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Railroads

AMANDA STAHLNEKER, P.E., HDR ENGINEERING, INC. (CHAPTER EDITOR); WILLIAM JANSEN, P.E., HDR ENGINEERING, INC. (TECHNICAL EDITOR); SHANE POTTS, P.E., HDR ENGINEERING, INC. (BRIDGES)

§ 8.1 Railway Industry Overview§ 8.1.1 Railroad Companies and Organization§ 8.1.2 Regulatory Agencies and Industry Associations

Regulatory AgenciesIndustry Associations

§ 8.2 Basic Operations§ 8.2.1 Types of Tracks

Main Line TracksSecondary and Branch LinesSidingsSpursIndustrial TracksYardsWyes

§ 8.2.2 Safety of Operations§ 8.2.3 Tracks and Authority of Movements

§ 8.3 Locomotives and Cars§ 8.3.1 Cars§ 8.2.3 Locomotives§ 8.3.3 Cabooses

§ 8.4 Roadbed and Track Components§ 8.4.1 Rail§ 8.4.2 Other Track Materials § 8.4.3 Ties§ 8.4.4 Ballast§ 8.4.5 Subballast and Subgrade

§ 8.5 Special Trackwork and Components§ 8.5.1 Turnout§ 8.5.2 Crossover§ 8.5.3 Diamond§ 8.5.4 Derails, Wheel Stops, and Bumping Posts§ 8.5.5 Highway Grade Crossing

§ 8.6 Track Geometry and Design§ 8.6.1 Horizontal Alignment§ 8.6.2 Vertical Alignment§ 8.6.3 Design Considerations

Tangent Track between Curves and TurnoutsOverlapping Horizontal and Vertical CurvesTrack Centers and Clearances

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§ 8.7 Hydrology and Hydraulics§ 8.7.1 Hydrology§ 8.7.2 Hydraulics

§ 8.8 Railway Structures§ 8.8.1 Bridge Components

SuperstructuresSubstructuresReinforced Concrete Piers

§ 8.8.2 Bridge TypesTimber BridgesConcrete BridgesSteel BridgesMoveable Bridges

§ 8.8.3 Tunnels§ 8.9 Loading

Live LoadImpact LoadLongitudinal Load

§ 8.10 Environmental Regulations and Permitting§ 8.10.1 National Environmental Policy Act§ 8.10.2 Waters of the United States and Wetlands§ 8.10.3 Threatened and Endangered Species§ 8.10.4 Cultural Resources§ 8.10.5 Hazardous Waste§ 8.10.6 Air Quality§ 8.10.7 Noise

§ 8.11 Right-of-Way§ 8.11.1 Valuation Maps§ 8.11.2 Fences§ 8.11.3 Utilities§ 8.11.4 Vegetation

§ 8.12 Communications and Signals§ 8.12.1 Basics of Signal Systems§ 8.12.2 Energy/Power Source§ 8.12.3 Track Circuits§ 8.12.4 Track Switches§ 8.12.5 Highway Crossings§ 8.12.6 Centralized Traffic Control (CTC)§ 8.12.7 Positive Train Control (PTC)§ 8.12.8 Defect Detectors

§ 8.13 Passenger Rail§ 8.13.1 Passenger Rail Modes§ 8.13.2 Passenger Equipment§ 8.13.3 Passenger Service Characteristics§ 8.13.4 Infrastructure Needs§ 8.13.5 Commuter and Intercity Rail

244 Infrastructure from the Ground Up


§ 8.13.6 High-Speed Rail§ 8.13.7 Rapid Transit§ 8.13.8 Light Rail Transit and Streetcar§ 8.13.9 Maintenance§ 8.13.10 Electrification

§ 8.14 Maintenance and Track Construction§ 8.14.1 Track Disturbance Activities§ 8.14.2 Rail Lubrication§ 8.14.3 Rail Grinding§ 8.14.4 Rail Defect Testing§ 8.14.5 Geometry Measurement§ 8.14.6 Gauge Restraint§ 8.14.7 Vegetation Control§ 8.14.8 Snow Removal§ 8.14.9 Production Gangs§ 8.14.10 Schedule Windows§ 8.14.11 Railroad versus Third-Party Construction§ 8.14.12 Third-Party Access§ 8.14.13 New Track Construction

§ 8.1 RAILWAY INDUSTRY OVERVIEW

Railways1 have existed since the sixth century BC, progressing from man-hauled carts along grooves in limestone to today’s technology. This long history of the railway industry includes the replacement of steam engines with diesel engines, the development of electric trains, and the launching of high-speed rail. Even with these advances in technology, the basic definition of a railway remains unchanged. A railway is an engineered structure that consists of two guiding rails that convey passengers and goods via wheeled vehicles.2

§ 8.1.1 Railroad Companies and Organization

The railroad industry encompasses a wide range of companies, organizations, and groups, including operating railroad companies; transit authorities; govern-mental regulatory agencies; railroad associations; professional organizations; manufacturers and suppliers of track materials and railcars; consultants; con-tractors; educational institutes; and the customers of the system—the shippers and passengers.

A railroad company is an entity that operates a railway (or track) and/or trains that operate on the railway. In the United States, some companies operate both the trains and the track; by contrast, in Europe, ownership of track and train operation is frequently separated into different companies.

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Various types of railroad entities exist, including the major freight “Class 1” railroads (e.g., Union Pacific Railroad and BNSF Railway), short-line or regional railroads (e.g., Dakota, Minnesota & Eastern Railroad, and Nebraska Central Railroad Co.), passenger or commuter railroads (e.g., Metra and Amtrak), and transit agencies (e.g., Chicago Transit Authority and Metropolitan Transportation Authority). Their ownership varies based on the type of service they provide. Government-owned freight railways are limited in current times to some regional rail lines while passenger rail-ways are generally owned or sponsored by governments. Transcontinental services are corporations solely owned by their respective federal govern-ments. Typically, passenger railroads do not own trackage infrastructures, except for certain connecting portions or dedicated high-speed rail corri-dors; rather, passenger railroads operate their equipment on existing tracks that are typically owned by freight railroads. Local rapid transit systems are usually operated as public utilities on their own trackage. Commuter services work in any way that best suits the needs of the service and can be operated by government or the private sector, either on their own tracks or on another entity’s railway.

§ 8.1.2 Regulatory Agencies and Industry Associations

Regulatory AgenciesThe United States has three major railway regulatory agencies: the Surface Transportation Board (STB), the Federal Railroad Administration (FRA), and the National Transportation Safety Board (NTSB). Other governmen-tal authorities can also exert regulatory control over railroads, including state agencies, state departments of transportation (DOTs), commerce commissions, and local governmental entities empowered to enact local ordinances.

Industry AssociationsVarious industry associations serve the differing aspects of the railroad indus-try. The main associations include the following:

• Association of American Railroads (AAR)• American Railway Engineering and Maintenance-of-Way Associa-

tion (AREMA)• Railway Engineering-Maintenance Suppliers Association (REMSA)• Railway Systems Suppliers, Inc. (RSSI)

All of these associations, including many others, meet annually to discuss the railroad industry. They help form the framework for the industry; transfer knowledge about markets, products, and practices; and support government initiatives that advance the industry.



§ 8.2 BASIC OPERATIONS

§ 8.2.1 Types of Tracks

As described in this section, the types of railway tracks are as numerous as the types of needs they serve.

Main Line TracksMain line tracks carry a majority of the traffic. They run through yards and between stations connecting various major points along the rail line. Main line tracks will always have a method of “control of operations” in place. Main lines are owned by railroad companies but may be used by multiple parties, based on their agreements with the owner.

“Single track” refers to one track (whether main line, secondary track, or branch track (see below)) controlled by one owner. Single track could have various sidings or industrial tracks operating off of it, but there is only one track that operates through the entire stretch of that track.

“Double track” refers to two tracks running parallel to each other, con-trolled by the same owner. These tracks can have various sidings or industrial tracks operating off of them, but two tracks operate through the entire stretch of that track.

Secondary and Branch LinesSecondary or branch lines are not used as heavily as main line tracks, but they operate similarly. The main distinctions between branch lines and main lines are the volume of the traffic and type of operation on the line rather than any physical difference in the track itself.

SidingsA siding is a track that is connected to the main line or secondary track and is used for meeting or passing trains. The siding is connected to the main line or secondary track at two ends, allowing access from either direction. When two

trains are traveling on the same track and one of the trains needs to pass the other, one of the trains will park on the siding to allow the other train to pass. An example of a siding track is shown in figure 8.1.

SpursSpurs, sometimes referred to as “stub tracks,” are tracks that diverge from main line or other tracks to provide access to an industrial or commercial area and end there. Spurs may be owned by railroads but are more commonly owned by the indus-trial or commercial carriers they serve.

Figure 8.1 Example of Siding Track

Photo courtesy HRD, Inc.

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Industrial TracksA railroad company or industry may own and operate industrial tracks. The track owner has an agreement in place that ensures delivery of cars to the industrial track and determines the limits of owner-ship and maintenance for each party.

Typically, limits of ownership and maintenance coincide, but they can vary depending on the agreement. The major-ity of the time, the limits of ownership are situated at the “right-of-way” line or the “clear point” of the track. The clear point is the intersection of the industry track and an offset distance from the track serv-ing the industry track. For most railroads, a minimum 13-foot offset designates the clear point.

YardsA yard is a system of tracks (other than main tracks or sidings tracks) that is used for, among other things, making up trains and storing cars. Typi-cally owned and operated by railroads, yards may be composed of a few tracks or dozens of tracks; the function of the yard determines the number of tracks. A photo of a yard is shown in figure 8.2.

WyesA wye is the arrangement of two tracks that forms a “Y,” used for turning engines, cars, and trains to travel in the opposite direction, as shown in figure 8.3.

§ 8.2.2 Safety of Operations

The first priority for railroads is the safety of operation for both employees and the trains that operate on the railway. All railroad employees and con-tractors are responsible for their actions and thus responsible for their safety and the safety of those around them.

The biggest misconception about trains is how quickly (or slowly) they can stop. The distance a train requires to stop is a function of its weight, speed, configuration, and other factors. A typical freight train operating at a normal speed requires approximately one mile to stop once it engages its brakes.

Figure 8.2 Example of a Yard

Photo courtesy Union Pacific

Figure 8.3 Example of a Wye

Source: Erik Baas; commons.wikimedia.org



To achieve the capacity to move traffic safely, efficiently, and produc-tively under all weather conditions, every railroad must have regulations in place to govern operations, commonly referred to as “operating rules.” Each railroad requires its staff to be trained on the applicable operating rules and certified at regular intervals (annually in the United States). In addition to operating rules, the FRA issues further regulations for maintenance and con-struction of railroads.

§ 8.2.3 Tracks and Authority of Movements

Tracks are generally divided into “main tracks” and “other than main tracks,” based on the level of control required for train or engine movements. “Main tracks” refer to the series of tracks that carry the majority of traffic, while “other than main tracks” refer to all remaining tracks.

