LCC-1 was so successful that in 1958 the Army contracted for a larger version, the TC-497 Overland Train Mark II. Generally similar to the LCC-1 in concept, the Mark II included a number of features to allow the train to grow to any length.
One change was the removal of the Cummins engines and their replacement with gas turbine engines of higher power and lower weight. Whereas the LCC-1 had a single 600-hp engine, the Overland Train had four 1,170-hp Solar 10MC engines, one in the "control car" and three others spread through the train. New power trailers could be added at any point along the train.To further reduce weight, most of the vehicle was built from welded aluminum.
Steering such a train proved to be a serious problem. If the train rounded a corner, the trailers would normally want to even the angles between themselves, forming into a long arc. If there was an obstacle that the driver had avoided, the trailers might eventually hit it as they rounded a corner. To solve this problem, the new trailers were all equipped with steerable wheels. Steering commands were sent from the control cab to each set of wheels in turn, so they started turning at the same point where the driver had. This allowed the train to make sharp right-angle turns, for instance.
The Mark II had a much larger six-wheeled cab that was over 30 feet (9.1 m) tall and was no longer articulated due to the ability for all the wheels to be steered. The turbine engine was much smaller than the diesel it replaced, allowing the interior to support a crew of six with sleeping quarters, toilets and a galley. It was even equipped with a radar. An additional two power cars and ten cargo cars were built for testing. In total the train now stretched over 570 feet (170 m). On flat ground it could carry 150 tons of cargo at about 20 mph. Range at full load was normally 350 to 400 miles (560 to 640 km), but additional fuel trailers could be added to extend it.
Final specifications were completed in 1960, and construction took most of 1961. After preliminary testing, it was handed to the Army in February 1962, and shipped to the Yuma Proving Ground in Yuma, Arizona. In testing under the "Project OTTER", for "Overland Train Terrain Evaluation Research", the vehicle performed well. But in the end the Army gave up on the idea as newer heavy-lift helicopters like the S-64 Skycrane made the train concept outdated.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, the rest was sold off to a local scrap dealer. The Mark II retains the record for the longest offroad vehicle in the world.