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(Redirected from Railroad track)
'Rail tracks' are used on railways (or railroads), which, together with railroad switches (or points), guide trains without the need for steering. Tracks consist of two parallel steel rails, which are laid upon sleepers (or cross ties) that are embedded in ballast to form the railroad track. The rail is fastened to the ties with rail spikes, lag screws or clips such as Pandrol clips.
The type of fastener depends partly on the type of sleeper, with spikes being used on wooden sleepers, and clips being used more on concrete sleepers.
Usually, a baseplate (or fishplate, although a fishplate is also a bar used to join rails) is used between the rail and wooden sleepers, to spread the load of the rail over a larger area of the sleeper. Sometimes spikes are driven through a hole in the baseplate to hold the rail, while at other times the baseplates are spiked or screwed to the sleeper and the rails clipped to the baseplate.
Steel rails can carry heavier loads than any other material. Railroad ties spread the load from the rails over the ground and also serve to hold the rails a fixed distance apart (called the gauge.)
Rail tracks are normally laid on a bed of coarse stone chippings known as ''ballast'', which combines resilience, some amount of flexibility, and good drainage. Steel rails can also be laid onto a concrete slab (a slab track). Across bridges, track is often laid on ties across longitudinal timbers or longitudinal steel girders.
Additional detail on tracks used for tram and light rail operations, as opposed to heavy rail, is available at tramway track.
★ Grooved rail
★ Vignoles rail
★ Charles Vignoles
★ Flanged T rail
★
There are different ways of joining rails together to form tracks. The traditional method was to bolt rails together in what is known as 'jointed track'. In this form of track, lengths of rail, usually around 20 metres (60 feet) long, are laid and fixed to ''sleepers'' (UK) (''crossties'', or simply ''ties'' in North American parlance), and are joined to other lengths of rail with steel plates known as ''fishplates'' (UK) or ''joint bars'' (N.A.).
Historically, North American railroads until the mid to late 20th century used sections of rail that measured 39 feet (11.9 m) long so they could be carried to and from a worksite in conventional gondolas, which often measured 40 feet (12.2 m) long; as car sizes increased, so did rail lengths.
Fishplates or joint bars are usually 60 centimetres (2 feet) long, and are bolted through each side of the rail ends with bolts (usually four, but sometimes up to six.) Small gaps known as expansion joints are deliberately left between the rails to allow for expansion of the rails in hot weather. The holes through which the fishplate bolts pass are oval to allow for expansion.
British practice was always to have the rail joints on both rails adjacent to each other, while North American practice is to stagger them.
Because of the small gaps left between the rails, when trains pass over jointed tracks, they make a "clickety clack" sound. Unless it is well maintained, jointed track doesn't have the ride quality of welded rail, and is unsuitable for high speed trains. A major problem is cracking around the bolt holes, which can lead to the rail head breaking. This was the cause of the Hither Green rail crash which caused British Railways to begin converting much of its track to Continuous Welded Rail. However, it is still used in many countries on lower speed lines and sidings. Jointed track is still extensively used in poorer countries due to the lower construction cost and lack of modernisation of their railway systems.
Where track circuits exist for signalling purposes, insulated block joints are required. These compound the weakness of ordinary block joints. Specially made glued joints, where all the gaps filled with epoxy resin increases the strength again. Audio frequency track circuits such as those made by CSEE replace the conventional block joint with a tuned loop which uses say 20m of the rail as part of the blocking circuit. Axle counters can also reduce the number of track circuits and thus the number of insulated rail joints.
Most modern railways use 'continuous welded rail' (CWR); in this form of track, the rails are welded together by utilising the thermite reaction or flash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance. Welded track has become common on main lines since the 1950s.
Because of the increased strength of welded track, trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs.
Rails expand in hot weather and shrink in cold weather. Because welded track has very few expansion joints, if no special measures are taken it could become distorted in hot weather and cause a derailment (a condition known in America as sun kink, referred in Britain as "buckling").