Main tracks can only be used once the train receives orders of author-ity and protection from the dispatchers/rail traffic controllers or tower opera-tors. Protective orders ensure that no train would be at risk of colliding with another train on that track. Once the protective order is in place on a par-ticular track, then the dispatcher will give authority to a train to move along that track. Portions of these tracks may be designated by limit signs in the field and/or by timetable or special instructions that permit certain types of movements without specific authority. These limits, often referred to as “Yard Limits,” normally include speed restrictions.

“Other than main tracks” do not require authority. These tracks rely on the locomotive engineer’s observance of other movements, obstruc-tions, and people working on the tracks to provide safe movement. As a result, these trains or engines must move at a restricted speed—a speed slow enough to stop suddenly for another train, a problem on the track, a stop sign, and so forth.

On “signaled tracks,” the entire trackage is bonded with track circuits and signals. Sidings and signaled tracks can either be controlled by the rules of main track or “other than main track.” Instructions regarding track con-dition restrictions and other information may be issued via general bulletin orders, train orders, daily operating bulletins, or track bulletins.

§ 8.3 LOCOMOTIVES AND CARS

§ 8.3.1 Cars

Locomotives and railcars continue to develop to meet the changing demands of the service provided. For instance, freight cars have a basic configura-tion of a car body that carries the freight sitting on two trucks,3 each with

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two axles. This basic configuration has not changed, but the car bodies have evolved to meet the specific requirements of the different freight they carry. Some examples of different freight cars are:

• Boxcars• Insulated boxcars and mechanical reefers• Intermodal Cars: piggy-back trailers and containers• Flatcars• Auto rack cars• Gondola cars• Hopper cars• Rotary gondola/hopper cars• Tank cars• Maintenance-of-way cars• Schnabel cars

Passenger cars serve a different purpose and, consequently, are designed and built to be safe and comfortable for the transport of people. Typical pas-senger cars are coaches, sleepers, dining cars, sightseeing domes, and bag-gage cars.

§ 8.3.2 Locomotives

Although historically several different power sources for locomotives existed, with the exception of a few tour trains and museum pieces, steam locomotives are mostly extinct. They have been replaced by diesel or electric locomotives. Figures 8.4 and 8.5 are examples of locomotives.

§ 8.3.3 Cabooses

A caboose was a railcar located at the end of the train that provided offices and quar-ters for the crew as well as a viewing posi-tion from which a crew member could observe the train during operations. Until the 1980s, the law required cabooses with a full crew for safety on all freight trains in the United States and Canada. As technology advanced, railroads saved money and reduced crew members by replacing cabooses with FREDs (flashing

Figure 8.4 Freight Locomotives

Figure 8.5 Passenger Locomotive

Photo by Danielle Scott; commons.wikimedia.org



rear-end devices) or EOTDs (end of train devices). Very few cabooses remain in operation today.

§ 8.4 ROADBED AND TRACK COMPONENTS

A track system is composed of elements divided into two major categories: (1) track structure and (2) track foundation (commonly referred to as “road-bed”). Without a proper track structure and foundation, the track system will not operate successfully. The specific requirements and dimensions of each element of the track system are specified by the owner of the track.

The track structure is composed of the rail, other track materials (OTM), ties, and ballast. The track foundation, composed of the subballast and sub-grade, forms the roadbed for the track structure. Figure 8.6 displays a typical track system.

§ 8.4.1 Rail

The rail provides the smooth running surface for trains to operate by guid-ing the wheel flanges of the railcars; it also serves as a means to transfer the weight of the trains to the ties. Rail has evolved over the years, but in North America, the standard is an inverted “T” rolled from steel.

Rail size can vary in weight and shape. The size of the rail used for a track is dependent on the tonnage that will be applied to the rail and the fre-quency of the tonnage. The weight of the rail is based on how much the rail weighs in pounds per yard. Weights of rail smaller than 90 pounds can be found in existing track but are not commonly used in new construction. As traffic increases on the track, the necessary weight of the rail increases. The largest rail commonly used today is 136-pound rail, but larger rail is becom-ing more common in main line construction. The cross section shape of the rail is commonly referred to as the rail section.

Another element of the rail that varies is the “gauge” of the track, which is the distance between the inner sides of the heads of two rails that make up a single rail line. Gauge is measured at right angles at 5/8 inches below the top of the rail. Approximately 60 percent of the world’s railways use “standard gauge,” being 4 feet, 8 1/2 inches, as shown in figure 8.7. Wider gauges are referred to as “broad gauge.” Smaller-than-standard gauges are referred to as “narrow gauges.” Modern North American railroads generally use standard gauge track.

TieRail

Tie plate

Ballast

Subballast Subgrade

Figure 8.6 Typical Track System

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Another characteristic of rail is its method of connection. Rail is deliv-ered in “sticks,” which are certain lengths of rail, to be installed. Jointed rail is track that is composed of sticks joined together at their rail ends by two angle bars. The angle bars hold the two ends of the rail in place and act as a bridge between the rail ends. Three basic types of rail joints are:

• Standard—connects two rails of the same weight and section• Compromise—connects two rails of different weights or sections• Insulated—used in tracks that have track circuits

Welded rail is referred to as “continu-ously welded rail” (CWR), whereby sticks of rail are welded together utilizing flash-butt welding to form a continuous rail. Thermite welding is utilized to repair or splice together existing CWR segments.

§ 8.4.2 Other Track Materials

Other track materials (OTM) refers to the components used to connect the rail to the ties. This section describes the basic OTM for a track system.

Tie plates, located between the rail and tie, provide a smooth and uniform

bearing surface and prevent the rail from cutting into the tie and help to main-tain the gauge of the track. Tie plates are designated as either single shoulder or double shoulder, depending on the rail size. They come in a variety of sizes, but the most common new plate produced is 7 3/4 inches x 14 inches.

Rail anchors are used to control the longitudinal creeping of the rail caused by changing temperatures, grades, traffic patterns, and braking action of trains. Anchors are applied directly to the rail base and lodged up against the tie. Anchors are made for a specific rail weight and base width.

Rail fasteners come in many types and can be grouped by their use: to connect rail or track components together; to fasten rail to the ties; or to reduce the movement between the tie plate and tie, vertically and horizon-tally. Some types of fasteners are:

• Spikes—used to maintain gauge between rail and secure the rail to the tie

• Lag screws—used to fasten elastic fastener plates and other specialty track components to timber ties

• Clips—used to fasten rail to plate; functions like a sturdy paper clip• Bolts—used to connect rail ends together at a joint

Figure 8.7 New Rail Line Next to Existing Track

Photo courtesy HDR, Inc.



§ 8.4.3 Ties

Ties are used to cushion and transmit the load of the train to the ballast sec-tion and to maintain the gauge of the track. Consequently, ties need to pro-vide durability and resistance to crushing and abrasion. The usage of the tie and traffic on the track dictate the makeup and length of the tie and the tie spacing. Ties are typically made of wood or concrete, although the use of steel and alternative materials is growing in popularity.

Timber ties are predominantly used in the United States. They are typi-cally pressure-treated with preservatives (such as creosote) to protect them from insect and fungal attack. Timber ties come in two types: hardwood, typically used for track and switch ties; and softwood, often used for bridge ties in open deck bridges. Hardwood ties provide a longer life and are less susceptible to mechanical damage.

Timber ties are graded with nominal dimensions and other physical char-acteristics. Timber ties are typically 7 inches wide x 9 inches deep, but length can vary. Ties of 8 feet, 6 inches are fairly standard, but 9 feet, 0 inch ties are used on moderately heavy to heavy traffic conditions and in curves of six degrees or more, because the increased length provides greater stability. A smaller tie used for sidings, industrial tracks, and very light density tracks is 6 inches x 8 inches x 8 feet. Physical characteristics such as having more bark, splits, or other surface-related defects can lead to the tie being graded as an industrial grade. The AREMA and the Railway Tie Association (RTA) publish specifications and standards related to the grading of timber ties.

Timber switch ties are commonly hardwood and run in 6-inch or 12-inch increments starting at 9 feet, 0 inches and extend up to 23 feet, 0 inches in length. The primary use for switch ties is within turnouts (hence the name), but they are also used for bridge approaches and crossovers, at hot box detectors and as transition ties.

Figure 8.8 Track Components


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Concrete ties are growing in popularity for heavily traveled main line tracks and for curvature greater than two degrees. Composed of pre-stressed concrete and containing reinforcing steel wires, a concrete tie weighs about 600 pounds, compared to 200 pounds for a timber track tie. A specialized pad is required beneath the base of the rail to cushion and absorb the load and to better fasten the rail to the tie. An insulator and an insulator clip are used to isolate the tie electrically.

Because of problems associated with the shunting of signal current flow to ground, steel ties have not been widely accepted in the rail industry. They do have strategic uses, however. Steel ties are often used for specialized plant locations or other locations that are not suited to concrete or timber ties. For instance, where heavy curvature is prone to gauge widening, steel ties are utilized.

Several alternative material ties have been developed and tested in research settings but have had limited real-world application or use. Alternative materi-als used for ties include ground-up rubber tires, glued reconstituted ties, and plastic milk cartons. All of these materials require the addition of appropriate polymers to produce a tie that meets specified criteria. The use of alternative materials for ties is growing as environmental consciousness increases.

§ 8.4.4 Ballast

Ballast serves the critical purpose of providing stability to the track structure. It anchors the track as trains travel over the rail, distributes the load from the railroad ties, and provides resistance against lateral, longitudinal, and vertical movement of the ties and rail. One key element of the ballast is that it facili-tates drainage of water on the tracks. Good drainage is vital for the stability of the tracks.

Ballast is installed between, around, and under the ties. The ballast between the ties fills the crib but does not rise above the top of the tie. Ideal qualities of ballast include hardness and toughness, ability to drain, durability to abrasion and weathering, resistance to deformation, freedom from delete-rious particles (dirt), workability, compactability, ease of cleaning, availabil-ity, and cost-effectiveness. It is important that ballast provides the maximum stability at a minimum overall cost, including post-installation elements (fre-quency of maintenance; life of rails, ties, and fasteners; and labor costs).

Factors that affect the stability and compactability of the ballast are the shape of the ballast particles, the degree of sharpness, angularity, and surface texture. Ballast sizes can also vary based on their usage and track ownership. The AREMA Manual for Railway Engineering (AREMA Manual) recommends ballast sizes, as do AASHTO and ASTM for some situations.

Angular stones are preferred for the ballast because they can interlock with each other and inhibit track movement. Soft materials, such as limestone, are unsuitable because they tend to degrade under the load when they are wet. Unfortunately, one of the best materials for ballast is granite, due to its strength and limited degradation, but its use is often not practical due to its high cost.



