10-Foot Traffic Lanes Are Safer—and Still Move Plenty of Cars

At first glance, it makes sense that wider traffic lanes could be safer traffic lanes. Drivers are prone to bad decisions and sleepiness and text messages and fits of rage. Providing some buffer room seems a reasonable way to keep them from veering into anything else sharing the road.

But as Jeff Speck persuasively argued during our Future of Transportation series, the conventional engineering wisdom that favors 12-foot traffic lanes to 10-foot lanes is deadly wrong—especially for city streets. The problem largely comes down to speed: when drivers have more room, cars go faster; when cars go faster, collisions do more harm. The evidence cited by Speck on the safety hazards of wider lanes is powerful, though to date it remains pretty scarce.