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A track geometry car (also known as a track recording car) is an automated track inspection vehicle on a
rail transport Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a prep ...
system used to test several parameters of the
track geometry Track geometry is concerned with the properties and relations of points, lines, curves, and surfaces in the three-dimensional positioning of railroad track. The term is also applied to measurements used in design, construction and maintenance of t ...
without obstructing normal railroad operations. Some of the parameters generally measured include position, curvature, alignment of the track, smoothness, and the crosslevel of the two rails. The cars use a variety of sensors, measuring systems, and data management systems to create a profile of the track being inspected.


History

Track geometry cars emerged in the 1920s when rail traffic became sufficiently dense that manual and visual inspections were no longer practical. Furthermore, the increased operating speeds of trains of that era required more meticulously maintained tracks. In 1925, the Chemins de fer de l'Est put a track geometry car into operation carrying an accelerograph developed by Emile Hallade, the inventor of the
Hallade method The Hallade method, devised by Frenchman Emile Hallade, is a method used in track geometry for surveying, designing and setting out curves in railway track. It involves measuring the offset of a string line from the outside of a curve at the centr ...
. The accelerograph could record horizontal and vertical movement as well as roll. It was fitted with a manual button to record
milestone A milestone is a numbered marker placed on a route such as a road, railway line, canal or boundary. They can indicate the distance to towns, cities, and other places or landmarks; or they can give their position on the route relative to so ...
s and stations in the record. Such car was developed by travaux Strasbourg now part of GEISMAR Group. By 1927 the
Atchison, Topeka and Santa Fe Railway The Atchison, Topeka and Santa Fe Railway , often referred to as the Santa Fe or AT&SF, was one of the larger railroads in the United States. The railroad was chartered in February 1859 to serve the cities of Atchison and Topeka, Kansas, and ...
had a track car in operation followed by the Estrada de Ferro Central do Brasil in 1929. These two cars were built by Baldwin using the
gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...
technology of
Sperry Corporation Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the 20th century. Sperry ceased to exist in 1986 following a prolonged hostile takeover bid engineered by Burroug ...
. The first track geometry car in Germany appeared in 1929 and was operated by
Deutsche Reichsbahn The ''Deutsche Reichsbahn'', also known as the German National Railway, the German State Railway, German Reich Railway, and the German Imperial Railway, was the German national railway system created after the end of World War I from the regiona ...
. The equipment for this car came from Anschütz in
Kiel Kiel () is the capital and most populous city in the northern German state of Schleswig-Holstein, with a population of 246,243 (2021). Kiel lies approximately north of Hamburg. Due to its geographic location in the southeast of the Jutland ...
, a company currently owned by
Raytheon Raytheon Technologies Corporation is an American multinational aerospace and defense conglomerate headquartered in Arlington, Virginia. It is one of the largest aerospace and defense manufacturers in the world by revenue and market capitali ...
. In Switzerland, the first track geometry recording equipment was integrated in an already existing dynamometer car in 1930. One of the earliest track geometry cars was Car T2 used by the U.S. Department of Transportation's Project HISTEP (High-Speed Train Evaluation Program). It was built by the
Budd Company The Budd Company was a 20th-century metal fabricator, a major supplier of body components to the automobile industry, and a manufacturer of stainless steel passenger rail cars, airframes, missile and space vehicles, and various defense products ...
for Project HISTEP to evaluate track conditions between Trenton and New Brunswick, NJ, where the DOT had established a section of track for testing high-speed trains, and accordingly, the T2 ran at 150 miles per hour or faster. Many of the first regular service geometry cars were created from old passenger cars outfitted with the appropriate sensors, instruments, and recording equipment, coupled behind a locomotive. By at least 1977, self-propelled geometry cars had emerged. Southern Pacific's GC-1 (built by Plasser American) was among the first and utilized twelve measuring wheels in conjunction with strain gauges, computers, and spreadsheets to give managers a clear picture of the condition of the railroad. Even in 1981, the ''Encyclopedia of North American Railroads'' considered this the most advanced track geometry car in North America.


Advantages

Track inspection was originally done by track inspectors walking the railroad and visually inspecting every section of track. This was hazardous as it had to be done while trains were running. It was also manpower intensive, and inspectors were limited in the amount of track they could inspect on a given day. Manual instruments had to be used to measure various parameters of the track. The primary benefits of track geometry cars are the time and labor saved when compared to doing manual inspections of track. Track geometry cars may travel up to 217 miles per hour (335 kilometers per hour), inspecting track the whole time. More commonly, on freight railroads, geometry cars travel at track speed (up to 70 miles per hour) to minimize service disruptions. Current track geometry cars may cover large portions of the system in a single day. Many times, maintenance gangs will follow the geometry car and fix defects as the geometry car moves along the track. Because track geometry cars are full-sized rail cars (with the exception of some lighter hi-rail geometry cars), track geometry cars also provide a better picture of the geometry of the track under loading (compared to manual methods which did not consider this). Finally, track geometry data is generally stored and can be used to monitor trends in the degradation of track. This data can be used to pinpoint and predict trouble spots in the track and plan maintenance programs accordingly.


