Education Part 3
Under construction
Railroad Infrastructure
Railroad infrastructure refers to the path or roadway over which rolling stock (locomotives, railroad cars and other equipment) travel as well as the rolling stock themselves. But it also includes buildings (terminals, maintenance facilities, offices, storage facilities), rail yards, bridges, tunnels and other things needed for successful operation.
Interestingly, many of these things must also be addressed by model railroad enthusiasts. We shall touch on these matters throughout this section.
Interestingly, many of these things must also be addressed by model railroad enthusiasts. We shall touch on these matters throughout this section.
What is a Train?
A train, for our purposes, is a set of one or more railroad cars (locomotives, goods cars, passenger cars, etc.) coupled together so as to move as a unit over the railroad tracks.
Trains can be categorized in various ways. For example, unit trains carry a single good (e.g., coal, crude oil, iron ore, wheat, cattle, gravel) to a single destination, whereas a wagonload train carries a variety of goods bound for a variety of destinations.
Motive power can also be used to categorize trains. We will discuss steam, diesel-electric and electric trains. There are also funiculars, rack, maglev and monorail trains, as well as passenger, freight and specialized trains. Of course, there are revenue-producing trains and non-revenue trains (e.g., maintenance-of-way trains). We will discuss some of these in due course.
Territory
Before a train can be seen operating along a rail line, a great deal of work must be done. For instance, a railroad organization must establish the territory within which it plans to operate. Country or countries would be the first level of operating territory. The amount of work required to establish an international railroad operation is substantial. What is the home base of the organization? What legal hurdles must be overcome? How would standards, rules and regulations affect operations. Are there time zone issues? How about taxation? You get the idea.
Perhaps it would be better (initially) to establish a territory such as the Mississippi River Valley. Or a territory that links two major cities. Railroad organizations have carved out territories similar to these. But in many cases, a much more limited territory can be established that makes economic sense. Consider the Philadelphia and Reading Rail Road (PRRR). This railroad founded in 1843 began with a route from Pottsville, PA through Reading and onward to Philadelphia following closely the Schuylkill River valley for roughly 93 miles (150 km). This was a double track route over which anthracite coal was hauled to the PRRR port facility in the Port Richmond area of Philadelphia, PA. From this relatively modest beginning, the PRRR developed into one of the world's largest corporations (see Railroad History for more about Reading Lines).
Routes
Once a territory has been defined, routes may be planned. For example, the Delaware, Lehigh, Schuylkill and Susquehanna Railroad Company (later, LVRR) was incorporated in 1847, having received authorization to operate in the state of Pennsylvania. From the name of the company you can imagine the thinking that underlay its business plan. In 1853 its name changed to Lehigh Valley Railroad (LVRR). Its initial operation (excluding passenger service) was the transport of anthracite coal from the area around today's Jim Thorpe, PA to terminals on the Delaware River where it would be transported by boat to various destinations (the distance from Easton to Jim Thorpe, Pennsylvania is some 40 miles following the Lehigh River). Eventually, LVRR expanded to operate a rail network that ran from Buffalo, NY to New York City through Ithaca, NY, Scranton, PA, Easton, PA and Jersey City, NJ across the Hudson River from NYC. For a variety of reasons, LVRR ceased operations in 1976 through merger (see Railroad History).
Layout
Once a territory is established, the layout of the railroad must be designed and built. This involves both the planned routes as well as various buildings and other facilities that will be needed for effective operation.
First, we need to discuss trackage.
What is Trackage?
In order for a railroad company to operate, it must first build trackage and this means it must have land upon which to build. Acquiring this land is brought with difficulty, especially today, because rail trackage frequently must pass through densely-populated areas which are often the ultimate source of revenue for the railroad company.
Planning
The railroad company draws up a plan for its trackage (which includes access by ground transport for maintenance and other purposes). A preferred route and one or more alternate routes may be laid out that identify things like ease and cost of construction, potential construction delays, convenience to potential customers, legal issues and various other factors.
Right-of-Way
This plan also identifies the parcels of land owned by others from whom a right-of-way (ROW) must be obtained. Obtaining right-of-way may be facilitated by various laws (after all, the railroad may be considered a public utility), but not without consideration of Amendments V and XIV of the United States Constitution (Takings) or equivalent laws in other countries. ROW may be obtained via lease, purchase or eminent domain.
Other Concerns
Other concerns include construction matters (e.g., soil conditions, grade, drainage, support structures such as bridges and tunnels; see Roadbed Components later), branching, environmental degradation, affect on health and well-being of neighbors, safety issues and "not-in-my-neighborhood" concerns. These matters will be touched on as we proceed.
A train, for our purposes, is a set of one or more railroad cars (locomotives, goods cars, passenger cars, etc.) coupled together so as to move as a unit over the railroad tracks.
Trains can be categorized in various ways. For example, unit trains carry a single good (e.g., coal, crude oil, iron ore, wheat, cattle, gravel) to a single destination, whereas a wagonload train carries a variety of goods bound for a variety of destinations.
Motive power can also be used to categorize trains. We will discuss steam, diesel-electric and electric trains. There are also funiculars, rack, maglev and monorail trains, as well as passenger, freight and specialized trains. Of course, there are revenue-producing trains and non-revenue trains (e.g., maintenance-of-way trains). We will discuss some of these in due course.
Territory
Before a train can be seen operating along a rail line, a great deal of work must be done. For instance, a railroad organization must establish the territory within which it plans to operate. Country or countries would be the first level of operating territory. The amount of work required to establish an international railroad operation is substantial. What is the home base of the organization? What legal hurdles must be overcome? How would standards, rules and regulations affect operations. Are there time zone issues? How about taxation? You get the idea.
Perhaps it would be better (initially) to establish a territory such as the Mississippi River Valley. Or a territory that links two major cities. Railroad organizations have carved out territories similar to these. But in many cases, a much more limited territory can be established that makes economic sense. Consider the Philadelphia and Reading Rail Road (PRRR). This railroad founded in 1843 began with a route from Pottsville, PA through Reading and onward to Philadelphia following closely the Schuylkill River valley for roughly 93 miles (150 km). This was a double track route over which anthracite coal was hauled to the PRRR port facility in the Port Richmond area of Philadelphia, PA. From this relatively modest beginning, the PRRR developed into one of the world's largest corporations (see Railroad History for more about Reading Lines).
Routes
Once a territory has been defined, routes may be planned. For example, the Delaware, Lehigh, Schuylkill and Susquehanna Railroad Company (later, LVRR) was incorporated in 1847, having received authorization to operate in the state of Pennsylvania. From the name of the company you can imagine the thinking that underlay its business plan. In 1853 its name changed to Lehigh Valley Railroad (LVRR). Its initial operation (excluding passenger service) was the transport of anthracite coal from the area around today's Jim Thorpe, PA to terminals on the Delaware River where it would be transported by boat to various destinations (the distance from Easton to Jim Thorpe, Pennsylvania is some 40 miles following the Lehigh River). Eventually, LVRR expanded to operate a rail network that ran from Buffalo, NY to New York City through Ithaca, NY, Scranton, PA, Easton, PA and Jersey City, NJ across the Hudson River from NYC. For a variety of reasons, LVRR ceased operations in 1976 through merger (see Railroad History).
Layout
Once a territory is established, the layout of the railroad must be designed and built. This involves both the planned routes as well as various buildings and other facilities that will be needed for effective operation.
First, we need to discuss trackage.
What is Trackage?
In order for a railroad company to operate, it must first build trackage and this means it must have land upon which to build. Acquiring this land is brought with difficulty, especially today, because rail trackage frequently must pass through densely-populated areas which are often the ultimate source of revenue for the railroad company.
Planning
The railroad company draws up a plan for its trackage (which includes access by ground transport for maintenance and other purposes). A preferred route and one or more alternate routes may be laid out that identify things like ease and cost of construction, potential construction delays, convenience to potential customers, legal issues and various other factors.
Right-of-Way
This plan also identifies the parcels of land owned by others from whom a right-of-way (ROW) must be obtained. Obtaining right-of-way may be facilitated by various laws (after all, the railroad may be considered a public utility), but not without consideration of Amendments V and XIV of the United States Constitution (Takings) or equivalent laws in other countries. ROW may be obtained via lease, purchase or eminent domain.
