 for additional discussion on Details this topic.

The ATEA had a switch point standard for use 6.6 FROGS with American Society of Civil Engineers (ASCE) rails that placed the top of the switch 6.6.1 Frog Design a mere 6 millimeters (l/4 inch) below the top of the stock rail as shown in Figure 6.58. Track and vehicle design teams must carefully These dimensions are not achievable with consider frog design in conjunction with the more modern rails that have broader gauge selection of a preferred wheel profile. corner radii. Some light rail operations have reduced the distance between the wheel tread If the light rail vehicle wheel is generally and the top of the switch point. This is identical to the AAR I-B wheel, then frog

6-29 Light Rail Track Design Handbook designs can generally conform to AREMA standards as cited in the Porffolio of Trackwork Plans. Suggested revisions are noted below. Such frogs should comply with the following standards: Frogs in primary track can ordinarily be railbound manganese steel, heavy wall design, conforming to details given in the AREMA Portfolio of Trackwork Plans. Frogs in secondary track can be either railbound manganese steel or solid manganese steel construction conforming to the details given in the AREMA Figure 6.6.1 Monoblock Frog Details PorIfolio of Trackwork Plans.

Railbound manganese frogs tend to l Frog arms should be longer than the introduce more noise and vibration at the current (1997) AREMA standard to ensure interface between the wing rail and the that the toe and heel spreads are wide manganese irregular running surface. enough to permit field thermite welding. Joint LRT/railroad systems should Additional length may be required to make consider solid manganese frogs with it possible to crop off a failed thermite welded rail joints to eliminate irregularities weld and make a second weld. in the rail surface to improve on reducing l Consideration should be given to special trackwork noise. depressing the point of frog slightly below the top of rail plane for a distance of Monoblock welded frog construction is approximately 100 millimeters beyond the extremely popular in Europe and has seen actual point of the frog. This will minimize increased use in North America. Monoblock frog point batter from the wheel’s gauge frogs have a central portion that is machined corner fillet, particularly on a transit from a block of either rolled steel or cast steel system that features a compound radius that is metallurgically consistent with normal wheel tread design, such as the AAR 1-B rail steel. Rolled steel rails are then welded to wheel (see Figures 6.6.2 and 6.6.3). the central portion to form the frog arms This design can be advantageous for production of POSITION OF WHEEL EXTREMERIGHT - AT LocAnoN OF LOAD TRANSFER FROM small quantities or one-of-a-kind frogs such as WHEEL POSITION \ FROG WlNC TO POINT CENTERED POSITION OF WHEEL EXTREMELEFT those required for crossing diamonds. See BETWEEN GAUGE--\ Figure 6.6.1 for the arrangement of a typical monoblock frog.

POINT r-r m-c 6.6.2 Frog Design Modifications LNO. 6 FROG POINT DEPRESSED 953mm IN 1524mm (3/a’ IN 6’) LNO 6 FROG POiNT DEPRESSED Even if AREMA frogs are chosen, track 9.53mm IN 1524mm (3/8” IN 6’) designers should consider several Figure 6.6.2 Plan View at Frog Area with modifications, including: 45-mm Flangeway

