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Speed limits in the United States (rail)
Encyclopedia
Rail speed limits in the United States are regulated by the Federal Railroad Administration
. Railroads also implement their own limits and enforce speed limits. Speed restrictions are based on a number of factors including curvature
, signaling, track condition
, the physical condition of a train, and the presence of grade crossings. Like road speed limit
s in the United States
, speed limits for rail tracks and the train
s that run on them use miles per hour
(mph).
s limit the speed of trains with respect to the signaling method used. Passenger trains are limited to 59 mph and freight trains to 49 mph on track without block signal systems. (See dark territory
.) Trains without "an automatic cab signal, automatic train stop
or automatic train control
system" may not exceed 79 mph. The order was issued in 1947 (effective 31 Dec 1951) by the Interstate Commerce Commission
following a severe 1946 crash in Naperville, Illinois
involving two Chicago, Burlington & Quincy Railroad trains. Following the 1987 Chase, Maryland train collision, freight trains operating in enhanced-speed corridors have been required to have locomotive speed limiters to forcibly slow trains rather than simply alerting the operator with in-cab signals. The signal panel in the Maryland crash had been partially disabled, with a muted whistle and a missing light bulb.
Following the 2008 Chatsworth train collision
in California
, a federal law was passed requiring positive train control
(PTC) to be implemented nationwide by 2015. While a primary goal of PTC is to prevent collisions, it also increases railroad capacity and fulfills the FRA requirements for increased speeds. However, several competing PTC technologies are being used in different regions of the country, and a clear winner has not yet emerged as of 2010.
, the Federal Railroad Administration
has developed a system of classification for track quality. The class of a section of track determines the maximum possible running speed limits and the ability to run passenger trains.
" which acts to overturn the train. To compensate for this force, the track is superelevated (the outer rail is raised higher than the inner rail). The speed at which the centrifugal force is perfectly offset by the tilt of the track is known as the balancing speed:
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 (30.5 m).
is given in miles per hour
.
Normally, passenger trains run above the balancing speed, and the difference between the balancing superelevation for the speed and curvature and the actual superelevation on the curve is known as unbalanced superelevation. Track superelevation is usually limited to 6 inches (152.4 mm), and is often lower on routes with slow heavy freight trains in order to reduce wear on the inner rail. Track unbalanced superelevation in the U.S. is restricted to 3 inches (76.2 mm), though 6 inches (152 mm) is permissible by waiver. There is no hard maximum set for European railways, some of which have curves with over 11 inches (279.4 mm) of unbalanced superelevation to permit high-speed transportation.
The allowed unbalanced superelevation will cause trains to run with normal flange contact. The points of wheel-rail contact are influenced by the tire profile of the wheels. Allowance has to be made for the different speeds of trains. Slower trains will tend to make flange contact with the inner rail on curves, while faster trains will tend to ride outwards and make contact with the outer rail. Either contact causes wear and tear
and may lead to derailment if speeds and superelevation are not within the permitted limits. Many high-speed lines do not permit the use of slower freight trains, particularly with heavier axle load
s. In some cases, the wear or friction of flange contact on curves is reduced by the use of flange
lubrication.
Federal Railroad Administration
The Federal Railroad Administration is an agency in the United States Department of Transportation. The agency was created by the Department of Transportation Act of 1966...
. Railroads also implement their own limits and enforce speed limits. Speed restrictions are based on a number of factors including curvature
Curvature
In mathematics, curvature refers to any of a number of loosely related concepts in different areas of geometry. Intuitively, curvature is the amount by which a geometric object deviates from being flat, or straight in the case of a line, but this is defined in different ways depending on the context...
, signaling, track condition
Rail tracks
The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast , plus the underlying subgrade...
, the physical condition of a train, and the presence of grade crossings. Like road speed limit
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...
s in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, speed limits for rail tracks and the train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...
s that run on them use miles per hour
Miles per hour
Miles per hour is an imperial unit of speed expressing the number of statute miles covered in one hour. It is currently the standard unit used for speed limits, and to express speeds generally, on roads in the United Kingdom and the United States. It is also often used to express the speed of...
(mph).
Signal speeds
Federal regulatorFederal Railroad Administration
The Federal Railroad Administration is an agency in the United States Department of Transportation. The agency was created by the Department of Transportation Act of 1966...
s limit the speed of trains with respect to the signaling method used. Passenger trains are limited to 59 mph and freight trains to 49 mph on track without block signal systems. (See dark territory
Dark territory
Dark territory is a term used in the North American railroad industry to describe a section of track not controlled by signals. Train movements in dark territory are controlled by track warrants or train order operation, with train dispatchers issuing orders by radio communication with train...
