newer heavy-lift helicopters like the S-64 Skycrane made the train concept outdated. The vehicle remained unused for a time, and was then put up for sale for $1.4 million in 1969. All that remains of the Mark II is the control cab which remains at Yuma Proving Ground Heritage Center, the rest was sold off to a local scrap dealer. The Mark II retains the record for the longest offroad vehicle in the world. See also Antarctic Snow Cruiser Road train Trackless train Sources References Further reading John Shamburger and Charles Kolb, "Project OTTER: Overland Train Terrain Evaluation Research", T.R. No. 3-588, US Army Corps of Engineers, December 1961 "No Highway Needed", Mechanical Engineering, Volume 62 (1962) Devon Francis, "LeTourneau: The Man Who Moves the Earth", Popular Science, September 1960, pp. 85–88, 244-247 "Cross-country freight train travels on 10-foot tires", Popular Science, July 1962, pp. 52–53 Peter Holderith, "The Incredible Story of the US Army's Earth-Shaking, Off-Road Land Trains". The Drive, May 2020. External links Military trucks of the United States