Other Concerns
Other concerns include construction matters (e.g., soil conditions, grade, drainage, support structures such as bridges and tunnels; see Roadbed Components later), branching, environmental degradation, affect on health and well-being of neighbors, safety issues and "not-in-my-neighborhood" concerns. These matters will be touched on as we proceed.
Track
Once ROW is established, trackage (rail lines) may be constructed. This involves several steps, including preliminary testing and evaluation of the land on which the track is to be laid (including environmental concerns), detailed design and preparation of engineering drawings and so on. Keep in mind the fact that trackage needs to embody as little inclination or declination as possible (no up and down hill). It also must be concerned with radius of curvature and other factors that affect the velocity at which trains may operate. After all, time is money.
The following discussion depends on several sources, including American Railway Engineering and Maintenance-of-Way Association (AREMA), CSX Transportation (CSX), Mississippi Information Website (ICRR), Kansas City Southern (soon to be Canadian Pacific Kansas City (CPKC)) (KCS), Union Pacific Railroad (UP) and Federal Railroad Administration (FRA). See for example Federal Railroad Administration, Track and Rail and Infrastructure Integrity Compliance Manual, Volume II Track Safety Standards, Chapter 2 Track Safety Standards Classes 6 through 9, March 2018, 114 pp. These reference sources specify the standards and constraints that must be adhered to in the construction of trackage.
Track Bed
The basic structure of the track bed is suggested in the following illustration. Because of the weight of trains passing over the railway, the foundation must be firmly established, adequate drainage provided and a sound layer of sub-ballast (fine crushed stone) and ballast laid down.
Once ROW is established, trackage (rail lines) may be constructed. This involves several steps, including preliminary testing and evaluation of the land on which the track is to be laid (including environmental concerns), detailed design and preparation of engineering drawings and so on. Keep in mind the fact that trackage needs to embody as little inclination or declination as possible (no up and down hill). It also must be concerned with radius of curvature and other factors that affect the velocity at which trains may operate. After all, time is money.
The following discussion depends on several sources, including American Railway Engineering and Maintenance-of-Way Association (AREMA), CSX Transportation (CSX), Mississippi Information Website (ICRR), Kansas City Southern (soon to be Canadian Pacific Kansas City (CPKC)) (KCS), Union Pacific Railroad (UP) and Federal Railroad Administration (FRA). See for example Federal Railroad Administration, Track and Rail and Infrastructure Integrity Compliance Manual, Volume II Track Safety Standards, Chapter 2 Track Safety Standards Classes 6 through 9, March 2018, 114 pp. These reference sources specify the standards and constraints that must be adhered to in the construction of trackage.
Track Bed
The basic structure of the track bed is suggested in the following illustration. Because of the weight of trains passing over the railway, the foundation must be firmly established, adequate drainage provided and a sound layer of sub-ballast (fine crushed stone) and ballast laid down.
Cross-section through railway track and foundation
In addition, the grade must be carefully established. Grade (gradient, slope, pitch, incline, rise) is the inclination or declination from level. Grade can be expressed in various equivalent ways, as shown in the following diagram. Trains operate best on level track. Grade, for most of railroad history, was kept to near 0 degrees (0°) by means of cuttings, tunnels, bridges and fills (see Roadbed Components, later on).
Today, the use of diesel-electric and electric motive power means that grade is of lesser concern but can by no means be ignored. For many years, the "ruling grade" was considered to be 1% (the steepest incline navigable by existing motive power). Today the ruling grade is considered to be 2.2% although steeper grades are in regular use where motive power is sufficient. Grade is as important going down hill (declination) as going up (inclination), because of the need for braking (see Braking in Transport).
Grade is also important on curves where it is referred to as cant. In essence, the rails are banked (outside rail higher than inside rail) to reduce the lateral force on the rails around a curve due to centrifugal force and allow for faster travel around the curve. Cant is especially important on passenger lines for the comfort of passengers. Too much cant on freight lines can cause extra wear on the inside rail because of the greater weight of freight trains.
Modern railway construction tends to favor the ballastless approach to track laying in which a concrete base (similar to a highway) is poured, upon which concrete or steel ties or sleepers are laid, often on a resilient pad, to support the rails and reduce vibration. This approach is most commonly used in railway terminals and on high-speed rail lines.
Ties (Sleepers)
The next step in railroad construction is placement of the ties (sleepers) upon which the rails rest. For most of railroad history, ties were made of wood having approximate dimensions of 7 x 9 x 102 inches (17.8 x 22.9 x 259 cm). Such ties suffered from weather, heavy use and frequent need of replacement. While wooden ties are still in use, modern track, laid on gravel beds or a ballastless foundation, uses prestressed concrete ties (sleepers) or steel ties. Wooden ties are usually laid with spacing at 19 inches (48-49 cm) on centers; concrete or steel ties with spacing of 24 inches (58 cm) to 30 inches (72.6 cm) on centers. This spacing reduces the number of ties needed per mile of track.
Grade is also important on curves where it is referred to as cant. In essence, the rails are banked (outside rail higher than inside rail) to reduce the lateral force on the rails around a curve due to centrifugal force and allow for faster travel around the curve. Cant is especially important on passenger lines for the comfort of passengers. Too much cant on freight lines can cause extra wear on the inside rail because of the greater weight of freight trains.
Modern railway construction tends to favor the ballastless approach to track laying in which a concrete base (similar to a highway) is poured, upon which concrete or steel ties or sleepers are laid, often on a resilient pad, to support the rails and reduce vibration. This approach is most commonly used in railway terminals and on high-speed rail lines.
Ties (Sleepers)
The next step in railroad construction is placement of the ties (sleepers) upon which the rails rest. For most of railroad history, ties were made of wood having approximate dimensions of 7 x 9 x 102 inches (17.8 x 22.9 x 259 cm). Such ties suffered from weather, heavy use and frequent need of replacement. While wooden ties are still in use, modern track, laid on gravel beds or a ballastless foundation, uses prestressed concrete ties (sleepers) or steel ties. Wooden ties are usually laid with spacing at 19 inches (48-49 cm) on centers; concrete or steel ties with spacing of 24 inches (58 cm) to 30 inches (72.6 cm) on centers. This spacing reduces the number of ties needed per mile of track.
Spacing of wooden railroad ties (sleepers)
Rails
Rails are made of steel. Over the years, research has enabled the steel used to be improved (metallurgy) and the rolling of it into rails improved to reduce failure due to internal flaws in the steel structure.
In the United States, rails have a cross-section such as specified in the drawings below. The rails are called flat-bottom rails. The particular shape of rails, as well as the composition of the steel used, varies with the load and speed to be supported and other factors.
Rail Classification
Rails are classified according to their weight per unit distance and to their cross-section. In the drawings, the PRR rail has a weight of 100 lbs/yard (49.6 kg/meter) of rail, while the 115 RE rail has a weight of 115 lbs/yard (57 kg/meter). Rails are manufactured in a variety of classes for use in particular applications, such as main-line freight, sidings and high-speed rail. Today, rails are most often 115 or 132 pounds per yard (57.5 or 66 kg/m).
Rails are made of steel. Over the years, research has enabled the steel used to be improved (metallurgy) and the rolling of it into rails improved to reduce failure due to internal flaws in the steel structure.
In the United States, rails have a cross-section such as specified in the drawings below. The rails are called flat-bottom rails. The particular shape of rails, as well as the composition of the steel used, varies with the load and speed to be supported and other factors.
Rail Classification
Rails are classified according to their weight per unit distance and to their cross-section. In the drawings, the PRR rail has a weight of 100 lbs/yard (49.6 kg/meter) of rail, while the 115 RE rail has a weight of 115 lbs/yard (57 kg/meter). Rails are manufactured in a variety of classes for use in particular applications, such as main-line freight, sidings and high-speed rail. Today, rails are most often 115 or 132 pounds per yard (57.5 or 66 kg/m).
Pennsylvania Railroad specification for rail dimensions
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American Railway Engineering and
Maintenance-of-Way Association (AREMA) specification for 115 lbs/yard (56.9 kg/meter) rail
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Rail Fastening
A rail may be fastened to a tie in a variety of ways. For many years, a rail was placed on a tie-plate (see below) then fastened to a tie with spikes of sizes from 9⁄16 to 10⁄16 inch (14 to 16 mm) square and 5½ to 6 inches (140 to 150 mm) long. Screws have also been used.
