Iowa study on raising the state's speed limit

Aug 20, 2013

Critics of the new speed limit say it will increase the level of accidents and fatalities on Illinois roads. One man who studied the impact of Iowa’s switch to a 70 mile-per-hour speed limit says that seems to be the case, but there are other factors involved.

Civil Engineering professor Reg Souleyrette led a study at Iowa State University, that looked at the impact of Iowa’s 2005 speed limit increase. He says the state-funded study compared traffic accidents in the four years before and four years after the speed limit increase.

“And we found that fatal crashes went up by 29 percent. And that’s a fairly high percentage, but the average year-to-year variation can go up or down by 21 percent. So it’s only slightly higher than what we expect to see going up or down on a year to year basis.”

And Souleyrette, who’s now at the University of Kentucky, says the number of accidents went up more than the number of fatalities, meaning that the percentage of accidents resulting in deaths went down.

Still, Souleyrette says some types of crashes went up dramatically in Iowa. Nighttime crashes went up 45 percent and cross-median crashes went up 52 percent.