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6.6.3 Flange-Bearing Frogs

Flange-bearing frogs are typically provided whenever continuous wheel support cannot be provided by the wheel tread. This condition is most prevalent on light rail systems that employ a narrow wheel tread but also can occur on a transit system with wider wheels. Inadequate support often occurs in Figure 6.6.3 Section at 15-mm Frog Point sharp angle frogs and crossing diamonds and is a universal problem as crossing frog angles l If the light rail vehicle wheel has a tread approach 90 degrees. It can also occur at the that is less than 100 millimeters (4 inches) mate opposite a tongue switch. wide, it may not have continuous support while passing over the opposite flangeway of the frog. Excessive impacts can occur 6.6.3.1 Flangeway Depth if the wheel tread has less than 25 Flange-bearing design carries the wheel load millimeters (1 inch) of support width as it past the point of inadequate wheel tread passes over the open flangeway, support by transferring the load to the wheel particularly if the operating speed is flange tip. Typically, the tread is elevated a relatively high. If tight control can be few millimeters above the normal top of rail maintained on both track gauge and elevation as this occurs. As the flangeway wheel gauge, it is usually possible to floor wears, equilibrium of both the flange and correct this situation by narrowing the tread bearing may be achieved. This may or flangeway widths from the customary 48 may not be acceptable depending on how millimeters (l-7/8 inches) to about 40 uniformly the system’s vehicle wheels are millimeters (l-9/16 inches) as shown in maintained. The depth of the flange-bearing Figures 6.6.3 and 6.6.4). portion of the frog should be 3 millimeters (l/8 inch) less than the nominal height of the LRV wheel flange. The flange-bearing section should extend longitudinally from about 300 millimeters (12 inches) ahead of the theoretical frog point to a location 200 millimeters (8 inches) beyond the actual frog point (see Figure 6.6.4) to ensure that the wheel is carried well past the point of non- tread support.

Figure 6.6.4 Section at 75-mm Frog Point, 6.6.3.2 Flangeway Ramping Flange Bearing The wheel flanges on most rail systems tend If open point frogs are not possible, then to get higher as the wheels wear since the either flange-bearing frogs, spring frogs, or wheel tread experiences virtually all of the movable point frogs are needed. wheel wear. In order for a flange-bearing frog to accommodate normal maintenance tolerances in wheel flange height, there must

6-31 Light Rail Track Design Handbook be a transition ramp from the ordinary recognizes flange-bearing design for the first flangeway depth of perhaps 50 millimeters (l- time, but limits operation over such frogs to 7/8 inches) to the flange-bearing depth. The FRA Class 1 speeds of 16 klhr freight and 24 slope of this ramp should be varied depending Whr passenger (10 mph freight and 15 mph on the desired vehicle speed so as to passenger). While the FRA standards do not minimize the impact. A taper as flat as I:60 is apply to most rail transit operations, they will not unusual in situations where a Range- in segments of light rail systems where bearing frog is used in a main line track. As a railroad freight operations are permitted. If guideline, the ramp ratio should be no steeper any flange-bearing construction is considered than 1 divided by twice the design speed in for joint use areas, system designers should kilometers per hour be aware that the operating speed of both freight and light rail passenger equipment will be restricted by federal mandate. If such 6.6.3.3 Flange-Bearing Frog Construction speed restrictions compromise the transit Flange-bearing frogs are typically fabricated system’s operations plan, it may be necessary as solid manganese steel castings or welded to forgo flange-bearing design and adopt other monoblocks. Hardened steel inserts have approaches to provide wheel support. also been used in bolted rail frog construction. The center manganese steel insert in a railbound maganese (RBM) frog may not be 6.6.3.5 Wheel Flange Interface long enough to obtain ramps of appropriate A light rail system with a minor amount of length for typical transit operating speeds. flange-bearing special trackwork can typically use a conventional wheel contour with a Flange-bearing frogs tend to develop a wheel rounded flange. On the other hand, if there is wear groove in the floor of the flangeway that a significant amount of flange-bearing special can steer the wheels. If one side of the frog is trackwork, a rounded flange tip tends to flatten only used rarely, this groove can become due to wear and metal flow under impact. deep enough to possibly cause wheel tracking This results in flanges that are shorter than problems when a vehicle passes through the design, which in turn could cause problems at rarely used flangeway. Flange-bearing frogs switch points. If a large amount of flange- may therefore require additional flangeway bearing specialwork is expected, floor maintenance, including grinding away consideration should be given to a wheel sharp edges and occasional welding to build flange design that is flat or nearly flat on the up the groove. bottom. This will minimize the likelihood that wheel flanges will experience damaging metal flow from traversing flange-bearing frogs. 6.6.3.4 Speed Considerations at Flange- Refer to Chapter 2, Figure 2.6.5F, for a typical Bearing Frogs wheel design intended for use with flange- The support between the wheel flange and the bearing special trackwork. flangeway floor can cause moderately disagreeable noise and vibration. For this It is important for track designers to recognize reason, flange-bearing design is usually that when an LRV wheel is running on a limited to relatively slow speed operations flange tip, its forward velocity is slightly (less than 25 Whr is common). The 1998 greater than when it is operating on the wheel revisions to the Track Safety Standards of the tread even though the rotational velocity in U.S. Federal Railroad Administration (FRA) terms of revolutions per unit time is

