Why do cars have crumple zones?

The risk of injury in car collisions can be greatly reduced thanks to the modern crumple zone - but how does it work?

It might look bad, but the crumple zone stops the outcomes of accidents from being far worse

If you watch any footage of a head-on collision between modern cars, you will see the front of the cars crumple, absorbing energy from the impact and leaving the rest of the car reasonably unscathed.

This relatively recent innovation – the crumple zone, or the crush space – saves thousands of lives every year. To see the difference between cars with and without a crumple zone, check out this video from BBC Four’s “Crash Test Dummies”:

Crumple zones don’t only exist at the front of cars – they can feasibly be anywhere – but statistics show that most collisions are front-on impacts.

Mercedes-Benz engineer Bela Barenyi came up with the idea for a crumple zone in the 1950s, messing with the traditional notion that safety meant rigidity. The passenger section remained rigid, but he introduced areas at the front and rear of the car that would deform on impact.

How does a crumple zone work?

If your car is moving at speed and then collides with another car or object, you and your passengers will continue to move forward inside the car thanks to inertia.
Because of gravity, you will hit the steering wheel or dashboard with a force greater than your normal weight.
The force will increase depending on the speed you are travelling at.
A crumple zone is intended to slow down the crash, and also absorb energy to reduce the difference between the speed of the car occupants (still travelling at speed due to momentum) and the car (abruptly halted.)
In effect, some parts of cars are “sacrificed” – designed to literally crumple on impact, leaving the solid cabin intact.
Impact energy that affects the reinforced cabin area will be distributed over a wider area.
All this reduces the harmful affects of collisions on drivers and passengers.

Basically – you were travelling at 60 mph, now your car is going at 0 mph but your body is still going at 60 mph. Anything you can do to slow yourself down will ultimately reduce any damage.

Does it save lives?

Like seat belts and air bags, a crumple zone slows down the driver and passengers to stop them hitting the windscreen at speed and with greater force. The force of the impact can be greatly reduced even with a slight reduction in deceleration.

Of course, a car colliding with a solid car without a crumple zone will absorb most of the energy and indeed damage of the crash. The same would be true if it collided with a solid concrete wall. However, two cars without crumple zones colliding would be pretty disastrous – so it’s always better to be in a car with a crumple zone!

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