To avoid this, welded rails are very often laid on concrete or steel sleepers, which are so heavy they hold the rails firmly in place. After new segments of rail are laid, or defective rails replaced (welded in), the rails are artificially stressed. Great attention is paid to compacting the ballast effectively, particularly the shoulder over the ends of the sleepers, to prevent them from moving. Even so, in extreme weather, foot patrols monitor sections of track known to be problematic.
The stressing process, involves either heating the rails causing them to expand,[1] or stretching the rails with hydraulic equipment. They are then fastened (clipped) to the sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretched elastic firmly fastened down.
Engineers try to heat the rail to a temperature roughly midway between the average extremes of hot and cold (this is known as the 'rail neutral temperature'). If temperatures reach outside normal ranges however, welded rail can buckle in a hotter than usual summer or can actually break in a colder than anticipated winter.
Joints are used in continuously welded rail when necessary; instead of a joint that passes straight across the rail, producing a loud noise and shock when the wheels pass over it, two sections of rail are sometimes cut at a steep angle and put together with a gap between them - a breather switch (referred to in Britain as an expansion joint). This gives a much smoother transition yet still provides some expansion room.
There are several methods used to fasten rail to wooden sleepers / ties. The worldwide standard type of rail used today is ''flat-bottomed rail'' (Vignoles rail), which has a flat base and can stand upright without support. A flat-bottomed rail has a cross-section like that of an upside-down 'T' and is usually held to the sleeper with a '''baseplate''', a metal plate attached to the sleeper; although for lower cost construction FB rails can be laid directly onto the sleepers.
Modern sleepers can be made of reinforced concrete and pressed steel, with rubber pads inserted between the sleeper and rail. This is done for two reasons: to give a smoother ride and to prevent the sleeper from shorting the track circuit, a low voltage passed through the rails for signalling purposes. This is different from a "traction current," which powers electric trains.
See also [1]
A variety of different types of heavy-duty clips are used to fasten the rails to the underlying baseplate, one common one being the ''Pandrol'' fastener (Pandrol clip), named after its maker, which is shaped like a sturdy, stubby paperclip.[2], [3] and [4]. Another one is the Vossloh Tension Clamp.[5]
North American practice normally uses ''rail spikes'', which are very large nails with over hanging heads to clasp the flat-bottomed rail. These are cheaper and simpler to install but can loosen if the tie rots, much more easily than the British chair (a type of baseplate) does. This is mitigated by using very large and solid creosoted ties or using another rot-proofing preservative. See also timber treatment.
In traditional British practice, cast metal ''chairs'' were screwed to the sleepers, which took a style of rail known as ''bullhead'' that was somewhat figure-8 in cross-section — wider at top and bottom (known as the ''head'' and ''foot'' respectively) and smaller in the middle (the ''web''). ''Keys'' (wedges of wood or sprung steel) were then driven in between chair and rail to hold it in place. This was common practice on British railways until the 1950s, but is now largely obsolete.
The idea behind ''bullhead'' rails was that because both the top and bottom of the rails were the same shape, when one side of the rail became worn, the rail could be turned over to the unused side, thus extending the rail's lifespan. However the bottom head turned out to get dented, rendering the original idea useless. Since the turnover requirement was no longer needed,
''bullhead'' rails came to have a flat base (narrower than flat-bottomed rail), and the top part has curved edges that fit the profile of the train wheels.
In recent years, methods have been developed to put tracks on concrete without using conventional sleepers or track ballast. While this method's construction cost is high, this system is expected to have significantly lower maintenance cost than conventional tracks. It is mainly used on high-speed lines and in tunnels, where maintenance access is difficult.
★ Track Details in photographs
Track needs frequent maintenance to remain in good order; the frequency increases with higher-speed or heavier trains. Without frequent maintenance, a slow zone may occur due to damage on the tracks. Track maintenance was formerly hard manual labour, requiring teams of labourers (US: gandy dancers, GB: plateplayers or navvies), who used levers to force rails back into place on steep turns, correcting the gradual shifting caused by the centrifugal force of passing trains. Currently, maintenance is facilitated by a variety of specialised machines.