§ 8.4.5 Subballast and Subgrade

The subgrade is the finished surface upon which the track is built; it is com-posed of four basic features:

1. Width of the top of the subgrade2. Height of fill or depth of cut3. Sideslopes of cut or fill4. Provisions for drainage

The subgrade is critical to developing a stable roadbed for the track. A geotechnical engineer’s analysis is often required to provide recommenda-tions for subgrade preparation. In cases where the subgrade is not suitable, a wide variety of options exist to increase its stability. The most common option is to overexcavate the poor soil material and replace it with more suit-able material. Another common option is to use a geotextile fabric or geogrid or a combination of the two to help stabilize the subgrade.

Subballast is a material placed directly on top of the subgrade to serve two main purposes: (1) divert water from the ballast into drainage ditches and (2) distribute the weight of the rolling stock and track onto the subgrade. The subballast typically only covers the subgrade top width but can be used along drainage ditches and sideslopes as necessary.

§ 8.5 SPECIAL TRACKWORK AND COMPONENTS

§ 8.5.1 Turnout

A turnout is a specialized track that guides trains from one track to another. The turn-out is composed of a switch, a “frog,” stock rails necessary to connect the switch to the frog, two guardrails (if the frog is not self-guarded), and a switch stand or switch machine to operate the switch. Figure 8.9 displays the basic components of a turnout.

The switch is a device used to deflect the wheels of a train from the track upon which it is running to another track. A switch refers to the portion of the turnouts from the point of switch (PS) to the heel of switch (HS).

A split switch is the most commonly used switch. Consisting of two switch rails connected by switch rods, it operates as a unit. The switch rails are a full section at one end (heel) and are tapered to 1/4 inch

Figure 8.9 Basic Components of a Turnout

Photo by Yaguchi; commons.wikimedia,org

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or 1/8 inch at the other end (point). Switch rails rest on metal plates fastened to the ties. The heel of each switch rail is connected to its lead rail by special joint bars, and the switch as a unit pivots about these connections. The point of switch moves through a distance of about 5 inches, referred to as the throw. The movement of the switch rails is controlled by a switch mechanism.

A switch mechanism moves the switch points and is placed outside of the track on the head block ties. Switch mechanisms operate the turnouts. When turnouts are hand-operated (operated by a switch stand), they are referred to as a hand-thrown turnout (HTTO). When they are power-operated (operated by a switch machine), they are referred to as a power-operated turnout (POTO).

Located at the intersection of two running rails, the frog permits the flange of a wheel moving along one rail to cross to the other rail, which is also referred to as the crossing point of two rails. This assembly resembles a frog with its legs extended.

The frog is designed to ensure that the wheel of the train crosses the gap in between the rails without falling into the gap; the frog ensures that the wheel is always supported by at least one rail.

There are three basic types of turnouts:

• Lateral• Equilateral• Lap

Lateral turnouts are either straight movement or diverging (right-hand or left-hand depending on the direction of the diverging track).

Equilateral turnouts do not have a straight movement, but are composed of two equally diverging routes. These turnouts are typically used in areas of higher operating speed or congestion, or at the ends of double track territory.

Lap turnouts (turnouts that are overlapping) are used when minimum clearances and maximum track lengths are required. A lap turnout contains two sets of switch points and three different frogs.

Turnouts are further identified by their size and are classified by their divergence and length. Regardless of the type and size, a turnout begins with the switch and ends with the frog. However, the term “turnout” often refers to the entire track structure resting on switch ties.

AREMA and many railroads have standardized their switch tie layouts, where all the ties throughout a turnout are longer than the track ties on either side of the turnout. The two switch ties under the switch mechanism are called the head block ties. The ties under the heel block assembly are called the heel block ties. The ties under the frog are called the frog ties.

§ 8.5.2 Crossover

Crossovers are used in much the same way as turnouts are but have a slightly different configuration. The track between the frogs is arranged to form a con-tinuous passage between two nearby and generally parallel tracks. An exam-ple is shown in figure 8.10.



§ 8.5.3 Diamond

In a diamond crossing, one track crosses another track at grade and consists of four connected frogs. An example is shown in figure 8.11.

§ 8.5.4 Derails, Wheel Stops, and Bumping Posts

A derail is a device that keeps tracks clear from unauthorized train movements or unsecured rolling stock. When properly placed, this device will guide the wheels of equipment or the train off the tracks as it rolls over or through the derail. Derails are designated as right-hand or left-hand depending on the direction of the desired derailment.

Typical applications include:

• Where spurs or sidings meet main line tracks or other through tracks

• Where yard tracks meet main line tracks or other through tracks

• Areas where crews are working on a railway

Wheel stops, bumping posts, and earthen bumpers are used to prevent railcars and equipment from rolling off the ends of tracks and to protect struc-tures from damage.

§ 8.5.5 Highway Grade Crossing

Highway grade crossings are the intersection of tracks at grade with roads, streets, or highways. Many different types of materials are used at road cross-ings in the United States, including:

• Unsurfaced—ballast is used to backfill to the top of rail to suffice as a crossing; typically used at temporary crossings locations

• Timber—constructed of either treated wood planks or full gumwood crossings; used for light to heavy traffic levels

• Asphalt—constructed by filling in the area between the rails with compacted base material covered by several inches of asphalt as sur-facing material; used for light to heavy traffic levels

Figure 8.10 Example of Crossover

Photo by Chris McKenna; commons.wikimedia.org

Figure 8.11 Example of Diamond Crossing

Photo by John Mueller; commons.wikimedia.org

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• Concrete—either cast in place or precast concrete; typically used for medium to heavy traffic levels

• Premanufactured rubber—can be either a full-depth rubber material or a system of wood shims that are placed on the ties with the rubber crossing material placed on top of the shims; used for crossings with heavy vehicular traffic

The type of crossing material to be used depends primarily on the amount of vehicular traffic that will be using the crossing.

Maintenance and safety are two big concerns at grade crossings. In addi-tion to the railroad’s basic standards to which crossings are constructed, AREMA and AASHTO have additional recommendations and requirements, as do some states and local agencies.

The FRA has a crossing inventory that contains a database of all high-way grade crossings in the United States, identified by a crossing number. The database includes information such as location, physical characteristics, railroad information, highway information, traffic control information, and accident data. Information regarding the crossing number designation can be found in an FRA document titled “Assignment of Crossing Inventory Num-bers,” dated March 25, 2009.

In initial or reconstruction, the crossing and 20 feet each side of it must utilize new tracks materials, tie plates, and double spikes with four rail-holding spikes per plate. In addition, all of the joints through the crossing and for 20 feet on each side of the crossing should be welded to prevent additional main-tenance problems.

Although it would be ideal for the tops of multiple rails at a crossing to be on the same plane, that is often not the reality. At minimum, the planes of the highway surface and the track should match for at least 24 inches to either side of the outside rails of the crossing.

The amount of pavement markings and signage required at a grade cross-ing is a function of the amount of vehicular traffic, the amount of rail traffic, the type of train operations, and the geometrics of the crossing. The mini-mum requirement for every crossing, whether public or private, is a railroad crossing sign (called a cross-buck) and an advanced warning sign. Additional warning signs, signals, and pavement markings may be used as necessary. Some cases may warrant the need for automatic warning devices, commonly referred to as flashers, which are activated by approaching trains to warn vehicles of their pending arrival at the crossing. Gates can be used in con-junction with flashers to further enhance safety at crossings.

The FRA issued the Final Rule on the Use of Locomotive Horns at Highway-Rail Grade Crossings (Final Rule), which became effective on June 24, 2005, and was amended in April 2006. The Final Rule preempts any state or local laws regarding the use of the train horn at public cross-ings. The Final Rule requires that locomotives sound their horns 15 to 20



seconds before entering a public crossing, but no more than one-quarter mile in advance of the crossing. The required pattern for horn blowing is two long, one short, and one long—repeated as necessary until the loco-motive clears the crossing. Locomotive engineers may sound the horn in emergency situations as well.

The Final Rule also provides public authorities the option to maintain and/or establish quiet zones, provided certain supplemental or alterna-tive safety measures are in place and the crossing accident rate meets FRA standards.4

§ 8.6 TRACK GEOMETRY AND DESIGN

Track geometry and design is composed of several elements and design con-siderations. Each railroad has its own standards for horizontal and vertical alignments, but the following describes these elements in general terms.

§ 8.6.1 Horizontal Alignment

Horizontal alignment, which is the position of the track in the horizon-tal plane, is composed of a series of tangents and curves. Tangent track refers to track that runs roughly straight for any given length, although it may have slight variations from traffic and other environmental elements. Curves connect two tangent segments of track. The curvature of tracks is measured in degrees based on the radius. Three parts of a curve should be considered:

• Full body of the curve• Transition spiral entering and leaving the curve• Super-elevation in the curve

The full body of the curve refers to the part of the curve that is perfectly circular, meaning that the radius of the curve at any point along the curve is the same length. Traffic, drainage, and other issues make it difficult to keep curves perfectly circular, as slight variations occur in the radius.

Transitions from tangent to circular curve (entering or leaving) are called spiral curves. These curves are gradual transitions that alleviate the drastic change from tangent to curve that introduces significant lat-eral acceleration. As a train goes around a curve, the cars naturally tend to lean toward the outside of the curve because of centrifugal force. The sharper the degree of curvature and the higher the speed, the greater the centrifugal force, especially in tall or top-heavy cars. Super-elevation helps

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to compensate for this force. Super-elevation is the raising of the outside rail to force the load back toward the inside of the curve, which is some-times referred to as cross level. The amount of super-elevation needed depends on the intended maximum train speed and degree of curvature. Super-elevation is constant for a given speed and is maintained through the full length of the circular curve. Spirals are utilized to transition from no super-elevation to full super-elevation. Spirals are typically not present when speeds are low.

Turnouts are ideally placed in tangent track for the entire length of the turnout. Most railroads require special approval for horizontal curves to be within the limits of a turnout.

Track locations are labeled with stationing and milepost. Most railroads refer to the milepost after a track has been constructed, but stationing may also be used for location. Mileposts identify structures, crossings, turnouts, and other important track features. Stationing, which appears as a value per 100 feet, refers to the measurement of length in feet. For instance, 100 feet will be stationed as 1 + 00, and 1,321 feet will be stationed as 13 + 21.

§ 8.6.2 Vertical Alignment

The vertical alignment of a track is the profile of the track in the vertical plane. As such, the term generally refers to the top of rail elevations along the track and includes vertical tangents and curves.

Depending on the use of the track, the amount of vertical grade changes and number of vertical curves may need to be limited. For instance, for heavy, long trains, tracks with a lot of grade changes and vertical curves can lead to problems with the coupling of the cars. In most situations, an undulat-ing track profile is not ideal.

Vertical curves are evaluated based on their V/L ratio. The V/L ratio is the average change in gradient per 100-foot station. Typically, values for curves range from 0 to 2.0 depending on the type of track and operating speed. Low values are ideal, especially for main line tracks or higher speed tracks. The V/L ratio requirements also depend on whether the curve is a sag or a sum-mit. A sag is a curve at the lowest portion of a grade where two grades of opposite or different inclinations meet. A summit or crest is a curve formed by two opposing grades.

