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AMERICAN RAILWAY ENGINEERING AND

MAINTENANCE OF WAY ASSOCIATION _________________________________________Practical Guide To Railway Engineering

Chapter


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A R E M A C O M M I T T E E 2 4 - E D U C A T I O N & T R A I N I N G

Basic Track

Joseph E. Riley P.E.

MetraChicago, IL 60661

[email protected]

James C. Strong P.E.

Parsons Transportation GroupMartinez, CA 94553-1845

[email protected]


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C H A P T E R 3 - B A S I C T R A C K

Basic Track

The engineer will frequently work from a set of standardized railway

or transit standards when making his or her selection of track

components for any given design project. However, a basic

understanding of elementary track componentry, geometry and

maintenance operations is necessary if intelligent decisions are tobe made within the options that are typically available.

3.1 Track Componentse begin our study with the prime component of the track – the rail.

3.1.1 Rail

Rail is the most expensive material in the track.1 Rail is steel that has been rolled intoan inverted "T" shape. The purpose of the rail is to:

• Transfer a train's weight to cross ties.

• Provide a smooth running surface.

• Guide wheel flanges.

Chapter


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The first rails were wooden.

Later iron straps were added tothe wooden rails to reduce wear. This was followed bycast iron rails and finally, steelrails were rolled from an ingot.(See Figure 3-1) Today, steelrail is rolled in a continuouscasting process.

Over the years, the shape of railhas also changed. However,the "T" rail section, first rolledin 1831, has been the standardin North America ever since.Rails vary in weight and shape (known as "section").

Identification of Rail

The weight of rail is based on how much the rail weighs in pounds per yard. Over thepast 200 years, increasingly heavier rail was required to handle the increased weight oflocomotives and rolling stock and traffic volume increases. The largest rail commonlyused today is 136 lb., although 140 lb. is still rolled and second-hand 152 lb. rail isavailable in limited quantities. AREMA has recently recommended a new rail sectionto maximize available head wear and minimize stress related failures. This section is

the 141 lb., but is not yet widely in use. A rail's weight, along with its section and otherinformation, is rolled as a raised character onto the web of the rail.

The rail section refers to the shape of the cross-section of a rail. For example, there areseveral sections of 100 lb. rail. Rail mills identify the different shapes and types of railsby codes rolled onto the rail's web. The section code appears right after the weight. The section codes signify different dimension and shape standards. These codesfurther represent the engineering group, which created the design plan (thus, the

standard) for that rail section. Some of the more common section codes are:

RE: American Railway Engineering Maintenance of Way Association(AREMA).

REHF: AREMA “head free” section.

Figure 3-1 Rolled Rail – Photo by J. E. Riley


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The rail section base dimension is important when choosing tie plates, rail anchors and

pre-drilled timber ties and concrete ties. The height of the rail and the width of thehead of the rail are important to determine the selection of joint bars. Next, themethod of hydrogen elimination is specified. CC indicates that the rail was controlledcooled. Controlled cooling was first utilized in the late 1930's. Rail rolled prior to thisdate has a proclivity to the formation of dangerous transverse defect type fissures.Other methods used in new rail today to eliminate hydrogen bubbles, includescontrolled cooling of blooms (BC) and Vacuum Degassing (VT). Finally, the railmanufacturer, the year rolled and the month rolled are also indicated. On the opposite

side of the web of the rail, additional information is hot stamped indicating whether therail has been end hardened (CH), the heat number, rail letter designation if notcontinuous cast, indicating from what part of the ingot the rail is from and if of aspecial metallurgy, the designation for special alloys.

The information provided by the rail branding and stamping provides valuable insightto the suitability for reuse of second-hand rail in a variety of situations. For example,many railways limit the use of rail stamped as an "A" rail within the ingot to slow speed

yards and sidings because of the potential for the creation of seams in the head and web of the rail called pipe rail or the development of vertical split heads. This does notmean that “A” rail cannot be used in main tracks, as rail chemistry is probably a betterindicator of the proclivity of the development of such defects.

In general, rail sections smaller than 90 lb. should not be utilized for new construction,but is available second-hand for replacing rail in trackage utilizing the given section.Ninety lb. and 100 lb. sections are adequate for many transit and light tonnage

industrial park trackage. New trackage, exposed to 100-ton or heavier cars, should notutilize rail sections smaller than the 11525 RE. Second-hand 11025 and 11228 RE arecomparable to the 11525 RE section, but have a proclivity to head and web separationsdue to the reduced radius in the fillet between the web and the head of the rail. Goodrail in these sections is becoming increasingly more difficult to find and the engineermay wish to give serious thought about the possibility of securing usable replacementrail in these sections for maintenance purposes in later years. The common 5-1/2"base sections (11525 RE and 119 RE) are commonly specified for medium tonnage

and/or commuter/passenger/transit lines. For heavy tonnage trackage, the 6" base railsections are preferable. These include 13225 RE, 133 RE, 136 RE, 140 RE and thenew 141 RE sections. Various 130 and 131 lb. sections are available second-hand, butmany have head and web separation related problems.

The engineer wishing to utilize second-hand rail must take into consideration the


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may make a rail unsuitable for welding. If available, the engineer should attempt to

secure the rail's defect history. The engineer should not be afraid of utilizing second-hand rail. Indeed, rail exposed earlier in its life to nothing heavier than the 70-ton carhas often become work hardened. New rail today exposed to unit train tonnage isabraded away before it ever becomes work hardened. On the other hand, today's railsteels possess improved rail chemistries that permit life expectancies exceeding a billiongross tons, whereas yesterday’s rail rarely lasted more than 600 million gross tons.

Whenever possible, the engineer should specify the use of welded rail. The elimination

of the joint will reduce future maintenance costs by exponential factors. New rail isrolled in lengths of either 39 or 80 feet in length. Construction is presently under wayto roll rail in even longer lengths. These rails are then welded in a controlledenvironment into individual strings of up to 1600 feet in length for delivery to the field.

3.1.2 Ties

Ties are typically made of one of four materials:2

• Timber

• Concrete

• Steel

• Alternative materials

The purpose of the tie is to cushion and transmit the load of the train to the ballastsection as well as to maintain gage. Wood and even steel ties provide resiliency andabsorption of some impact through the tie itself. Concrete ties require pads betweenthe rail base and tie to provide a cushioning effect.

Timber Ties It is recommended that all timber ties be pressure-treated with preservatives to protectfrom insect and fungal attack.3 Hardwood ties are the predominate favorites for trackand switch ties. Bridge ties are often sawn from the softwood species. Hardwood tiesare designated as either track or switch ties.


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adequate seasoning, treatment with chemical preservatives, and protection against

mechanical damage. Hardwood ties provide longer life and are less susceptible tomechanical damage.

Track Ties

Timber track ties are graded with nominal dimensions of 7" x 9" x 8'-6" or 9'-0" orsmaller ties which are 6" x 8" x 8'-0". (See Figure 3-2) The 6" x 8" x 8'-0" are typicallyutilized for sidings, industry tracks and very light density trackage. An industrial grade

of both ties is also available. These ties have more wane, bark, splits or other surfacerelated defects than recommended under the timber grading rules. Both AREMA andthe Railway Tie Association (RTA) publish specifications and standards relating to thegrading of timber and the definitions for the above timber physical characteristics. Thecost savings may make industrial grade ties attractive for some plant trackage exposedto infrequent and light tonnage. It is generally acknowledged that the quality ofhardwood tie available today does not meet yesteryear's standards. Thus, the additionalcost of providing gang plates, S-irons or C-irons for the tie ends may be a worthwhile

investment in extending tie life from end splitting failures. Track ties may be orderedadzed and pre-drilled for the appropriate rail section to be used if desired. Second-hand ties, reclaimed from line abandonments, may also be available. There is widedebate regarding the suitability and cost effectiveness of using recovered ties.Deterioration of that part of the tie previously buried in the ballast occurs rapidly oncethe tie is exposed to the air. If second-hand ties are used, do not turn the tie over, thusproviding a fresh surface for the top of the tie. These ties will deteriorate very quickly.Better to plug the tie, adze the surface if necessary and insert the tie as it was originally

orientated. Occasionally, softwood ties may be specified for a track tie. Their use islimited to temporary track situations such as shoe-fly's, etc., or where tonnage is verylight or hardwood species are prohibitive in cost.

For quality maintenance, ties should be notless than 8 ft. 6 in. in length. For moderatelyheavy or heavy-traffic conditions, especiallyon curves of 6 degrees or more, the 9-ft. tie is

preferred, 7 in. by 9 in. in cross-section,because of the greater stability from the largersupport and friction area. It also assists inrestraining continuous welded rail.