The profile of the track is maintained by using a railgrinder.
Common maintenance jobs include spraying ballast with weedkiller to prevent weeds growing through and disrupting the ballast. This is typically done with a special weedkilling train.
Over time, ballast is crushed or moved by the weight of trains passing over it, and periodically it needs to be leveled (tamped) and eventually cleaned or replaced. If this is not done, the tracks may become uneven causing swaying, rough riding and eventually the risk for derailment.
Rail Inspections utilize nondestructive testing methods to detect internal flaws in the rails. This is done by using specially equipped HiRail trucks, inspection cars, or in some cases handheld inspection devices.
Broken or worn-out rails also need replacing periodically. Mainline rails that get worn out usually have life left in branch line or rail siding use and are "cascaded" to those branch lines.
''See also Maintenance of way''
During the early days of rail there was considerable variation in the gauge used by different systems. Today, sixty percent of the world's railways use a gauge of , which is known as the standard or international gauge. Gauges wider than standard gauge are called broad gauge, those smaller than standard narrow gauge. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to share the same track. [2].
In the United States, the Federal Railroad Administration has developed a system of classification for track quality. The class a track is placed in determines speed limits and the ability to run passenger trains.
★ The lowest class is referred to as excepted track. Only freight trains are allowed to operate on this type of trackage, and they may run at speeds up to 10 mph (16 km/h). Also, no more than five cars loaded with hazardous material may be operated within any single train. Passenger trains of any kind are prohibited, including chartered excursions or fantrips.
★ Class 1 track is the lowest class allowing the operation of passenger trains. Freight train speeds are still limited to 10 mph (16 km/h, and passenger trains are restricted to 15 mph (24 km/h).
★ Class 2 track limits freight trains to 25 mph (40 km/h) and passenger trains to 30 mph (48 km/h).
★ Class 3 track limits freight trains to 40 mph (64 km/h) and passenger trains to 60 mph (96 km/h). There is currently a legal battle between Amtrak and the Guilford Rail System over its trackage from Haverhill, MA, to Portland, ME. Amtrak is fighting for the Class 3 trackage to be used to operate its Downeaster at 79 mph (126 km/h).
★ Class 4 track limits freight trains to 60 mph (96 km/h) and passenger trains to 80 mph (128 km/h). Most track, especially that owned by major railroads the Union Pacific, BNSF, CSX, and Norfolk Southern is class 4 track. Due to a technicality in law, Amtrak trains are limited to 79 mph (126 km/h) on this track, unless cab signaling or automatic train stop are employed.
★ Class 5 track limits freight trains to 80 mph (128 km/h) and passenger trains to 90 mph (144 km/h). The most significant portion of Class 5 track is part of the Burlington Northern Santa Fe's Chicago–Los Angeles mainline, the old Santa Fe main, upon which Amtrak's Southwest Chief can operate at up to 90 mph (144 km/h). This is notable as the only area outside Amtrak-owned trackage or trackage upgraded through state funds where Amtrak trains can operate above 79 mph (126 km/h).
★ Class 6 limits freight trains and passenger trains to 110 mph (176 km/h). Amtrak is currently working with the Iowa Interstate Railroad and the state of Illinois to upgrade a portion of its Chicago, Illinois–Kansas City, Missouri line to Class 6.
★ Class 7 limits all trains to 125 mph (200 km/h). Most of Amtrak's Northeast Corridor is Class 7 trackage.
★ Class 8 limits all trains to 160 mph (256 km/h). A few small lengths of the Northeast Corridor are the only Class 8 trackage in North America.
★ Class 9 trackage limits all trains to 200 mph (320 km/h). There is currently no Class 9 trackage.
In addition to class, maximum track speed is also subject to specific regulatory restrictions known as rules. For example, the rules restrict speeds within recognized rail yards to 10 mph. The rule governing the maximum permissible speed of a train operating on curved track is determined by the following formula:
:
where is the amount in inches that the outside rail is superelevated above the inside rail on a curve and is the degree of curvature in degrees per 100 feet. is given in miles per hour.