Turnouts are ideally located in a constant grade without vertical curves. The profile for each leg of the turnout must maintain the same grade until after the turnout. However, situations may require some portion of the track between the last long ties and the heel of frog to be in a vertical curve. The inside of the heel of frog cannot be in a vertical curve. When vertical curves occur within the turnout, the two legs of the turnout are not required to con-tain the curve. For most railroads, special approval is required for turnouts to be located within vertical curves.



§ 8.6.3 Design Considerations

Tangent Track between Curves and TurnoutsAlmost all railroads have standards for required distances between horizon-tal curves, between vertical curves, and between the points of switches for turnouts facing away from each other on a single track. Each railroad has different requirements, but special circumstances may prohibit the align-ments from achieving the standard distances. In those cases, the maximum distances achievable should be obtained with consideration for other design elements. The operating railroad will most likely need to approve the layout for a nonstandard tangent distance.

Overlapping Horizontal and Vertical CurvesIdeally, railroads do not like to overlap horizontal and vertical curves. When overlapping is necessary, the goal of the vertical profile is to limit the overlap as much as possible. Special approval is often required by railroads for this configuration.

Track Centers and ClearancesTrack centers are the perpendicular distance between the centerlines of two tracks. The required separation between the tracks depends on the type of operation on the track, speed, and amount of traffic on adjacent tracks. When limited right-of-way is available or obstructions limit the location of tracks, track centers may be adjusted from the standards of that railroad to accommodate and/or eliminate other issues.

The clearance envelope for tracks is the horizontal and vertical clear-ances around a track, based on the centerline of the track and top of rail profile. AREMA and the railroads all have standard horizontal and vertical clearances for the protection of the trains and surrounding elements, includ-ing bridges, buildings, signage, and so forth. The clearance envelope for a track can vary based on the types of cars that will operate on the tracks. Because tracks are built to last for many years, railroads will try to accom-modate a variety of car types in setting the clearance envelope, in case future needs alter the type of train car operating on the track. This advance planning avoids limiting the track’s operations.

§ 8.7 HYDROLOGY AND HYDRAULICS

Adequate drainage is the key to keeping track components in good condition and is the driving force behind type, size, and location criteria for railroad structures. Therefore, nearly all railroad components need to be evaluated for the effects of storm water runoff or drainage. Railroads are, necessarily, knit into communities, municipalities, and adjacent properties. Consequently,

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railroads have to be cognizant of the effects of drainage not only on their right-of-way, but also on adjacent property owners who can be affected by railroad decisions. The evaluation and implementation of adequate drainage plans is carried out through hydrology and hydraulics. The railroad’s evaluation of these issues can produce good relationships with affected property owners and municipalities and, thus, may prevent lawsuits against the railroads.

§ 8.7.1 Hydrology

Hydrology is the study of the movement and distribution of water as it relates to rainfall and storm-related runoff. Drainage control measures are needed in a railroad setting to accommodate this movement of water; these drainage measures are designed for 50-year and 100-year storm events. A 100-year storm event has a 1 percent chance of occurring in any single year, while a 50-year storm event has a 2 percent chance of occurring in any given year. Storm events with a low probability of occurrence are usually of higher mag-nitude and intensity and require higher design requirements to accommodate them. Higher design requirements generally equate to higher construction costs. For adequate design, the water surface elevation of a 100-year storm event must be lower than the top of rail elevation on a section of track.

Hydrologists’ predictions of storm-related events eventually lead to the calculation of the actual discharge rate of a watershed. The discharge rate is used to size railroad structures, determine adequate ditch size, and deter-mine the flood risk of an area. Two important variables are used in deter-mining the discharge rate: rainfall and time of concentration. Rainfall can be expressed as intensity or total rainfall. Rainfall numbers can be found in various charts, maps, and tables on the local level and vary greatly between geographic regions. Time of concentration is the time needed for one drop of water to flow from the most remote point in a watershed to the watershed outlet. Time of concentration is heavily dependent on topography, geology, and the different land uses within a given watershed. Time of concentration is useful in predicting flow rates that would result from hypothetical storms.

Once these input variables have been determined, different methods and programs are used to calculate and simulate discharge. Various government agencies also publish hydrographs—charts for various watersheds through-out the United States—which can also provide discharge information.

§ 8.7.2 Hydraulics

Once a hydrology analysis is complete, a hydraulic analysis is next. Hydrau-lics is the study of water movement through conduits (usually under pres-sure) or open channels. Hydraulic engineers determine the safest and most economical means to dispose of excess or runoff water without negatively



impacting railroad property or adjacent property owners. Although engineers may utilize standard equations, charts, and diagrams, when possible, to simplify and expedite the design process, they must be cognizant of the fact that each geographic situation is unique and involves many different variables. Thus, standard tools should only be used as a reference and guide in the design phase.

The two most common methods to dispose of runoff on railroad property are open channel and closed conduits. Open channel hydraulics transport water through various channels that are open or

exposed to atmospheric pressure. The flow through these channels can be varied or uniform; the most common assumption is uniform flow.

The most common type of closed conduit system on railroad property is the pipe culvert. Pipe culverts come in many different types and materials, including corrugated metal, concrete, and steel. Another type of closed con-duit system is the reinforced box culvert shown here in figure 8.12.

§ 8.8 RAILWAY STRUCTURES

The railroad industry utilizes a vast assortment of structures to move trains effectively from point A to point B along each network system. Bridges, cul-verts, inspection pits, maintenance facilities, intermodal cranes, tunnels, mov-able bridges, retaining walls, towers, and station platforms are types of these structures, just to name a few. But understanding the intricacies of each struc-ture type is not the focus here. Rather, this section will cover different compo-nents of bridges, a few of the main structures outside of the bridge category, and the various design considerations important in the railroad industry.

The primary guidance code for the planning, design, and maintenance of structures within the railway industry is Volume 2 of the AREMA Manual. This document provides in-depth technical guidance to engineers and tech-nical experts as well as overall guidance to people with an interest of how railway operations work.

§ 8.8.1 Bridge Components

The main components of a railway bridge are essentially the same as bridge components in other industries: the superstructure and the substructure.

Figure 8.12 Reinforced Box Culvert


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These two components may be constructed from various materials available throughout all industries, but the dominant materials used in the railroad industry are timber, concrete, and steel. Each material has unique economic and engineering-related characteristics that railroads utilize for their struc-tures. Research and development and better performance have made steel and concrete the materials of choice for railroads. See chapter 9 for a full analysis of bridge design and construction.

SuperstructuresThe superstructure is the portion of a railway bridge that spans an opening, supports the live load, and transfers the live load to the substructure elements. Short span bridges may consist of either steel or concrete spans, while long span bridges (generally more than 50 feet in length) are usually constructed from steel, due to limitations of concrete design at these lengths. Material selection in the shorter spans is based on many factors, including overall life cycle costs, horizontal and vertical clearance requirements, availability of material, project site variables, cost of construction, etc. Each railroad com-pany will often have preferences and standards, determined in advance, that they utilize when selecting material type for a new bridge.

Although similar to other industries, railroad superstructures have one unique element that sets them apart: the decking system. The bridge deck system is the portion of the railway superstructure that directly supports the steel rails on which the trains run. Railway bridge decks consist of either open decks or ballast decks.

Open decks (figure 8.13) consist of the steel rail fixed directly to either a wood or concrete tie, which in turn is fixed directly to the load-bearing floor system of the superstructure. This type of deck reduces the dead load of a span, but the direct fixation of the rail and tie to the floor structure does not allow for distribution of live load and increases the dynamic loading that the floor system and substructure will have to support. Open decks often give a rough ride to the passing train because there is no give between the rail and the supporting members. These types of decks can be cost-effective, due to the reduced dead load, reduced material costs, and the fact that they are free-

draining and used extensively with long-span bridges over waterways. Open decks become less cost-effective over roadways due to the need for reducing the risk of falling objects through the spaces between ties.

Ballast decks (figure 8.14) consist of the steel rail fixed directly to either a wood or concrete tie that is seated in a layer of ballast and supported by a deck fixed directly to the load-bearing floor system of the superstruc-ture. This type of deck greatly increases the dead load of a span, but the layer of ballast

Bridge ties

Girder

Girder

Figure 8.13 Open Timber Deck Bridge

Source: Courtesy of AREMA, Canadian National



helps distribute the live load and decreases the dynamic loading that the floor system and substructure will have to support. Ballast decks provide a smooth track for pass-ing trains and also allow mainte-nance crews to continue unimpeded between bridges and regular terrain. These types of decks can be cost-effective over open decks because the layer of ballast provides a layer of protection between the train and the span floor system. For most rail-roads, ballast decks are favored over

open decks in all situations, unless site conditions and other factors call for open deck bridges.

SubstructuresThe substructure is the portion of a railway bridge that supports the bridge loads, including dead load, live load, and secondary forces, and transmits them to the underlying soil strata. Prior to design and construction, an in-depth investigation and analysis on the underlying soil properties and their ability to support and transmit the required loads must be completed by an experienced geotechni-cal engineer. The investigation consists of test borings at the locations specified with corresponding analysis done on the samples that are taken. Substructures consist of abutments and piers supported on shallow or deep foundations.

Abutments have many features, including the cap, stem, backwall, and wingwalls that support the end span of a bridge, as well as the earth embank-ment at the end of the bridge. The bridge seat is the portion of the abutment that supports the bridge superstructure, while the wingwalls, backwall, and stem are used to retain the earth embankment. Abutments are primarily con-structed out of reinforced concrete and can be supported on both shallow and deep foundations. When completing an abutment design, designers must include adequate safety against train overturning and sliding.

Reinforced Concrete PiersPiers are used as intermediate supports for a bridge when constructed with more than one span. Older construction was generally gravity piers, with the loads directly transmitted to suitable soil strata below. Newer construction uses both shallow and deep foundations.

A shallow foundation transfers bridge loads to the earth very near the surface, rather than to a deeper subsurface soil strata. Shallow foundations for railroad bridges primarily consist of spread footings that bear directly to a bedrock layer near the surface of the earth. Spread footing foundations con-sist of strips or pads of reinforced concrete that transfer the loads from walls

Track ties Curb

Concrete slab

GirderGirder

Figure 8.14 Ballast Deck Bridge

Source: Courtesy of AREMA, Canadian National

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and columns to the soil or bedrock. Shallow foundations are uncommon in railroad bridge applications due to the large unit loads that need to be accommodated in design.

A deep foundation gets its support deep in the subsurface soil. Geotech-nical engineers often recommend deep foundations over shallow foundations for railroad bridges because of very large design loads, poor soil at shallow depth, or property constraints at the site. The main deep foundations used in railroad bridge applications are piling and drilled shafts.

Piling can be made out of timber, steel, reinforced concrete, or pre-tensioned concrete, and can garner support by end bearing, skin friction, or a combination of the two. The type and material selection for piling is dependent on site conditions and the required material properties needed to support the design loads. Piles can support other footing components, such as piers of spread footings, or they can continue to become part of the sup-port members (“bents”) in trestle construction.

