The bodies of commercial vehicles that transport goods are designed for that specific purpose. Tankers transport fluids.
Tippers carry earth, or bulk grains.
And flat-beds and vans are used for general goods transport.
A goods transport vehicle can be a rigid vehicle, a rigid vehicle with a trailer, or an articulated vehicle.
Articulated vehicles carry goods on a semi-trailer, with the power unit or prime mover connected to the semi-trailer by a coupling, called a 5th-wheel coupling.
The 5th-wheel coupling lets the traction unit pivot on the semi-trailer. This gives more manoeuvrability than with rigid vehicles, or rigid-trailer combinations.
A road train connects extra trailers by a small inter-connecting trailer called a dolly. It has a fifth-wheel coupling, and it’s connected to the leading trailer by a draw bar.
Up to 3 trailer-and-dolly-sets can be drawn by 1 prime mover, and each set contains brakes for each wheel, and lights for each trailer.
A B-Double vehicle has a 5th-wheel on the rear of the first trailer, and the 2nd trailer is coupled to the 5th-wheel. This removes the dolly wheels from the combined unit, which reduces the length of the vehicle. But since there are fewer supporting wheels, the vehicle payload is also reduced.
Heavy goods vehicles can have normal control, with the operator seated behind the engine. A light-weight bonnet that can be tilted or raised allows easy access to the engine for servicing.
In forward control, the operator cabin is mounted over the engine. This design gives greater load length to the vehicle. The cabin can be tilted for easy access to the engine. Some designs only have a hinged flap over the engine bay.
