When there is a car crash, the car, its contents and the passengers decelerate rapidly. They experience great forces because of the change in momentum which can cause injuries. Modern cars have safety features that absorb kinetic energy in collisions. These typically include:. These features reduce injuries to the people in the car by absorbing energy from the impact. They increase the time taken for the change in momentum on the occupants' bodies, and so reduce the forces involved and any subsequent injuries. These features absorb energy when they change shape.