For lines of moderate to medium tonnage, ai i i l 22 i 39 f il Fi 3 2 H d d T k Ti Ph b J Ril


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Switch Ties

Switch ties (Figure 3-3) are commonlyhardwood species, usually provided in either6" or 12" increments beginning at 9'-0" upto 23'-0" in length. Nominal cross-sectiondimensions are 7" x 9", although larger tiesare specified by some railways. The primaryuse for switch ties is relegated to turnouts

(thus their name). However, they are alsoused in bridge approaches, crossovers, at hotbox detectors and as transition ties. Somerailways use switch ties in heavily traveledroad crossings and at insulated rail joints.Switch ties ranging in length from 9'-0" to 12'-0" can also be used as "swamp" ties. The extra length provides additional support for the track in swampy or poor-drainedareas. Some railways have utilized Azobe switch ties (an extremely dense African

wood) for high-speed turnouts. The benefits associated with reduced plate cutting andfastener retention may be offset by the high import costs of this timber.

Softwood Ties

Softwood timber (Figure 3-4) ismore rot resistant than hardwoods,but does not offer the resistance of

a hardwood tie to tie plate cutting,gauge spreading and spike holeenlargement (spike killing).Softwood ties also are not aseffective in transmitting the loads tothe ballast section as the hardwoodtie. Softwood and hardwood tiesmust not be mixed on the main

track except when changing fromone category to another.Softwood ties are typically used inopen deck bridges.

Figure 3-3 Switch Timber – Photo by Craig Kerner

Figure 3-4 Softwood Timber - Photo by J. E. Riley


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Concrete Ties

Concrete ties (Figure 3-5) are rapidlygaining acceptance for heavy haulmainline use, (both track andturnouts), as well as for curvaturegreater than 2°. They can be suppliedas crossties (i.e. track ties) or as switch

ties. They are made of pre-stressedconcrete containing reinforcing steel wires. The concrete crosstie weighsabout 600 lbs. vs. the 200 lb. timber

track tie. The concrete tie utilizes aspecialized pad between the base of therail and the plate to cushion and absorb the load, as well as to better fasten the rail tothe tie. Failure to use this pad will cause the impact load to be transmitted directly to

the ballast section, which may cause rail and track surface defects to develop quickly. An insulator is installed between the edge of the rail base and the shoulder of the plateto isolate the tie (electrically). An insulator clip is also placed between the contact pointof the elastic fastener used to secure the rail to the tie and the contact point on the baseof the rail.

Steel Ties

Steel ties (Figure 3-6) are oftenrelegated to specialized plantlocations or areas notfavorable to the use of eithertimber or concrete, such astunnels with limited headwayclearance. They have alsobeen utilized in heavycurvature prone to gage widening. However, theyhave not gained wideacceptance due to problemsassociated with shunting ofsignal current flow to ground

Figure 3-5 Concrete Ties – Photo by Kevin Keefe

Figure 3-6 Steel Ties


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Alternative Material Ties

Significant research has been doneon a number of alternative materialsused for ties. These include ties with constituent componentsincluding ground up rubber tires,glued reconstituted ties and plastic

milk cartons. Appropriate polymersare added to these materials toproduce a tie meeting the requiredcriteria. To date, there have beenonly test demonstrations of thesematerials or installations in lighttonnage transit properties. It remains to be seen whether any of these materials willprovide a viable alternative to the present forms of ties that have gained popularity in

use. (Figure 3-7)

3.1.3 Ballast Section

A principal purpose of the ballast section is to anchor the track and provide resistanceagainst lateral, longitudinal and vertical movement of ties and rail, i.e., stability.4 Additionally, the ballast section bears and distributes the applied load with diminishedunit pressure to the subgrade beneath, gives immediate drainage to the track, facilitates

maintenance and provides a necessary degree of elasticity and resilience. Good drainageis of utmost importance to assure required stability.

Ideal qualities in ballast materials are hardness and toughness, i.e., freedom fromshattering under impact, durability or resistance to abrasion and weathering, freedomfrom deleterious particles (dirt), workability, compactability, cleanability, availability,and low first cost. The principal desired characteristic is maximum stability at minimumover-all economic cost, including frequency of maintenance cycle, life of rails, ties and

fastenings, and the labor costs. Quality maintenance requires that more attention begiven to the quality and characteristics of ballast. The practice of buying ballast purelybecause of low first cost or accessibility is clearly suspect.

The ballast sizes recommended in the AREMA Manual for Railway Engineering aretime-proven and acceptable. However, a number of AASHTO and ASTM gradations

i il AREMA’ d b bl f i i i Thi b

Figure 3-7 Alternative Type Material Tie


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highway rock gradations are available. The comparison chart found at the back of this

chapter cross-references various gradations.

More important factors, probably, are the shape of the ballast particle, its degree ofsharpness, angularity, and surface texture or roughness. These factors have been shownto have a significant effect upon the stability and compactability of aggregates ingeneral.

The ballast types most nearly meeting the ideal requirements, in order of preference,

are granite trap rock, hard limestone, open hearth and blast furnace slags, otherlimestones, prepared gravels, chat, volcanic ash, pit-run gravel and coarse sand (as a lastresort). There are other materials of local deposition that may be usefully considered,especially for light-traffic and industrial switching tracks.

Keeping ballast in a clean, free-draining condition begins with the selection of a ballastmaterial that is tough, durable, not subject to abrasion, and free of clays, silts, and softand friable pieces. Beyond that, maintaining adequate drainage and cleaning or renewal

should be performed as needed.

Shoulder and intertrack cleaning are satisfactory until the ballast becomes cemented,too finely abraided, or until mud and dirt have collected under the ties and in the cribs. At this point, undercutting and cleaning, or undercutting, wasting and replacing withnew ballast is in order. Undercutting may also be a necessary alternative to raising trackduring the surfacing and re-ballasting program where overhead clearances arerestrictive. (See the Appendix – Maintenance Processes for specific procedures used in

undercutting.)

The depth of ballast required is a function of the supporting capacity of the subgrade.It should be sufficient to distribute the pressures to within the bearing capacity of thesubgrade. Uniform distribution of pressures is another factor that varies with depth.Usually, a minimum depth of 18 to 24 inches is necessary to achieve uniformdistribution. This depth may be distributed between ballast and sub-ballast. The greaterthe height of ballast around the tie, the greater is the resistance to vertical displacement.

The same holds true for shoulder and lateral displacement. A full crib of high-gradeballast should be maintained for continuous welded rail with a ballast shoulder width of10 to 12 in. beyond the ends of tie considered as ideal. Check individual railwaystandards for designated ballast shoulder widths. Typically, 12” is required on the highside of curves and some railways will specify as little as 6” on tangent shoulders and thelow side of curves. For jointed track, a minimum height of no more than two inchesb l f i h ld b h ld i h 6 8 i f b ll h ld id h d f


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3.1.4 Rail Joints The purposes of the rail joint (made up of two joint bars or more commonly calledangle bars) are to hold the two ends of the rail in place and act as a bridge or girderbetween the rail ends.5 The joint bars prevent lateral or vertical movement of the railends and permit the longitudinal movement of the rails for expanding or contracting. The joint is considered to be the weakest part of the track structure and should beeliminated wherever possible. Joint bars are matched to the appropriate rail section.Each rail section has a designated drilling pattern (spacing of holes from the end of the

rail as well as dimension above the base) that must be matched by the joint bars. Although many sections utilize the same hole spacing and are even close with regard to web height, it is essential that the right bars are used so that fishing angles and radii arematched. Failure to do so will result in an inadequately supported joint and willpromote rail defects such as head and web separations and bolt hole breaks.

There are three basic types of rail joints (Figure 3-8)

• Standard

• Compromise

• Insulated

Figure 3-8 Conventional Bar, Compromise Bar & Insulated Joint Bar – Photo by J. E. Riley


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Standard Joints

Standard joint bars connect two rails ofthe same weight and section. (See Figure3-9) They are typically 24" in length with4-bolt holes for the smaller rail sections or36" in length with 6-bolt holes for thelarger rail sections. Alternate holes are

elliptical in punching to accommodate theoval necked track bolt. Temporary jointsin CWR require the use of the 36” bars inorder to permit drilling of only the twooutside holes and to comply with the FRA Track Safety Standard’s requirement ofmaintaining a minimum of two bolts ineach end of any joint in CWR.

Compromise Joints

Compromise bars connect two rails ofdifferent weights or sections together.(See Figure 3-10) They are constructedsuch that the bars align the runningsurface and gage sides of different rails

sections. There are two kinds ofcompromise joints:

• Directional (Right or Left hand)compromise bars are used where adifference in the width of the headbetween two sections requires theoffsetting of the rail to align the gage

side of the rail.

