Development of automobile transport requirements continue to increase the carrying capacity of the vehicle, but the axle load and the outside dimensions of ordinary cars is limited road regulations, can not be made too heavy too large, so there is a trailer in the form of car trains. It has a large number of axes of the bearing area and larger than ordinary cars, which have a greater carrying capacity. Passenger car train was composed by buses and trailers. Truck train by a combination of forms can be divided into the following four categories: 

Lorry car trains. By car or tractor and trailer consisting of car trains. Trailer has a uniaxial and multiaxial to biaxial most widely used. Trailer with a hanging ring and drawbar trailers or towing hook or hinge with auto body connection. Multi-trailer truck with ordinary traction, traction vehicles can pick up and separate action, flexibility. Mostly laden trailer tailgate cargo compartment, some use flat cargo units. Lorry car train traveling less stable and prone to lateral deflection. Meanwhile steering offset (towing vehicle and trailer axle front axle center trajectory deviation from the center of the track) larger trailer to follow the poor, not by road width narrower chicane road. Therefore, the length of the trailer is not too long, the trailer in the number of trains in general should not more than two. 

Semitrailer trains. Composed by tractor and trailer car trains. The multi-axle trailer is uniaxial, and a 2 to 3-axis, a support connected to the front end device can be connected to the tractor's saddle post, so that part of the total weight carried by the trailer tractor and semi-traction transmitted to the trailer. In order to meet the different loading supplies, trailer also has two forms steeplechase and flat cargo compartment cargo units, which usually means the front hanging from a support, and can pick up and put down at the ground, so that the trailer stability stop. Semitrailer train carrying a large quantity, better stability when traveling in motor transport developed countries increased use of said benefits, and to develop in the direction of heavy and special.  

Double-hung car trains. Composed by a tractor and two trailers car trains. Generally in the back of a train and a semi-trailer tractor trailer composed by a supporting turn the trolley, the trolley and then connect a trailer. This car train can be a single or double hung hung use, suitable for rejection linked transport.  

Long cargo car trains. Long pieces specifically for the transport of goods such as steel, cable column, wood and other car trains. Long goods train car by a special towing vehicle and a trailer with a long cargo towbar connections. Towbar made telescopic adjustable and can adapt to changes in the length of the carriage of goods. This car train on the tractor and trailer, respectively, with the carrier and shipment rotatable locking beam device, and by carrying long cargo link them. When the steering train, the carrier can change with a long cargo transferring position is correspondingly deflected. This car train loadmaster convenience goods, reliable, but larger turning radius, lateral yaw when traveling great maneuverability and stability are poor. Because not load other cargo, so often return empty.