Track unbalanced superelevation in the U.S. is restricted to 3 inches, though 4 inches is permissible by waiver. There is no hard maximum set for European railways, some of which have curves with over 11 inches of unbalanced superelevation to permit high-speed transportation. [3]
In the early years of railways, there was much experimentation with rails and sleepers and fixtures, before the better designs emerged.
Wooden rails with a metal strap on top was tried to save costs, but the straps had a tendency to come loose and penetrate the carriages going over them.
Barlow rail had a wide cross section to spread the load, but the rail itself tended to spread and go out of gauge.
Brunel's Great Western Railway used longitudinal sleepers, with piles to hold the track down, but as the earthworks settled, the piles came to hold the track up.
1. Continuous Welded Rail
2. message in the mailing list '1520mm' on Р75 rails
3. The Shasta Route - Curve speeds: what's possible and what's real. [6]
★ Pike, J., (2001), ''Track'', Sutton Publishing, ISBN 0-7509-2692-9
★ Simulation of the Dynamic Behavior of Bedding-Foundation-Soil in the Time Domain, Firuziaan, M., Estorff, o., Springer Verlag, 2002
★ Table of North American tee rail (flat bottom) sections
★ ThyssenKrupp handbook, Vignoles rail
★ ThyssenKrupp handbook, Light Vignoles rail
★ Track Details in photographs
'Rail tracks' are used on railways (or railroads), which, together with railroad switches (or points), guide trains without the need for steering. Tracks consist of two parallel steel rails, which are laid upon sleepers (or cross ties) that are embedded in ballast to form the railroad track. The rail is fastened to the ties with rail spikes, lag screws or clips such as Pandrol clips.
The type of fastener depends partly on the type of sleeper, with spikes being used on wooden sleepers, and clips being used more on concrete sleepers.
Usually, a baseplate (or fishplate, although a fishplate is also a bar used to join rails) is used between the rail and wooden sleepers, to spread the load of the rail over a larger area of the sleeper. Sometimes spikes are driven through a hole in the baseplate to hold the rail, while at other times the baseplates are spiked or screwed to the sleeper and the rails clipped to the baseplate.
Steel rails can carry heavier loads than any other material. Railroad ties spread the load from the rails over the ground and also serve to hold the rails a fixed distance apart (called the gauge.)
Rail tracks are normally laid on a bed of coarse stone chippings known as ''ballast'', which combines resilience, some amount of flexibility, and good drainage. Steel rails can also be laid onto a concrete slab (a slab track). Across bridges, track is often laid on ties across longitudinal timbers or longitudinal steel girders.
Additional detail on tracks used for tram and light rail operations, as opposed to heavy rail, is available at tramway track.
Railway rail
See also
★ Grooved rail
★ Vignoles rail
★ Charles Vignoles
★ Flanged T rail
★
Jointed track
Track joint.
Alternative view of track joints
There are different ways of joining rails together to form tracks. The traditional method was to bolt rails together in what is known as 'jointed track'. In this form of track, lengths of rail, usually around 20 metres (60 feet) long, are laid and fixed to ''sleepers'' (UK) (''crossties'', or simply ''ties'' in North American parlance), and are joined to other lengths of rail with steel plates known as ''fishplates'' (UK) or ''joint bars'' (N.A.).
Historically, North American railroads until the mid to late 20th century used sections of rail that measured 39 feet (11.9 m) long so they could be carried to and from a worksite in conventional gondolas, which often measured 40 feet (12.2 m) long; as car sizes increased, so did rail lengths.
Fishplates or joint bars are usually 60 centimetres (2 feet) long, and are bolted through each side of the rail ends with bolts (usually four, but sometimes up to six.) Small gaps known as expansion joints are deliberately left between the rails to allow for expansion of the rails in hot weather. The holes through which the fishplate bolts pass are oval to allow for expansion.
British practice was always to have the rail joints on both rails adjacent to each other, while North American practice is to stagger them.