6-32 Special Trackwork unchanged. Thus, if one wheel is running on many locations. In locations where an its flange and the other wheel on the same embedded turnout is used only very axle is rolling on the tread surface, the flange- infrequently, such as an emergency bearing wheel will attempt to travel slightly crossover, some light rail systems have further ahead. This condition cannot persist employed what is known as either a “lift over’ for long before wheel slip will force both or “jump frog” (see Figure 6.6.5) wheels to resume their normal orientation opposite each other. This is rarely a problem A jump frog provides a flangeway only for the provided that each axle is independently main line movement. When a movement powered. However, if the LRV truck design occurs on the diverging route, the frog powers both axles from a single motor flangeway and wing rail portion is ramped up (“monomotor” truck design) flange-bearing to a level that allows the wheel to pass over design can introduce loadings that may the main line open flangeway and running rail overstress mechanical portions of the LRV head. To protect the direction of the raised drive train as one wheel attempts to travel wheel, a restraining guard rail is provided on further than the other three to which it is rigidly the opposite wheel. The lift over action will connected. Failures of gearbox connections introduce noise and vibration comparable to a between the axles and the monomotors have flange-bearing frog. However the more been common and vehicle manufacturers in frequent straight through main line part blame flange-bearing special trackwork. movements will have a continuous wheel To minimize this problem, some European tread support and the overall amount of street track designers include a flange-bearing noise attributable to the light rail system will grooved head girder rail opposite any flange- be reduced. bearing frog. 6.6.6 Frog Running Surface Hardness

6.6.4 Spring and Movable Point Frogs Regardless of frog design, the portions of the frog that support the wheels should have a When continuous support is required and minimum surface hardness of 385 BHN. This flange-bearing design is not appropriate due can either be inherent in the material from to operating speed or.other conditions, either which the frog is fabricated or achieved by spring frogs or movable point frogs can be post-fabrication treatments such as explosive considered. Such components are costly, hardening. If flange-bearing design is high maintenance items and should be used employed, the flangeway floor should also be only when unavoidable. If the system hardened. includes tracks where high vehicle speeds are required, system designers should seriously reconsider whether the use of narrow wheel 6.7 FROG GUARD RAILS treads is advisable. Guard rails must be installed opposite from frog points both to protect the fragile frog point 6.6.5 Lift Over (“Jump”) Frogs and to prevent wheel flanges from tracking on the wrong flangeway through the frogs. Any frog will generate noise and vibration, which can be an environmental concern at If transit wheel gauge standards are followed, it may be necessary to provide a very narrow

6-33 ’ Light Rail Track Design Handbook

p-6’/,’ SPECIM TOE LENCTN WJNLINE

-SLOPE 0.675” N 12”

NO. 8 TURNOUT FROG - LIFT OVER DESIGN- RIGHT HAND (SHOWN)

SLOPE 0.125” N 2.5” SLWE 0.878 I 1N R&SE0 mC TREK) RISER)

20- LEVEL LFLOOR OF FLYlCEWAY FL*NGEWAT ’ TOP OF RIL RISER I’ SLOPE OS N l2- SLOPE 05’ N 12” 5- LEVEL -SLOPE IN FLANGEWAy SLOPE H FLYK;EWAY TOP OF RM- FLOOR 0.679 N 17.5’ FLOOR 0.875” N 173-

