The Transportation Technology Center is a field test site for the railroad transportation industry, located in a remote site in the plains of central Colorado. It is probably the largest railway R&D center in the country, with over 48 miles of dedicated, looped track for developing and testing rolling stock, and for recreating accidents in order to understand their dynamics. It also has other test facilities used to develop new technologies related to the railway industry, including high-bay engineering buildings with vibration rigs, model railroads used for testing, engineering and metallurgical labs, and impact walls for full-scale crash tests. Emergency and hazardous spill response are also developed at the TTC. The TTC is owned and operated by the Association of American Railroads, a railway industry trade organization. The AAR also owns the Bureau of Explosives, an explosives transportation organization which operates at the Transportation Technology Center.