Crumple zone

He divided the car body into three sections: the rigid non-deforming passenger compartment and the crumple zones in the front and the rear.

[11][15][16] A more recent development for these curved longitudinal members is to be weakened by vertical and lateral ribs to form telescoping "crash can" or "crush tube" deformation structures.

Crumple zones work by managing crash energy and increasing the time over which the deceleration of the occupants of the vehicle occurs, while also preventing intrusion into or deformation of the passenger cabin.

[19] Seatbelts restrain the passengers so they don't fly through the windshield, and are in the correct position for the airbag and also increase the time over which the occupants decelerate.

Seat belts also absorb passenger inertial energy by being designed to stretch during an impact, again to increase the time over which an occupant decelerates.

This difference in deceleration is analogous to the difference between slamming someone into a wall headfirst (fracturing their skull) and shoulder-first (bruising their flesh slightly) – the arm, being softer, takes tens of times longer to slow its speed than the hard skull, which must deal with extremely high pressure the moment it comes in contact with the wall.

The sequence of speed-reducing technologies (crumple zones → seat belt → airbags → padded/deformable interior) are designed to work together as a system to reduce the peak force of the impact on the outside of the passenger's body by lengthening the time over which the crash energy is transferred.

In fact, crumple zones are typically located in front of and behind the main body of the car (which forms a rigid "safety cell"), compacting within the space of the engine compartment or boot/trunk.

[17] In order to tackle this problem, more recent SUV/off-roaders incorporate structures below the front bumper designed to engage lower-height car crumple zones.

The lower cross-member strikes the oncoming car's protective structure, activating its crumple zone as intended so the occupants can be given the maximum level of protection.The front of the bumper is designed to withstand low speed collisions, e.g. as in parking bumps to prevent permanent damage to the vehicle.

This aspect of design has received more attention in recent years as NCAP crash assessment has added pedestrian impacts to its testing regime.

20 km/h), the bumper and outer panel design should ensure that the crumple zone and the load-bearing structure of the vehicle is damaged as little as possible and repairs can be carried out as cheaply as possible.

These experiments culminated in a joint project by the Forschungsgemeinschaft Automobil-Technik (FAT), a conglomeration of all seven German car makers (Audi, BMW, Ford, Mercedes-Benz, Opel (GM), Porsche, and Volkswagen), which tested the applicability of two emerging commercial crash simulation codes.

These simulation codes recreated a frontal impact of a full passenger car structure (Haug 1986) and they ran to completion on a computer overnight.

Now that turn-around time between two consecutive job-submissions (computer runs) did not exceed one day, engineers were able to make efficient and progressive improvements of the crash behaviour of the analyzed car body structure.

The drive for improved crashworthiness in Europe has accelerated from the 1990s onwards, with the 1997 advent of Euro NCAP, with the involvement of Formula One motor racing safety expertise.

Combined with a front crumple zone and airbag, this system could greatly reduce the forces acting on the driver in a frontal impact.