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External Airbag Designed to Protect Pedestrians
Thanks to researchers at Cranfield University, you don't have to feel bad when you plow into a group of pedestrians who are crossing the street too slowly. They have designed an external airbag that mounts to your hood at the base of the windshield. Research shows that this is the area where a pedestrian's head is most likely to hit in an accident. "Test results indicate that the system works extremely well. When fitted to a demonstrator vehicle not originally designed with pedestrian protection in mind, the results were well inside all current legal criteria for pedestrian protection currently in force in Europe," Roger Hardy of the university's Cranfield Impact Centre said.
Note that this story is coming out of the UK, not the US. The majority of the car-driving world drives smaller vehicles.
The problem is, impacts are not predictable.
The "most likely spot" to hit, is actually depending on the following factors:
- Speed of collision
- Braking/coasting/accelerating (braking typically causes a vehicle's nose to dip, accelerating causes it to rise)
- Height of the pedestrian in relation to the height of the vehicle's front bumper/grille.
- Angle of collision (pedestrian motion will be different if hit head-on, as opposed to someone trying to whip around a right-hand turn and blindsiding someone who's crossing properly; angle also changes if you're not at a right-angle intersection)
The other problem is, does this truly cushion the blow, taking the energy into the crashbag and causing the pedestrian to be more likely to remain on the stopped vehicle, or is it more elastic, imparting acceleration back into the poor pedestrian in time for them to slide off the car - now accelerated to a good 15-20mph or higher - and then hit their head on the cement?
Most cars on the road today are not compliant to the new standards beacause they were changed last year and are only enforced on NEW vehicles. However, I don't believe even all new vehicles have to comply this year already but have a few year's time to adapt.
The most notable change you can see is that all new European cars (model year 2009) have an extremely high front bumper and are incredibly round on that end making them look somewhat chubby. Most of them are also made so the bonnet can collapse under a pedestrian's weight while also making sure they don't hit the engine or something on it.
Another very noticable change is that the edge between bonnet and wind screen is no longer a sharp metalic edge on most cars, but has a smooth transition made of plastic.
I am saying this as an armchair crash test fanatic, not an expert in the field so I might be marginally incorrect on some points.
An airbag is not like a beachball- it's not elastic. In fact, it has to be inelastic for it to work. If in-car airbags acted like you described, they would simply cause the driver's head to bounce back into the headrest, causing massive brain injury. The airbag works by decelerating the head more slowly than the steering wheel would. 40 mph to 0 mpg in a few milliseconds versus a much larger fraction of a second is HUGE in terms of physics.
The best way to protect a falling egg is to drop it onto something inelastic yet yielding- a pile of goose down would work well, for example. Airbags work on this principle (as do crumple zones): Slow the deceleration, absorb the energy (as opposed to transferring it like a bouncy ball), person lives (usually).
A pedestrian airbag would work like that- more a pile of leaves than a trampoline. Find a video on youtube or something of the airbags used by stuntmen in movies- they don't bounce, they deflate.
Hope this helps.
-b
No offense, but I've stopped responding to AC's.