Why Do Cars Have Crumple Zones?

Until the late 1950s, engineers believed that the best way to maximise driver and passenger safety was to build cars with rigid frames. The theory was that the toughest, most inflexible cars were the safest. Research has since proved this theory to be wrong. When a car with a rigid frame is in a head-on crash, for example, everything within the vehicle continues travelling forward. In this context, “everything” includes the internal organs of a body. These organs hit muscle and bone. The result can be serious internal injuries.

Seat belts and air bags provide a degree of protection. But these safety measures do not stop internal organs, including the brain, rushing forward.

Crash Energy

Crumple zones absorb some of the energy of a crash. And by absorbing it, they divert the energy away from a car’s occupants. Crumple zones can therefore reduce the effects of a car accident on the human body.

First Crumple Zones

Béla Barényi was an engineer who worked for the Mercedes-Benz car company. He first proposed the idea of “passive safety” and crumple zones. Mercedes-Benz took out a patent on the idea in 1952. Seven years later, they launched the Mercedes-Benz W111, also known as the “Fintail”. This car had crumple zones at the front and rear.

Impacts

The nature of car crashes dictated the position of the crumple zones in the W111. About 65% of car crashes are front impacts. 25% are rear collisions. Of the remaining 10%, half of the accidents occur on the right side of a car and half on the left.

Continuing Development

Where Mercedes-Benz led, other manufacturers followed. Gradually, crumple zones became a feature of all cars. One of the most notable developments came from Volvo. In the 1990s, the company launched its Side Impact Protection System (SIPS). This crumple zone feature absorbs crash energy when a car has a side-on collision.

Concerns

Crumple zones have faced criticism, however. Some motorists have said that when a car crumples up in a crash it may trap and even crush the occupants. Engineers have answered this concern by enclosing the driver and passenger compartments of cars in steel frames. They have also paid careful attention to the design of crumple zones. In a crash the metal and plastic of the zones fold in on themselves.

In a head-on accident, for example, the front crumple zone folds into the engine area. Similarly, in a rear collision, the crumple zone folds into the boot.

Different Vehicle Designs

Another safety issue concerns the design of different vehicles. One saloon car crashing head-on into another will, in theory, activate the crumple zones of both. These zones each absorb as much crash energy as possible. But if a large four-wheel drive car hits a saloon head-on, there can be a problem. Because the four-wheel drive vehicle stands higher off the road than the saloon, its crumple zone may not activate to the same extent as the saloon’s. As a result, the two cars do not share the absorption of the crash energy. The saloon absorbs more than the four-wheel drive vehicle. The saloon, and its occupants, may therefore suffer greater damage and injury.

Some four-wheel drive manufacturers are tackling this issue. They are introducing crumple zone structures below the bumpers. In a crash, these hit the crumple zones of lower, standard cars and absorb crash energy.

Crumple zone development is therefore ongoing. Together with other safety measures, however, crumple zones are a certain way of helping to avoid the worst effects of a crash.