Parameters measured

The tolerances of each parameter varies by the
track class 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, ...
of the track being measured. In the United States, geometry cars generally classify each defect as either "Class II" or "Class I" (though the exact name may vary by the railroad). A class II defect is known as a maintenance level defect, meaning that the track does not meet a particular railroad's own standards. Each railroad has their own standard for a maintenance level defect. A class I defect is a defect in violation of the Federal Railroad Administration's (FRA) track safety standards. Railroads must fix these defects within a certain period of time after their discovery or else they risk being fined. *
Alignment Alignment may refer to: Archaeology * Alignment (archaeology), a co-linear arrangement of features or structures with external landmarks * Stone alignment, a linear arrangement of upright, parallel megalithic standing stones Biology * Struc ...
– "Alignment is the projection of the track geometry of each rail or the track center line onto the horizontal plane," (FRA Definition). Also known as the "straightness" of the tracks. * Crosslevel – The variation in
cant Cant, CANT, canting, or canted may refer to: Language * Cant (language), a secret language * Beurla Reagaird, a language of the Scottish Highland Travellers * Scottish Cant, a language of the Scottish Lowland Travellers * Shelta or the Cant, a la ...
of the track over the length of a predetermined "chord" length (generally sixty-two feet). On straight or tangent track, ideally there should be no variation, while on curves, a cant is generally desired. *
Curvature In mathematics, curvature is any of several strongly related concepts in geometry. Intuitively, the curvature is the amount by which a curve deviates from being a straight line, or a surface deviates from being a plane. For curves, the can ...
– The amount by which the rail deviates from being straight or tangent. The geometry car checks the actual curvature (in degree of curvature) of a curve versus its design curvature. *
Overhead line An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as: * Overhead catenary * Overhead contact system (OCS) * Overhead equipm ...
s (or catenary) – Measures the height and stagger of contact wire, the position of catenary masts or poles, and the positions of the wire bridges if applicable. *
Track gauge In rail transport, track gauge (in American English, alternatively track gage) is the distance between the two rails of a railway track. All vehicles on a rail network must have wheelsets that are compatible with the track gauge. Since many ...
– The distance between the rails. Over time, rail may become too wide or too narrow. In North America and most of the world,
standard gauge A standard-gauge railway is a railway with a track gauge of . The standard gauge is also called Stephenson gauge (after George Stephenson), International gauge, UIC gauge, uniform gauge, normal gauge and European gauge in Europe, and SGR in E ...
is . * Rail profile – Looks for rail wear and deviations from standard profile. *
Warp Warp, warped or warping may refer to: Arts and entertainment Books and comics * WaRP Graphics, an alternative comics publisher * ''Warp'' (First Comics), comic book series published by First Comics based on the play ''Warp!'' * Warp (comics), a ...
– The maximum change in crosslevel over a predetermined chord length (generally sixty-two feet). Track geometry cars used by the
New York City Subway The New York City Subway is a rapid transit system owned by the government of New York City and leased to the New York City Transit Authority, an affiliate agency of the state-run Metropolitan Transportation Authority (MTA). Opened on October ...
also measure: * Corrugation of running rail surface * Tunnel and station platform clearances * Third rail height and gauge * Vertical gap between third rail and protective board


Non-contact measurement and inspection methods

* Laser measurement systems – Measures rail profile and wear, crosslevel, and
track gauge In rail transport, track gauge (in American English, alternatively track gage) is the distance between the two rails of a railway track. All vehicles on a rail network must have wheelsets that are compatible with the track gauge. Since many ...
* Accelerometers ** Used to measure alignment by finding the acceleration in a certain direction and then integrating until a position is obtained. These positions are then used to create artificial chords to measure various parameters. ** Used to obtain ride quality measurements. If certain accelerations are reached or exceeded freight can be damaged or passengers may become uncomfortable. * Video system – Captures video of the right-of-way for further analysis, as well as for
machine vision Machine vision (MV) is the technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision refers to ...
inspections of certain track components *
Gyroscope A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...
– Oriented in the vertical direction, used to measure cross level and warp. These are now obsolete, having been replaced by laser measurement systems. *
Proximity sensor A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for ...
– Used to measure surfaces, alignment, and gauge. These are now obsolete, having been replaced by laser measurement systems.


