The Need for Speed

I saw an article today about stepped up speed limit enforcement in my hometown. Apparently, authorities regularly excuse speeding up to 10 mph over the limit, focusing on the most egregious speeders. That squares with my experience, which usually involves tacking the cruise control to 10 over on the interstate. I've never been pulled over.

But the issue of speed limits un-enforced begs a question. Why a limit at all?

The state of Montana eliminated daytime speed limits several years back before re-imposing them to prevent out of state drivers from coming to test their maximum speeds. A follow-up analysis shows accident rates were lower when the freeways were limitless. The very libertarian Cato Institute noted the same effect nationally. "The injury rate per 100 million vehicle miles traveled fell to its lowest level ever recorded in 1997," two years after the national 55 mph speed limit was repealed and many states raised their limits.

Furthermore, other studies show that decreasing or increasing speed limits by as much as 15 mph has little effect on motorists actual speed. In other words, people drive the speed they feel comfortable going. The German Autobahn experience shows that this works - accident rates in Germany are even lower than in the United States.

So why do we have limits? The Minnesota Department of Transportation says (link to pdf) that it's to maintain traffic flow to prevent accidents. But studies show that no limits means fewer accidents.

I'd say the traffic engineers are losing the battle to human experience. When the average speed on a given highway exceeds the posted limit by 10 mph, the collective experience of the millions of annual drivers knows better than an engineer. Furthermore, speed limits actually cause more traffic flow problems than they solve because slow drivers feel entitled to be in the passing (left) lane as long as they are going the speed limit (because obviously no one should be going faster).

Speed limit enforcement is a waste of time and money. If we nab those who drive recklessly or are impaired, we'll get the baddies. Going fast is no offense.