Originally Posted by
FBinNY
If you're going to argue physics, you have to keep the facts straight. The vehicle's weight (compared to other vehicles) makes much less difference than you imply.
What matters most is it's speed and angle of impact. While there's marginal difference between the effects of being hit by a 6,000# vehicle and one half it's weight, there's a great difference between one moving at 40 vs. 30mph
However, as you point out, shape is critical. The difference in grill/hood height of SUVs and trucks vs. that of typical cars determines whether you'll tend to be lifted allowing the car to slide under you, vs. being driven forward and/or down.
IMO the difference in fleet mix accounts for a large part of the difference in consequences, though it wouldn't factor in the number of crashes.
If you double the weight, you double the kinetic energy. I don't think a linear relationship is marginal. Yes, the other effects of size and speed may by themselves have larger effects, but it's the interaction of shape, weight and speed that's making US vehicles especially deadly when compared to the averages for other countries.
I'm not sure if it does factor into the number of crashes, but it does factor into the severity of injury.