Making Car Collisions Safe(r) with Crumple Zones

The biggest issue in automotive safety engineering is how to remove energy after a collision. A car traveling at highway speeds has a lot of kinetic energy—in fact, even a car traveling at low speeds has a lot of kinetic energy—and in the event of a collision, all that energy needs to go somewhere. And preferably "somewhere'' isn't "the driver.''

It's impossible to just suck up excess energy, so instead automotive engineers design cars that break strategically. Older cars without this innovation tend to break catastrophically in a crash, sending a large percentage of the energy of the crash straight to the people in the car. But newer cars use "crumple zones,'' sections of the car (not around the passenger compartment, don't worry) that fold and buckle in the event of a collision.

A car with a well-designed crumple zone may look absolutely destroyed after a bad crash—but the middle section, where the driver and passenger sit, will look untouched. All of the energy that goes into bending and crushing the metal of the crumple zone is energy that isn't ever going to be transferred to bending and crushing the people inside.

No matter how good the crumple, however, some energy will still make it to the driver. That's where crumple zones' other advantage comes into play: by deforming as the car hits an object (say, a wall), the crumple zone increases the amount of time the car is in contact with the wall.

See, the same amount of momentum transfer is happening—unless you're driving the Marauder, which would just keep going—but the longer time given by crumple zones reduces the force felt by the driver immensely, according to the formula for impulse (Δp = FΔt). Less force is always a good thing when we're talking about large metal objects and soft human bodies.