Today, prestressed concrete or steel ties are often used in which the equivalent of tie plates are embedded in the tie. A rail is held in place by some form of clamp. See Fasteners for more detail.
A rail may be fastened to a tie in a variety of ways. For many years, a rail was placed on a tie-plate (see below) then fastened to a tie with spikes of sizes from 9⁄16 to 10⁄16 inch (14 to 16 mm) square and 5½ to 6 inches (140 to 150 mm) long. Screws have also been used.
Today, prestressed concrete or steel ties are often used in which the equivalent of tie plates are embedded in the tie. A rail is held in place by some form of clamp. See Fasteners for more detail.
Example of tie plates
Track Gauge
Tie plates (or other fasteners) are positioned on a tie so as to achieve the gauge the railroad operates on. Gauge (sometimes spelled gage) is a measure of distance between the rails forming a track. "Gauge" is also used for other measures, such as model railroad track (e.g., HO gauge), wire diameter, air pressure and so on. In railroading, gauge refers to the distance between rails of a track, measured from the inside of the head of the rail.
In much of the world, standard gauge, which is 4 ft 8-1⁄2 inches (1,435 mm), is used but there are several other gauges in use as well. The following table shows several railroad gauges that have been or are in use presently.
Tie plates (or other fasteners) are positioned on a tie so as to achieve the gauge the railroad operates on. Gauge (sometimes spelled gage) is a measure of distance between the rails forming a track. "Gauge" is also used for other measures, such as model railroad track (e.g., HO gauge), wire diameter, air pressure and so on. In railroading, gauge refers to the distance between rails of a track, measured from the inside of the head of the rail.
In much of the world, standard gauge, which is 4 ft 8-1⁄2 inches (1,435 mm), is used but there are several other gauges in use as well. The following table shows several railroad gauges that have been or are in use presently.
Various railroad gauges that have been used
Use of spikes has engendered many references to them in song and folklore (we mention the golden spike, denoting the initial completion of Shannondell Model Railroad, in Club History). Today, when spikes are used, a special spiking machine does the job; in former times a spiker was expected to drive a spike with a spike maul in three blows. Given that each tie-plate required 5-6 spikes, the spiker had to drive a large number of spikes per mile of roadway. (No, John Henry was not a spiker but a miner.) The following photo shows the typical connections when wooden ties, tie plates, spikes and bolted rail are used.
Older rail laid on wooden ties with tie plates, spikes and bolted rail connectors
Track Classification
In the United States, track carries a classification that specifies the upper velocity limit permitted on the class of track. The classes and velocity limits are shown in the following table.
Classes of track and operating velocity limits as specified by Federal Railroad Administration in 49 CFR 213.9 and 49 CFR 307
Track Laying
Once track foundation, drainage and ballast have been laid down (usually by earth-moving equipment), track can be laid. Today this is done by track-laying equipment. There are two basic approaches to mechanized track laying. In one, ballast, prestressed concrete or steel ties and rails are brought to the construction site on the track-laying machine and assembled as the machine travels along the newly-laid track. In the other, track sections (rails, ties and all) are fabricated in factories designed for this work. The sections are then loaded on railroad cars for transport to the site where they are put in place. Special sections of track, such as turnouts and crossovers (see Track Configurations, below) are usually fabricated before transport to the installation site. However, when a section is too large to transport by rail, it is assembled on site.
The best way to understand mechanized track laying is to watch a video, such as this one of a track-laying machine (7.3 minutes). In this video, the machine is rebuilding a high-speed railroad track, replacing the older prestressed concrete ties (which are stored somewhere on the machine), leveling the ballast, placing new ties and eventually laying the rails, welding the newly-laid rails to those already in place (producing continuous welded rail or CWR), tamping the new rails and then rolling onto them for the next section. Another video further helps to understand machine-installed track (17.5 minutes).
Installation and maintenance of trackage is now heavily mechanized, compared with former methods, thus reducing time required and improving both accuracy and safety. We will have more to say about maintenance later.
Track Configurations
If only it were merely a matter of connecting two points by railroad track, but it is not. Trains often need to negotiate curves, move from one track to another, or need one track to cross over another track. So special sections of track must be designed and installed to permit such movement.
If only it were merely a matter of connecting two points by railroad track, but it is not. Trains often need to negotiate curves, move from one track to another, or need one track to cross over another track. So special sections of track must be designed and installed to permit such movement.
Curves
The simplest deviation from a linear track is a curved track. Curves introduce a number of problems not encountered in straight track. Speed, radius, cant, and centrifugal force all come into play.
Radius of curvature is a critical factor in designing and building curved track. On main lines, the minimum radius of curvature is usually considered to be 175 meters or a little more than 1/10th mile. On a siding, 84 meters (276 feet) is the minimum radius of curvature, because the velocity of the train is much less than on a main line. The following illustration shows curves of increasing radius of curvature.
The simplest deviation from a linear track is a curved track. Curves introduce a number of problems not encountered in straight track. Speed, radius, cant, and centrifugal force all come into play.
Radius of curvature is a critical factor in designing and building curved track. On main lines, the minimum radius of curvature is usually considered to be 175 meters or a little more than 1/10th mile. On a siding, 84 meters (276 feet) is the minimum radius of curvature, because the velocity of the train is much less than on a main line. The following illustration shows curves of increasing radius of curvature.
Curves of radius 3,000, 4,000 and 5,000 feet
The following table shows the relationship between velocity and radius of curvature.
Table showing the relation between train velocity and radius of curvature of railroad track
This table also takes into account cant or superelevation, a measure of the amount of inclination from the inside rail to the outside rail in a curve. In the table, cant is assumed to be 160 mm. The purpose of cant is to balance the force exerted on the two rails within a curve. Cant is beneficial for fast-moving trains (high centrifugal force), but is detrimental for slow moving trains (lower centrifugal force). This problem is sometime corrected for by building “tilting” trains (usually fast passenger trains).
Other issues with curves include the limits placed on curvature by the couplings of the rolling stock. Most coupling designs place significant limits on minimum curvature if damage to the couplings is to be avoided.
Train length also governs radius of curvature, since the pulling force may cause railroad cars near the middle of the train to leave the track. This problem can be overcome by reducing velocity, by placing locomotives near the middle, by placing the lightest loaded cars at the end of the train and/or by increasing the radius of curvature of the track.
Other issues with curves include the limits placed on curvature by the couplings of the rolling stock. Most coupling designs place significant limits on minimum curvature if damage to the couplings is to be avoided.
Train length also governs radius of curvature, since the pulling force may cause railroad cars near the middle of the train to leave the track. This problem can be overcome by reducing velocity, by placing locomotives near the middle, by placing the lightest loaded cars at the end of the train and/or by increasing the radius of curvature of the track.
Transition Curves
As a train enters or exits a curve in the track, there should be a section of straight track at either end to facilitate curve negotiation. In the following illustration, the radius of curvature of the two curved sections of track are 1000 feet. The length of straight track is also about 1000 feet. Ignoring this precaution may result in derailment. Why?
As a train enters or exits a curve in the track, there should be a section of straight track at either end to facilitate curve negotiation. In the following illustration, the radius of curvature of the two curved sections of track are 1000 feet. The length of straight track is also about 1000 feet. Ignoring this precaution may result in derailment. Why?
A transition curve with a length of strait track between to permit a train to return to horizontal before shifting to the opposite centrifugal force
Vertical Curves
Vertical curves (inclination followed by declination) are of less concern than the other issues we have discussed, but not negligible. Think of this issue as a transition curve in the vertical plane rather than the horizontal plane, with small changes in grade.
Vertical curves (inclination followed by declination) are of less concern than the other issues we have discussed, but not negligible. Think of this issue as a transition curve in the vertical plane rather than the horizontal plane, with small changes in grade.
Turnouts
A railroad turnout, also called a switch or points, is a mechanical unit enabling railway trains to be directed from one track to another. Turnouts are both handed (left or right) and directional (said to be facing or trailing). This is illustrated below.
A railroad turnout, also called a switch or points, is a mechanical unit enabling railway trains to be directed from one track to another. Turnouts are both handed (left or right) and directional (said to be facing or trailing). This is illustrated below.
