User:Slopes09/Track Geometry Car

Current Article: A track geometry car is an automated track inspection vehicle on a rail transport system used to test several geometric parameters of the track 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.

Trakmezurila vagono Путеизмеритель

History
By at least 1967, geometry cars had emerged. One of the earliest was Car T2 used by the U.S. Department of Transportation's Project HISTEP (High-Speed Train Evaluation Program). It was built especially for Project HISTEP to evaluate track conditions between Trenton and New Brunswick, NJ. Many of the first regular service geometry cars were created from old passenger cars outfitted with the appropriate sensors, instruments, and recording equipment; they were then 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 seventy miles per hour) in order 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 track geometry car under track loading. Finally, track geometry data is generally stored and can be used to track 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 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 doesn't 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 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 (road/rail) 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 (road/rail) is generally desired.
 * Curvature - 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 lines (or catenary) - Measures the height and stagger of contact wire, the position of catenary masts or poles, and thee positions of the wire bridges if applicable.
 * Rail gauge - The distance between the rails. Over time, rail may become too wide or too narrow In North American and most of the world, standard gauge is 4 feet, 8.5 inches.
 * Rail profile - Looks for rail wear and deviations from standard profile.
 * Warp - The maximum change in crosslevel over the length of a predetermined chord length (generally sixty-two feet).

Technologies Utilized
Track geometry cars use a variety of technologies to inspect the track and manage the large amounts of data being collected by them. Today most geometry cars use computers to process and display data gathered by the systems. Some of the original geometry cars only produced long spreadsheets worth of data.

Non-Contact Measurement and Inspection Methods

 * Laser Measurement Systems - Measures Rail profile and wear, crosslevel, and Rail gauge
 * Accelerometers
 * Used measuring 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 several 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 Machine vision inspections of certain track components
 * Gyroscope - Oriented in teh vertical direction, used to measure cross level and warp. These are now obsolete, having been replaced by lasers.
 * Proximity Sensor - Used to measure surfaces, alignment, and gauge. These are now obsolete, having been replaced by lasers.

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

Other Systems Used

 * Global Positioning System - Tracks the progress of the geometry car and provides the exact location of defects found by the geometry car. The coordinates of a defect are generally forwarded to a roadmaster or track inspector who can use them to pinpoint defects once found.
 * Paint Spray System - Marks the location of a defect on the track once a defect is found.

Regulatory Compliance in the United States
In the United States, the Federal Railroad Administration(FRA) maintains a fleet of three geometry cars as part of it's Automated Track Inspection Program (ATIP). The FRA runs its fleet of geometry cars around the country to check railroads for compliance with their track safety standards. According the the FRA, their geometry cars travel approximately 30,000 miles per year and find approximately 10,000 defects per 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. The Transportation Technology Center, Inc. (TTCI) in Pueblo, CO has been doing tests using 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.