I think there's a lot of factors going into the Prius (and other compact cars) safety record. As orange4boy said, 10,000 people die each year in SUV rollovers. What percent of the vehicle fleet is SUV's versus compact cars? I'd like to know percent of deaths in SUVs versus that of compact cars (like for every 1000 SUVs the death rate is .05 or something, then the same measure for compacts) that would give an apples to apples comparison.
The argument of whether a small car is as safe as a truck/SUV keeps coming up. Why? A quick look at the physics seems conclusive. The human body suffers damage as a result of the -impulse- sustained in a collision. The change in momentum (mass times velocity) over a short time span exerts tremendous forces on human tissue, ie neck, brain, chest, organs). The less change in velocity you have during an accident the better your survival rate is (thus why people walk away from a 10mph parking lot bump). Extending the
same change in velocity over a slightly longer time span also results in large reductions in the forces applied to your body. In a head-on collision of two vehicles traveling at the same speed:
For an elastic collision (kinetic energy conserved, like billiard balls, its not but assume)
The heavier vehicle -always- maintains more of its initial velocity (and thus, less impulse on the occupants)
For an inelastic collision (kinetic energy not conserved, but momentum is, more like a car accident)
The heavier vehicle -still- maintains more of its initial velocity (and thus, less impulse still) than the smaller car.
Go ahead, check it out, Georgia State University says so:
Standard Collision Examples
Put in your own values for masses, and velocities... you always want to be riding in the vehicle that sustains a smaller impulse. And this does not take into account the smaller crush zone available on the small car, which compounds the impulse problem. Nor does it account for the point of impact problem. (If my Silverado T-boned a Prius the truck bumper is about level with the door handle, mostly passing over the Prius' relatively rigid door rail and floorboards).