• Non-directional (Gage or Field Side) are used where the difference betweensections is only in the heights of the head or where the difference in width of railhead is not more than 1/8" at the gage point. Gauge point is the spot on the gaugeside of the rail exactly 5/8" below the top of the rail

Figure 3-9 Standard Head-Free Joint Bar –Photo by J. E.Riley

Figure 3-10 Compromise Joint Bar – Photo by J. E. Riley


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• The joint on your right is a "right hand".

• The joint on your left is a "left hand".

Insulated Joints

Insulated joints are used in tracks having track circuits. They prevent the electricalcurrent from flowing between the ends of two adjoining rails, thereby creating a track

circuit section. Insulated joints use an insulated end post between rail ends to preventthe rail ends from shorting out.

There are three types of insulated joints:

• Continuous

• Non-continuous

• Bonded

Continuous insulated joints (Figure 3-11) are called continuous because theycontinuously support the rail base.No metal contact exists between thejoint bars and the rails. Insulated fiber

bushings and washer plates are used toisolate the bolts from the bars. Thejoint bars are shaped to fit over thebase of the rail. This type of insulatedjoint requires a special tie plate calledan "abrasion plates" to properlysupport the joint.

Non-continuous insulated rail joints are called non-continuous because these jointsdon't continuously support the rail base. A special insulating tie plate is required on thecenter tie of a supported, non-continuous insulated joint. Metal washer plates areplaced on the outside of the joint bar to prevent the bolts from damaging the bar.

There are two common kinds of non-continuous insulated joints:

Figure 3-11 Continuous Insulated Joint – Photo by J. E. Riley


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The glass fiber insulated rail joint (See the bar to the right in Figure 3-8) replaces the

joint bar with a reinforced glass filament bar. Metal washer plates are placed on theoutside of the joint bar to prevent the bolts from damaging the bar.

The polyurethane encapsulatedinsulated bar (Figure 3-12) is a steeljoint bar completely encapsulated inpolyurethane over the entire jointbar surface. The Poly joint uses

insulating bushings to insure thattrack bolts do not short out thetrack.

Bonded insulated rail joints(commonly called plugs or slugs)(See Figure 3-13) are made up oftwo pieces of rail, which utilize anepoxy resin to glue the insulatedbars to the rail sections. They arebolted together using bushings toisolate the bar from the rail steelitself. The bolts maintain thealignment of the bars and rail untilthe epoxy cures. The bars aretypically of a heavier section (D-section) to provide extra support forthe epoxy. These units can be

purchased in a variety of made up lengths. The completed assembly is then thermit welded into the track structure. This is the preferred type of insulated joint to use incontinuous welded rail (CWR).

Figure 3-12 Poly Insulated Joint – Photo by J. E. Riley

Figure 3-13 Bonded Insulated Joint (Plug) – Photo by J. E. Riley


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3.1.5 Tie Plates The primary purpose of a tie plate is toprovide a smooth and uniform bearingsurface between the rail and the tie.6 Thisprevents the rail from cutting into the tie. The plate also helps to maintain gauge.Plates that are canted (typical cant is 1 in 40)

tip the rail slightly to better distribute the wheel load to ties.

Tie plates are designated as either singleshoulder or double shoulder (Figure 3-14).Single shoulder plates are typically used forrail weights running from 56 lb. through 100lb. Rail sections larger than 100 lb. generally use a double shouldered plate. Tie plates

can be ordered in a variety of sizes all the way up to 8" x 18", although the 7-3/4" x14" plate is probably the most common new plate produced. Eleven inch and 13"double-shouldered plates are also available in readily available quantities. Some railwaysbelieve that CWR should not be used with second-hand plates, although it is acommon practice on other railways.

Specialty plates (Figure 3-15) used forelastic type hold-down fasteners, are

also produced in large quantities. Various types of specialty plates areused at insulated joint locations wherethe rail ends are supportedimmediately underneath by a tie. Anon-conductive plate must be used toprevent the shorting out of the twoinsulated rail ends.

Past practices sometimes constructedtrackage without tie plates. However, under today's wheel loading conditions, tie life will be severely shortened if the rail is spiked directly to the tie without using a plate todistribute the applied load.

Figure 3-15 Pandrol Plate & Fastener on a Concrete Tie

Figure 3-14 7-3/4” X 14” Double Shoulder Plates – Photo by J. E. Riley


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3.1.6 Rail Anchors

Rail anchors are used to control the longitudinal running or creeping of the rail causedby changing temperature, grades, traffic patterns and braking action of trains.7 Anchors are applied directly to the rail base and lodge up against the tie. The tie isembedded in the ballast and the completed system together provides resistance againstlongitudinal and lateral movement. Anchors are made for a specific rail weight andbase width.

Anchors manufactured today can be classified into two major groups: (See Figure 3-16)

• Drive-On

• Spring-Type

Figure 3-16 Tru-Temper Channeloc Drive On Anchor; Adjacent Photo: Woodings-Verona Spring Anchor, Unit Spring Anchor,Portec Improved Fair Drive-On Anchor – Photos by J. E. Riley

3.1.7 Fasteners

There are many different types of fasteners commonly used.8 Fasteners can be

grouped by use as either connecting rail or track components together or to fasten railsto ties. Fastenings and hold-down devices, with modern tie plate design, are aimedprimarily at reducing movement between the tie plate and the tie, both vertically andlaterally. As the track deflects under a wheel load, a reverse curve with upward bendingis formed immediately in front of and behind the wheel. Lateral restraint is necessaryto prevent wide gauge and plate cutting. Vertical restraint also reduces plate cutting.


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plate and tie. The AREMA Manual for Railway Engineering gives a recommended

spiking procedure. However, the Engineer should check to make sure that the railwayhas adopted the AREMA spiking standard.

SPIKES

Track Spikes

The purpose of the track spike is to first maintain gage between the running rails and

to secondly secure the rail to the tie. The underside of spike head is sloped to fit thetop surface of the rail base (Figure 3-17).

Spikes come in different lengths to ensure an adequate length of spike penetrates intothe tie. The most common track spikes used are the 5/8" x 6" and the 9/16" x 5-1/2"for smaller rail sections. Spikes can be commonly secured in either 200 lb. kegs or 50lb. kegs (Figure 3-18).

Figure 3-17 Cut Track Spike (5/8” x 6”) Figure 3-18 200# Kegs of Spikes - Photos Taken By J. E. Riley

Ship Spikes

Ship spikes, also commonly called line spikes, are used to secure timber crossing planksand to secure shims used in frost heaved track. Ship spikes come in a variety of sizes.

Lag Screws

Lag screws are used to fasten elastic fastener plates as well as other specialty trackcomponentry to wood ties. The tie must be bored before installing the lag screw.


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BOLTS

Track bolts

The track bolt (Figure 3-19) is used toconnect rail ends together at a joint. Trackbolt sizes are determined by the section ofrail in use. Check the applicable railwaystandard to determine the proper boltdiameter and length. Track bolts are

normally supplied as oval neck to preventthe bolt from turning when torqued. Trackbolts are heat-treated and will stretch a little,thus they must be tightened after initialapplication. Track bolts are used withsquare nuts and spring washers. Over-torquing track bolts creates frozen joints, which in most cases, is undesirable.

Frog/Guard Rail Bolts

Frog bolts are square headed and come in a variety of lengths and diameters dependingon the rail section in use and the location of the bolt in the frog.

Rod and Clip Bolts

Rod bolts are typically square headed anddrilled for a cotter pin to prevent the nut fromfalling off. They secure the switch rods in aturnout to the jaw clips mounted on theswitch points. The clip bolts secure the clip orside jaw to the switch point and are alsosquare headed with often a milled head that will permit the switch point to fit up tight

against the stock rail. (See Figure 3-20)

3.1.8 Specialized Components

Figure 3-19 1” x 6” Oval Necked Track Bolts – Photoby J. E. Riley

Figure 3-20 Rod & Clip Bolts – Photo by J. E. Riley


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• Wheel stops or bumping posts

• Gauge rods

• Sliding joints

• Miter rails

• Bridge/tunnel guard rails

Derails

The purpose of the derail is to keep tracks free of unsecured rolling stock. Whenproperly placed and in the derailing position, the derail will guide the wheels off thetrack. This prevents unintentional movement of rolling stock from fouling the mainline.

The derail should be left in the derailing position whether or not there are cars occupying thetrack. Derails are designated as right hand or lefthand for derailing in the desired direction. Theengineer must select the appropriate model ofderail on the basis of the rail section to beutilized. An under-sized derail will not properly

cover the rail head and may not derail the car asintended. An over-sized derail may be damagedbecause of inadequate support.

