There are two kinds of connection mode of the tractor and the trailer: the first one is the front half of a trailer traction saddle in the tractor rear section on the top of the back of the car bridge under traction Trailer part weight, which is half hanging; second is the front end of the tractor trailer even the rear of the towing vehicle only provide forward force, dragging the trailer go, but does not bear the weight down trailer, this is the whole hanging