Abstract: A tow tractor having a pair of front steerable wheels and a pair of rear steerable wheels is provided with attachment means for selectively connecting it to a vehicular trailer either by an articulated draft connection to permit swiveling movement therebetween or by a rigid unitary connection for operating the tractor and trailer as a straight truck. Steering mechanism is provided on the tractor for selectively affording four-wheel simultaneous steering of both said front and rear pairs of wheels in the same direction, or conventional front wheel steering only of the front pair of wheels while maintaining the rear pair of wheels locked in normal straightahead running position.

Abstract: A conventional over-the-road tractor is modified to include a rail car coupling assembly mounting a rail car coupler in tandem behind the conventional fifth wheel for selective movement into and out of the path of conventional trailer coupling movement to permit of selective coupling with a trailer or rail car.When operating in the rail car coupling mode the conventional fifth wheel boom assembly is actuated to effect, via the rail car coupling assembly, a partial weight transfer from the rail car to the traction unit.