Track geometry car

Automated railway track inspection vehicle

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 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.

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 accelerograph could record horizontal and vertical movement as well as roll. It was fitted with a manual button to record milestones 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 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 technology of Sperry Corporation. The first track geometry car in Germany appeared in 1929 and was operated by Deutsche Reichsbahn. The equipment for this car came from Anschütz in Kiel, a company currently owned by Raytheon. In Switzerland, the first track geometry recording equipment was integrated in an already existing dynamometer car in 1930. 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.

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.

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. (TTCI) at the Transportation Technology Center in Pueblo, Colorado, 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.