Study: Higher Freeway Speeds Increase Crashes on Adjacent Roads

A new study reveals that increased speed limits on interstate freeways have a rippling effect, raising the number of speeding-related crashes in adjacent neighborhoods.

As Kea Wilson explains in Streetsblog USA, “In an analysis of three U.S. highway segments whose maximum speeds were increased at some point in the last decade — I-85 in Georgia, I-84 in Oregon and I-75 and I-69 in Michigan — researchers found that all reported significant new "clusters" of speeding-related crashes within a one-mile radius of the interstate.”

The findings belie the popular belief that interstate speeds don’t affect people traveling on other roads — including pedestrians and cyclists who never enter freeways. According to Dr. C.Y. David Yang, president and executive director of the AAA Foundation for Traffic Safety, “similarly to the ‘distraction hangover’ that drivers experience even after they stop using a cell phone behind the wheel, motorists don't immediately register just how quickly they need to slow down after they exit the interstate — especially when local roads themselves are designed like highways where it's perfectly fine to go fast.”

Wilson points out that interstate routes and speed limits are controlled at the state level, giving local communities little say in the process. “While Yang stops short of saying that speed limits should never be raised on the highway, he says it's critical that stakeholders like state, county, and city departments of transportation communicate in advance of those increases, so the locals can take action to slow drivers down, like modifying road designs.”