Drilled shafts are constructed by drilling a deep hole into the ground and backfilling the hole with unreinforced or reinforced concrete. See chapter 9 on bridges for a full discussion of drilled shafts. Drilled shafts are used exten-sively in longer span bridges of new construction because of the research and development that has gone into constructing these deep foundations.

§ 8.8.2 Bridge Types

Railroad bridges can consist of many dif-ferent types and materials.

Timber BridgesTimber bridges, such as that shown in figure 8.15, consist of timber stringers (superstructure) supported on timber caps and piles (substructure). Timber was used extensively in early railroad construc-tion due to its low cost, ease of construc-tion, and relative ease of repair. With the advent of modern steel and concrete con-struction, however, timber bridges are not seen on many new lines or replace-

ment structures. Timber structures are primarily saved for short line and low-density line construction.

Concrete BridgesFour main types of concrete bridges are used in railroad applications: arches, rigid-frame bridges, slabs, and girders.

Figure 8.15 Timber Bridge Showing Stringers, Bent Caps, and Piles




• Arches were used in older vintage structures and were constructed from stone or masonry.

• Rigid-frame bridges are constructed so the horizontal member is structurally integral with the upright supports. These structures do not tolerate foundation settlement and, consequently, are not heavily used. They were primarily used in grade-separation projects due to their shallow superstructure depth in relation to the span length.

• Slab bridges are used in short span situations of less than 25 feet and in concrete trestle bridges.

• Girders are the most economical superstructure and are used exten-sively in new line construction today with spans in the 25-foot to 60-foot range. The most common type of girder span is the precast/pre-stressed double box cell girder with integral top slab. These spans can be easily constructed under traffic and do not require an

additional cast-in-place deck, such as individual concrete girders would require.

Steel BridgesSteel bridges, like those shown in figures 8.16 and 8.17, are the most versatile type of railroad bridge and are used in both short- and long-span applications. Girder spans can be rolled steel shapes or built-up sections. Rolled steel shapes are used up to about 60 feet; built-up sections can be used up to around 180 feet.

Moveable BridgesMoveable bridges are not prevalent in railway structures but may be used in lim-ited instances. The vast majority of mov-able railroad bridges are used in rivers or streams with navigable channels, where horizontal or vertical clearances of a fixed structure would not be adequate. Water level elevations and surrounding grade elevations control the placement and need for movable bridges. Moveable bridges must be designed and constructed to meet strict tolerances in order to be effective and maintained correctly. The three main types of moveable bridges are: bascule bridges, which pivot at one end; swing span bridges,

Figure 8.16 Deck Plate Girder and Through-Plate Girder Diagrams


Figure 8.17 Steel Truss Bridge

Photo courtesy of BNSF

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which use a center pivot to open the span; and vertical lift bridges, which use towers to lift the span vertically. The U.S. Coast Guard often has jurisdiction when moveable bridges cross navigable channels of the United States and should be involved with the planning and coordination of any bridges in these locations.

§ 8.8.3 Tunnels

Tunnels are not exclusive to the railroad industry but are used extensively to move a track alignment through, rather than around, obstacles like moun-tains and underneath cities, rivers, and so forth. Key issues in tunnel design are clearance, ventilation, drainage, and ballast. Clearances must be ade-quate for the types of trains using the tunnels, especially given the increase of double-stack freight train cars. Adequate drainage is critical to tunnels, because tunnels often have an inflexible and impermeable base layer.

§ 8.9 LOADING

Railway structures are unique from other structures because of the extreme magnitude of the rolling stock loads that the structures need to support. The fol-lowing loads must be accounted for in railroad applications: dead, live, impact, centrifugal, lateral, longitudinal, wind, stream flow, buoyancy, ice, and seis-mic loads. The AREMA Manual sets forth the standard requirements for railway structures. Because the AREMA Manual is a living document that is updated frequently, railroad designers must be sure to use the most current information. Although the designer must carefully and adequately account for all loads, a select few loads distinguish railroad bridge loading from other structures.

Live LoadTrains, whether in motion or at rest, produce massive vertical loads on structures. Per the AREMA Manual, standard railroad bridge vehicle load-ing utilizes the Cooper E-series loading, or Cooper E80 live loading. First established by Theodore Cooper in the late nineteenth century, the Cooper E-series has a long history within the rail industry, but has been primarily utilized by all railroads since the 1930s. The loading diagram consists of two steam locomotive engines with large axle loads spaced intermittently with a uniform load trailing the engines, as seen in figure 8.18.

Although modern equipment axle loads and spacings vary greatly from the Cooper E80 series, the series provides a standard base of reference and adequate design for the industry to use. The AREMA Manual also provides an Alternate Live Load Series, shown in figure 8.19, for select steel structures. The combination of these two vehicle loading diagrams makes railroad bridge live loading unique from other bridge and structural loading applications.



Impact LoadAs distinguished from a force applied gradually and maintained over a period of time, impact load is a dynamic, impulsive load, delivered by the blow of the rolling stock wheel on the track. This load is significant on railroad bridges due to the scale of the axial loads as well as the many varying charac-teristics of the rolling stock and the different track geometry. According to the AREMA Manual, impact produced on a bridge can be up to 200 percent of the vertical axle load if a train wheel is found to have a flat spot and be out of round. The AREMA Manual provides equations, based on empirical research, that increase the vertical axle loads by a percentage as a result of many fac-tors, including the type of superstructure material. For instance, depending on the type of bridge deck, the impact load can be directly applied to the superstructure on open deck structures or be reduced due to the distribution through the ballast section.

Longitudinal LoadLongitudinal load is derived from the braking and acceleration (traction) of the rolling stock on the bridge. The load acts parallel to the bridge and is distributed to the supporting substructures by various methods. The AREMA Manual requires the designer to calculate both the braking and traction forces and use the larger of the two for the design. Longitudinal load is significant in longer bridges, such as trusses and viaducts, which often require some type of braced foundations to accommodate this large load.

Figure 8.18 Cooper E80 Axle Load Diagram from AREMA Manual

5' 6'

100,

000

100,

000

100,

000

100,

000

5'

Figure 8.19 E80 Alternate Live Load Diagram from AREMA Manual

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§ 8.10 ENVIRONMENTAL REGULATIONS AND PERMITTING

As discussed in detail in this book’s environmental chapter (chapter 2), nearly all construction activities that disturb the land in the United States must com-ply with various environmental regulations and laws. Environmental regu-lations are continually evolving in order to better protect natural resources. These regulations are constantly changing, yet they must be accounted for when designing new, or improving existing, railroad infrastructure. Due to the broad reach of many environmental regulations, railroad designers need to begin coordinating the permitting process early in the life of any project to determine any potential environmental impacts and develop potential mitiga-tion strategies. This section will highlight various regulations that affect rail-road design and development.

§ 8.10.1 National Environmental Policy Act

The U.S. National Environmental Policy Act (NEPA), signed into law in 1970, marked the beginning of environmental regulation in the United States and continues to be one of the primary laws for protecting environmental resources. The Council on Environmental Quality administers NEPA, which is invoked whenever federal funds, land, or major federal decisions, including permit-ting, are involved in a project. Similarly, all federal agencies must comply with NEPA and consider its environmental factors when making decisions. NEPA documents generally fall into three major categories: categorical exclusions, environmental assessments (EA), and environmental impact statements (EIS).

Categorical exclusions generally apply to smaller projects that have no sig-nificant effect on the environment. Larger projects, or those with minor impacts, typically follow the EA process: submitting a statement of purpose; descriptions of the proposed improvement and alternatives considered; a statement of the affected environment and any environmental consequences; and any mitiga-tion required. If no significant environmental impacts are found, a Finding of No Significant Impact (FONSI) will be issued and the project may proceed.

If significant environmental impact is possible from a railway project, or if a large and complex railway project may cause environmental impacts that require mitigation, NEPA requires an environmental impact statement (EIS). An EIS involves the following process: submitting a statement of pur-pose; describing the proposed improvement, alternatives considered, and the affected environment; and identifying any environmental consequences and mitigation required. The EIS process requires public involvement and pro-vides several opportunities for public comment. At the end of the EIS process, the governing agency will issue a Record of Decision (ROD) that will allow the railway project to proceed as proposed, allow the project to proceed with certain conditions, or block the project.



§ 8.10.2 Waters of the United States and Wetlands

Railways often intersect, cross, or run adjacent to U.S. waterways and wet-lands, which requires an evaluation of potential impact from construction and/or railway operation. “Waters of the United States” include, as defined at 40 C.F.R. 230.3(s):

• Waters used for or that affect interstate or foreign commerce (including those subject to the ebb and flow of tide)

• All interstate waters including interstate wetlands• The territorial seas• Tributaries of and wetlands adjacent to Waters of the United States

“Wetlands” are the transitional area between terrestrial and aquatic envi-ronments, where the water table is at or near the surface. Wetlands are more fully defined at 40 C.F.R. 230.3(t) and have the following attributes:

• At least periodically, the land must support predominantly vegetation adapted for life in saturated soil conditions (hydrophytic vegetation)

• The substrate must be composed of predominantly undrained soil that is saturated long enough to develop anaerobic conditions (occurring without free oxygen) (hydric soil)

• The substrate is saturated or covered by shallow water at some time during the growing season each year

Best Management Practices (BMPs) are procedures used to prevent sur-face water degradation from an activity. BMPs can at least partially mitigate wetland impacts from railroads.

Section 404 of the Clean Water Act (CWA) (33 U.S.C. § 1251 et seq.) is jointly administered by the United States Army Corps of Engineers (USACE) and the Environmental Protection Agency (EPA) and regulates the discharge of dredged or fill material into waters of the United States, including wet-lands. The USACE and other agencies issue three types of permits for activi-ties in wetland areas:

• Nationwide permits—set national wetland standards with a total of 43 authorized activities specified, including general and specific conditions

• General permits—issued when the local USACE district requires spe-cific regulations not covered by a nationwide permit

• Individual permits—required for large projects that cause significant potential for wetland impact; are open to public comment; typically require mitigation

The following nationwide permits are often associated with railroad activities and require preconstruction notification (PCN) threshold for each activity:

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TABLE 8.1 USACE Nationwide Permits Applicable to Rail Activity

No. Title/Description Examples PCN Threshold

7 Outfall Structures and Maintenance

• New outfall structure

• Removal of sediment from outfall structure

Construction, removal, repair, or maintenance of intake and outfall structures

All activities

12 Utility Activities

• New substation or foundation

• New permanent access roads

Construction of a storm sewer or other utility through a wetland

One-tenth acre of site disturbance or 500 feet of access road

14 Linear Transportation Crossings

• New crossings

Construction of tracks through a wetland or a bridge over Waters of the United States

One-tenth acre or any discharges into special aquatic sites

39 Residential, Commercial, and Institutional Developments

• Building pads, foundations, and associated features

Construction of buildings and associated roads or parking in wetlands

One-tenth acre

41 Reshaping Existing Drainage Ditches

• Modification of currently serviceable drainage ditches

Grading ditch sides and dumping excess material into the ditch

500 feet or involvement of Waters of the United States

§ 8.10.3 Threatened and Endangered Species

Section 10 of the Endangered Species Act regulates activities that affect plants and animals designated as threatened or endangered, and their habitats. Activ-ities that affect these species, including those that harm, harass, pursue, hunt, shoot, wound, kill, trap, capture, or collect listed wildlife, are prohibited with-out a permit from the United States Fish and Wildlife Service or the National Marine Fisheries Service. These protections apply to live or dead plants or animals, their progeny, and parts or products derived from listed species.

