Education Part 3
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 be addressed by model railroad enthusiasts. We shall touch on these matters throughout this section.
Interestingly, many of these things must 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 railroads Lehigh Valley Railroad: ...
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 coal from the area around today's Jim Thorpe, PA to termials on the Delaware River where it would be transported by boat to various destinations. 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 NYC. For a variety of reasons, LVRR ceased operations in 1976 through merger.
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 tricky, especially today, because rail trackage often 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). ROW may be obtained via lease, purchase or eminent domain.
Other Concerns
Other concerns include construction matters (e.g., grade, drainage, support structures such as bridges and tunnels), branching, environmental degradation, affect on health of neighbors, safety issues and "not-in-my-neighborhood" concerns.
Finish This topic
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 railroads Lehigh Valley Railroad: ...
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 coal from the area around today's Jim Thorpe, PA to termials on the Delaware River where it would be transported by boat to various destinations. 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 NYC. For a variety of reasons, LVRR ceased operations in 1976 through merger.
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 tricky, especially today, because rail trackage often 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). ROW may be obtained via lease, purchase or eminent domain.
Other Concerns
Other concerns include construction matters (e.g., grade, drainage, support structures such as bridges and tunnels), branching, environmental degradation, affect on health of neighbors, safety issues and "not-in-my-neighborhood" concerns.
Finish This topic
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 (not up and down hill).
The following discussion depends on several sources, including AREMA, CSX, ICRR, KCS and UP. These references 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 (not up and down hill).
The following discussion depends on several sources, including AREMA, CSX, ICRR, KCS and UP. These references 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. Grade is as important going down hill (declination) as going up (inclination), because of the need for braking (see Braking).
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 and allow for faster travel around the curve. Can't is especially important on passenger lines for the comfort of passengers. Too much can't 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 and allow for faster travel around the curve. Can't is especially important on passenger lines for the comfort of passengers. Too much can't 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. In the United States, they have a cross-section such as specified in the drawings below. The rails are called flat-bottom rails. The particular shape of rails 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.
Rails are made of steel. In the United States, they have a cross-section such as specified in the drawings below. The rails are called flat-bottom rails. The particular shape of rails 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.
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 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 laid. 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 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,/font>
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 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 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.
Turnout
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 frogs and serve to help insure wheels continue on the proper line as they travel over such gaps. They also help reduce wear on these more delicate parts.
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).
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 frogs and serve to help insure wheels continue on the proper line as they travel over such gaps. They also help reduce wear on these more delicate parts.
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.
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.
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
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 and 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. 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
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
Management, Control and Maintenance
In addition to the infrastructure discussed above, one must also consider various other components of a railroad, such as buildings (especially terminals), yards, communication and control systems, maintenance facilities and perhaps manufacturing facilities.
Complete this part
In addition to the infrastructure discussed above, one must also consider various other components of a railroad, such as buildings (especially terminals), yards, communication and control systems, maintenance facilities and perhaps manufacturing facilities.
Complete this part