In the 1950s, LeTourneau Inc. developed several overland trains, essentially oversized semi-trailer trucks that could travel over almost any terrain. Their intention was to be able to handle logistics needs without being dependent on local road or rail systems, allowing them to operate in back-country areas. The US Army had three experimental units built, the largest reaching almost long, which holds the record for the longest off-road vehicle. Road trains are in use in certain roles today, but the US Army examples and a few derivatives appear to be the only off-road examples built. History LeTourneau In the early 1950s, LeTourneau, Inc., a heavy-equipment maker based in Longview, Texas, developed the idea of using a diesel-electric transmission to drive multi-wheeled vehicles. Each wheel was driven by a separate electric motor, which gave the vehicles much better traction as the force of the engine was spread across a number of wheels. In general terms these vehicles were similar to the diesel-electric locomotives that were being widely introduced by the railways at the same time, but they replaced the steel wheels with rubber ones. The earliest vehicles using the system were a number of 6x6 graders, wheel tractor-scrapers and other earthmovers. In 1953, R. G. LeTourneau sold the earthmoving portions of the business to Westinghouse, a sale that included a five-year moratorium before LeTourneau could sell into the market again. While the moratorium ran out, LeTourneau developed a number of new vehicles based on the same drivetrain. These included a number of special-purpose military designs like launchers for the Corporal missile, engineering vehicles that could quickly haul crashed bombers off runways, and even an enormous vehicle intended to pick up beached landing craft. VC-12 Tournatrain The overland train concept first developed as a way to haul trees out of the bush, without the need to prepare a road capable of supporting a traditional truck. A truck would need to have a surface flat and strong enough for its driven wheels, normally four at the rear of the cab, to gain traction needed to climb any grades. With multiple driven wheels, LeTourneau's 6x6 diesel-electrics were an obvious solution, but a single vehicle was too small to justify their purchase costs. The solution was to turn the 6x6 into an extendable design, using flexible connections to allow any number of driven wheels to be added, as needed. The first of these designs was the