§ 8.10.4 Cultural Resources

Section 106 of the National Historic Preservation Act requires any undertak-ings of a federal agency to account for their effect on historic properties. The agency must take a survey to determine if any cultural resources that require



protection exist in the project area. Examples of typical cultural resources include historic buildings or districts, burial sites, campsites, spiritual sites, churches and cemeteries, trails, tunnels, towers, and bridges.

§ 8.10.5 Hazardous Waste

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), or Superfund, was enacted to allow for response to releases of hazardous waste from inactive sites, establish regulations controlling inactive hazardous waste sites, provide liability for releases from inactive sites, and establish a Hazardous Substance Superfund. Additionally, owners and opera-tors of facilities are required to maintain Material Safety Data Sheets (MSDS), emergency and hazardous chemical inventory forms, and toxic chemical release reports for any hazardous materials.

§ 8.10.6 Air Quality

The Clean Air Act sets national primary ambient air quality standards that define the levels necessary to protect the public health and secondary stan-dards that define levels necessary to protect public welfare from adverse effects of pollutants. Title I of the Clean Air Act defines air pollution control requirements for non-attainment areas that fail to meet applicable standards. Designated non-attainment pollutants include ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, particulate matter, and lead. Non-attainment areas often have restrictions or certain activities required to improve air qual-ity in the region.

§ 8.10.7 Noise

The Noise Control Act and Quiet Communities Act regulate noise genera-tion in the United States. Federal funding was phased out in 1982, however, because the government determined these issues are best handled at the state or local level. As a result of the potential for increasing noise levels in an area, many states and municipalities have since enacted noise regulations that must be considered when railroad activities are undertaken.

§ 8.11 RIGHT-OF-WAY

The right-of-way is the strip of land on which the railroad, its subgrade, and its supporting elements are built. Railroad rights-of-way contain much more

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than the track structure utilized by trains for the movement of goods and people. Often, they are also used to convey different types of utilities and contain a variety of railroad structures and fencing to protect the railway infrastructure. Included in the right-of-way are space for adjacent improve-ments to support the railway and its maintenance. Typically, these improve-ments include trackside ditches and related drainage structures as well as any necessary retaining walls, fences, signs, utilities, and railroad structures.

Many of the railroad rights-of-way were defined over a century ago when the majority of railroads in North America were constructed. The land was typically obtained via land grants, land purchases, and/or easements. Rights-of-way are typically measured from the centerline of the track in single-track territory and from the center of multiple tracks or from the centerline of one of the tracks in multiple-track territory. These distances are typically set even numbers from the centerline, ranging from 50 feet to 200 feet depending on the railroad and the terrain the tracks are traversing. Over time, the tracks may be realigned to broaden curves or otherwise improve geometry, and, as a result, the centerline of the current track is not always the centerline of the right-of-way.

§ 8.11.1 Valuation Maps

Valuation maps are the official property use records for the railroads. In addi-tion to the railroad tracks and any railroad structures, the maps show right-of-way limits, adjacent property owners, and highway or bridge crossings for a particular section of railroad. They also show easements for utility crossings or utilities that run parallel to the railroad. Valuation maps include stationing and mileposts for the alignment, which locate points of switches, bridges, culverts, road crossings, and other prominent features along an alignment. Mileposts indicate the distance along a railroad in miles from a given point on the route. It is important to note, however, that mileposts for most North American railroads were laid out 100 to 150 years ago and, therefore, may or may not equal 5,280 feet per mile; this discrepancy is due primarily to inac-curacies in early surveying equipment and alignment changes that may have occurred over the past century.

§ 8.11.2 Fences

Fencing is an important part of many railway rights-of-way. Many railways have standards for types of fencing for particular applications. A fence may mark the edge of a railroad’s right-of-way and/or property line, though that is not always the case. In rural areas of some states, laws dictate that the railroad install barbed wire fences to keep livestock off the tracks; other states require the cattle owners to install a fence to keep the livestock in. In urban areas,



chain link security fences are common to prevent trespassing or vandalism and promote safety and security for the railroad and the general public.

Portions of the railway that receive significant snowfall may also have snow fencing along the alignment to prevent snow from drifting across the track or accumulating in adjacent ditches. Sand fences may be utilized in des-ert environments for a similar purpose. These fences are generally installed at right angles to the prevailing wind in such a manner that neither the fence nor the drifts would block sight distances. Slide fencing is used in some areas along mountain railways to deter falling or sliding rocks that might otherwise damage or block the tracks. Slide fence can also signal oncoming trains of a hazard through interconnects with the existing railroad signal system.

§ 8.11.3 Utilities

Historically, railroads preferred to keep their rights-of-way free of nonrailroad utilities. Over time, however, railroads began to realize the value of their rights-of-way that often traversed hundreds of miles, reasonably unencum-bered. In response to that market for utility access, railroads began to lease utilities easements along the length of their alignment as an additional source of income.

Railways generally split utility occupations into wireline (above grade) and pipeline (below grade) subcategories. Clearance to the wires is the pri-mary concern for wireline crossings; sagging wires must be accounted for in various environmental scenarios. Pipeline crossings typically require encase-ment in a carrier pipe when passing beneath the railroad embankment to provide additional protection to the utility from railroad loading.

§ 8.11.4 Vegetation

Control of vegetation along a railroad right-of-way is a necessary part of ongoing railway maintenance. Uncontrolled vegetation can clog ditches and culverts, grow within the ballast section, and otherwise interfere with proper drainage, which can create additional maintenance issues. Vegetation can also obstruct sightlines at grade crossings or block signals and other signage from the train crew, all of which can create safety concerns for the railroad and the traveling public.

Mechanical or chemical methods exist to control vegetation. Mechani-cal methods for trimming the brush include track-mounted equipment, mobile equipment operating from the right-of-way, or hand-held equip-ment. Chemical methods for killing brush include herbicides sprayed from track-mounted or other mobile equipment. Any chemical methods for veg-etation control must abide by all federal and local laws. All states require licensure for herbicide applicators on railway right-of-way. In addition, the

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EPA regulates the chemical application rate for different terrain types and provides guidelines on what herbicides may and may not be used on par-ticular plant species.

§ 8.12 COMMUNICATIONS AND SIGNALS

Modern signal systems are what allow railroads to continue to move large volumes safely and efficiently. These systems are continually improving to better communicate conditions ahead of a train and to intervene before a collision can happen.

Unlike other modes of transportation, trains do not have the ability to get out of the way of each other as they operate on a fixed alignment. Early in railroad history, individual railroads rarely operated more than one train over any particular segment of track, so this risk did not arise. But growing freight and passenger volumes necessitated that trains operate in both directions over a single track and that higher priority trains, such as passenger trains, be able to pass lower priority trains traveling in the same direction. The need to control these passing trains ultimately led to the communications and signal systems in place today.

§ 8.12.1 Basics of Signal Systems

Timetables were the industry’s initial solution to the problem of multiple trains meeting and passing on a track. Timetables provided a schedule of all known train movements over a given section of the railroad, such that indi-vidual trains would know where and when they would meet each other and whether they were supposed to wait in the siding or continue along the main track for these meetings. Soon, the industry added dispatchers whose written train orders modified the timetable if a train did not meet the schedule or if an extra train had to be run. Mechanical fixed signals were then added at stations to indicate whether trains needed to stop to pick up the dispatcher’s orders or could proceed as normal. These mechanical signals were the fore-runners of modern wayside signals.

The next major advancement for communicating to trains along a section of track was automatic block signals, which utilize track circuits to detect a train in a given portion of track, work in conjunction with other track circuits, and automatically indicate that a track section is open, has a train already on it, or has a train on the next section of track. The signal system’s automatic indications enhanced the efficiency and safety of existing timetable opera-tions by giving advance warning to a train of the need to stop to accommo-date a train ahead on the track that had fallen behind schedule.



§ 8.12.2 Energy/Power Source

A railroad’s safety and efficiency depend on a reliable power source to oper-ate its signals. Most signal systems operate on commercial power with bat-tery backup. The battery provides power to the signal in the event of a power failure, and the commercial power charges the battery when it has been depleted. Another important element of power for signal systems is lightning protection, as rails are an excellent conductor for lightning strikes to reach the signal system. Lightning arrestors are installed throughout a signal system to divert lightning from the signal system into the ground.

§ 8.12.3 Track Circuits

Track circuits are electrical circuits formed by the following components: the rails on a specific section of track; a power source; and miscellaneous con-nections, relays, and resistors. Track circuits detect the presence of a train within a specific segment of track.

§ 8.12.4 Track Switches

Switches provide a means for trains to transfer from one track to another. When located within signalized territory on a railroad, the switches must be integrated with the signal system to improve safety and reduce unneces-sary delay. Switches may be either hand-thrown or power-operated. Hand-thrown switches are typically used at locations with lower speeds and/or traffic volumes and are designed to switch the signal indication to stop if the switch is thrown from its normal position. In areas with track speeds over 20 mph, an electric switch lock is added to hand-thrown switches to prevent the switch from operating unless traffic conditions permit. Power-operated switches are used for high-volume, high-speed locations; they are typically controlled from a central location, such as a dispatching cen-ter, and utilize a motor to operate the switch points rather than a manual switch stand.

§ 8.12.5 Highway Crossings

Active crossing protection is typical for at-grade intersections with high vol-umes of vehicle traffic, train traffic, or both. All signaled grade crossings contain flashing lights and a bell to warn vehicular traffic of an oncoming train; gate arms are typically added at locations with high-traffic volumes or multiple tracks. Older crossing signals detect trains a set distance from the crossing and activate the signal regardless of train speed or direction.

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Modern signals utilize an electrical current in the rail to determine train speed, direction, and distance from the signal before activating the signal a set time prior to train arrival at the crossing. These signals can also deter-mine if a train has stopped or reversed directions and stop the crossing operation, if warranted.

§ 8.12.6 Centralized Traffic Control (CTC)

Centralized traffic control (CTC) consists of multiple blocks controlled from a central dispatching location. CTC typically allows for multiple trains to occupy a block by allowing: (a) the dispatcher to control signals at control points and (b) trains to operate independently between control points utiliz-ing automatic block signals, often referred to as intermediate signals.

§ 8.12.7 Positive Train Control (PTC)

The Railroad Safety Act of 2008 requires positive train control (PTC) by the end of 2015 on all Class I railroads and other railroads designated by the FRA that carry commuters, intercity passengers, or toxic inhalation hazards. Positive train control is designed to prevent the following hazards with the following steps:

• Train-to-train collisions—system must recognize the possibility of a rear-end collision, a head-on collision, or an incursion at a turnout or crossover and brake a train prior to the incursion occurring.