There are several different types of derails. These include:

• Hinged derails, which are manually applied. The derail is rotated in a verticalsemicircle to move the derail on or off the rail.

• Sliding derails (Figure 3-21) are mounted on two switch ties and are operated by aswitch stand.

• Switch point derails are used at special locations such as steep gradients or wherethe possibility of high-speed movement, for example at movable bridges, could

Figure 3-21 Sliding Derail


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either rigid, which bind securely to the rail or cast which are one-piece half moons that

are easy to install.

Bumping posts are used for heavier service. Some models actually engage the coupler.

Gauge Rods

The purpose of a gauge rod is to maintain track gauge. They are often used tosupplement the tie in preventing lateral movement of the rail in sharp curvature

locations. They can also be used as a temporary means of maintaining traffic indefective tie conditions. They are not a permanent alternative to replacing a defectivetie. Most gauge rods are adjustable with a nut on one end.

Gauge rods are provided as either insulated for signaled territory or non-insulated, where track circuits are not used.

Sliding (Conley) Joints

The purpose of a sliding joint (Figure 3-22) is to accommodate the longitudinalexpansion and contraction of the rail onlong open decked bridges. Rail anchorsare not typically used on open deckedbridges because of the damage done to the

softwood bridge ties. The sliding jointaccommodates the thermal expansionproduced by enabling the beveled rail endsto move but yet still maintain thecontinuity of the running rail.

Mitre Rail

Whenever track is to be opened andclosed at frequent intervals, it will be costlyand cumbersome to use regular joint bars.Mitre rails (Figure 3-23) allow easyopening of track at drawbridges and swingspans Each rail of a track is cut through

Figure 3-22 Conley Joint to Permit Expansion on BridgeDeck


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ends to allow proper opening and closing of the joint structure.

Bridge/tunnel/overpass Guard Rails

The purpose of installing bridge guard rails(Figure 3-24) is to keep derailed equipmentfrom falling off an overpass or deck of abridge, or striking the sides of a structure orpiling up in a tunnel. Typically, the inner

guard rail will be a T-rail section, which doesnot extend to the height of the running rail. The outside guard rails are usually timbermembers.

3.2 Turnouts A turnout is a combination of a switch, a frog, the rails necessary to connect the switchand the frog, two guard rails, unless the frog is self-guarded, and a switch stand orswitch machine for operating the switch.10 A turnout begins with the switch and ends with the frog. The purpose of a turnout is to permit engines and cars to pass from onetrack to another.

3.2.1 Types of Turnouts

Turnouts can be categorized into threegroupings:

• Lateral turnouts

• Equilateral turnouts

• Lap turnouts

Lateral turnouts (Figure 3-25) are defined

Figure 3-24 Inner Bridge Guard Rails -Photo by J. E.Riley

Figure 3-25 Lateral Right Hand Turnout


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Equilateral turnouts (Figure 3-26) are

common at the ends of double trackterritory (where two tracks go to oneand vice versa). Both routes curve ordiverge as opposed to only one routediverging in the lateral turnout. They areused for higher operating speeds or incongested areas. Half of the curvature ison the main track side and the other half

is on the turnout side.

Lap turnouts (Figure 3-27) are used whenmaximum track lengths and minimum

clearance points are required, for examplein hump yards. They contain two sets ofswitch points and three different frogs. The turnout's direction is determined by which way the first set of points diverge.

Basic Turnout Terminology• Straight side called the main track or straight (normal) route.

• Curved side termed the turnout or diverging route.

• Facing point move is from points toward frog, either route.

• Trailing point move is from frog toward points, either route.

• Point of switch (PS) is the location where the diverging or straight route isdetermined.

• Heel of switch (HS) is the location at which the switch point pivots about.

Figure 3-26 Equilateral Turnout - Photo by J. E. Riley

Figure 3-27 Lap Turnout


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• One-half inch point of frog (PF) is the location behind theoretical point of frog,

where the gauge spread is ½”.

• Heel of frog (HF) is the joint location behind the point of frog.

The true definition of a turnout is the portion of the track assembly from PS to HF.But we commonly refer to all of the track structure resting on switch ties as theturnout.

Each turnout is identified as a number(e.g. # 10). The number of the turnout isdetermined by the angle of the frog(discussed later).

Every turnout consists of the followingcomponents:

3.2.2 Switch

A switch is a device to deflect, at will, the wheels of a train from the track upon whichthey are running.11 A switch refers to portion of turnout from Point of Switch (PS) to

Heel of Switch (HS).

The split switch (Figure 3-28) is the most common switch used, although the tongueswitch may be used on transit properties operating within pavement. The split switchconsists of two switch or point rails connected by switch rods and operated as a unit. The switch rails are of full section at one end, and are tapered to a 1/4-in. or 1/8-in.point at the other end. The tapered end is called the point of switch and the other endis called the heel of switch. The switch rails rest upon metal plates fastened to the ties.

The heel of each switch rail is connected to its lead rail by means of special joint bars,or in some cases is continuous, and the switch as a unit pivots about these connections. The point of switch moves through a distance of about 5 inches, which is called thethrow. The movement of the switch rails is controlled by a switch stand placed outsidethe track on the head block ties. The distance between the gage lines of the main trackand of the turnout at the heel of the switch rails is called the heel spread and varies

Figure 3-28 Switch Section of a Turnout – Photo by J. E.Riley


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Figure 3-29 Switch Angle

Switch rails vary in length from 11 to 39 ft. and even longer for high turnout numbers,depending on the weight of the rail and the curvature of the turnout.

3.2.3 Switching Mechanism

There are two means of moving the switch points12:

• Hand operated (switch stand).

• Power operated (machine).

Hand operated switching mechanisms can be rigid (See Figure 3-30) or spring switch

type. A spring switch has special components enabling points to close automaticallyafter being trailed through from the diverging side. There are also dual-control powerswitches (See Figure 3-31) that can be operated either by hand (using the hand throwlever) or power operated remotely by the dispatcher.

Figure 3-30 Hand Throw Switch Stand Figure 3-31 Dual Control Switch Machine – Photo by J. E. Riley


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3.2.4 Turnout Rails

Turnouts are made up of a combination of rails. Some have special names andpurposes, for example.

Stock rails are the outside rails in a switch that the points bear against.

Closure rails are the connection rails between the heel of the switch points and the toeof the frog.

Knuckle rails (Figure 3-32) are the railsthat the movable point in a movablepoint frog or the rail that the centerpoint in a double slip switch bearsagainst.

3.2.5 Frog

A frog is a device at the intersection of two running rails to permit the flange of a wheel moving along one rail to cross the other rail.13 Turnout frogs may be classifiedas rigid frogs or spring-rail frogs. Both types of frogs are made with straight gage lines,except those used on street railways. The point is finished with a blunt point about 1/2

in. wide. The distance “P” between the actual frog point and the theoretical point(intersection of gage lines) equals the width of the blunt point multiplied by the frognumber (i.e., 1/2 N).

Rail Bound Manganese (RBM)

This is a heavy-duty frog used on mainlines

because of its durability.

14

The insert ismade of a one-piece manganese casting.Lengths of machined rail (binder rails) arebolted to the insert. (See Figure 3-33)

Figure 3-32 Knuckle Rails in a Double Slip Switch - Photo by J. E. Riley


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Spring Frog

The spring frog (Figure 3-34) providescontinuous support for the wheel as ittransits through the frog flangeway. Thisfrog has a moveable wing rail. The wing railis held closed by a spring assembly. It alsohas an anchor block, thimble and a bentjoint bar at the toe end to allow the wing railto pivot. The guardrail pulls the wheelsover, forcing the wing to open on thediverging side. The wing rail springs closedagain after the wheels are through. Springfrogs are supplied as either right or left hand. To determine the hand of a spring frog,stand at the rigid wing end, facing the frog. The side the moveable wing is on indicatesleft or right.

The spring frog is used for trackage with predominate main line traffic, especially highspeed movements, because there is less pounding and a smoother ride. Thedisadvantage is that it requires more maintenance than conventional frogs. Recentadvancements in spring frog design have eliminated some of the rigorous maintenanceneeded to keep a spring frog functional.

Solid Manganese Self-guarded Frog

The solid manganese self-guarded frog, alsocalled SMSG (Figure 3-35) has a built-in guardrail to prevent wheels from mis-routing. Thus,conventional guard rails are not required.SMSG frogs are supplied either with plates aspart of the casting or utilize hook plates tosecure the frog to the switch ties. SMSG frogsare normally limited to yard use primarily

because of the resultant impact that theguarding face would suffer at higher speeds. AREMA does not recommend their use inmain line trackage with speeds over 30 mph.

