Risk of Serious Car Accidents Drop with Daylight Saving Time: Study

The extra hour of light in the summer evenings leads to a reduction in auto accidents, researchers concluded.

New research has found there are fewer serious car accidents during daylight savings time, suggesting efforts to eliminate the transition back to standard time could also make U.S. roads safer, and reduce costs associated with property damage, medical expenses and insurance premiums.

In findings published last month in the journal Health Economics, researchers with the University of Surrey found that the rates of severe car accidents dropped nearly a quarter in the days closest to the daylight savings time transition. They also determined that minor road accidents increase during the autumn transition back to standard time, suggesting motorists may benefit significantly from additional hours of light while driving and an adoption of permanent daylight savings time.

Clocks throughout the U.S. “spring forward” each year at the beginning of day light savings, generally in early March, resulting in an hour less daylight during the morning and an extra hour of evening daylight. The return to standard time in early November, known as “fall back,” reverses this pattern, providing an extra hour of daylight in the early morning, but one less hour in the evening.

The findings are similar to prior research suggesting the natural lighting shifts between standard time and daylight savings time significantly affect motorists, making them more susceptible to crashes.

Health experts attribute this phenomenon to changes in motorist sleep patterns and circadian misalignment during daylight savings transition periods, making drivers drowsy as they adjust to the sudden natural lighting changes. A 2017 National Highway Traffic Safety Administration (NHTSA) study found that drowsy driving car accidents cause thousands of deaths and injuries annually.

More Evening Sunlight Linked to Fewer Serious Car Accidents

In this latest study, researchers examined Greek road accident reports between 2006 and 2016. The data included time, location, accident type, and severity (fatal, serious, or minor.)

Researchers found that serious car accidents decreased by 15-20% during the days closest to the spring transition to daylight savings time, and minor road accidents increased by 13% during days closest to the fall transition back to standard time.

The researchers attribute this disparity to the extra hour of sunlight afforded to drivers in the evening during daylight savings time; especially from 6:00 pm to 9:00 pm, an established heavy traffic period. They theorize that motorists are particularly sensitive to road lighting conditions, and the extra hour of natural evening light during daylight savings time improves their driving ability overall.

Researchers also determined that abolishing the fall standard time transition would result in a permanent decrease in serious car accidents, with corresponding cost savings. For Greece it would be about $8.2 million annually in property damage, insurance premiums, and medical bills, but that number would vary widely from country to country.

“Not transitioning back to Standard Time in the Autumn and keeping that extra hour of sunlight appears to not only be a lifesaver, but cost-effective for the taxpayer,” lead researcher Dr. Giuseppe Moscelli said, also noting in a University of Surrey press release that more artificial lighting in high accident zones could also help. “Our analysis suggests that changes in road accidents are not influenced by factors such as fuel prices or road usage but by lighting conditions. It begs the question of whether improving artificial lighting conditions in accident hotspots could improve outcomes for drivers.”