Contact measurement and inspection methods

* Measuring wheels – Mostly obsolete, originally used for measuring nearly all parameters, these have now been replaced by lasers * Strain gauges – Used in conjunction with the measuring wheels to translate the various movements of the measuring wheels into a usable format


Regulatory compliance in the United States

In the United States, the
Federal Railroad Administration The Federal Railroad Administration (FRA) is an agency in the United States Department of Transportation (DOT). The agency was created by the Department of Transportation Act of 1966. The purpose of the FRA is to promulgate and enforce rail sa ...
(FRA) maintains a fleet of three geometry cars as part of its Automated Track Inspection Program (ATIP). The FRA runs its fleet of geometry cars around the country to check railroads for compliance with Federal Track Safety Standards (FTSS). According to the FRA, each geometry car travels approximately 30,000 miles and finds approximately 10,000 defects every year, which are then fixed by the railroads.


Future

In the United States, railroads are looking into new ways to measure geometry that cause even less interference to train operations. Testing performed by
Transportation Technology Center, Inc. MxV Rail (full legal name: Transportation Technology Center, Inc.) is a subsidiary of the Association of American Railroads (AAR) which conducts railroad equipment testing and training for member railroads. From 1982 until October 2022, AAR m ...
(TTCI) at the
Transportation Technology Center The Transportation Technology Center (TTC) is a railroad equipment testing and training facility located northeast of Pueblo, Colorado, owned by the Federal Railroad Administration (FRA). It was built in 1971 as the High Speed Ground Test Center ...
in
Pueblo In the Southwestern United States, Pueblo (capitalized) refers to the Native tribes of Puebloans having fixed-location communities with permanent buildings which also are called pueblos (lowercased). The Spanish explorers of northern New Spain ...
,
Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...
, uses a portable ride quality monitoring system attached to a standard freight car. TTCI has also been promoting a move to "Performance Based Track Geometry" or PBTG. Most current track geometry systems only look at the condition of the track itself, while a PBTG system also looks at vehicle dynamics caused by track conditions.


Examples

*
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
Federal Railroad Administration The Federal Railroad Administration (FRA) is an agency in the United States Department of Transportation (DOT). The agency was created by the Department of Transportation Act of 1966. The purpose of the FRA is to promulgate and enforce rail sa ...
DOTX-216, -217, -218, -219, -220 * –
SNCF TGV Iris 320 Iris 320 is a modified TGV train operated by SNCF International as a dedicated track recording train for high-speed railways. The train can run at and consists of two power cars and eight trailer coaches, providing a long laboratory. It was c ...
* –
ICE S ICE S is Deutsche Bahn's train for high-speed tests. The letter "S" abbreviates the German expression ''Schnellfahrt'', which translates into ''high speed run''. The train replaced the InterCityExperimental (ICE V). History The train was ori ...
* –
Doctor Yellow is the nickname for the high-speed test trains that are used on the Japanese Shinkansen ("Bullet Train") dedicated express passenger train routes. The trains have special equipment on board to monitor the condition of the track and overhead wire ...
* – New Measurement Train,
British Rail Class 950 The British Rail Class 950 is a diesel multiple unit that was purpose-built by British Rail Engineering Limited's Holgate Road carriage works for the British Rail Research Division for use as a track assessment unit. It is currently operated by ...
, London Underground Track Recording Train * – SVGP-1 * – TCDD HT80001 (for high speed electric sections only) in * – Standard gauge AK track recording cars


See also

*
Cant (road/rail) The cant of a railway track or camber of a road (also referred to as superelevation, cross slope or cross fall) is the rate of change in elevation (height) between the two rails or edges. This is normally greater where the railway or road is cur ...
*
Coordinate-measuring machine A coordinate measuring machine (CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. Various types of probes are used in CMMs, the most common being mechanical and ...
* Rail inspection * Rail tracks *
Track gauge In rail transport, track gauge (in American English, alternatively track gage) is the distance between the two rails of a railway track. All vehicles on a rail network must have wheelsets that are compatible with the track gauge. Since many ...
*
Track geometry Track geometry is concerned with the properties and relations of points, lines, curves, and surfaces in the three-dimensional positioning of railroad track. The term is also applied to measurements used in design, construction and maintenance of t ...


References


External links


Federal Railroad Administration – Automated Track Inspection Program (ATIP)Example Track Geometry Data
– Taken after the
2008 Chatsworth train collision The 2008 Chatsworth train collision occurred at 4:22:23 p.m. PDT (23:22:23 UTC) on September 12, 2008, when a Union Pacific freight train and a Metrolink commuter train collided head-on in the Chatsworth neighborhood of Los Angeles, ...
{{Authority control Maintenance of way equipment
Track geometry car A track geometry car (also known as a track recording car) is an automated track inspection vehicle on a rail transport system used to test several parameters of the track geometry without obstructing normal railroad operations. Some of the p ...