AASHTO does not show either tankers or automobile carriers, but I would try to design around a WB-67, which is the largest semi-trailer rig. FHWA might be a source, or your state highway department.

Do a web search and you'll probably be able to find the information from a variety of sources. AASHTO's green book has dimensions of various vehicles and their turning movements. There are also units with double or triple trailers, desidnated with a D or T after the number. The number that follow refer to the wheelbase, measured from the front wheels of the truck tractor to the most rear wheels of the trailer. WB is the designation for a semitrailer vehicle (tractor and trailer).