The self-propelled trailer (SPT) is similar to a conventional trailer but with a motorized module on the front. The SPT is Custom to transport a load that is too big and too heavy for a truck or low loader. A self-propelled conventional trailer can carry loads up to 36 metric tons per axle line Perfect Steerable Transfer Cartluding its own weight. Standard SPTs are 3 meter wide. They can be moved on a normal flatbed truck.