Abstract: An auxiliary trailer for towing behind a tractor and main trailer combination adapted to carry an elongated self supporting load. A forward end of the load is carried on a bunk on the tractor, and the bunk that normally supports the aft end of the load is removed and fitted on a turntable of the auxiliary trailer. A lower portion of the turntable fitted on the main trailer receives a complementary forward portion of the auxiliary trailer and the load now extends between bunks fitted on the tractor and the auxiliary trailer, the main trailer serving merely to support a forward end of the auxiliary trailer and to transmit turning forces to the auxiliary trailer. In this manner, the number of load bearing axles and spacing between the axles is increased, thus increasing capacity of the vehicle. Normal onboard load measuring gear is adaptable to indicate vehicle load. Equivalent structure for coupling the auxiliary trailer to the main trailer can be substituted for the turntables.