Figure 3-34 Spring Frog - Courtesy of the Union PacificRailroad

Figure 3-35 Solid Manganese Self-Guarded Frog


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Bolted Rigid Frogs

Bolted rigid frogs (Figure 3-36) are made ofmachined rail bolted together. They are cheapto make and are used primarily in yards andsecondary lines. They are designated as rightor left hand. The straight route side of thebolted rigid frog point is continuous, whereasthe diverging side of the frog point is milled tointersect the straight side frog point rail, hencethe need to differentiate the hand of thefrog.

Movable Point Frogs

Movable point frogs (Figure 3-37) are used

in locations where the crossing anglebetween two sets of tracks is less than 14°15’. The excessively long throat created by usingconventional crossing diamond frogs wouldbe impractical to maintain and to guard. Amovable point frog consists of two movablecenter point rails. The free points face eachother a few inches apart where each pair

may be alternately operated against twoknuckle rails kinked to a point between the free ends of the movable points. Theclosed movable point, thereby maintains the flangeway. High-speed, high-numberturnouts may also utilize a variation of the movable point frog described above in orderto gain the benefits of the continuous flangeway too.

Determining Frog Number

The frog used in a turnout determines the number of the turnout, e.g.:

• # 10 turnout uses a number 10 frog.

• # 12 uses a number 12 frog.

Figure 3-36 Bolted Rigid Frog - Photo by J. E. Riley

Figure 3-37 Movable Point Frog


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• Utilizing a tape measure, find the location behind the point of frog where the

spread between the gauge lines equals an even increment of inches.

• Starting at that point, measure along the gauge line to the location where the spreadbetween gauge lines equals one inch more than that previously measured.

• The distance in inches between the two locations where the gauge spread differedby one-inch equals the frog number.

3.2.6 Switch Ties

AREMA as well as many railways havestandardized plans for the switch tie layoutfor the turnouts utilized on their property. The two switch ties under the switchmechanism are called head block ties

(Figure 3-38). The ties under the heelblock assembly are called heel block tiesand those under the frog are called frogties.

3.2.7 Stock Rails

The stock rails (Figure 3-39) are made of rail of the same weight and section as theswitch point. The stock rail on the diverging side is bent (Figure 3-40) so that a properfit is maintained between the switch point and the stock rail and to protect the pointfrom wheel impact. In the case of an equilateral turnout, both stock rails are bent.

Stock rails are either Samson (called "undercut" when ordered) or standard. Thebeveled samson stock rail allows the samson point to tuck underneath the stock rail,thus protecting the point from impact.

Figure 3-38 Head Block Ties


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3.2.8 Switch Points

The switch points (Figure 3-41) arethe movable rails that permit achange of route direction in theturnout.15 There are different typesof switch points, each with someunique characteristics. But thefollowing parts of switch point are

common to all:

• Tip

• Heel

• Planed (or "machined") portion

• Reinforcing bar

• Switch clips

• Stop blocks

The switch points are machined from rails, so that the middle ofthe rail becomes the middle of the actual point, to give it

structural support. The switch points are planed at an angle forabout 1/2 of their length down to approximately 1/8 in. wide atthe tip. This permits a snug fit against the stock rail. (See Figure3-42) As the point begins to move away from the planedsupporting portion, it loses its horizontal support against flexing. A stop block is mounted on the switch point between the planedportion and the heel block. The block bears against the stock rail when the point is in the closed portion, thereby providing

support as the lateral forces from the wheel pushes outward.

The turnout number or the angle of the frog normallydetermines the length of the point required, as well as whether the switch is a curved switch or straight. Allswitch points are either standard or Samson (Figure 3 43)

Figure 3-41 Switch Points - Photo by J. E. Riley

Figure 3-42 Switch Point Fit


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Samson points must be used with a Samson (undercut) stock rail.

Identifying Left or Right Hand Points

The hand of a switch point (Figure 3-44) can be determined by standing at the tip endof the point and looking along its length:

• If switch clips are on the right side of the point, the point is a left hand switchpoint (and vice versa).

Another method when not installed:

• If it looks like an "L" when viewed from the point end, then it is left hand:

3.2.9 Specialty Components

Figure 3-44 Switch Specialty Components – Courtesy of Bernie Forcier

Switch Clips

The switch clips connect the switch rods to thepoints. There are different styles such as thehorizontal transit type vs the vertical MJ type


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Switch Rods

The switch rods hold the switch points together at a fixed distance.16 They restrict theup and down movement of the points. The number of rods used depends on thelength and type of switch point. The longer the point, the more rods are required(from 1 to 7). The rods are spaced from the tip of the point to 1/2 or 2/3 the pointlength (depending on the type of point). Switch point rods may be supplied as eitherinsulated or non-insulated type.

The first rod is called the front or head rod. The last rod is called the back rod and the

others are called intermediate rods.

Types of Switch Rods

There are a variety of available switch rods including:

Horizontal, non-adjustable switch rods (Figure 3-

46) typically are used in conjunction with multiple-hole switch clips to provide adjustment. The rodbolts can be used in various holes when adjusting,but they must be in corresponding holes in theclips, i.e. the same on each side. The rod must beable to move inside the clips as the points are linedback and forth. The rod bolts must be installed with the nut up and cotter pin installed.

Horizontal, adjustable switch rods secure its lengthadjustment by interlocking the serrated edges ofthe rod to various positions and then bolting therod back together. One must ensure that the teethproperly interlock when installing or adjusting.

Vertical switch rods are used in conjunction withMJ and MJS type switch clips. (Figure 3-47)

Figure 3-46 Horizontal Non-Adjustable SwitchRod - Photo by J. E. Riley

Figure 3-47 SMJ Rod - Photo by J. E. Riley


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Connecting Rod Connecting rods are also called the operating orthrow rod. The connecting rod connects thefront switch rod to the switch stand. It may beattached by an adjustable connection (called aclevis) to the crank eye bolt in the switch standand (by a rigid connection) to the front switchrod. There are different types of connecting

rods. Some are adjustable, some are not. Theycome in a variety of lengths depending on theiruse and the type of switch stand being used.(Figure 3-48) On a power switch, the throw(operating) rod is attached to a barrel shaped basket (Figure 3-47), which is connectedto the No. 1 switch rod. Adjustment of the lock nuts to either side of the basketenables adjustment of the switch throw.

3.2.10 Special Turnout Plates

Each type of turnout has a specific set of plates.17 The plates differ in type andquantities for each turnout. These plates include the gauge, switch, heel, hook and frogturnout plates.

Gauge Plates

Gauge plates are placed under the tip endand on the first tie ahead of the point ofswitch to hold the rails in proper gauge. Additional gauge plates are used on springand power switches to provide rigidity.Gauge plates are machined to enable thestock rails to sit in the plate and points to

sit on the plate. A rail brace assembly isthen used to fasten the stock rails to theplate. (Figure 3-49) Gauge plates areeither right or left hand. They may besupplied as insulated or non-insulated. Agauge plate is angle cut on the turnout side

Figure 3-48 Connecting Rods - Photo by J. E. Riley

Figure 3-49 Gauge Plates - Photo by J. E. Riley


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Switch Plates

At the point of switch, the point is beveled back such that it is below the top of thestock rail. (See Figure 3-44) However, the base of the point is elevated above the baseof the stock rail. Switch or slide plates are used under the switch points. (Figure 3-50)Depending on the turnout, they are either of the graduated riser style or the uniformstyle. Slide plates maintain the required elevation of the switch points above the top ofthe stock rail as one moves back to the heel of switch and presents a smooth surface,upon which the points may move right or left. (Figure 3-51) The graduated riser platehas a riser that decreases in thickness, such that at the heel, the elevation of the stockrail and point are the same. The uniform riser plate is the same thickness all the wayback to the heel, such that the switch point is above the stock rail at the heel. Specialtyturnout plates then lower the raised rail behind the heel back down to the elevation ofthe closure rail. In both slide plate types, the riser provides a shoulder to preventinward lateral movement of the stock rail. The stock rail is secured against outwardmovement by spiking to the ties and by rail braces. One cannot mix the type of switchplates being used.

Figure 3-50 Graduated Riser Plates - Photo by Figure 3-51 Switch Point Raised Above Stock Rail - Photo by J. E. Riley J. E. Riley

Rail Braces

A rail brace is used to resist the lateralthrust on the point and stock rails. Railbraces bear against the outside of the stockrails. They are secured to the gauge andswitch plates There are two general types


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guard rail). An adjustable separator block along with the end castings are used to spacethe flangeway opening initially at 1-7/8 inches. As the outside flange of the wheelabrades away the gage face of the guard rail, this dimension will increase. The FRAsets limits defined by the guard face and guard check dimensions to ensure that the wheel is properly contained through the frog flangeway.

