Each 10 percent reduction in weight improves the fuel economy of a new vehicle design by approximately 8 percent. The result was a CAFE-driven downsizing of approximately 500 pounds per car. Smaller cars, however, are less crashworthy than similarly equipped large cars in practically every type of accident. The overblown nature of that threat is demonstrated by a study issued last month by the Insurance Institute for Highway Safety. Journalists widely reported the study as re-emphasizing the need for action against SUVs, but its findings indicate otherwise.
Cars are most vulnerable in side impact collisions.
But when this relative risk is broken down by car weight categories, it turns out that car-SUV mismatches are frequently outweighed by other common collision disparities. That is, there is a greater mismatch between light cars and heavy cars than there is between heavy cars and SUVs. What this means is that upsizing the car fleet may well be the most important step we could take toward improving safety. But upsizing, of course, is what CAFE currently restricts. And the effect of this passenger car upsizing was found to be statistically significant, unlike the SUV downsizing.