Crumple zones help absorb some of the energy of a car collision and divert that energy away from car occupants. Crumple zones help increase your “ride-down time” (the amount of time it takes your body to come to a complete stop during an impact). Basically, what happens during a car collision is that the rigid frames of the cars stop within a small fraction of an instant. But everything in the car, including you and your internal organs, continues to move forward. So your head can be thrown against the car at high speed. Your internal organs can be forced into a loose seatbelt harness at high speed. And anyone not belted in might get ejected from the car, which vastly increases the chances of death from a car collision.
After the rigid parts of the car frame have already come to a complete stop, the crumple zones continue moving, crumpling in upon themselves. This provides precious extra fractions of seconds for the people inside the car to gradually slow down too. Each fraction of a second gained in ride-down time decreases the force on your body from the car collision and reduces your chances of severe injuries or death concurrently.
Béla Barényi, a Mercedes engineer, first came up with the idea of providing passive safety through crumple zones in 1959. A few years thereafter, Mercedes produced the first car to have front and rear crumple zones. Mercedes remains a leader in car safety innovation to this day and continues to find ways to increase your ride-down time.
About 65% of car accidents consist of frontal crashes. Another 25% occur as rear-end crashes. The remaining 10% of car collisions involve side impact crashes. Side area crumple zones remain minimal. There’s very little side area in which to place side crumple zones, and the high percentages of frontal and rear crashes dictates that carmakers concentrate their efforts on front and rear crumple zones to improve ride-down time.