Guard rails are supplied in different lengths as specified by the railway’s standard plan. They use a variety of plates, which must be spiked on each end, plus spiked betweenrunning rail and guard rail.

3.2.12 Switch Stands

There are a variety of switch stands inuse.19 Typically, high stand switch standsare used in main line applications; whereasthe ground throw stands (Figure 3-59) areused in industry or yard applications. Automatic switch stands are used toenable the stand to line when points aretrailed through from either route. Mainline switch stands are equipped with atarget that is colored green when theswitch is lined for the normal route andred if the switch is reversed. Yard switches equipped with targets are usually green for

the normal route and yellow for the reverse route.

Spring Switch

This is a hand throw switch equipped with a spring mechanism instead of a rigidconnecting rod. It is often called a mechanical switchman because the points return tonormal position after the passage of each wheel. It is designed to allow trailing pointmovements from the diverging route without having to stop and reset the switch. The

spring switch stands must be bolted to the ties and be of the rigid type. The springswitch is typically provided with a target marked “SS” or other designation.

Power Switch

A power switch is an electrically powered machine that lines the switch Some power

Figure 3-59 Ground Style Switch Stand



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C H A P T E R 3 B A S I C T R A C K

As with the rest of the track, but even moreso, quality turnout and crossing maintenancedemand initially a strong, stable base andexcellent drainage. This may require specialsubgrade preparation including asphaltic orconcrete pads, especially under crossings with high traffic densities. The use of catchbasins and subsurface drainage systems arerecommended where moisture conditions

and traffic are both severe. The proper location of a crossing or turnoutis important. It should be placed off ofcurves. Sharp curvatures or reversals shouldbe avoided at the back of the frog to avoid excessive lurching and lateral thrust in thefrog area.

All parts of a turnout or crossing subject to excessive wear and thrust should be ofhigh-wear resistant materials. Heat-treated or manganese switch points, frogs andguard rails, and heat-treated stock rails are recommended for heavy tonnage locations.

3.3 Railway Crossings &

CrossoversCrossovers (Figure 3-61) can beconsidered as two turnouts, withminor limitations. The trackbetween the two frogs follows thefrog angle. Thus the timber layoutfor half of the crossover is differentfrom that of a turnout.

A crossing is a device used at theintersection of two tracks.20 Itconsists of four frogs and thenecessary connecting rails. Any one

Figure 3-60 Dual Control Power Switch - Photo by J. E.Riley

Figure 3-61 Crossover



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Crossings are designated as singlecurve, double curve or straight,according to one, both or neither ofthe tracks being curved. Crossings areusually made of rolled rails ormanganese castings fitted together. When the crossing angle is greaterthan about 25°, the various pieces arecut to fit against each other and areunited by filling blocks and heavystraps well bolted. This is frequentlytermed solid construction. For anglesunder about 25°, regular frog pointconstruction is used, and such crossings are termed frog crossings versus a crossingfrog.

The end frogs of a frog crossing are similar to a standard rigid frog in that there is a

single point on which the wheels run. The middle frogs, however, have two runningpoints and are therefore frequently termed "double-pointed frogs.”

When "slip switches" are used, thecrossing is made to a standard frognumber, and if located at aninterlocking plant, the middle frogsare frequently made with movable

points. That is, with movable pointsjoined in pairs and moving together,similar to a split switch, in such a way that the wheels have a solidbearing and no flangeway to jump.

A "slip switch" or "combinationcrossing" (Figure 3-63) is acombination of a small anglecrossing with a pair of connecting tracks placed entirely within the limits of thecrossing. They are used in large yards and terminals and are usually made to somestandard frog number.

Very few railways construct their own crossings, but have them built by manufacturers

Figure 3-62 Crossing Frog (Diamond)

Figure 3-63 Double Slip Switches - Photo by J. E. Riley



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- The crossing angle.

- The gage of each track.

- The curvature - degree of curve, radii, or the equivalent.

- The direction of curvature.

- The length along each gage line from one gage line intersection (theoretical P.F.) tothe nearest rail joint.

- Length overall along each gage line.

- The height, weight and style of rail of which the crossing is to be made.

- The height, weight, and style of rail in the intersecting track if offset orcompromise joints are to be furnished.

- The spacing and size of holes for joint bars.

- The type of crossing, etc., unless covered by general specifications.

This information can best be given by means of a small sketch. Field dimensionsshould he taken to the nearest 1/8 in. (0.01 ft.). Occasionally, the field engineer iscalled on to compute the dimensions of a crossing. The values required are the frogangles F1, F2, F3, F4, the length of sides along the gage lines, and the two diagonals. The computations should be made with sufficient accuracy to give results correct tothe nearest 1/16 in., which is the working limit of the manufacturers.

3.4 Highway Crossings The renewal of road crossings represents one of the largest budgetaryexpenditures faced by the Maintenance of Way and Signals Departments.

Typically, railways will look for governmental partnership and participation whencontemplating crossing renewal projects on all but farm and private crossings.Chapter 5, Part 8 of the AREMA Manual for Railway Engineering gives specificguidelines for the design, construction and maintenance of road crossings. TheCommerce Commission of each state in the United States regulates the design,

i d i ll i f bli d i i hi h i i



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Road Crossings are where roads, streets or highways intersect the track at grade.21 Road crossings, or grade crossings as they are sometimes called, result in increasedmaintenance requirements of the track and the road itself. In addition to themaintenance requirements, public safety is obviously of serious concern at roadcrossings.

There are many different types of road crossing materials that are commonlyfound throughout North America. These include: unsurfaced, timber, asphalt,asphalt with timber headers, concrete (both cast in place and precast) andpre-manufactured rubber. Some transit and light rail systems utilize specialty railchairs to support an inner rail, thereby creating a proper flangeway in highwaycrossings. The type of crossing material used is determined primarily by theamount of vehicular traffic that uses the crossing.

Unsurfaced crossings are typically used at temporary crossing locations such asshoe-flys or where construction traffic is required to cross the railway. Thesecrossings may consist of ballast backfilled to the top of rail. Where unsurfacedcrossings are used, care must be taken to maintain a sufficient flangeway for the

train wheels.

Timber crossings may be constructedof either treated wooden planks (oftenused in farm or private crossings)(Figure 3-64) or full gumwoodcrossings, which have beensuccessfully used for many years. This

type of crossing can be used for alltypes of traffic levels from light toheavy. Figure 3-65 presents a typicalcross section for a full-depth timbercrossing.

Figure 3-64 Plank Crossing - Photo by J. E. Riley



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Asphalt or Bituminous crossings(Figure 3-66) are used for crossings with all levels of traffic from light toheavy. These crossings areconstructed by filling in the areabetween the rails with compactedbase material covered by severalinches of asphalt as surfacingmaterial. In some cases, full-depthasphalt may be used between therails. Depending on the level of trainand highway traffic, the flangewaysmay either be formed in the asphaltitself or formed by the use of timberflangeway headers.

Concrete road crossings (Figure 3-67) may be either cast-in-place orconstructed from pre-cast panels.Concrete crossings are typically usedat locations with medium to heavy vehicular traffic. Precast concretecrossing panels are available fromseveral different suppliers.

For road crossings with heavy volumes of vehicular traffic, pre-manufactured rubber road crossingsare often used. (Figure 3-68) Thistype of crossing may be either afull-depth rubber material or asystem of wood shims that areplaced on the ties with the rubbercrossing material placed on top ofthe shims.

3.4.1 Crossing

Figure 3-66 Asphalt & Timber Flangeway Crossing - Photo byRobert Schuster

Figure 3-67 Precast Concrete Crossing - Photo by J. E. Riley



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recommended that all of the ties in the crossing itself, and for 20 feet beyond eachend of the crossing, should be replaced with new high-quality, properly treated, 7”X 9” hardwood ties. Each tie should be tie plated and double spiked with 4 rail-holding spikes per plate. Box anchor all ties through the crossing. For crossingshaving heavy volumes of rail and highway traffic, it may be desirable to install tiepads beneath the tie plates in the crossing area. The presence of bolted rail jointsin a road crossing compounds the maintenance problems normally associated withjoints. All of the joints in the crossing area and for 20 feet to either side of thecrossing should be welded to prevent these problems.

