Newtonian traffic safety

Jan. 5, 2004
The sport utility vehicle (SUV)—beloved object of a peculiarly American escalation of mass on the roadway—will get a political workout in 2004.

The sport utility vehicle (SUV)—beloved object of a peculiarly American escalation of mass on the roadway—will get a political workout in 2004.

An election year already has aroused the passions of SUV haters, who consider the appetites of these boxy roadsters for fossil energy to be nothing less than social injustice.

In service to this view, sympathetic politicians recently have talked about tightening fuel-economy standards for SUVs.

Yet SUVs are wildly popular in the US. They're so popular, in fact, that any move to shrink them, which a tightening of fuel-economy standards would require, would surely start a political fight.

SUV haters believe the social benefits presumed to accompany any reduction in fuel consumption warrant a restriction on the freedom of people to buy the outsized vehicles so many of them obviously want.

SUV lovers counter the fuel-consumption argument with safety. Big vehicles are safer than small ones, they insist. That sincere belief surely underlies the desire of many SUV buyers for mass.

Safety vs. economy

As commonly articulated, then, the issue comes down to safety vs. fuel economy.

But that formulation has problems, not least of which is that it omits the question of freedom of people to buy what they want.

It also takes a dangerously narrow view of safety. And it forces safety and fuel economy into needless conflict.

A broader view of the issue is in order.

In the interest of disclosure, this writer confesses that he doesn't and won't own an SUV. That's an aesthetic and economic judgment, not a moral one. This writer thinks people who want to drive around in barns should be free to do so if they're willing to pay the upkeep.

By the same token, people who don't want SUVs shouldn't feel compelled to buy them in self-defense. The mass that confers safety to people inside an SUV also jeopardizes people outside it.

Streets and highways do not automatically become safer as average vehicle size grows. To defend SUVs on the basis of safety is persuasive only to SUV drivers.

Safety, in fact, comes less from the size of a vehicle than from how it is driven. Too many vehicles are driven carelessly, including too many SUVs.

Discussions of vehicle safety shouldn't ignore the chronic recklessness of American driving. It's this fact of life on the road that makes many drivers, understandably fearful, want to armor themselves.

What the US needs is a system that both encourages fuel-use efficiency and promotes safety without compromising personal choice.

The key lies in a deeper reading of Newtonian physics than the one that underlies the safety argument advanced on behalf of SUVs.

Yes, mass can be protective in a collision. But the force of impact increases as a function of speed and mass.

If you drive an SUV, you will do more damage in a collision at a given speed than if you drive a compact car. Isaac Newton proved it.

So what if traffic laws accommodated this law of motion? What if traffic laws calibrated penalties to mass?

It could work like this: There would be a baseline vehicle weight. It might be, say, the national average vehicle weight for a given year.

Penalties for traffic violations involving speed would be indexed to that weight.

If you drove a vehicle that weighed 20% more than the baseline, your penalty for a speeding ticket would be 20% more than the index, which is what someone driving a vehicle of exactly the baseline weight would pay for the same infraction.

If you drove a vehicle 20% lighter than the baseline, your penalty for the violation would be 20% less than the index.

Mass matters

It wouldn't make any difference what type of vehicle you drove. What mattered would be mass. The law under this system would imply that the more vehicle you drove, the more you would pay if you drove recklessly.

If traffic penalties varied as a function of the potential to inflict damage, the potential cost of driving large vehicles would rise for reasons other than amounts of fuel consumed.

That new economic factor would affect vehicle-purchase decisions without usurping freedom. It also would affect the handling of heavy vehicles.

This is just an idea with ramifications worth thinking about. And it's offered here free to any political candidate wanting to stir things up.