The largest such vehicles are similar to railroad tanktainers which are also designed to carry liquefied loads.
[1] The U-1 semi-trailer was a liquid-hydrogen trailer designed in the 1950s to carry cryogenic liquid hydrogen (LH2) on roads being pulled by a powered vehicle.
It was constructed by the Cambridge Corporation and had a capacity of 26,000 liters (6,900 U.S. gal; 5,700 imp gal) with a hydrogen loss rate of approximately 2 percent per day.
The specifications for its successor the U-2, a double axle semi-trailer, were issued on 15 March 1957.
[2] Liquid hydrogen trailers are referenced by their size or volume capacity.