The construction technique uses a separate chassis rigid frame that supports the entire weight and force of the engine and transmission. The body, in this technique, plays little or no structural function.

This construction technique was only used until 1923, which launched the first monocoque car, the Lancia Lambda. The self-supporting body, throughout the twentieth century, were replacing the separate chassis. Currently only several separate chassis built with off-road vehicles, sport utility vehicles, and most large trucks and some light trucks as well as several American cars.  >> more advanced modification is custom front grill

The first independent frame made of wood, construction techniques inherited from the carriages. In the 1930′s were widely replaced by steel chassis.

There are racks of chassis rails on a ladder, two parallel longitudinal beams crossed by transverse beams with X-shaped cross and the central tube (Backbone frame).

In the United States independent frame lasted more than other countries because the U.S. practice of annual change was more difficult to design with monocoque structures. From the 90 most used passenger cars monocoque construction, only trucks, buses, heavy duty SUVs and large cars are still using the separate chassis, but has increasingly incorporated the self-supporting structure.

The separate chassis remains the choice for commercial vehicles, which have to carry or drag heavy loads. Of the few great series cars are still made with separate chassis include the Ford Crown Victoria, Mercury Grand Marquis and Lincoln Town Car The advantages are ease of repair in a collision (which would be preferred as it police vehicle) and extend to a limousine.