.) Trains without "an automatic cab signal, automatic train stop
Automatic Train Stop
An automatic train stop is a system on a train that will automatically stop a train if certain situations happened to prevent accidents from happening....
or automatic train control
Automatic Train Control
Automatic Train Control is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC-enabled lines. Its main advantages include making possible the use of cab signalling instead of track-side signals and the use of smooth deceleration patterns in lieu of the...
system" may not exceed 79 mph. The order was issued in 1947 (effective 31 Dec 1951) by the Interstate Commerce Commission
Interstate Commerce Commission
The Interstate Commerce Commission was a regulatory body in the United States created by the Interstate Commerce Act of 1887. The agency's original purpose was to regulate railroads to ensure fair rates, to eliminate rate discrimination, and to regulate other aspects of common carriers, including...
following a severe 1946 crash in Naperville, Illinois
Naperville train disaster
The Naperville train disaster occurred on April 26, 1946, at the Chicago, Burlington and Quincy Railroad station in Naperville, Illinois when the railroad's Exposition Flyer rammed into the Advance Flyer, which had made an unscheduled stop to check its running gear. The Exposition Flyer had been...
involving two Chicago, Burlington & Quincy Railroad trains. Following the 1987 Chase, Maryland train collision, freight trains operating in enhanced-speed corridors have been required to have locomotive speed limiters to forcibly slow trains rather than simply alerting the operator with in-cab signals. The signal panel in the Maryland crash had been partially disabled, with a muted whistle and a missing light bulb.
Following the 2008 Chatsworth train collision
2008 Chatsworth train collision
The Chatsworth train collision occurred at 16:22 PDT on Friday September 12, 2008, when a Union Pacific freight train and a Metrolink commuter train collided head-on in the Chatsworth district of Los Angeles, California, in the United States...
in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, a federal law was passed requiring positive train control
Positive Train Control
Positive train control is a system of monitoring and controlling train movements to provide increased safety.-Overview:The main concept in PTC is that the train receives information about its location and where it is allowed to safely travel, also known as movement authorities...
(PTC) to be implemented nationwide by 2015. While a primary goal of PTC is to prevent collisions, it also increases railroad capacity and fulfills the FRA requirements for increased speeds. However, several competing PTC technologies are being used in different regions of the country, and a clear winner has not yet emerged as of 2010.
Track classes
In the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the Federal Railroad Administration
Federal Railroad Administration
The Federal Railroad Administration is an agency in the United States Department of Transportation. The agency was created by the Department of Transportation Act of 1966...
has developed a system of classification for track quality. The class of a section of track determines the maximum possible running speed limits and the ability to run passenger trains.
Curves
Assuming a suitably maintained track, maximum track speed is limited by the "centrifugal forceCentrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...
" which acts to overturn the train. To compensate for this force, the track is superelevated (the outer rail is raised higher than the inner rail). The speed at which the centrifugal force is perfectly offset by the tilt of the track is known as the balancing speed:
where
is the amount in inches that the outside rail is superelevated above the inside rail on a curve and is the degree of curvatureDegree of curvature
Degree of curve or degree of curvature is a measure of curvature of a circular arc used in civil engineering for its easy use in layout surveying....
in degrees per 100 feet (30.5 m).
is given in miles per hourMiles per hour
Miles per hour is an imperial unit of speed expressing the number of statute miles covered in one hour. It is currently the standard unit used for speed limits, and to express speeds generally, on roads in the United Kingdom and the United States. It is also often used to express the speed of...
.
The allowed unbalanced superelevation will cause trains to run with normal flange contact. The points of wheel-rail contact are influenced by the tire profile of the wheels. Allowance has to be made for the different speeds of trains. Slower trains will tend to make flange contact with the inner rail on curves, while faster trains will tend to ride outwards and make contact with the outer rail. Either contact causes wear and tear
Wear and tear
Wear and tear is damage that naturally and inevitably occurs as a result of normal wear or aging. It is used in a legal context for such areas as warranty contracts from manufacturers, which usually stipulate that damage due to wear and tear will not be covered.Wear and tear is a form of...
and may lead to derailment if speeds and superelevation are not within the permitted limits. Many high-speed lines do not permit the use of slower freight trains, particularly with heavier axle load
Axle load
The axle load of a wheeled vehicle is the total weight felt by the roadway for all wheels connected to a given axle. Viewed another way, it is the fraction of total vehicle weight resting on a given axle...
s. In some cases, the wear or friction of flange contact on curves is reduced by the use of flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
lubrication.
See also
- Rail regulations in CanadaRail regulations in CanadaRail regulations in Canada are set by Transport Canada and the Canadian Transportation Agency.-Scope:Federal regulations apply only to certain railways which meet one or more of the following conditions:* They operate in more than one province....
- Cant (road/rail)Cant (road/rail)The cant of a railway track or a road is the difference in elevation between the two edges...
- Level crossingLevel crossingA level crossing occurs where a railway line is intersected by a road or path onone level, without recourse to a bridge or tunnel. It is a type of at-grade intersection. The term also applies when a light rail line with separate right-of-way or reserved track crosses a road in the same fashion...
- Railroad operations
- Rail tracksRail tracksThe track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast , plus the underlying subgrade...
- Railway signallingRailway signallingRailway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being guided by fixed rails, trains are uniquely susceptible to collision; furthermore, trains cannot stop quickly, and frequently operate at speeds that do not enable them to stop...
- Speed limits in the United StatesSpeed limits in the United StatesSpeed limits in the United States are set by each state or territory. Speed limits in the United States vary according to many factors, including each state or territory's laws, the type of road, land use, and more. Increments of five miles per hour are used. Additionally, these limits sometimes...
(road)