A study by the Insurance Institute for Highway Safety has shown that adding bollards and rubber curbs that prevent drivers from cutting across intersections at a diagonal can make streets safer for pedestrians.  A little more than half of all crashes involving pedestrians took place at intersections in 2018, resulting in more than 6,700 serious injuries to pedestrians and more than 1,500 pedestrian fatalities. In one of the more common scenarios, a driver making a left turn crashes into a pedestrian crossing the road the driver is turning onto. These left-turn crashes accounted for nearly a third of all pedestrian-involved crashes at intersections in 2018. A vehicle's speed in a pedestrian crash is correlated with the risk of serious injury. Left-turning vehicles don't travel as fast as those going straight, which account for more than half of all pedestrian fatalities at intersections. But the odds of a pedestrian sustaining a serious injury rise from 1 in 10 to 1 in 4 as the impact speed increases from 17 mph to 25 mph.

Installing "centerline hardening" devices at these intersections effectively blocks the diagonal path through the crosswalk, forcing drivers to turn more slowly at close to a right angle. In Washington, D.C., the infrastructure changes reduced the number of times drivers had to swerve or brake suddenly or pedestrians had to dodge out of the way by 70 percent, says IIHS Senior Research Transportation Engineer Wen Hu, the author of the paper.  "This study suggests that simple infrastructure changes can deliver big benefits," Hu says. "Communities looking for ways to make pedestrians safer should add centerline hardening to their toolbox."  The calming infrastructure also resulted in a reduction in average left-turn speeds and decreased the odds that drivers made the turn at speeds exceeding 15 mph.  New York City has used these methods at more than 300 intersections since 2016. The District of Columbia began a similar effort as part of its Vision Zero program in 2018, with plans to target 85 intersections by the end of this year. One turn-calming technique the city uses is centerline hardening, which consists of rubber curbs and bollards installed on the yellow center line.  Seeking to determine how effective the practice is, Hu collected data from 10 D.C. intersections over similar observation windows during two months before and three months after the infrastructure changes and compared them with eight control sites where no centerline-hardening features were installed. Hu found that the average turning speed dropped 7 percent after the installation of the centerline-hardening features. The average turning speed at the control sites increased 3 percent.  She also observed that the portion of drivers who made the turns at speeds greater than 15 mph fell 36 percent at the modified intersections.