Drive

Your car crumples to save your life, not because it's made badly

In a crash, there is a major difference between an old car and a newer one. The old car is rigid and will stand up to the collision, while the new car will crumple up.

Many people think it’s because newer cars are flimsy, but that’s not the case. Instead, unlike the old car, it’s folding up to help save your life.

“Having a very strong, rigid body throughout means that any impact is transmitted directly into the vehicle and the occupants,” says Ted Lalka, vice-president of product planning and marketing for Subaru Canada. “When panels flex and absorb the impact, it reduces the force of the impact to the occupants inside. Essentially, the vehicle is sacrificing itself to protect the occupants.”

An auto crash actually involves three separate collisions. The initial one is when the vehicle hits something. The second is when the occupants are thrown around, hitting surfaces and objects inside the car. The third is when their bodies come to a stop, such as when the seat belt tightens, but their internal organs continue their trajectory until they slam into muscle or bones. This can cause serious injury or death.

If the car crushes as it’s hit, much of that deadly crash energy is dissipated before it gets to the passenger compartment. The car contains “crumple zones” that progressively scrunch in around the cabin, which must remain sturdy and intact. If the cabin also folds inward, known as intrusion, occupants can be injured.

Automakers use different techniques to achieve this level of safety. “Subaru starts off with a ring-shaped body structure, made of high-tensile steel, which provides strength and protection,” Lalka says. “Essentially, it’s a roll cage around the entire occupant area. The body panels can then be made out of lighter-weight sheet metal, which weighs less and results in better fuel economy, and the force of the impact is absorbed by these panels.

“The other key is that the door openings must be functional even after a severe crash, so you can get out of the vehicle.”

While the front end provides a long, larger area for crumpling, the vehicle’s sides, and the abbreviated rear ends on hatchbacks and SUVs, are challenging. Engineers use beams and ring structures that channel the energy to the floor and roof, away from the passenger cabin.

The engineers also have to balance the car’s attributes. While it needs to crumple, it can’t be too flexible or it won’t handle properly, and it has to have enough rigidity that a minor fender-bender won’t require major repairs.

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