When a crossing is constructed, care must be taken to insure that the trackstructure is sound and durable prior to placing the crossing cover. The rail, tieplates, spikes and ties should be new. Once the crossing cover is on, trackmaterial replacement become difficult and costly. The track geometry (gage,surface and alignment) should be near perfection prior to placing the crossingcover. The ballast in and around all of the ties should be well compacted. It isimportant that fouled ballast materials be removed during crossing reconstructionfor a distance of at least 20 feet off the ends of the crossing. However, it is equallyimportant that excavation not penetrate the hardpan found below the ballast/sub-ballast section. Whenever possible, full closure of a highway crossing from vehicular traffic is desirable for the longest period possible. This ensures that theentire crossing can be raised to an elevation that permits surface water drainageaway from the crossing and that provides the greatest amount of train traffic overthe crossing prior to sealing it up. This helps to prevent settlement and othermovement of the crossing that would be difficult to adjust later. Closecommunication with local and state/province authorities, arranged well inadvance, can do much towards mitigating problems associated with temporarycrossing closures.

In multiple track territory, it is desirable that the top of the rails for all tracks be inthe same plane (See Figure 3-69). The highway surface should match the plane ofthe tracks for at least 24” to either side of the outside rails of the crossing.Connect this plane to the grade line of the highway each way by vertical curvessufficiently long enough to provide adequate sight distance and a smooth ridingcondition for approaching highway traffic (See Figure 3-70). AREMArecommends that the highway elevation at 30 feet from the nearest rail be notmore than 3” higher or 6” lower than the top of rail unless track superelevationdictates otherwise. Tractor trailer rigs can get hung up on a humped crossing. The engineer should verify that the vertical curve gradients utilized are within local



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drainage leads to water ponding in the crossing area. Water should not be allowedto pond anywhere on or near the track. Drainage facilities such as ditches, gutters,catch basins, subdrains and culverts should be in-place, free of debris and workingproperly. The use of geotextile fabrics and/or perforated CMP between thesubgrade and the sub-ballast/ballast section is highly recommended to carry away water trapped within the crossing proper.

Figure 3-69 Maintenance of the Plane Across All Superelevated Figure 3-70 Highway Approach Grade – Photo by J. E. Riley Tracks - Photo by J. E. Riley

3.4.2 Crossing Warning Devices

The safety of a grade crossing to both the motor vehicles and trains should be apriority item for both the engineer and the railway. Past experience has shown

that drivers familiar with a crossing may be very cautious when they know thattrain traffic is either very heavy or irregular. Conversely, a driver may give littlethought to the grade crossing if experience has shown that trains rarely operateover it. Therefore warning signs, signals and pavement markings are importantand must be visible and legible to the motor vehicle operators approaching thecrossing. The state/providential Commerce Commission regulates the type ofsignage, pavement markings and appliances required. In most cases, they refer to“The Manual on Uniform Traffic Control for Streets and Highways.”

The U.S. Department of Transportation, Federal Highway Administration Manualon Uniform Traffic Control Devices provides guidance on marking and signage ofrailway grade crossings. The amount of marking and signing required is a functionof the amount of vehicular traffic using the road, the amount of rail traffic, thet f t i ti ( d di ti it hi ti t ) d th



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warn vehicles of the train. Gates are sometimes used in conjunction with this typeof signal. Automatic warning devices must be inspected and tested monthly toinsure that they are in proper working order. All inspections and tests conductedon these automatic signals must be documented and kept on file per FRArequirement. This provides valuable information in the event of an accident orother sources of litigation. (See Chapter 7 of the Practical Guide To RailwayEngineering for a complete explanation of how highway crossing warning devicesare activated by the track circuits.)

3.5 Utility CrossingsBecause tracks usually traverse great distances, railways will encounter many utilitycrossings such as pipes, wires, cables and other conduits.22 These can be longitudinalalong the right-of-way, perpendicular or crossing diagonally. They can also be eitheroverhead or underground. Most railways and many regulatory agencies have standardsand rules for such installations.

The following are general standards for utility crossings. Check first with the railway to verify acceptance therewith.

1. Overhead crossings must have adequate support at or above the prescribedclearances above the top of the high rail.

2. Underground crossings must be in carrier pipes or casings at or below the

prescribed distances below the lowest base of cross tie or other baselinemeasurement.

3. Underground crossings must be in carrier pipes or casings of sufficient strengthto withstand dynamic railway loading in addition to the weight of soiloverburden at the crossings.

4. Underground pipes carrying volatile substances often require vented casingunder the railway rights-of-way.

5. Underground pipes, wires and cables should have warning signs at groundsurface identifying the utility type, as well as contact names and telephonenumbers.



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7. Prior to beginning any excavations on a railway right-of-way, the entity undertakingthe work should have arranged for the location and surface marking of allunderground pipes, wires and cables (including those owned by the railway). Dothis by checking existing records and through field investigations.

8. Avoid underground crossings very near the ground surface, or those traversing thetrack ballast or existing drainage structures. These present tripping hazards to traincrews and expose the utilities to breakage, possibly causing dangerous situations,contamination and/or erosion.

3.6 Track GeometryHaving now acquired a basic knowledge of the components making up the trackstructure, the engineer needs to understand what drives the need for maintenance,component replacement or track structure rehabilitation and how decisions are madeto prioritize their replacement. For most railways, the decision for component

replacement and the basis of funding justification is driven by:

Maintenance of Safe Operation at Track Speeds - Ensuring the train stays on the track at timetable speeds and that cars, equipment and lading or passengers are not unduly damagedor injured.

On-Time Performance & Service Reliability - Minimizing speed restrictions by performinginterim maintenance consisting of small-scale replacement of components, touch-up

work (smoothing) and other functions that ensure that the track structure remainsserviceable until it is no longer cost effective to maintain for given speeds or thatcustomer service commitments are endangered.

Ride Quality - Maintaining the geometry of the track structure, such that it complies notonly with minimum safety standards demanded by the FRA, but also minimizes damageto lading, as well as ensuring a comfortable ride for the riding public for passenger/transitrailways.

Secure Expected Component Life of the Entire Track Structure - Premature failure of onecomponent will produce a reduced life span for the remaining track components becauseof the interdependent relationships.

Cycle Based Renewals - E.g., tie replacement of 20% of ties every 6-7 years in a given mile to



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the cost of capital required to achieve a cycle based program. It is not desirable to replace1200 to 1400 ties per mile (out of the normal 3,200 ties found per mile) just so that onemeets the minimum safety standards required to operate at the speeds desired.

Now let's look at how each of the criteria mentioned are utilized. Safe operation at trackspeeds and On-Time Performance (reliability) are for the most part speed related. TheFRA (Federal Railroad Administration) Track Safety Standards defines minimumrequirements to which the track structure must be maintained for a given range of speeds. The following table defines the permissible speed ranges for the Class of Track for freighttrains running up to 80 mph and passenger trains running up to 90 mph.

Over track that meets all ofthe requirements prescribedin this part for

The maximumallowable speed forfreight trains is

The maximumallowable speed for passenger trains is

Excepted 10 N/A1 10 152 25 303 40 604 60 80

5 80 90

An additional table for passenger trains defines the class of track for speeds between 91mph and 200 mph (FRA Class 6 – 9). It must be understood that the FRA Track SafetyStandards set the minimum requirements for safe operation of trains. Maintenancestandards must be much more rigorous in order to continue to operate at a given speed.Design and new construction standards require significantly tighter tolerances than that

employed by maintenance standards i.e., it may not be cost effective to maintain therailway at the same level of design/new construction standards if safety and servicereliability are not compromised.

In general, track is dynamic. Other than timber ties, it does not degrade under the absenceof train operations. It, however, degrades exponentially as train speeds are increased. Thus, as speeds go up, the variance or acceptable tolerances from desired parametersmust become tighter. These parameters are broken down into:

- Roadbed

- Geometry

- Track Structure



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Specific minimum parameters dependent on the class of track operated (speedoperated) are defined. Railways, not meeting the minimum requirements for the class

of track being operated, are left with several immediate options to remedy the problem. They may immediately make repairs such that the track is now in compliance. Theymay reduce the speed to a class of track that would be in compliance. They mayclassify the track as Sub-Class 1 and operate at Class 1 speeds for a period not toexceed 30 days prior to repairing the track (assuming the track is safe to operate), orthey may remove the track from service.

On trackage where occupied revenue passenger trains do not operate, and

simultaneous movement at track speeds in excess of 10 mph does not occur within 30feet of the centerline of track on any adjacent track, and trains do not contain morethan 5 placarded Haz-Mat cars (with several other restrictions), track may be declaredas Excepted Track. Such track may be operated at Class 1 speeds and is exempt fromthe 213 Track Safety Standard’s requirements except for a maximum gage limit and therequirement to perform track inspection at Class 1 frequencies.