Illustration of turnouts with the upper pair right-hand and the lower pair left-hand
A turnout consists of a pair of interlocked, tapering rails, called points (switch rails or point blades), lying between the diverging outer rails (the stock rails). Points are shown in red in the above diagram. These points can be moved laterally, in tandem, into one of two positions. In the top example in the above illustration, the points, approached from left, will direct a train along the straight track. In the second example, the points will direct a train along the diverging track (toward the right). A train moving from the left toward the point blades (i.e., it will be directed to one of the two tracks, depending on the position of the points) is said to be executing a facing-point movement or is traveling facing the diverging tracks. If a train approaches from the right (on either track) it is said to be traveling in the trailing direction.
The bottom two examples in the above illustration are left-handed turnouts.
Notice that if a train is approaching from the right side of the illustration, it can continue only on the straight track, regardless of the point settings. Why is that so?
One other aspect of the above illustration is the short bits of rail seen near or opposite a gap in a rail. These are called guard rails and serve to help insure wheels continue on the proper line as they travel over over the point rails (two inner rails that end in a point). The complete assembly of the point rails and wing rails is called a frog (see illustration below).The frog also helps reduce wear on these more delicate parts.
The bottom two examples in the above illustration are left-handed turnouts.
Notice that if a train is approaching from the right side of the illustration, it can continue only on the straight track, regardless of the point settings. Why is that so?
One other aspect of the above illustration is the short bits of rail seen near or opposite a gap in a rail. These are called guard rails and serve to help insure wheels continue on the proper line as they travel over over the point rails (two inner rails that end in a point). The complete assembly of the point rails and wing rails is called a frog (see illustration below).The frog also helps reduce wear on these more delicate parts.
Illustration of a frog (from AGICO Group) showing the components, usually cast as a unit.
Turnouts are numbered (e.g., #4, #5, #6,. ...#18, #20, #24) to differentiate the maximum velocity a train may travel in order to diverge via the turnout. The lower the turnout number, the smaller the radius of curvature of the diverging track, thus the slower one must travel through the turnout. The numbers signify the number of units of linear run per unit of divergence. For instance #24 means the turnout has 24 units of length (run) for 1 unit of divergence; a very shallow curve used on high-speed train lines. The following diagram illustrates how turnout numbers are measured.
The turnout number indicates a ratio of X/1. X will be a number of units equal to the turnout number (e.g., #8). X is measured along the center lines of the through track and the diverging track, from the heel joint of the switch point adjacent to the outer rail of the through track. X will be the distance along the center lines to the point where the center lines are separated by 1 unit of distance (arrow).
Turnouts may be assembled in the field (see this video - 19:42 minutes), but they are more likely to be factory fabricated and moved by rail to the installation site. This video (15 minutes) shows the installation of a pre-fabricated turnout on the Florida East Coast (FEC) Railroad.
Crossover
A crossover is a pair of turnouts that connect two adjacent tracks, allowing a train on one track to cross over to the other. Like turnouts, crossovers can be described as directional (facing or trailing).
A typical crossover
When two crossovers are present in opposite directions, one after the other, the four-turnout configuration is called a double crossover, that allows trains traveling in either direction on one track to cross over to the other track. If the crossovers in different directions overlap to form an X, it is named a scissors crossover, or a diamond crossover. This makes for a very compact track layout at the expense of using a level junction (see a bit later).
An example of a scissors crossover
Wye Turnout
A wye turnout (Y points) has trailing ends which diverge symmetrically and in opposite directions (left and right). The name originates from the similarity of their shape to that of the letter Y or a similar configuration seen in the hoof of a horse. Wye turnouts are usually used where space is at a premium. Ordinary turnouts are more often associated with mainline speeds, whereas wye turnouts are generally low-speed yard turnouts or serve to provide access to single track bridges or tunnels. See The Amazing Feather River Railroads and the Keddie Wye video for an amazing example of a wye.
Other Configurations
Level Junction
A level junction (or flat crossing) involves two or more tracks that cross but do not allow change of track. Such crossings might be used to permit the tracks of two different railroads to cross. Tracks of different gauges may also cross using level junctions.
A wye turnout (Y points) has trailing ends which diverge symmetrically and in opposite directions (left and right). The name originates from the similarity of their shape to that of the letter Y or a similar configuration seen in the hoof of a horse. Wye turnouts are usually used where space is at a premium. Ordinary turnouts are more often associated with mainline speeds, whereas wye turnouts are generally low-speed yard turnouts or serve to provide access to single track bridges or tunnels. See The Amazing Feather River Railroads and the Keddie Wye video for an amazing example of a wye.
Other Configurations
Level Junction
A level junction (or flat crossing) involves two or more tracks that cross but do not allow change of track. Such crossings might be used to permit the tracks of two different railroads to cross. Tracks of different gauges may also cross using level junctions.
Example of a level junction
Level Crossings
Railroad track frequently must cross roadways (streets, highways) and occasionally an airport runway. Such crossings (also called grade crossings) require special construction so as to give bicycles, cars, trucks, etc. a relatively smooth path over the rails, while insuring that there is no interference with the wheels of a passing train. In general, such crossings are well marked so as to avoid accidents (although accidents do occur). In the United States there are some 200,000 level crossings, one of which is shown below.
Railroad track frequently must cross roadways (streets, highways) and occasionally an airport runway. Such crossings (also called grade crossings) require special construction so as to give bicycles, cars, trucks, etc. a relatively smooth path over the rails, while insuring that there is no interference with the wheels of a passing train. In general, such crossings are well marked so as to avoid accidents (although accidents do occur). In the United States there are some 200,000 level crossings, one of which is shown below.
Waiting for an East Penn Railroad train to pass across Route 1 along the west side of Brandywine Creek in Chadds Ford, PA
A recent accident at a level crossing on the Southwest Chief line near Mendon, Missouri shows what a poorly-designed level crossing can cause. The dump truck that caused the collision is not seen in the following photo.
Amtrak train, in route from Los Angeles to Chicago, derailed after hitting a dump truck at a level crossing near Mendon, Missouri (Philadelphia Inquirer 2022 Jun 29, A10)
Roadbed Components
Railroad tracks do not run along only open ground. In order to keep grade close to 0°, it is necessary to make cuttings, fill culverts, dig tunnels or build bridges. For our purposes, we shall assume that careful surveying, testing, analysis, engineering and design are employed before any actual construction work is begun. A treatment of these matters is beyond the scope of this brief discussion.
Cutting
A cutting involves removal of part or all of a hill so as to avoid traveling up or down hill. Sometimes cuttings only involve removing soil and rock, and leveling, but it is often necessary to construct a retaining wall to prevent material further up hill from falling or collapsing onto the track to be laid.
A famous cutting and fill section of the main line between Harrisburg and Pittsburgh, Pennsylvania is Horseshoe Curve, built by the Pennsylvania Railroad in 1854 to facilitate moving freight over the Allegheny Mountains. Horseshoe Curve is now a three-track railroad curve (formerly four tracks) lying midway between Altoona and Gallitzin, PA. Between these two towns, the line climbs 1.85°. The trackage is now part of Norfolk Southern Railway. A visitor center, operated by Railroaders Memorial Museum, welcomes visitors year round. The curve is on the National Register of Historic Places (1966) and was designated a National Historic Civil Engineering Landmark in 2004. Below is an aerial photo of the curve in 2006.
Horseshoe Curve on the main line between Harrisburg and Pittsburgh, Pennsylvania surrounding a visitor center and reservoir
Tunnel
If a cutting is insufficient to achieve a level way and rerouting is infeasible, a tunnel will have to be dug. Historically, tunnels were dug by hand with the aid of explosives and perhaps by the use of the already finished part of the track(s). Today, tunnels are created using tunnel-boring machines (TBM). The longest railroad tunnel in the world is the Gotthard Base Tunnel at some 35 miles (57.09 km) in length (running slightly northwest from Bodio to Erstfeld, Switzerland. The grade northbound is 4.055% (max) and southbound is 6.76% (max). For that tunnel, boring began at four places (there are actually two tunnels, East and West). A video (6.3 minutes) helps to understand the operation of a tunnel boring machine.