SECTION ALONG LIFTOVER FROG FLANGEWAY (LIFTOVER DESIGN)

Figure 6.6.5 Lift Over Frog Design

6-34 Special Trackwork guard rail flangeway in order to ensure that wheel tread. The designer must not only the wheel flange remains in the proper path consider the as-new width of the wheel tread, through the frog. Widened track gauge may but also the allowable wear limits on both the be required. Guard rails should extend ahead side of the wheel flange and on the gauge line of the point of frog for a distance not less than of the rail as well as any allowable metal that given in the AREMA Potiolio of overflow on the outer edge of the wheel. Trackwork Hans. They should extend beyond Wheel tread clearance will rarely be less than the frog point to at least the location of the 125 mm (5 inches) except for systems with heel end of the frog wing rail. Where the narrow wheel treads. For additional closure curve radius of the turnout is sharp information on wheel profiles refer to Section enough that curve guarding is required, the 2.6.4. required restraining rail system and the frog guard rail on the diverging side of the turnout should be continuous. 6.9 SWITCH TIES

Frog guard rails should be adjustable and While domestic hardwoods are the most generally compatible with the restraining rail popular materials for North American switch design adopted for the project. ties, significant advances have been made in the design of concrete switch ties. Particularly Installing an adjustable guard rail in on any system that elects to use concrete embedded track is difficult; therefore crossties for main line ballasted track, traditional street railway operations typically consideration should be given to the installed a section of girder guard rail in lieu of employment of alternative materials for switch a conventional guard rail. Some ties. contemporary embedded track installations provide a segment of U69 guard rail fastened Tropical hardwoods from forests in Africa and to chairs in a manner that nominally permits South America, such as Azobe, Jarrah, and adjustment (provided that the fastenings do Quebraco, were briefly popular in North not become corroded and unusable). If the America for switch ties and crossties in guard rail cannot be adjusted in the installed special applications. They have fallen out environment, complete removal and favor in recent years due to environmental replacement of both the pavement and the concerns relative to rain forest depletion and guard rail may be required. In addition, frog unsatisfactory experiences that some guard rail rarely need adjustments if properly railroads and transit agencies have had with installed. Designers should carefully consider these products. They remain in common use, whether frequent guard rail wear is likely however, on railways and transit systems in before selecting a complex design that may countries that do not have large hardwood have limited value. forests.

Trackwork designers must consider 6.8 WHEEL TREAD CLEARANCE requirements for stray current control when choosing the type of switch tie to be used. If Throughout any special trackwork unit, it is insulated installations are required, the important to be certain that nothing projects designer must consider the dielectric above the top of rail plane into a zone where it properties at each rail seat and the switch might be struck by the outer edge of the LRV plate must be evaluated on both timber and