Because of the small gaps left between the rails, when trains pass over jointed tracks, they make a "clickety clack" sound. Unless it is well maintained, jointed track doesn't have the ride quality of welded rail, and is unsuitable for high speed trains. A major problem is cracking around the bolt holes, which can lead to the rail head breaking. This was the cause of the Hither Green rail crash which caused British Railways to begin converting much of its track to Continuous Welded Rail. However, it is still used in many countries on lower speed lines and sidings. Jointed track is still extensively used in poorer countries due to the lower construction cost and lack of modernisation of their railway systems.
Insulated joints
Where track circuits exist for signalling purposes, insulated block joints are required. These compound the weakness of ordinary block joints. Specially made glued joints, where all the gaps filled with epoxy resin increases the strength again. Audio frequency track circuits such as those made by CSEE replace the conventional block joint with a tuned loop which uses say 20m of the rail as part of the blocking circuit. Axle counters can also reduce the number of track circuits and thus the number of insulated rail joints.
Continuous welded rail
welded rail joint
Most modern railways use 'continuous welded rail' (CWR); in this form of track, the rails are welded together by utilising the thermite reaction or flash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance. Welded track has become common on main lines since the 1950s.
Because of the increased strength of welded track, trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs.
Rails expand in hot weather and shrink in cold weather. Because welded track has very few expansion joints, if no special measures are taken it could become distorted in hot weather and cause a derailment (a condition known in America as sun kink, referred in Britain as "buckling").
To avoid this, welded rails are very often laid on concrete or steel sleepers, which are so heavy they hold the rails firmly in place. After new segments of rail are laid, or defective rails replaced (welded in), the rails are artificially stressed. Great attention is paid to compacting the ballast effectively, particularly the shoulder over the ends of the sleepers, to prevent them from moving. Even so, in extreme weather, foot patrols monitor sections of track known to be problematic.
The stressing process, involves either heating the rails causing them to expand,[1] or stretching the rails with hydraulic equipment. They are then fastened (clipped) to the sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretched elastic firmly fastened down.
Engineers try to heat the rail to a temperature roughly midway between the average extremes of hot and cold (this is known as the 'rail neutral temperature'). If temperatures reach outside normal ranges however, welded rail can buckle in a hotter than usual summer or can actually break in a colder than anticipated winter.
Joints are used in continuously welded rail when necessary; instead of a joint that passes straight across the rail, producing a loud noise and shock when the wheels pass over it, two sections of rail are sometimes cut at a steep angle and put together with a gap between them - a breather switch (referred to in Britain as an expansion joint). This gives a much smoother transition yet still provides some expansion room.
Methods of fixing rail to sleepers/ties
Cross-sections of flat-bottomed which can rest directly on the sleepers, and bullhead rails which sit in chairs (not shown).
Screwed rail attachment
Rail Bender
There are several methods used to fasten rail to wooden sleepers / ties. The worldwide standard type of rail used today is ''flat-bottomed rail'' (Vignoles rail), which has a flat base and can stand upright without support. A flat-bottomed rail has a cross-section like that of an upside-down 'T' and is usually held to the sleeper with a '''baseplate''', a metal plate attached to the sleeper; although for lower cost construction FB rails can be laid directly onto the sleepers.
Modern sleepers can be made of reinforced concrete and pressed steel, with rubber pads inserted between the sleeper and rail. This is done for two reasons: to give a smoother ride and to prevent the sleeper from shorting the track circuit, a low voltage passed through the rails for signalling purposes. This is different from a "traction current," which powers electric trains.
See also [1]
A rail clip
A variety of different types of heavy-duty clips are used to fasten the rails to the underlying baseplate, one common one being the ''Pandrol'' fastener (Pandrol clip), named after its maker, which is shaped like a sturdy, stubby paperclip.[2], [3] and [4]. Another one is the Vossloh Tension Clamp.[5]
North American practice normally uses ''rail spikes'', which are very large nails with over hanging heads to clasp the flat-bottomed rail. These are cheaper and simpler to install but can loosen if the tie rots, much more easily than the British chair (a type of baseplate) does. This is mitigated by using very large and solid creosoted ties or using another rot-proofing preservative. See also timber treatment.