Another famous railroad tunnel is on the Canadian Pacific line in the area between Lake Louise and Field, British Columbia. The route includes two spiral tunnels dug in three-quarter circles into the walls of the Kicking Horse River valley. The higher tunnel is about 1,000 yards (0.91 km) long, dug into Cathedral Mountain. When the line emerges from this tunnel it has doubled back, running beneath itself some 50 feet (15 m) lower. It then descends the valley in almost the opposite direction to its previous heading, before crossing the Kicking Horse River and being dug into Mount Ogden north of the river. This lower tunnel is a few yards shorter than the higher one and the descent is again about 50 feet (15 m). From the exit of this tunnel the line continues down the valley on the original heading, toward Field, BC. This scheme effectively doubles the distance traveled on this section of the line, but reduces the gradient from the earlier 4.5% to 2.2%. The route just described is illustrated below.
Spiral tunnels on the Canadian Pacific Line
Other famous railroad tunnels include the Channel Tunnel (Tunnel sous la Manche) at 31.35 mi (50.46-km) and the Seikan Tunnel in Japan at 33.5 mi (53.85 km). There are at least 31 other railroad tunnels of 12 miles or more throughout the world.
Culvert Filling
Material removed from cuttings, or else brought in from other sources, may then be used to fill culverts or low places somewhere else along the intended path of the track. This work may also require installation of drainage to prevent flooding when a culvert is filled, since a culvert is usually created by running water, whether continuous or periodic.
Bridge
If a culvert or valley is too great to fill, a bridge must be built. Sometimes an existing bridge can be modified to carry rail traffic as well as automobile or other traffic. In many cases, however, a new bridge must be built, either because of the load to be carried, the desired location or both. Bridges are fairly common along railroads and several can be seen in your local area. One of the most famous railroad bridges is Glenfinnan Viaduct over the River Finnan in Scotland. The bridge, built 1897-1901, has appeared in numerous films, including four of the Harry Potter series. Here is a photo of the bridge with the The Jacobite crossing.
The Jacobite crossing the Glenfinnan Viaduct
Other well known railroad bridges include the Hell Gate Railroad Viaduct linking New York City with New England; Tyne Bridge in Newcastle, England and the Sydney Harbour Bridge in New South Wales, Australia (both based on Hell Gate). There was also the Florida East Coast Railway extension (Overseas Railroad) consisting of several bridges connecting the Florida Keys all the way to Key West. This very significant achievement was terminated by the hurricane of September 2-3, 1935.
Other Railroad Components
In addition to the infrastructure discussed above, one must also consider various other components of a railroad, such as buildings (especially stations or terminals), yards, communication and control systems, maintenance facilities and manufacturing facilities.
In addition to the infrastructure discussed above, one must also consider various other components of a railroad, such as buildings (especially stations or terminals), yards, communication and control systems, maintenance facilities and manufacturing facilities.
Stations and Terminals
Railroads require places where goods or passengers are loaded and/or unloaded. Such places are often called stations, sometimes railway or railroad stations, depots, railway depots, train stations and others. There are two kinds of stations, through stations and terminal stations. Through stations are those in which trains may stop for loading and unloading, but then continue onward to other destinations. Terminal stations (sometimes just terminals) are those in which a train may not proceed further but must reverse direction to exit the terminal (e.g., Reading Terminal in Philadelphia, PA and Grand Central Terminal in New York City - also called Grand Central Station, a correct but more generic designation than "terminal"). Some stations operate as both terminal and through station (e.g., Union Station in Washington, DC).
Passenger Stations
Stations may be quite simple facilities, ranging from a sign indicating a place where a train will stop on request but not on any schedule, to grand palatial structures that may even include hotels. The following photos illustrate two points on the spectrum of railway stations (both through stations).
Railroads require places where goods or passengers are loaded and/or unloaded. Such places are often called stations, sometimes railway or railroad stations, depots, railway depots, train stations and others. There are two kinds of stations, through stations and terminal stations. Through stations are those in which trains may stop for loading and unloading, but then continue onward to other destinations. Terminal stations (sometimes just terminals) are those in which a train may not proceed further but must reverse direction to exit the terminal (e.g., Reading Terminal in Philadelphia, PA and Grand Central Terminal in New York City - also called Grand Central Station, a correct but more generic designation than "terminal"). Some stations operate as both terminal and through station (e.g., Union Station in Washington, DC).
Passenger Stations
Stations may be quite simple facilities, ranging from a sign indicating a place where a train will stop on request but not on any schedule, to grand palatial structures that may even include hotels. The following photos illustrate two points on the spectrum of railway stations (both through stations).
A simple station on the Alaska Railroad Hurricane Line at Curry, AK offering shelter but no services
Philadelphia's William H. Gray III 30th Street Station viewed from Market Street
Passenger stations usually are comprised of one or more tracks with adjoining platforms, signage and other amenities. The Curry station shown above represents the minimum. Lacking a platform, a passenger need either climb aboard in some way or a conductor or the railroad car must provide a step mechanism to facilitate embarking and debarking. A platform is a structure that is level with the door(s) on a railroad car and facilitates entry and exit with safety.
Signage
Stations are usually equipped with signs giving the name of the station, directional indications, safety information and so on. Signs may also be provided that show train arrivals and departures, together with information such as train name and number, arrival time, departure time, status (on-time, late) and other pertinent data. The following photo shows an automatic schedule board.
Signage
Stations are usually equipped with signs giving the name of the station, directional indications, safety information and so on. Signs may also be provided that show train arrivals and departures, together with information such as train name and number, arrival time, departure time, status (on-time, late) and other pertinent data. The following photo shows an automatic schedule board.
Schedule board at William H. Gray III 30th Street Station, Philadelphia, PA
Passenger Station Services
In general, railway stations provide a range of services from ticket sales (staffed, automated or on board), waiting areas, luggage services (porter, luggage cart, left-luggage), freight services (handling, forwarding, storage), toilets, food and beverage services (e.g., fast food, restaurants, bars), taxi and ride share services, bus service and car parking. Some stations even offer hotel accommodations.
Larger stations may operate 24 hours/day but the majority of stations are open only when traffic warrants. Nevertheless, trains may stop at such stations on a scheduled basis. Tickets may then be purchased through automated machines or through the conductor on board. Weekly or monthly passes may also be offered. These are a convenience for regular travelers.
In many African, South American, and Asian countries, stations are also used as a locale for public markets and other informal businesses. This is especially true on tourist routes or stations near tourist destinations.
In general, railway stations provide a range of services from ticket sales (staffed, automated or on board), waiting areas, luggage services (porter, luggage cart, left-luggage), freight services (handling, forwarding, storage), toilets, food and beverage services (e.g., fast food, restaurants, bars), taxi and ride share services, bus service and car parking. Some stations even offer hotel accommodations.
Larger stations may operate 24 hours/day but the majority of stations are open only when traffic warrants. Nevertheless, trains may stop at such stations on a scheduled basis. Tickets may then be purchased through automated machines or through the conductor on board. Weekly or monthly passes may also be offered. These are a convenience for regular travelers.
In many African, South American, and Asian countries, stations are also used as a locale for public markets and other informal businesses. This is especially true on tourist routes or stations near tourist destinations.
Freight Stations
Freight stations or depots, in contrast with passenger stations, need to be equipped with loading and unloading equipment. Such equipment depends, in part, on the type of railroad car (see Transport) to be loaded or unloaded. For instance, hopper cars usually have doors that open under the car, so below-grade facilities are needed to receive goods and above-grade facilities for loading. Materials may also be loaded and unloaded with the help of conveyors of various kinds. Today, robots increasingly are being used for these purposes.
Platforms are also often needed for loading and unloading freight. Platforms permit forklifts or lift trucks, for instance, to operate level with railroad car doors when loading box cars or flat cars. However, railroad cars designed to carry automobiles must be loaded from the end rather than the side. Since these are bi- or tri-level cars, a flexible loading ramp is used rather than a fixed platform.
With intermodal freight, entire terminals must be designed to facilitate loading of containers onto specially-designed railroad cars (well cars). Loading and unloading are usually done with overhead cranes that lift whole containers rather than the contents thereof. Transporting containers requires careful attention to the loading gauge, that is, the maximum dimensions of loaded railroad cars so that they will clear tunnels, bridges, overhead catenaries, platforms and other possible hindrances. In the Unites States, well cars permit double-stacked containers on many rail lines whereas single containers are the norm in Europe.
