[TylerE]

Because you WANT it to deform. A stiff structure would increase deceleration on the occupants - in addition to being more likely to get in accident in the first place - additional weight will cause the vehicle to brake less rapidly, be more likely to roll over, etc, in addition to reducing efficiency.

[InclinedPlane]

Indeed. You can drive some older cars right into a brick wall at 50mph and only need to replace the bumper. But that's less good for the occupants who would be killed during a crash like that. Modern car design sacrifices the vehicle for the sake of protecting the occupants.

[abstractbill]

I've often wondered about this. Instead of just having a single thin metal skin that deforms, wouldn't it be even better to have multiple skins sandwiching a kind of honeycomb structure? That way you have even more stuff to deform and absorb the impact.

[Retric]

The only stuff that actually matters is keeping people from being squashed and the occupant's deceleration profile which you can already customize by changing how the car deforms. To really make a difference vs a high end car we could mandate 3 point seat-belts and helmets like you have in racing world.

Still a 70MPH a head on collision is already fairly safe assuming people are belted the real killers are unbelted passengers, collision debris, and rolling. Edit: Head on collisions still kill a lot of people but they tend to be higher speeds accidents and often involve unbelted individuals. Also we are slightly below 1 death per 2 million hours in a car we just spend a lot of time in our cars.

PS: Worldwide it was estimated that 1.2 million people were killed and 50 million more were injured in motor vehicle collisions in 2004. http://en.wikipedia.org/wiki/Epidemiology_of_motor_vehicle_c...

[bagels]

Nearly every form of motorsport racing requires the following:

5, 6 or 7 mounting point harnesses Head and Neck restraints Helmets

[rdl]

They do this; for front (especially) and rear impact, you have the entire crumple zone, with lots of cross-hatched struts and other components to take away energy in deformation.

There are various side impact technologies to try to 1) prevent ultimate penetration and 2) absorb energy. The problem is the doors need to be relatively thin, relatively light, and contain a bunch of other components, as well as function as doors. Multiple layers is one.

The best right now seems to be use the door to prevent penetration, and use a side curtain airbag to reduce peak acceleration on passenger (along with seat design and seat belts).

I personally picked used cars no earlier than ABS and side curtain airbags whenever friends asked for cheap used car options.

[rgbrenner]

Yes, you're right.. that's why it's more than just the skin of the car.. it's called the crumple zone:

http://auto.howstuffworks.com/car-driving-safety/safety-regu...

The idea is that the entire front of the car is a crumple zone (to absorb the impact), and there's a rigid frame around the passenger compartment.

[arg01]

Honeycombs are a difficult structure to manufacture. They often get mentioned in relation to 3d printing as one of the useful application. They're actually a very strong structure for the amount of material used and were even hand pieced together from wood for some aircraft during world war 2 rather than using more easily manufactured materials due to this advantage.

[AnimalMuppet]

You know how the original Volkswagen Bugs had that empty front hood, because the engine was in the rear? My dad advocated filling the front hood with bags full of empty aluminum cans.

[bagels]

Right now, you have multiple skins sandwiching air.

[sp332]

In a frontal collision, the engine is directed down underneath the drive and passenger. That design alone gives you a few extra feet.

[megablast]

You have often thought of this, but never did any research into what they currently do?

[abstractbill]

What they currently do is crumple zones. That's not what I was talking about (the entire skin of the car being a honeycomb sandwich).

[kiba]

If there's a way to increase safety, I am sure that they had thought of it.

[jstanley]

So you're saying we're at the theoretical optimum of car safety and that there are no possible improvements?

[bdamm]

High performance aircraft and cars already do this. They thought of it - and it's expensive.