* Drive axles for trailers
Stewart & Stevenson is partnering with a United Kingdom company, MultiDrive, for technology to deliver mechanical power to the trailer axle. The idea is to run a driveline from the PTO output of a truck drive axle to a corresponding drive axle mounted on the trailer. The rear axle that drives the trailer is the same one used as the intermediate axle of the 6 × 6 trucks Stewart & Stevenson produces.
I had thought long ago about this but I thought of an on board motor this is smarter.
http://trailer-bodybuilders.com/mag/trucks_keep_towing/