Railroads are not always responsible for freight stations. Rather, the customer may be required to prepare a siding and freight facilities. CSX (among others) offers a detailed specification for private sidings. Construction of such facilities would generally be contracted for with the many firms that provide such service. See for example ... complete
Railroad Yards
A railroad yard is an area where trains or parts of trains can be assembled or reassembled (marshaling, classification or sorting yard), stored (storage yard), maintained (maintenance or repair yard) or loading/unloading yard. Large railroad yards will usually be subdivided into an arrival yard, a classification yard, an assembly yard and a departure yard.
Arrival Yard
The arrival yard is the area where a train "parks" upon arrival at the railroad yard. The arrival yard serves several purposes, the most important of which is to clear the main line so as to avoid interfering with the normal flow of traffic. The arrival yard also is where a train is first broken up to allow cars to be classified or sorted. This yard also provides the opportunity to inspect all cars of the train for necessary maintenance and repair. The contents of cars in need of extensive repair may have to be moved to another car. This would involve the loading/unloading yard and then the maintenance yard.
Loading/Unloading Yard
This yard is where goods are either loaded into un-powered cars or are unloaded for transfer to other cars or to ground transportation for transport to final destination. This yard may be situated near manufacturing facilities or shipping facilities such as ports or freight terminals.
Classification or Marshaling Yard
The classification (marshaling, sorting) yard is perhaps the most important, as this is where individual cars (mostly freight), uncoupled from an arriving train, are sent to a branch line consisting of cars to be delivered to a particular destination, cars carrying a particular product, cars that must be maintained, cars destined for storage and so on. Here is a video (1:27 minutes) and a second video (4:35) that illustrate the classification process.
Cars also may be sorted by owner, by weight (empty, light-weight goods, etc.), by type (flat, tank, hopper, etc.), by goods, by destination (drop-off or final), by route (specific cars may not be suited for all routes), or other categories.
Assembly Yard
Once cars are sorted, they may be assembled into one or more trains in the assembly yard. For example, a group of cars may be attached to a unit train (see What Is a Train, above) going to either an intermediate drop-off point or to the same final destination. Otherwise, one or more groups of sorted cars may be assembled into a train headed by the appropriate motive power.
Maintenance Yard
Any powered or unpowered cars in need of maintenance are moved to the maintenance yard. Here one may find a round house and perhaps several buildings focused on performing various types of maintenance such as truck (bogie) repair or replacement, brake work and car body repair. In the case of under-body work, a building with a "grease pit" provides space for workers to service otherwise hard-to-reach parts.
Unit Yard
Where traffic necessitates, a railroad yard may also have a unit yard where unit trains may park for crew changes, servicing and perhaps inspection for problems. Unit trains do not undergo classification (why?).
A railroad yard is an area where trains or parts of trains can be assembled or reassembled (marshaling, classification or sorting yard), stored (storage yard), maintained (maintenance or repair yard) or loading/unloading yard. Large railroad yards will usually be subdivided into an arrival yard, a classification yard, an assembly yard and a departure yard.
Arrival Yard
The arrival yard is the area where a train "parks" upon arrival at the railroad yard. The arrival yard serves several purposes, the most important of which is to clear the main line so as to avoid interfering with the normal flow of traffic. The arrival yard also is where a train is first broken up to allow cars to be classified or sorted. This yard also provides the opportunity to inspect all cars of the train for necessary maintenance and repair. The contents of cars in need of extensive repair may have to be moved to another car. This would involve the loading/unloading yard and then the maintenance yard.
Loading/Unloading Yard
This yard is where goods are either loaded into un-powered cars or are unloaded for transfer to other cars or to ground transportation for transport to final destination. This yard may be situated near manufacturing facilities or shipping facilities such as ports or freight terminals.
Classification or Marshaling Yard
The classification (marshaling, sorting) yard is perhaps the most important, as this is where individual cars (mostly freight), uncoupled from an arriving train, are sent to a branch line consisting of cars to be delivered to a particular destination, cars carrying a particular product, cars that must be maintained, cars destined for storage and so on. Here is a video (1:27 minutes) and a second video (4:35) that illustrate the classification process.
Cars also may be sorted by owner, by weight (empty, light-weight goods, etc.), by type (flat, tank, hopper, etc.), by goods, by destination (drop-off or final), by route (specific cars may not be suited for all routes), or other categories.
Assembly Yard
Once cars are sorted, they may be assembled into one or more trains in the assembly yard. For example, a group of cars may be attached to a unit train (see What Is a Train, above) going to either an intermediate drop-off point or to the same final destination. Otherwise, one or more groups of sorted cars may be assembled into a train headed by the appropriate motive power.
Maintenance Yard
Any powered or unpowered cars in need of maintenance are moved to the maintenance yard. Here one may find a round house and perhaps several buildings focused on performing various types of maintenance such as truck (bogie) repair or replacement, brake work and car body repair. In the case of under-body work, a building with a "grease pit" provides space for workers to service otherwise hard-to-reach parts.
Unit Yard
Where traffic necessitates, a railroad yard may also have a unit yard where unit trains may park for crew changes, servicing and perhaps inspection for problems. Unit trains do not undergo classification (why?).
Yard Structure
Railroad yards originated as flat yards in which cars were moved around using switching or shunting locomotives. Later, yards were sometimes built on land that had a useful slope (gravity yard). In this way, gravity could be used to move cars, thus saving the cost of switching locomotives. However, workers were still required to operate hand brakes to prevent cars crashing into one another and causing damage.
Major railroad yards are built around the hump concept (hump yard). A large mound or hump is constructed so a car pushed over the hump can be directed under gravity power to a classification yard. A hump may be as high as 10 meters (32.8 feet). A car is moved from the arrival yard, by means of a switching locomotive, up the hump and released. The car then moves under gravity power and a control tower directs the car to the correct siding in the classification yard. Retarders along the descending track(s) control the velocity of the car as it travels to a specific track where other cars of the same class are waiting.
Railroad yards originated as flat yards in which cars were moved around using switching or shunting locomotives. Later, yards were sometimes built on land that had a useful slope (gravity yard). In this way, gravity could be used to move cars, thus saving the cost of switching locomotives. However, workers were still required to operate hand brakes to prevent cars crashing into one another and causing damage.
Major railroad yards are built around the hump concept (hump yard). A large mound or hump is constructed so a car pushed over the hump can be directed under gravity power to a classification yard. A hump may be as high as 10 meters (32.8 feet). A car is moved from the arrival yard, by means of a switching locomotive, up the hump and released. The car then moves under gravity power and a control tower directs the car to the correct siding in the classification yard. Retarders along the descending track(s) control the velocity of the car as it travels to a specific track where other cars of the same class are waiting.
Major Yards
There are many railroad yards around the world. The largest of these is the Union Pacific Bailey Yard located in North Platte, NE. This yard covers 4.5 sq mi; 11.5 sq km) and is over 8 miles (13 km) in length and 2 miles (3.2 km) wide at its widest point. The yard has about 200 separate tracks totaling 315 miles (507 km) of track, 1,751 turnouts (switches) and 17 receiving and 16 departure tracks. The Bailey Yard handles an average of about 140 trains/day with some 14,000 non-powered cars. The yard has two humps and sorts or classifies some 3,000 cars/day (maximum capacity is about 5,800 cars/day. The yard has facilities for servicing trains as they pass through and can also repair both locomotives and non-powered cars.
The second largest railroad yard, DB Cargo AG - Werk Maschen, is located in Seevetal, Germany, south of Hamburg. It is operated by Deutsche Bahn (DB).
The following illustration shows the Conway Yards of Norfolk Southern (NS), also a quite large yard, that is located in Conway, PA along the Ohio River about 25 miles northwest of Pittsburgh, PA.
A diagram showing the layout of Norfolk Southern's Conway Yards in Conway, PA (the size of the yard necessitates this orientation)
Communication and Control Systems
A significant part of railroad infrastructure consists of communication and control systems. From early in railroad history, communication was considered a necessity for satisfactory railroad operation and for safety of passengers, crews, goods, equipment and infrastructure.
A significant part of railroad infrastructure consists of communication and control systems. From early in railroad history, communication was considered a necessity for satisfactory railroad operation and for safety of passengers, crews, goods, equipment and infrastructure.