A fishplate between two sections of jointed bullhead rail, with a rail chair screwed into a wooden sleeper, the keys are on the opposite side of the rail and not visible here. This example of traditional British practice was photographed at Cardiff Bay railway station
In traditional British practice, cast metal ''chairs'' were screwed to the sleepers, which took a style of rail known as ''bullhead'' that was somewhat figure-8 in cross-section — wider at top and bottom (known as the ''head'' and ''foot'' respectively) and smaller in the middle (the ''web''). ''Keys'' (wedges of wood or sprung steel) were then driven in between chair and rail to hold it in place. This was common practice on British railways until the 1950s, but is now largely obsolete.
The idea behind ''bullhead'' rails was that because both the top and bottom of the rails were the same shape, when one side of the rail became worn, the rail could be turned over to the unused side, thus extending the rail's lifespan. However the bottom head turned out to get dented, rendering the original idea useless. Since the turnover requirement was no longer needed,
''bullhead'' rails came to have a flat base (narrower than flat-bottomed rail), and the top part has curved edges that fit the profile of the train wheels.
In recent years, methods have been developed to put tracks on concrete without using conventional sleepers or track ballast. While this method's construction cost is high, this system is expected to have significantly lower maintenance cost than conventional tracks. It is mainly used on high-speed lines and in tunnels, where maintenance access is difficult.
See also
★ Track Details in photographs
Track maintenance
An abandoned railroad trestle in Skagway, Alaska
Track needs frequent maintenance to remain in good order; the frequency increases with higher-speed or heavier trains. Without frequent maintenance, a slow zone may occur due to damage on the tracks. Track maintenance was formerly hard manual labour, requiring teams of labourers (US: gandy dancers, GB: plateplayers or navvies), who used levers to force rails back into place on steep turns, correcting the gradual shifting caused by the centrifugal force of passing trains. Currently, maintenance is facilitated by a variety of specialised machines.
The profile of the track is maintained by using a railgrinder.
Common maintenance jobs include spraying ballast with weedkiller to prevent weeds growing through and disrupting the ballast. This is typically done with a special weedkilling train.
Over time, ballast is crushed or moved by the weight of trains passing over it, and periodically it needs to be leveled (tamped) and eventually cleaned or replaced. If this is not done, the tracks may become uneven causing swaying, rough riding and eventually the risk for derailment.
Rail Inspections utilize nondestructive testing methods to detect internal flaws in the rails. This is done by using specially equipped HiRail trucks, inspection cars, or in some cases handheld inspection devices.
Broken or worn-out rails also need replacing periodically. Mainline rails that get worn out usually have life left in branch line or rail siding use and are "cascaded" to those branch lines.
''See also Maintenance of way''
History
Gauge
During the early days of rail there was considerable variation in the gauge used by different systems. Today, sixty percent of the world's railways use a gauge of , which is known as the standard or international gauge. Gauges wider than standard gauge are called broad gauge, those smaller than standard narrow gauge. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to share the same track. [2].
U.S. track classes
In the United States, the Federal Railroad Administration has developed a system of classification for track quality. The class a track is placed in determines speed limits and the ability to run passenger trains.
★ The lowest class is referred to as excepted track. Only freight trains are allowed to operate on this type of trackage, and they may run at speeds up to 10 mph (16 km/h). Also, no more than five cars loaded with hazardous material may be operated within any single train. Passenger trains of any kind are prohibited, including chartered excursions or fantrips.
★ Class 1 track is the lowest class allowing the operation of passenger trains. Freight train speeds are still limited to 10 mph (16 km/h, and passenger trains are restricted to 15 mph (24 km/h).
★ Class 2 track limits freight trains to 25 mph (40 km/h) and passenger trains to 30 mph (48 km/h).