• Over-speed derailments—system must recognize locations of trains in relation to permanent and temporary speed limits and brake a train prior to it entering the speed limit faster than is permitted.

• Work zone incursions—system must recognize locations of all work zones and automatically brake a train before it can enter the work zone.

• Open switch protection—system must recognize the position of all switches and the route of all trains on a controlled portion of track and brake a train before reaching any switches that were left in the wrong position.

§ 8.12.8 Defect Detectors

Defect detectors are installed along the railroad at regular intervals to iden-tify potential problems with a train or a segment of track before a derailment occurs. Examples of defect detectors include:



• Hot Box Detector—scans infrared signature of the wheel bearings on a passing car and sends a signal to the dispatcher if the heat is above a given level. Overheated bearings can melt and may cause a wheel/axle separation and derailment.

• Hot Wheel Detector—scans infrared signature of the web of the wheel on passing cars and sends a signal to the dispatcher if the heat is above a certain threshold. Overheated wheels, typically caused by sticking brakes, can break and cause a derailment.

• Dragging Equipment Detector—utilizes a series of paddles con-nected to a shaft so that when struck by dragging equipment, the shaft is rotated and a signal is sent to the dispatcher.

• Wheel Defect Detector—utilizes strain gauges to measure the impact to the rail of a specific wheel set. Damaged wheels notify the dispatcher so that the car can be sent out for repair before it causes damage to the track.

• Slide Fence—utilizes a network of wires across areas where falling or sliding rock is likely to occur and signals trains to stop if a wire is broken.

• Flood Detector—utilizes either an energized grid or a float to detect high water and signals trains to stop prior to entering a flooded seg-ment of track.

• Fire Detector—utilizes a wire strung across a wooden structure; if a fire occurs, the wire melts and the detector signals approaching trains to stop.

• High/Wide Load Detector—utilizes a frame with a network of wires or a system of laser beams that, when broken, notify a train that its load has shifted or is too large to pass safely through a tunnel, under a bridge, or adjacent to other trains in an area of double-track with narrow track centers.

§ 8.13 PASSENGER RAIL

A driving factor in the development of the North American railroad system was the transportation of people and goods. But when the twentieth century brought mass-production of the automobile and widespread availability of air travel, passenger operations declined from a source of revenue for the railroads to a liability that threatened to bankrupt many carriers. In 1970, Congress created the National Railroad Passenger Corporation (Amtrak), to take over passenger service previously operated by the private freight rail-roads. The recent renaissance of passenger rail transportation in North Amer-ica is causing many railway and transit operators to rethink how they design, operate, and maintain their systems. Vehicle congestion on highways and

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local streets and at major airports has caused public officials to look at the benefits that rail transportation provides in terms of capacity and efficiency.

§ 8.13.1 Passenger Rail Modes

Passenger service can be separated into the broad categories of railway oper-ations and transit operations. Railway operations include commuter, inter-city, and more recently, high-speed operations that are typically conducted on portions of the freight rail network or on dedicated lines with comparable design standards. Railway operations fall under the jurisdiction of the FRA. Transit operations include rapid transit, light rail, and streetcar systems that are typically operated on dedicated rights-of-way. Transit operations gener-ally do not fall under the jurisdiction of the FRA.

§ 8.13.2 Passenger Equipment

Passenger equipment utilized for railway operations is typically comparable to equipment utilized for freight operations: One or more locomotives pull or push a chain of cars, called a consist. A consist is a grouping of cars or loco-motives making up a train. Most intercity and commuter passenger corridors in North America utilize diesel-electric locomotives. A few notable excep-tions operate on electrified corridors, including Amtrak’s Northeast Corridor (NEC), many commuter operations in the Northeast, and some commuter operations in Chicago. These electrified corridors use either electric locomo-tives to pull a set of passenger cars or a multiple unit system where each car contains its own electric propulsion system that operates in conjunction with the other cars in the consist to move the train.

Electric and diesel multiple units (EMU or DMU, respectively) are gain-ing popularity in urban areas due to their ability to adjust easily the number of cars in a consist and their relatively high acceleration capabilities. Transit operations typically utilize some form of EMU system, although DMU sys-tems are gaining popularity due to the high infrastructure costs of electrifica-tion for EMU systems. Older transit systems typically use track and wheel standards similar to freight operations, although with tighter curvature and steeper grades. Newer transit systems often use European track and wheel standards that have been developed specifically for transit operations.

§ 8.13.3 Passenger Service Characteristics

Railway operations tend to run less frequently at higher speeds over longer distances, while transit operations usually have more frequent service and



operate at lower speeds over shorter distances. Transit operations also typi-cally have higher passenger densities than railway operations because of their presence in higher density urban areas and the emphasis on commuting passengers. Table 8.2 summarizes key service aspects of the various types of passenger rail.

TABLE 8.2 Key Service Aspects of Passenger Rail

Type Service Speed Vehicles

Commuter Service between suburban areas and city centers—typically operates several times daily with higher frequency during morning and evening peak travel times

40–90 mph Locomotive Hauled

Push-Pull

EMU/DMU

Intercity Service between cities between 100 and 1,500 miles apart—typically operates between a few times a week and several times a day

40–90 mph Locomotive Hauled

Push-Pull

EMU/DMU

High-Speed Expedited intercity service with routes usually between 100 and 500 miles long—typically operates several times daily

90+ mph Integral Train-set

Locomotive Hauled

Rapid Transit High-capacity service within urban or high-density suburban areas – typically operates every 5 to 30 minutes

30–70 mph EMU

Light Rail Medium-capacity service within urban or between urban and suburban areas—typically operates every 10 to 30 minutes

30–50 mph EMU/DMU

Streetcar Urban circulator and tourist routes on average 1 to 5 miles long—typically operates every 5 to 60 minutes

15–30 mph Electric or Diesel Possibly with MU capability

§ 8.13.4 Infrastructure Needs

The type of passenger operation heavily impacts the infrastructure needs of each type of operation. For instance, railway operations that carry heavier equipment at higher speeds require more stringent track alignment standards and robust trackage that typically is designed and built in accordance with AREMA-recommended practices. Transit operations that carry lighter equip-ment at lower speeds, but in more restrictive urban environments, require more flexibility and are often designed and built to individual transit agency standards. Table 8.3 summarizes key infrastructure features of the different types of passenger rail.

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TABLE 8.3 Key Infrastructure Features of Passenger Rail

Type Route Signalization

Commuter Private rights-of-way, often owned by or shared with freight rail

Curvature typically greater than 1,000 foot radius, 500 foot minimum

Typical

Currently mandatory over 80 mph

PTC required starting in 2016

Intercity Private rights-of-way, often owned by or shared with freight rail

Curvature typically greater than 1,000 foot radius, 500 foot minimum

Typical

Currently mandatory over 80 mph


High-Speed Private rights-of-way, mostly grade-separated road crossings

May or may not be shared with freight rail

Curvature typically greater than 5,000 foot radius

Required


Rapid Transit Private rights-of-way

Curvature typically 100 foot–300 foot radius

Typical with high-end systems incorporating Automatic Train Operation (ATO)

Light Rail Mix of rights-of-way including private, side-of-road, street median, and in street

Curvature typically greater than 5,000 foot radius

Varies from line-of-sight to full signal coverage

Streetcar Mix of rights-of-way including some private with mostly median or in-street alignments

Curvature typically 35 feet–50 feet radius

Typically line-of-sight

§ 8.13.5 Commuter and Intercity Rail

Commuter and intercity rail operations are similar in nature as they gener-ally use similar equipment, operate at similar speeds, and operate on similar rights-of-way. In most cases, commuter and intercity operations share track-age with freight rail, and often the freight railroad owns the track with the passenger service operating as a tenant. The primary differences between commuter and intercity rail service are the length of the route and the density of passenger stations along the route.

North American passenger railroads typically operate on freight rail lines that provide a satisfactory level of service in most applications. On segments with a higher percentage of passenger traffic, the rail line is often maintained



to higher standards to improve operating speed, reliability, and passenger comfort. Regardless of traffic makeup, passenger trains can generally operate at higher speeds over the same segment of track than freight trains due to the higher horsepower-to-weight ratio of passenger trains.

The Federal Railway Administration requires that service operating at less than 90 mph comply with FRA, 49 C.F.R. pt. 213, subpts. A–F, which address track safety standards. Service above 90 mph must comply with subpart G, which addresses performance of the track and equipment as a system. Equip-ment that is operated at speeds less than 125 mph must comply with FRA, 29 C.F.R. pt. 238 Tier I requirements, while equipment operated at speeds over 125 mph must comply with Tier II requirements.

§ 8.13.6 High-Speed Rail

High-speed rail (HSR) in North America has generally been limited to Amtrak’s Northeast Corridor (NEC), although planning for other high-speed corridors in the Northeast, Florida, and California is in progress. The NEC is built primarily on the alignments of its predecessors and, therefore, does not have many of the features of European or currently proposed North Ameri-can HSR corridors, although incremental improvements have been made to increase speed over time.

An alignment designed and built specifically for HSR will typically have broader curves and steeper grades than an alignment built for freight operation. This is the case because the high horsepower-to-weight ratio of HSR trains allows them to build up momentum to climb short, steep grades with minimal speed loss, but the lateral forces created by curvature quickly become uncomfortable for passengers. Track design practice for HSR typi-cally uses the broadest curves possible with higher super-elevation and longer spirals to reduce the lateral acceleration experienced by passengers. Some HSR equipment also includes car body tilt mechanisms that slant the body of the car in a curve to further reduce lateral acceleration, especially on shared freight corridors where high amounts of super-elevation are not desirable.

§ 8.13.7 Rapid Transit

Rapid transit usually operates on dedicated rights-of-way that can include at-grade, elevated, and tunnel sections. The alignments generally reflect their historical precedents so that while New York and Chicago have systems with short cars and sharp curves, San Francisco has a system with broad curves and long cars. In most cases, these alignments are grade-separated, fenced, or otherwise separated from vehicular and pedestrian traffic due to the fre-quent service interval and common use of third rail power.

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The urban environment in which most rapid transit systems operate requires tighter geometry than that typically found on commuter railroads. Curves and turnouts often have guardrails to minimize rail wear and reduce the possibility of the wheels climbing over the rails within a curve, leading to a derailment. It is common to see No. 6 and smaller turnouts on many rapid tran-sit systems, while most railway operations use No. 9 turnouts, at a minimum.