Communication
Communication is, in its most general meaning, any form of signaling between a sender and a receiver (any two entities whatsoever). The sender and receiver are usually considered to be transceivers. That is, they both can send and receive. The signal is carried from one party to the other by some form of channel (air, light, sound, wire, fiber, etc.). Because the sender and receiver may not be able to directly access a given channel, a transducer might be required to transform the channel into one compatible with each entity. Similarly, a transducer might be required to transform the signal of the sender into one recognized by the receiver. For example, in a face-to-face conversation between a speaker of French and a speaker of Japanese, a transducer (usually called an interpreter) would be needed. (A conversation is a succession of signals exchanged between sender and receiver.)
Railroad communication was necessary between stations, between stations and trains, and so on. Along the tracks, control points were needed to handle switching, derailments, hot boxes, track problems and other matters. Thus communication between control points was needed. The telegraph was quickly adopted as a means of communication, replacing hand signals, flags, semaphores, lamps and other means of signaling.
Telegraphy required operators who could tap out characters on a telegraph key using Morse Code and who could recognize such codes sent from another operator. (Keep in mind that punched paper tape came later and printed output even later still.) Telegraphy allowed voice signals to be encoded (Morse Code), sent over wires as a sequence of electrical pulses and received as clicks produced by the receiver (essentially an electromagnet that was energized briefly by the succession of pulses coming along the wire) thus causing the receiver to emit sounds corresponding to the code sent.
Communication with moving trains was another matter. One solution was to post printed messages on a pole at the correct height for a train staff member (usually someone in the locomotive cab) to reach out and grab. Such messages certainly included conditions ahead on the line (track), but could also deal with almost any other matter. This means of communication continued until radio communication became available. Initially, radio communication employed Morse Code to send messages (wireless telegraphy). But as radio technology advanced, voice communication became possible.
Today, almost any kind of data can be communicated via radio signals. It is important to note that communication via radio waves is regulated by law, coordinated by an international body called the International Telecommunication Union (ITU), which allocates frequency bands in the radio spectrum for a multitude of uses. In the United States, such communication is regulated by the Federal Communications Commission (FCC) in coordination with the ITU.
Radio communication with trains was at first supplemented by telephone communication between stations or other control points along the track (from about 1900). Larger railroads established their own telephone systems, supplemented with public telephone service. Today, much of railroad communication is via some form of radio frequency transmission. Communication within a railroad company among its personnel and among its many other parts, is most likely managed and controlled via computer. It is beyond the scope of this Web site to delve into the details of these technologies, but we will mention some of these in what follows.
Communication is, in its most general meaning, any form of signaling between a sender and a receiver (any two entities whatsoever). The sender and receiver are usually considered to be transceivers. That is, they both can send and receive. The signal is carried from one party to the other by some form of channel (air, light, sound, wire, fiber, etc.). Because the sender and receiver may not be able to directly access a given channel, a transducer might be required to transform the channel into one compatible with each entity. Similarly, a transducer might be required to transform the signal of the sender into one recognized by the receiver. For example, in a face-to-face conversation between a speaker of French and a speaker of Japanese, a transducer (usually called an interpreter) would be needed. (A conversation is a succession of signals exchanged between sender and receiver.)
Railroad communication was necessary between stations, between stations and trains, and so on. Along the tracks, control points were needed to handle switching, derailments, hot boxes, track problems and other matters. Thus communication between control points was needed. The telegraph was quickly adopted as a means of communication, replacing hand signals, flags, semaphores, lamps and other means of signaling.
Telegraphy required operators who could tap out characters on a telegraph key using Morse Code and who could recognize such codes sent from another operator. (Keep in mind that punched paper tape came later and printed output even later still.) Telegraphy allowed voice signals to be encoded (Morse Code), sent over wires as a sequence of electrical pulses and received as clicks produced by the receiver (essentially an electromagnet that was energized briefly by the succession of pulses coming along the wire) thus causing the receiver to emit sounds corresponding to the code sent.
Communication with moving trains was another matter. One solution was to post printed messages on a pole at the correct height for a train staff member (usually someone in the locomotive cab) to reach out and grab. Such messages certainly included conditions ahead on the line (track), but could also deal with almost any other matter. This means of communication continued until radio communication became available. Initially, radio communication employed Morse Code to send messages (wireless telegraphy). But as radio technology advanced, voice communication became possible.
Today, almost any kind of data can be communicated via radio signals. It is important to note that communication via radio waves is regulated by law, coordinated by an international body called the International Telecommunication Union (ITU), which allocates frequency bands in the radio spectrum for a multitude of uses. In the United States, such communication is regulated by the Federal Communications Commission (FCC) in coordination with the ITU.
Radio communication with trains was at first supplemented by telephone communication between stations or other control points along the track (from about 1900). Larger railroads established their own telephone systems, supplemented with public telephone service. Today, much of railroad communication is via some form of radio frequency transmission. Communication within a railroad company among its personnel and among its many other parts, is most likely managed and controlled via computer. It is beyond the scope of this Web site to delve into the details of these technologies, but we will mention some of these in what follows.
Control Systems
At the same time communication systems were being developed and deployed, there was a growing need for control systems along the tracks. In order to increase revenues and to meet the growing demand for rail transportation, it was necessary to have multiple trains traveling between various transportation centers. But it was also necessary to insure against conflicts between trains operating on the same track. As a consequence, signals along the tracks were erected to inform train drivers of conditions ahead. These signals, at first fairly crude, soon became more standardized and well built, if not much more sophisticated.
Electrification made possible signaling by light and use of light to encode particular conditions ahead of a train. Over the years, communication and control has continually improved and today all the Class I railroads operate under computer-based communication and control systems. Let us explore these systems in more detail.
At the same time communication systems were being developed and deployed, there was a growing need for control systems along the tracks. In order to increase revenues and to meet the growing demand for rail transportation, it was necessary to have multiple trains traveling between various transportation centers. But it was also necessary to insure against conflicts between trains operating on the same track. As a consequence, signals along the tracks were erected to inform train drivers of conditions ahead. These signals, at first fairly crude, soon became more standardized and well built, if not much more sophisticated.
Electrification made possible signaling by light and use of light to encode particular conditions ahead of a train. Over the years, communication and control has continually improved and today all the Class I railroads operate under computer-based communication and control systems. Let us explore these systems in more detail.
Railroad Traffic Control
In general, railroad traffic control involves the movement of many trains over a multitude of track linking many geographic locations for business or leisure purposes. Traffic may be thought of in relation to trains, but it must also be viewed in relation to customer needs and requirements, the requirements of regulatory agencies and standards and to economics.
A railroad must operate its trains in such a way that railroad assets are employed safely and judiciously. "Safely" means that assets such as rolling stock, trackage, passenger and freight facilities, etc., must be operated without damage nor loss that might occur through negligence, carelessness or excessive wear and tear. But safety also concerns the goods and/or passengers carried by the railroad since customers expect (and have the right to expect) that such carriage will permit the goods and passengers to arrive at their destination without damage or loss.
Judicious use of railroad assets means that the assets are employed so as to meet capacity and scheduling requirements of both the railroad and customer. In general, customers want the fastest transport time at the lowest cost. A railroad is obliged to work out the most satisfactory compromise possible in order to thrive in a competitive enterprise.
Standards and regulations are formulated to provide a basis for operation across any industry or enterprise. Standards are often formulated to foster safety, to modulate the competitive spirit, to improve interoperability and to provide a basis for quality and durability. Standards are sometimes formulated by an industry as "best practices". Regulations, on the other hand, are generally government-promulgated rules that govern permissible operations or behaviors that a business must adhere to. See, for example, FRA.
Finally, economics must be carefully analyzed and used to insure the railroad operates profitably, avoids unnecessary taxes or penalties as a result of operations, enables the railroad to gain and retain competitive advantage and operate within the compass of existing law.
In general, railroad traffic control involves the movement of many trains over a multitude of track linking many geographic locations for business or leisure purposes. Traffic may be thought of in relation to trains, but it must also be viewed in relation to customer needs and requirements, the requirements of regulatory agencies and standards and to economics.
A railroad must operate its trains in such a way that railroad assets are employed safely and judiciously. "Safely" means that assets such as rolling stock, trackage, passenger and freight facilities, etc., must be operated without damage nor loss that might occur through negligence, carelessness or excessive wear and tear. But safety also concerns the goods and/or passengers carried by the railroad since customers expect (and have the right to expect) that such carriage will permit the goods and passengers to arrive at their destination without damage or loss.
