Why can't the make cars from shock-absorbing material?

I don’t want to sound too much like Homer Simpson, but why can’t they make cars from something like india-rubber, which, in the event of collisions, would bounce off each other? Sure, you’d still get deaths and injuries, but at least you’d avoid those (and there must be many) which result from twisted pieces of metal piercing body parts.
I have my D’oh! ready at hand when the obvious flaw in my thinking is brought to light.

Think about this with more specificity. What parts do you propose be made of rubber exactly? What range of characteristics do those parts need to have for normal everyday car operation? Are those characteristics that rubber has?

The frame would still need to be metal, the window would still need to be made of glass. The engine, transmission, and such would also be metal.
Simply, the amount of rubber you could put on after you had used metal wherever you had to wouldn’t be worth it.

I would also note that in an accident, crumpling is possibly more effective than bouncing off (slower deceleration.)

The first thing that comes to mind is you can’t have a rubber engine. (OK, someone will come along and show a highly advanced polymer composite that doubles as a car engine and a sex toy, but on most budgets that isn’t feasible). There’s just too much stuff in a car that has to be metal, and how do you bolt that to a rubber chassis?

The second thing that comes to mind is “flaming inferno of death”.

Plus, cars sorta are made out of shock-absorbing material… if the energy of the crash weren’t absorbed by the body and chassis crinkling up, something else would have to absorb that energy, and it would probably be you. Undesirable.

I was thinking specifically of the shell of the car and of a material which would be strong enough to absorb the shock waves of an impact without fracturing (I haven’t the scientific knowledge to assess the qualities of any particular substance but one thinks of rubber balls which deform on impact and then spring back to their original shape.)
Or, if not the whole chassis, how about surrounding the whole car with a rubber bumper, on the principle of Dodgem cars at a fairground?
I’m thinking out loud here and probably making more of an idiot myself with each word, but, given the right material, ie one with the requisite physical properties, where’s the flaw in this thinking?

The couple of intervening posts as I composed my last reply have revealed all too fully the drawbacks to my brainwave.


If you made it out of a big rubber tube filled with gel and with seams designed to break at high velocities, this would probably be helpful. But there doesn’t seem to be a big market for a car with bumpers that explode in a shower of gel in minor collisions and need to be completely replaced.

maybe if it were a minty gel… but there I go, thinking out loud again.

The ideal car would be one that absorbs as much as possible of the force of impact over the longest possible span of time - thus decelerating the occupant as gently as possible; a car covered with twenty foot thick layer of polyurethane foam would be really good at gradually absorbing the force of impact, but it would be rather impractical to drive.

If we were to insist that the force of impact be absorbed by only reversably-deformable structures, this would give us less space/distance (and therefore time) in which to decelerate the occupant of the vehicle. Modern cars maximise the deceleration time of the occupant by making as much as possible of the car structure deformable - unfortunately, this means things (hopefully other than the occupant) will get irreversibly bent and broken during a serious collision.

I’ve got my Credit Card details ready…

Essentially, cars are made from shock absorbing material. Crumple zones, bumpers, and so on. The difference from what you’re suggesting is that right now, in an accident, the car is sacrificial. When push comes to high speed shove, we don’t care what happens to the car as long as the occupants make it through intact.


The idea is to avoid absorbing the force of an impact and instead to disperse it.

As Finagle said, steel is a shock-absorbing material. And a wonderful one, too - it tends to bend gracefully rather than shattering into sharp pieces.

You really don’t want to bounce off an obstacle when you hit it. Suddenly going from, say, 40mph to zero is a big enough strees on the human body. But a perfectly elastic rubber car would go from 40mph to -40mph (move backwards) in the same amount of time, maybe much less. That would double the stress on the occupants.

Does this remind anyone else of that SNL commercial about a car made out of adobe, that way after an accident you could just reshape it by hand.

They do. The Saturn is covered in Plastic (over a steel frame). In a small accident, you bounce (not very far mind you) off with little damage.

Having the car bounce would make collisions more violent. The car has to push harder against the target if it is going to leave the collisions at high velocity backwards.

Crumple zones and energy absorption is already a beautifully refined art. Stroll around a junkyard and see how cars look after bad accidents. The designers have done an amazing job of preserving a big enough space for a human to survive in (though room for the feet is pretty hard to include).

“Hey hey! We’re Adobeeee. The little car that’s made out of clay.”
“We’re gonna save you some moneeeey…”