§ 8.13.8 Light Rail Transit and Streetcar

Light rail transit (LRT) is quickly gaining popularity in North America and around the globe because it is flexible and can often be integrated into exist-ing roadway and transit networks more readily than other rail modes. Street-car systems are in many ways similar to LRT systems and tend to be used as circulators or for tourism, in some cases sharing portions of their alignment with LRT systems. The right-of-way for LRT can vary from ballasted sections capable of up to 70 mph to medium speed street-side and median align-ments to low speed in-pavement corridors that interact with vehicular traffic in urban cores. Often, LRT routes combine a variety of typical sections along their length as they transit from suburban to urban areas. Streetcar systems tend to operate only in urban areas at relatively low speed utilizing in-street, street-side, or median trackage.

Horizontal alignments for LRT systems often resemble rapid transit alignments in that they use tighter curves and smaller turnouts than railway operations require, but unlike rapid transit, light rail transit readily adapts to operating at-grade with other vehicles in urban environments and therefore rarely utilizes tunnels or elevated track structures. Because of the lower weight of LRT operations, LRT wheels tend to be smaller with narrower treads and flanges than railway or rapid transit environments. This, in turn, allows the rail to be smaller and the flangeway opening to be narrower in in-pavement applications, which minimizes impact to the roadway and vehicular traffic.

§ 8.13.9 Maintenance

All railway and transit systems must be maintained over time. Passenger ser-vice is more sensitive to service disruption than freight service, and extended delays for maintenance or service disruptions caused by a track failure can lead passengers to seek other modes of transportation. Commuters expect service to be reliable and run on time day after day. These expectations require that passenger service trackage be maintained to a high standard to reduce the possibility of service outages and that maintenance be performed during windows that interrupt service as little as possible. To avoid delays on busy corridors due to maintenance activities, work is often scheduled on nights and weekends when ridership is down, and often, some alternative means of transportation, such as buses, are provided as an alternative.



§ 8.13.10 Electrification

Steam was the power source of choice for early railroads, but the large amount of smoke produced by steam locomotives soon became an issue in many urban areas and in long tunnels without adequate ventilation. The use of pure electric locomotives that draw their power from remote generation plants provided a solution to the pollution generated by steam locomotives. Although diesel-electric locomotives replaced steam locomotives in the middle of the twentieth century, electric propulsion continues to offer many advantages over traditional locomotives. Pure electric locomotives gener-ally have a higher top speed, accelerate more quickly, have lower operating costs, and operate more effectively on steep grades than diesel-electric loco-motives. Electrification does, however, require a much higher initial capi-tal investment to construct the infrastructure required for transmission of the power from the plant to the locomotive.

Electrification requires four main components: a primary power source; substations to convert power from the primary source to a form used for train operations; a distribution system; and locomotives or power cars to draw the current. The electric power is generally distributed along the alignment by means of either an overhead catenary system or an at-grade third rail. In the case of overhead catenaries, the power is supplied to the locomotive via either a trolley pole or a pantograph; for third rail systems, a contact shoe is utilized.

§ 8.14 MAINTENANCE AND TRACK CONSTRUCTION

Maintenance and track construction are vital components of keeping rail-roads operating efficiently and safely. Regular maintenance of the railroad will maximize the life of track components and prevent track deterioration. Because the train track works as a system, one improperly maintained com-ponent can quickly cause other parts of the track system to deteriorate and/or fail. As a result, railroads invest significant amounts of money in regular track maintenance and rehabilitation to keep their systems in good condition and minimize the costs and downtime associated with a failure at some point in the future. The perpetual challenge becomes one of scheduling; as traffic volume increases, windows for scheduled maintenance necessarily decrease. Consequently, productivity and efficiency of track maintenance and con-struction becomes increasingly important.

§ 8.14.1 Track Disturbance Activities

Most maintenance activities that are performed on the track structure dis-turb the track to some degree, especially in areas of continuously welded rail (CWR). An unrestrained section of rail will elongate as the temperature rises.

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To prevent kinks in a section of CWR, the track is restrained by the rail ties, which are, in turn, restrained by the ballast section. Any activity that disturbs the ballast section reduces the amount of restraint provided and increases the risk of a kink until the ballast has had time to properly consolidate again. Modern maintenance equipment can quickly obtain approximately 80 per-cent of the original track stability by utilizing dynamic track stabilizers. The remaining 20 percent is obtained over time as trains operate over the main-tained area.

§ 8.14.2 Rail Lubrication

Lubrication of the inside face of the rail is necessary through some curves, as it minimizes friction between the rail and the wheel flange and the possibility of rolling one of the rails onto its side. Lubrication also generally maximizes rail life. Rails get lubricated by on-board locomotive lubricators, wayside lubricators located along the track, high-rail equipped systems, or by-hand application. The lubrication must only be applied to the inside (or gauge) face of the rail; lubrication on the top, or tread, of the rail would interfere with and reduce locomotive traction and braking control. Several factors affect how a track is lubricated: the location and curve of the track; the speed of the trains operating on the track; and the types and weights of the train cars operating on the track.

§ 8.14.3 Rail Grinding

Whenever a train car is on a track, the rail and the wheel are both on a curve at the contact point. Thus, it is critical to extended rail life that the radii of the rail head have a favorable profile to accommodate those curves and reduce friction and stress in the rail. The rail profile is maintained through grind-ing—specialized grinding machines or trains remove small amounts of metal in a highly controlled manner to achieve the optimal rail section. Grinding can be performed over longer stretches of rail, to remove surface imperfec-tions and corrugations in the rail, or in localized areas, to maintain individual components of turnouts and crossing diamonds.

§ 8.14.4 Rail Defect Testing

Defects in a rail section may be present from the manufacturing process (“internal defects”) or may develop over time as a result of environmental factors and loading (“external defects”). Internal defects typically give some external indication of their presence, but may not be recognized before a fail-ure occurs. Ultrasonic and/or electro-inductive technologies detect internal



defects by reviewing the way a wave of energy travels through the rail. The FRA requires inspection of rail for defects at varying frequencies, depending on the rail’s operating speed, tonnage, and the presence of revenue passen-ger traffic.

§ 8.14.5 Geometry Measurement

Most large railways now use geometry cars on a regular basis to check track line and gauge for compliance with FRA requirements. Newer geometry cars use optical rail scanning to measure gauge and track geometry in real time at speeds up to 70 mph. Older cars use a system that physically measures these attributes and operate at much slower speeds.

§ 8.14.6 Gauge Restraint

The “gauge” of a track is the distance between the inside faces of the rails. Because a consistent gauge is one of the most significant components to a safe, stable track system, gauge must be monitored regularly. North Ameri-can standard gauge is 4 to 8 1/2 inches. The tolerance for gauge variation is determined by the FRA track classification. The gauge can be measured by hand and track classification determined by the number of nondefective ties in a given length of track. Large railways are now using the Gauge Restraint Measuring System (GRMS), which uses a sliding axle to apply different lateral and vertical loadings to a section of track and measure the movement of the rail as a result of applied loads.

§ 8.14.7 Vegetation Control

As discussed above in section 8.11 on rights-of-way, undesirable vegetation can be a menace to railroad operations, because it can block sight lines or interfere with smooth train operations on the track. As such, vegetation con-trol is a key maintenance issue for the railroads. For more details, see specifi-cally section 8.11.4.

§ 8.14.8 Snow Removal

The weight and momentum of a loaded train is enough to power through minor snow drifts in isolated areas, but larger drifts or track that is contin-uously covered by several feet of snow requires specialized equipment to clear the track. Consequently, in northern climates, snow removal is a chal-lenge to keeping freight and passenger traffic moving. Heavy rail equipment

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can be fitted with large blades to clear the tracks in most situations. In deeper snows, wedges and plows utilize a V-shaped blade to push snow to either side of the track, or rotary snowplows can break through the snow and throw it to the side of the right-of-way. Yet another option is the high-rail-mounted snow blower, which is often used to keep snow and ice out of the moving parts of the turnout.

§ 8.14.9 Production Gangs

Significant track renewal projects are typically completed by production gangs that are dedicated to a specific task or group of tasks. The specializa-tion of production gangs allows for high levels of efficiency and safety in their work. Specific examples of production gangs include:

• Rail Gangs—replace worn-out rail and lay new rail• Tie Gangs—replace deteriorated ties along a track segment• Undercutting Gangs—remove, clean, and replace fouled or muddy

ballast• Surfacing Gangs—restore track alignment and profile

§ 8.14.10 Schedule Windows

Maintenance and construction activities must be completed within sched-ule windows to minimize delays to rail traffic. On regional and secondary railroads, schedule windows may range from several hours to multiple days without significantly impacting rail traffic. On Class I main lines, however, maintenance crews may only have a few hours at a time to perform their work before needing to reopen the track to rail traffic. On major routes, maintenance activities commonly occur in windows of a few hours, then pause to allow train traffic through the work area, after which maintenance work resumes.

§ 8.14.11 Railroad versus Third-Party Construction

The Class I railroads and some larger regional and commuter railroads have workforces that perform all construction and maintenance on their active rail lines. For new track construction or new alignments, these railroads may have their labor forces perform the work, or they may contract the work out to third-party contractors. Smaller railroads often do not have maintenance and construction labor forces large enough to perform major maintenance or construction activities; instead, they contract the work out to third-party contractors.



§ 8.14.12 Third-Party Access

Prior to performing any work on railroad right-of-way, a contractor must obtain a right-of-entry agreement and railroad protective liability insurance. The level of effort required to obtain a right-of-entry agreement typically depends on the railroad requiring the work and the type of work to be performed. Similarly, railroad protective liability insurance limits are typically based on the type of work to be performed. Insurance may be purchased through third-party insur-ance companies or, in some cases, through the railroad.

§ 8.14.13 New Track Construction

New track may be constructed either adjacent to existing tracks on existing railroad right-of-way or on new alignments away from existing tracks. The determining factors in how a track is constructed are the size of the pro-ject and the particular railroad. Smaller projects may be either “jig-built,” by placing the individual components and constructing the track in place, or “panel-built,” where track panels including rails, ties, and all fasteners are preassembled into panels 39 to 80 feet long, delivered to a jobsite, and connected in their final location. Larger projects often utilize a track laying machine (TLM) that is pulled over the proposed alignment by a crawler trac-tor. The TLM lays out ties at the proper spacing, threads rail onto the ties, and fastens the rail to the ties in one operation. After the track is constructed and in place, a separate production gang ballasts and surfaces the track to its final alignment and profile.

When new track connects to an existing track, the crew makes a “cutover” by cutting the existing track where the new connection or turnout is to be made, lifting or dragging the track to be removed out of the way, and lifting or dragging the new track or turnout into place. Once the new track or turnout is in place, the crew fastens it to the existing track, performs any needed surfacing, and opens the track to traffic.

NOTES

1 The terms “railway” and “railroad” are often used interchangeably. For the purposes of this chapter, railway will generally refer to the track and other closely related items, and railroad will refer to the bigger rail system. 2. A detailed history of the American railway industry can be found in American Railroads (2d ed. 1997), by John F. Stover. 3. A “truck” is the wheels, axles, and certain suspension components assembled together to guide and support each end of rolling stock car bodies. 4. Information regarding the process for maintaining or creating a quiet zone and addi-tional quiet zone information can be found on the FRA website, www.fra.dot.gov/.

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