★ Class 3 track limits freight trains to 40 mph (64 km/h) and passenger trains to 60 mph (96 km/h). There is currently a legal battle between Amtrak and the Guilford Rail System over its trackage from Haverhill, MA, to Portland, ME. Amtrak is fighting for the Class 3 trackage to be used to operate its Downeaster at 79 mph (126 km/h).
★ Class 4 track limits freight trains to 60 mph (96 km/h) and passenger trains to 80 mph (128 km/h). Most track, especially that owned by major railroads the Union Pacific, BNSF, CSX, and Norfolk Southern is class 4 track. Due to a technicality in law, Amtrak trains are limited to 79 mph (126 km/h) on this track, unless cab signaling or automatic train stop are employed.
★ Class 5 track limits freight trains to 80 mph (128 km/h) and passenger trains to 90 mph (144 km/h). The most significant portion of Class 5 track is part of the Burlington Northern Santa Fe's Chicago–Los Angeles mainline, the old Santa Fe main, upon which Amtrak's Southwest Chief can operate at up to 90 mph (144 km/h). This is notable as the only area outside Amtrak-owned trackage or trackage upgraded through state funds where Amtrak trains can operate above 79 mph (126 km/h).
★ Class 6 limits freight trains and passenger trains to 110 mph (176 km/h). Amtrak is currently working with the Iowa Interstate Railroad and the state of Illinois to upgrade a portion of its Chicago, Illinois–Kansas City, Missouri line to Class 6.
★ Class 7 limits all trains to 125 mph (200 km/h). Most of Amtrak's Northeast Corridor is Class 7 trackage.
★ Class 8 limits all trains to 160 mph (256 km/h). A few small lengths of the Northeast Corridor are the only Class 8 trackage in North America.
★ Class 9 trackage limits all trains to 200 mph (320 km/h). There is currently no Class 9 trackage.
In addition to class, maximum track speed is also subject to specific regulatory restrictions known as rules. For example, the rules restrict speeds within recognized rail yards to 10 mph. The rule governing the maximum permissible speed of a train operating on curved track is determined by the following formula:
:
where is the amount in inches that the outside rail is superelevated above the inside rail on a curve and is the degree of curvature in degrees per 100 feet. is given in miles per hour.
Track unbalanced superelevation in the U.S. is restricted to 3 inches, though 4 inches is permissible by waiver. There is no hard maximum set for European railways, some of which have curves with over 11 inches of unbalanced superelevation to permit high-speed transportation. [3]
Other types
In the early years of railways, there was much experimentation with rails and sleepers and fixtures, before the better designs emerged.
Wooden rails with a metal strap on top was tried to save costs, but the straps had a tendency to come loose and penetrate the carriages going over them.
Barlow rail had a wide cross section to spread the load, but the rail itself tended to spread and go out of gauge.
Brunel's Great Western Railway used longitudinal sleepers, with piles to hold the track down, but as the earthworks settled, the piles came to hold the track up.
References
1. Continuous Welded Rail
2. message in the mailing list '1520mm' on Р75 rails
3. The Shasta Route - Curve speeds: what's possible and what's real. [6]
★ Pike, J., (2001), ''Track'', Sutton Publishing, ISBN 0-7509-2692-9
★ Simulation of the Dynamic Behavior of Bedding-Foundation-Soil in the Time Domain, Firuziaan, M., Estorff, o., Springer Verlag, 2002
See also
★ Railroad switch (points) ★ Rail terminology (including US/UK and other regional/national differences) ★ Rail transport ★ Grand union ★ Third rail ★ Rack railway ★ Monorail ★ LGV construction ★ TGV tracks ★ Double track ★ Grooved rail ★ Single track | ★ Rail siding ★ Passing loop ★ Vignoles rail ★ Wagonway ★ Wye ★ Railway station layout ★ Flanged T rail ★ |
External links
★ Table of North American tee rail (flat bottom) sections
★ ThyssenKrupp handbook, Vignoles rail
★ ThyssenKrupp handbook, Light Vignoles rail
★ Track Details in photographs
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