Judicious use of railroad assets means that the assets are employed so as to meet capacity and scheduling requirements of both the railroad and customer. In general, customers want the fastest transport time at the lowest cost. A railroad is obliged to work out the most satisfactory compromise possible in order to thrive in a competitive enterprise.
Standards and regulations are formulated to provide a basis for operation across any industry or enterprise. Standards are often formulated to foster safety, to modulate the competitive spirit, to improve interoperability and to provide a basis for quality and durability. Standards are sometimes formulated by an industry as "best practices". Regulations, on the other hand, are generally government-promulgated rules that govern permissible operations or behaviors that a business must adhere to. See, for example, FRA.
Finally, economics must be carefully analyzed and used to insure the railroad operates profitably, avoids unnecessary taxes or penalties as a result of operations, enables the railroad to gain and retain competitive advantage and operate within the compass of existing law.
Freight Traffic Management and Control
Railroad Freight traffic management and control (FTM&C) is part of the discipline of logistics. FTM&C involves planning to transport goods over a fixed set of routes (trackage). This planning requires coordination with a number of entities, such as the manufacturer or producer, the wholesaler, the deliverer, forwarder and receiver. Coordination involves route (and alternate routes), timing (scheduling) and velocity control, necessary equipment (railroad cars, lift equipment, etc.), break-up and assembly of trains (yard work), crew assignments, weather, trackage conditions, un-planned incidents, and other factors.
Many approaches to FTM&C have been proposed and implemented. We discuss only the most modern of these approaches: Centralized Traffic Control (CTC), and Advanced Train Control System (ATCS)
CTC consists of a centralized train dispatcher's office that controls railroad interlockings and traffic flows in portions of the rail system designated as CTC territory.
The train dispatcher (or team of dispatchers) is also responsible for safe and cost-effective movement of physical and human resource assets (trains and crews). This may involve a crew dispatcher responsible for tracking train crews and their assignments. This includes assignment of crews to trains based upon scheduled rosters as well as necessary adjustments based on rail traffic conditions and delays. The crew dispatcher is also responsible for checking that each train and engine crew are properly qualified for their assignments and have had proper rest according to labour regulations.
Other personnel in a CTC might be employed to handle specific sorts of events or circumstances (e.g., public safety, maintenance of way management and control).
CTC territory is all or part of a railroad operating division (an organizational unit focused on effective operation of a railroad within a defined geographic area). Some parts of a railroad may continue to operate under older rules and procedures. However, such parts must be compatible with rules and procedures used by the CTC. A CTC office will most likely be located near a busy yard or major station within the operating division.
The operation of CTC is mainly computer-based, employing databases, video monitors, graphical user interfacing, telecommunication systems and networks, voice communication via network (mainly voice over Internet (VoIP), and an array of track-side and on-board sensing, monitoring, controlling and reporting equipment to make possible near-fool-proof operation. We will examine some of these types of equipment below.
First, it is important to discuss the Advanced Train Control System (ATCS). This system is specified by the Association of American Railroads. The system is defined in "Manual of Standards and Recommended Practices. Section K: Railway Electronics." Archived March 27, 2009, at the Wayback Machine. AAR publications are usually available to members for a fee, so access to the above publication is controlled.
ATCS is railroad independent whereas CTC is not. This means that the implementation of ATCS by one railroad will be compatible with that implemented by any other railroad.
The ATCS architecture is comprised of five major systems. Four of these systems are: Information Processing System (or Central Dispatch Computer) resident in the central dispatch office; On-board Locomotive System (or On-Board Computer); On-board Work Vehicles System (or Track Forces Terminal); In-The-Field System (or Wayside Interface Unit). These four systems collect, process, and distribute data with minimal input from dispatchers, enginemen, and foremen. The fifth system is the modern Data Communications System, which ties the various information processing systems together and significantly reduces the need for voice communications. This is the ATCS keystone system.
ATCS is designed for modular and step-wise implementation so as to permit each railroad to avoid the "all at once" approach to automation. Each railroad can choose to implement ATCS according its needs and resource availability.
The primary ATCS functions are:
Railroad Freight traffic management and control (FTM&C) is part of the discipline of logistics. FTM&C involves planning to transport goods over a fixed set of routes (trackage). This planning requires coordination with a number of entities, such as the manufacturer or producer, the wholesaler, the deliverer, forwarder and receiver. Coordination involves route (and alternate routes), timing (scheduling) and velocity control, necessary equipment (railroad cars, lift equipment, etc.), break-up and assembly of trains (yard work), crew assignments, weather, trackage conditions, un-planned incidents, and other factors.
Many approaches to FTM&C have been proposed and implemented. We discuss only the most modern of these approaches: Centralized Traffic Control (CTC), and Advanced Train Control System (ATCS)
CTC consists of a centralized train dispatcher's office that controls railroad interlockings and traffic flows in portions of the rail system designated as CTC territory.
The train dispatcher (or team of dispatchers) is also responsible for safe and cost-effective movement of physical and human resource assets (trains and crews). This may involve a crew dispatcher responsible for tracking train crews and their assignments. This includes assignment of crews to trains based upon scheduled rosters as well as necessary adjustments based on rail traffic conditions and delays. The crew dispatcher is also responsible for checking that each train and engine crew are properly qualified for their assignments and have had proper rest according to labour regulations.
Other personnel in a CTC might be employed to handle specific sorts of events or circumstances (e.g., public safety, maintenance of way management and control).
CTC territory is all or part of a railroad operating division (an organizational unit focused on effective operation of a railroad within a defined geographic area). Some parts of a railroad may continue to operate under older rules and procedures. However, such parts must be compatible with rules and procedures used by the CTC. A CTC office will most likely be located near a busy yard or major station within the operating division.
The operation of CTC is mainly computer-based, employing databases, video monitors, graphical user interfacing, telecommunication systems and networks, voice communication via network (mainly voice over Internet (VoIP), and an array of track-side and on-board sensing, monitoring, controlling and reporting equipment to make possible near-fool-proof operation. We will examine some of these types of equipment below.
First, it is important to discuss the Advanced Train Control System (ATCS). This system is specified by the Association of American Railroads. The system is defined in "Manual of Standards and Recommended Practices. Section K: Railway Electronics." Archived March 27, 2009, at the Wayback Machine. AAR publications are usually available to members for a fee, so access to the above publication is controlled.
ATCS is railroad independent whereas CTC is not. This means that the implementation of ATCS by one railroad will be compatible with that implemented by any other railroad.
The ATCS architecture is comprised of five major systems. Four of these systems are: Information Processing System (or Central Dispatch Computer) resident in the central dispatch office; On-board Locomotive System (or On-Board Computer); On-board Work Vehicles System (or Track Forces Terminal); In-The-Field System (or Wayside Interface Unit). These four systems collect, process, and distribute data with minimal input from dispatchers, enginemen, and foremen. The fifth system is the modern Data Communications System, which ties the various information processing systems together and significantly reduces the need for voice communications. This is the ATCS keystone system.
ATCS is designed for modular and step-wise implementation so as to permit each railroad to avoid the "all at once" approach to automation. Each railroad can choose to implement ATCS according its needs and resource availability.
The primary ATCS functions are:
- management of track occupancies through centralized route and block interlocking logic;
- issuance of movement authorities via the data link to equipped trains and work vehicles, and via voice radio to unequipped trains and work vehicles;
- tracking of equipped train location and track occupancies via the data link, and unequipped train location and track occupancies via voice reports and manual entry;
- speed enforcement for equipped trains (also called Positive Train Control);
- enforcement of limits of authority for equipped trains;
- pacing for fuel economy for equipped trains;
- monitoring and control of wayside measuring, monitoring and reporting units;
- reporting of equipped train diagnostics and operating parameters;
- and general exchange of instructions and messages.
An Example
In order to give an idea of the operation of a system with some of the capabilities of the ATCS, we present a realistic but fictional description of a railroad with advanced computing and telecommunication capabilities in the following paragraphs.
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Passenger Traffic Management and Control
Under construction ...
Maintenance Facilities
Either railroad owned or service company owned
Either railroad owned or service company owned
Manufacturing Facilities
Just list some near by: Altoona, Erie, etc.
Just list some near by: Altoona, Erie, etc.