In response to the possibility that fuel-economy regulations might be strengthened, safety experts of major US manufacturers, the National Highway Traffic Safety Administration, the Insurance Institute of Highway Safety, and a 2001 study at the National Research Council have concluded that light vehicles are fundamentally less safe than heavy vehicles. ... However, attributing the safety records of today’s vehicles primarily to their masses is misleading. The average heavier vehicle tends to be more protective of its occupants also because of its size, higher general quality, and the incorporation of more recent safety features. ... We have found that among cars, risk correlates much more strongly with the blue-book price of the used car than with its mass.

Robert Zobel, head of accident research at Volkswagen, has analyzed the safety of front-to-front crashes of car models that have “passed” the standard frontal crash test ... two cars could, in principle, safely dissipate their combined kinetic energy if their closing speed is less than 70 mph, independent of their masses.

But there are two important caveats. First, if one car’s front is unnecessarily stiff, the other car may have to absorb so much of the energy that its passenger compartment is compromised. Second, if the fronts of the colliding cars are not sufficiently similar and homogeneous to assure so-called structural interaction in a head-on crash, there may be penetration into the passenger compartment. ... The disparity in height, stiffness, and mass between light trucks and passenger cars is a major safety issue. On a pickup or SUV, the height and localized stiffness of its front is particularly hazardous for others. The typical pickup truck chassis shown in figure 7 has two horizontal “rails” that are high and extend far to the front. Pickups and body-on-frame SUVs impose high risks on occupants of other vehicles.

... we have estimated that replacing with passenger cars all the light trucks in the US that are used only as “car substitutes” would save three to four thousand lives a year.