Service reliability demands that immediate repairs are made. The other avenues for

remediation are unacceptable, except for very short duration. As noted before, day-to-day deviations are taken care of under the normal operating budget. When, however,undue labor or materials are required to remain in compliance for the speed to beoperated, railways must seek capital funding for component replacement orrehabilitation. Rail relays are classic cases of the above. Elimination of jointed rail andreplacement with Continuous Welded Rail (CWR) lowers significantly maintenancecosts. Rail wear occurs not only on the top of the head of the rail (tread) and at thegauge corner (wheel flange contacts the rail), but also where the joint bar comes into

contact with the rail. As this contact area becomes worn (bar and rail), it becomesimpossible to keep the joint bolts tight. This accelerates tie deterioration, as well aspromoting secondary batter of the rail end, chipped joints, dangerous rail defects, mudpumping and a host of other problems related to poor track.

The maintenance of good track geometry is essential to securing good ride quality. When the parameters defined by geometry begin to deteriorate, one very quicklymoves from poor ride quality to component deterioration and outright failure.

3.6.1 Gage

Consider the parameters making up geometry. The first parameter is gage, which is the



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Standard gage is 4' 8-1/2" (56-1/2").Railways are concerned about not only

wide gage, which comes from rail headabrasion in curves, worn spike killed ties which allow the rail to move outward, worn rail base eaten away by salt incrossings and numerous other factors, butalso by tight rail that may cause the wheelto climb up onto the ball of the rail andthen drop in. Dependent on location, typeand wear of wheel and a host of otherfactors, the wheel may fall in when thegage exceeds 58-1/2" (2" wide gage). Under the 49 CFR 213 FRA Track SafetyStandards, one is not allowed to operate trains at any speed if the gage exceeds 1-3/4" wide. In comparison, to operate at Class 4 (80 mph passenger/60 mph freight),trackage may not exceed more than 1" wide gage under load.

Maintenance of gage is a priority not only because of the need to not have trains falling

through between the rails, but also because it permits the flange of the train wheel tohunt from rail to rail, thus knocking the track out of alignment . Replacement of curve worn rail in curves or the transposition of rail (making the low rail the high and vice versa) and replacement of deteriorated ties (the primary cause of wide gage) are thechief weapons in combating wide gage problems.

3.6.2 Alignment Another parameter of geometry alreadymentioned is alignment. Alignment isthe position of the track or rail in thehorizontal plane. It is expressed as beingtangent or curved. (See Figure 3-72) Alignment is measured in straight trackby stretching a 62' string between two

points along the gage corner of the rail. The offset measurement between thestring and the gage corner of the rail istaken at the midordinate (center of thestring (31')). If the track is perfectly

Figure 3-71 Measuring Gage – Photo by Larry Slater

Figure 3-72 Curved Alignment - Photo by Bill Ross



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components of a curve. There are three specific elements of a curve that must beconsidered:

- Full Body of the Curve

- Transition Spiral Entering and Leaving the Curve

- Superelevation in the Curve

Full Body of the CurveIn a perfectly circular curve, the radiusof the curve at any point along the curveis the same length. (Figure 3-73) It justso happens, that when one stretches a62' chord (string) with either end of thestring at the gage corner of the rail (5/8inches below the top of rail), at any

point throughout the curve, themeasured offset (between the string andthe gage corner of the rail) at the mid-ordinate (center of the string) in inchesis also the degree of curvature of thecurve at that point. (See Figure 3-74)(See the Appendix for diagrams and literature detailing the relationship between midordinate measuredand degree of curve.)

The degree of curvature should be the same at every point checked around the fulllength of the full body of the curve. But curves are hard to keep in line, especially where gage and surface related problems are present. By taking successivemeasurements around the curve and then averaging these measurements, one candetermine an average existing midordinate or degree of curvature. Dependent on theclass of track operated, the FRA in the Track Safety Standards defines the procedureutilized for determining the average midordinate for the curve.

The difference, then, from the measuredmid-ordinate (degree of curvature) at apoint of concern, and the averagemidordinate determined for the curve as

Figure 3-73 Full Body of Curve - Photo by Larry Slater



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will lead to surface related problems.

Transition Spiral of the Curve

A train progressing at speed down tangenttrack would undergo a significant lateralacceleration if it instantaneously went fromtangent track to full degree of curvature where the tangent track ended and the curvebegan. To combat this problem, a transitioncurve called a spiral is introduced at thebeginning of the curve and at the end beforethe curve returns to tangent. (See Figure 3-75) The degree of curvature of a spiral(cubic parabola) starts at zero and ends up atthe full curvature over its length at roughlyan even rate. (See Chapter 6 Railway Track Design for a complete discussion of the spiral curve. Asample calculation illustrating the calculation of deflection angles and other required curve componentscan be found in the Appendix.)

Curve Elevation

The other element of a curve that must be considered is the effect of centrifugal force asthe car moves around the curve. The sharper the curve (the shorter the curve radius)and the higher the speed, the greater the centrifugal force. This force tends to cause the

wheels to move towards the outside rail as much as one may have experienced on anamusement park ride. To counter this force, railways elevate the outside rail of thecurve, or in railway parlance add superelevation, to counter the effects of centrifugalforce. Through the full body of the curve (the circular segment of the curve), theelevation required to offset the effects of centrifugal force is constant for a given speed.

The amount of superelevation required is determined by the speed of the fastest trainand the degree of curvature present. Excessive elevation for the speeds operated willmash the low rail or even cause low rail turnover. Too little elevation for the speedoperated may cause the wheel to climb the high side and derail. Not all trains operate atthe same speed through a curve. Railways are permitted to operate with a maximum ofthree inches of unbalance for conventional equipment and with approval of the FRA, athigher levels of unbalance for specialty equipment per Subpart B. This enables thebalancing of elevation for both the highest and slowest speed trains operating through

Figure 3-75 Transition Spiral Curve - Photo by LarrySlater



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used to also transition in the increase in elevation until at the end of the spiral when fullelevation is reached. At the end of the full body of the curve, a spiral is used to

transition the full elevation back to zero when the tangent section is again reached. (SeeChapter 6 Railway Track Design for a complete discussion on the use of the spiral curve to transition in full superelevation.) Thus, both lateral and vertical increase in acceleration of the car bodyoccurs at a constant rate without feeling an abrupt change. The weight of the train,deviation in gage and alignment, as well as resultant surface track problems, make itdifficult to maintain these elements in the desired state. Deterioration of other trackcomponents further exacerbates the maintenance of curves and tangent track. Thecorrection of alignment, surface and how these two relate to curves is called surfacing.

It is a key component in the renewal or rehabilitation of the track structure.

3.6.3 Surface

The next primary element of geometry is surface. Surface describes the verticalrelationship of the track structure and is comprised of run-off, profile, crosslevel,reverse elevation in curves and warp or twist (difference in crosslevel).

Each category of surface affects the train's response to the track and must beconsidered in performing all track construction and repair tasks. Speed-sensitivemaximum tolerances have been establishedfor all of the elements of surface.

The top of rail elevation of newly workedtrack must be blended into the elevation of

the existing track during surfacingoperations, where the track is raised, whenrenewing the deck of a bridge or performing work on other track structure elementschanging the top of rail elevation. If notcareful in blending the new elevation of thetrack, a car traversing over the blended tracksection will get a severe bounce, which in

some cases may uncouple the train. We call this abrupt change in elevation run-off.(See Figure 3-76) The greater the speed, the greater the bounce, if the run-off is tooabrupt. Run-off allowable limits are determined by stretching a string along the top ofthe rail and by measuring the change in elevation of either rail in 31'.

Figure 3-76 Run-off Between Bridge Segments - Photoby James Bertrand



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Figure 3-77 Measuring Profile Figure 3-78 Measuring Crosslevel

Surface also includes crosslevel (Figure 3-78), which is the difference in elevationbetween two rails at any given point. In tangent track, the crosslevel should be zero.Both rails should be at the same elevation.

In curved track in the full body of thecurve, the crosslevel should be at

whatever is the designatedsuperelevation. In the spiral, thecrosslevel should be whatever theincremental amount of elevation isbetween zero and full elevation for thatpoint in the transition curve. Thedifference between what the crosslevel isand what it should be at that point is

known as the deviation in crosslevel.Specific limits are also set on the amountof reverse elevation permissible in curves (i.e., the outside rail in a curve is lower thanthe inside rail at a given spot).

Difference in crosslevel or warp (Figure 3-79), the fourth category of surface, can causethe front of the car to lean in one direction and the rear of the car to lean in the othersimultaneously. The resultant wracking action on the car may cause a wheel to lift. Warp is also the cause of the famous rock-n-roll phenomena, whereby successive lowjoints at critical speeds will cause certain types of cars to go into resonance (reach theirnatural frequency). They wi

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