all of the wheels are driven by the vehicle motor not shown drivingly connected to the wheels through conventional transmissions and at least two of the wheels and possibly all four are steerable the vehicle body includes wheel fenders 20 and the cab includes side window 22 and windshield 24 and lights and other common vehicle accessories are mounted upon the vehicle and towing hitches not shown are usually mounted upon the vehicle at both the front and rear the basic component of the vehicle is the chassis or frame 14 and the novel aspect of the instant invention pertains to the frame as the traction of a vehicle is directly proportional to the vehicle weight with a towing tractor or other heavy duty vehicle of this type it is of advantage to have a high vehicle weight and in accord with the invention a substantial portion of the vehicle weight occurs in the frame itself in fig1 4 the illustrated frame 14 consists of an elongated main or primary metal plate 26 having a front end 28 and a rear end 30 and the plate includes an upper flat surface 32 and a lower flat surface 34 the vertical thickness of the.