h a l f b a k e r y"This may be bollocks, but it's lovely bollocks."
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Before you call me on advocacy let me show you my artistic
license.
There.
Now I propose that roads be
widened by 10 feet and all cars be required to have big, BIG
air filled bumpers on all sides and the top. It will decrease
efficiency but less so since the cars don't have to be
made of
heavy, strong material any more. It will also protect the
environment by cars not being damaged/replaced nearly as
much. I bet after all is considered you're losing only a few
kilometers per liter for a massive safety improvement.
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Massive stinking piles of bones by the roadside from all the cyclists and pedestrian casualties. |
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//I bet after all is considered you're losing only a few kilometers per liter for a massive safety improvement// |
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At cruise speed, most of the loss is through aerodynamic drag. This will most definitely hurt efficiency in a big way. |
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What you'd have is a very long bumper car 'rink' (is
that what they are called?) with a lot of dead
pedestrians and cyclists smushing around amongst the
cars who are loving bashing into each other. |
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Bumper cars are great fun when you are in a funfair and crashing into each other at about 5mph but once you start doing 30mph+ an inflatable bumper will be much less effective. It would probably reduce damage/injury, but you'd still end up with wrecked cars and casualties. |
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A brief study on the subject of elastic collisions would show that an inflatable bumpered car, colliding with a pedestrian, will often result in the pedestrian being thrown away from the collision at a speed considerably greater than the speed of the car. |
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Result = casualties UP by 95%. |
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[Twizz] Not obvious to me why that would increase
injuries. Can
you explain? You seem to know something about the
topic. |
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Let's suppose the collision is so elastic that the kinetic
energy gets transferred to the pedestrian without causing
any injury. The pedestrian then flies through the air, and
is decelerated inelasticly by the pavement, suffering
injuries as a result. Why does this do more injury than
cutting out the middleman, i.e. having the car do the
same as the pavement (albeit with opposite
sign)? |
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If the collision with the car isn't perfectly elastic, then the
pedestrian suffers some injury from the initial collision,
but also flies a shorter distance, and suffers less injury on
encountering the pavement. |
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If we assume a perfectly spherical chicken, it should all
balance out, no? |
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only if the chicken is of uniform density... |
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mouse; almost any car will deform plastically to some degree on collision with a pedestrian. The fact that it is possible to kick a dent into the front of a car without injury illustrates this point. |
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So, the best case scenario is that on collision, the difference in speed between the car and the pedestrian is accounted for by a uniform acceleration of the pedestrian (and slight deceleration of the car) spread over the maximum possible distance by yielding of the car's body panels. The car and pedestrian then slow (as the car is presumably braking) to a halt. |
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The worst case is for the collison to store energy in the elastic medium of the bumper and that energy to accelerate the pedestrian, potentially to a speed much greater than the speed of the car. The pedestrian then has a great deal of kinetic energy to dispose of. This will happen on contact with the largely non-compliant scenery (road, trees, walls etc.) |
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While it is true that there would be less injury at the point of collision between car and pedestrian, there would be more at the time when the pedestrian comes to rest. |
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The vast majority of injuries happen in car-to-car
collisions. |
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[Twizz] Ah, I see. Would this idea work better if the
bumpers were filled with, say, Play-Doh? Or, more realisticly,
if the bumpers were vented? |
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Seems like the problem you raise must have been solved in
the case of airbags. (Or else the passeger really does
rebound violently off the airbag and the whole benefit of
airbags is that the inelastic collision is with your occiput
rather than your face.) |
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//If we assume a perfectly spherical chicken// |
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Mouse - yes, holes in the bumpers would allow energy to be absorbed by the inelastic displacement of gas. This is the case with airbags. |
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//the best case scenario is that on collision// |
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//the whole benefit of airbags is that the inelastic
collision is with your occiput rather than your
face// |
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I just wanted to see these two quotes in the same
anno. Grim. |
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Re:second quote:I'd rather have the occiput absorb
the collision than any part of me. They just grow
their legs back, I'm pretty sure...oh, wait, that's
starfish. Never mind. |
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