6-35 Light Rail Track Design Handbook concrete switch ties. For more information on track designer should consider integrating the rail seat insulation refer to Chapter 5. restraining rail into the turnout by design to avoid makeshift connections between them in Concrete switch ties can improve the stability the field. of turnout and crossing installations and will provide a track modulus comparable to main line concrete crosstie track. Concrete switch 6.11 PRECURVlNGlSHOP CURVING OF ties must be individually designed to fit at RAIL each specific location within a turnout. Hence, a concrete switch tie designed for use at a Precurved rail is also considered special particular location in a No. 6 turnout will likely trackwork since shop fabrication or special not be usable in a No. 10 turnout. However, processing is required to bend the rail steel because of their size-they generally are 250 beyond its elastic limit. millimeters (10 inches) wide-concrete switch ties require a spacing layout that is distinctly 6.11-l Shop Curving Rail Horizontally different from that used with timber switch ties. The new tie layout can impact turnout switch For additional information on precurving of tee design by requiring alternate switch rod rail and girder groove rail refer to Chapter 5. positions. The two ties at the point of switch area that support the switch machine must remain at the 559-millimeter (22-inch) AREMA 6.11.2 Shop Curving Rail Vertically for standard center distance if they are to Special Trackwork accommodate power standard North American switch machines. Figures 6.9.1 If a special trackwork unit is within a vertical and 6.9.2 illustrate typical Number 8 and 10 curve, as often happens when embedded concrete tie ballasted turnouts using SI units. trackwork must conform to existing street For addition information on switch ties, refer to geometry, it may be necessary to shop curve Chapter 5. rails vertically so that they lay uniformly without kinked joints or welds to adjoining rails. This is particularly true when it is 6.10 RESTRAININGRAIL FOR GUARDED necessary to field weld adjoining rails. TRACK An 1189-mm (39-foot) long 115 RE rail is As noted in the beginning of this chapter, the supported only at its ends, can assume a sag broad definition of special trackwork includes vertical radius of about 1524 meters (5,000 restraining rail systems for guarded track. For feet). A similar crest radius can be achieved details concerning these topics refer to the by a rail supported only in the center. These following: equate to a mid-ordinate deflection of about l For additional information on guarded 25 mm (1 inch) over the length of the rail. If trackwork, refer to Chapter 4. the requisite vertical radius is sharper than this, the rails should be shop curved vertically l For addition information on restraining rail designs for guarded track, refer to to avoid assembly problems in the field. Chapter 5. Technically, the shapes assumed by such simply supported rails are neither circular When curves with restraining rails are curves nor parabolic curves, but are close adjacent to turnouts and track crossings, the enough for practical field purposes.

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NO. 10 llJRNOU1 BAllASlEO AND m P.1. EllC I -50 Special Trackwork

In extremely sharp horizontal curves, it will be Regardless of the source of supply, special necessary to account for rail cant when trackwork units should be standardized to the bending the rails. This requires that the rails maximum degree possible so that economies be cambered vertically prior to horizontal of scale are possible during both initial project bending construction and subsequent long-term maintenance. One-of-a-kind assemblies should be avoided. 6.12 PROPRIETARY SPECIAL TRACKWORK DESIGNS AND LIMITED SOURCES OF SUPPLY 6.13 SHOP ASSEMBLY

Many of the innovative transit-specific special Special trackwork layouts, particularly trackwork designs developed by European complex layouts involving more than one fabricators are not produced by North turnout, should be preassembled at the American special trackwork manufacturers. fabrication shop. This will enable inspectors Some of these designs are proprietary, but, in to verify that all components fit together as general, North American special trackwork specified and are in accordance with manufacturers have been disinterested in approved shop drawings. Any allowable undertaking the investment necessary to deviations from the approved shop drawings satisfy the limited demand for such products. should also be noted on assembly plans so Instead, they concentrate on the materials that field installation crews can make any customarily required by their largest necessary adjustments to the trackwork. customers-North American freight railroads. The trackwork designer must carefully During shop assembly all components should consider the prudence of designing a system be fully assembled ready for installation in the where essential trackwork products will be field. The only exception would be insulated difficult to obtain at reasonable cost through joints that are glued during field installation, competitive bidding. Use of sole-source which can be assembled dry in the shop. If products or proprietary designs should crossties and rail fastenings are to be generally be avoided. Because complex furnished with the layout, they should be interrelationships can exist between the installed during shop assembly. If timber various elements of the overall trackwork switch ties are included as a part of the design, this evaluation should be performed assembly, they can be permanently preplated before design details are selected and during the shop assembly, particularly if procurement and construction contracts are elastic rail fastenings are being used. advertised. The designer should also consider whether the same products or 6.14 REFERENCES interchangeable substitutes are likely to be available for future maintenance and [I] American Railway Engineering and expansion of the system. Caution is Maintenance of Way Association, recommended if special trackwork sources Manual for Railway Engineering, 1964. are limited solely to overseas manufacturers or a single domestic supplier.

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