The twice-yearly time change is not a major factor in America’s ongoing road safety, according to David Harkey, president of the Insurance Institute for Highway Safety (IIHS). Speaking at a congressional hearing on April 10, he said: “Whatever you decide to do about the clock, I hope you will also consider actions to keep pedestrians and bicyclists safe, especially after sundown.”

Harkey’s comments came in written testimony submitted to the U.S. Senate Committee on Commerce, Science and Transportation, which convened the hearing on whether to continue switching back and forth between daylight saving and standard time every year.

Harkey told the Senate committee that changing the clocks twice a year is relevant to road safety because it affects the amount of ambient light during peak times for travel. We know that darkness is associated with an increased risk of fatal crashes. According to data from the National Highway Traffic Safety Administration and the Federal Highway Administration, less than a quarter of trips begin during nighttime hours, but nearly half of motor vehicle occupant deaths and 77% of pedestrian deaths occur in the dark.

Obviously, adjusting the clock cannot increase the number of daylight hours, but it can only shift how they align with work and school schedules. Because people travel at all times of day and the risk created by darkness varies by the types of road users, the effects of these time changes on crashes are complex.

A recent IIHS study of morning and evening crashes in the weeks surrounding the time change showed that pedestrian fatalities fall while vehicle occupant fatalities rise with the conversion to daylight saving time. When standard time resumes, vehicle occupant deaths drop and pedestrian deaths rise.

Notably, the fluctuation in pedestrian crash deaths was tied to increases or decreases in the amount of daylight, while there was no clear connection for vehicle occupant fatalities. We should keep in mind that an extra hour of light on one end of the workday is counterbalanced by an extra hour of darkness on the other end.

“If you are looking for concrete guidance on whether to keep the current twice-yearly time changes, the evidence does not point definitively one way or another,” Harkey said. “What our study does reinforce is that pedestrians and bicyclists are at greater risk in low light conditions.”

Harkey urged the committee members to focus on solutions known to be effective in combating that problem, such as infrastructure improvements, such as crosswalk lighting, rectangular rapid flashing beacons, which were installed several years ago on U.S. Route 11 in Malone and pedestrian hybrid beacons. Lower speed limits and other measures to reduce vehicle speeds, such as speed safety cameras and road features that force drivers to slow down, could also play a key role.