What it is and what it does
The occupant compartment (outlined in pink in the diagram on the right) is the largest part of the car and is the space for the passengers to be seated in. Occupant compartments act as crash protection features and can vary in size and shape depending on the type of car. However, they are usually made of similar sturdy materials and serve the same purpose: to keep passengers safe during a crash.
How it works
The occupant compartment’s role is to absorb the crash’s kinetic energy, so that it does not injure passengers. It should also be strong enough to hold its shape and prevent passengers from being crushed from the force of the impact. In order for it to do these things, the occupant compartment’s structure must have the ability to deform whilst leaving enough room for the passengers, as well as enough room to let the airbags deploy. The occupant compartment’s ability to do this is referred to as “crashworthiness”.
The occupant compartment also works closely with the crumple zone. The crumple zone absorbs majority of the crash’s impact to help the occupant compartment retain its shape and keep passengers safe.
Development
In the 1920s occupant compartments were built from wood panels and steel brackets. However, these materials did not provide enough protection to passengers. Now, occupant compartments are very strong and are built from sturdy materials that are highly likely to retain their shape during a crash. Some modern cars also have safety cages built around the occupant compartment to help it further hold its shape.