When the speed limit is lowered in an area, it’s usually in an effort to improve safety. Reducing the speed limit too much, however, may actually cause more crashes, according to a group of Penn State researchers.
The study found reducing speed limits by 5 mph decreases the amount of total and fatal crashes.
The catch, however, is reducing speed limits by 10 mph or more has the opposite effect because drivers “stop paying attention,” according to Penn State assistant professor of civil engineering Vikash Gayah.
The group collected the data in Montana, a state that posts speed limits lower than engineers recommend.