Car Crash Risk Increases Shortly After Daylight Saving Time Changes: Study

New research indicates the biannual changing of the clocks for Daylight Savings Time is associated with a six percent increase in fatal motor vehicle crashes, warning that the adjustment period of the time change leaves motorists more susceptible to crashes.

The study was published in the journal Current Biology on January 30. Researchers from the University of Colorado identified a trend of increased motor vehicle fatalities within the week following the forwarding of the clock for Daylight Savings Time, suggesting the reduced natural lighting during the morning rush hour commutes is the likely cause.

Researchers reviewed data from the U.S. National Highway Traffic Safety Administrations (NHTSA) Fatality Analysis Reporting System (FARS) from 1996 to 2017, and identified 732,835 fatal motor vehicle accidents during the time period.

The study focused on the weeks surrounding the rewinding and forwarding of the clocks to determine whether there were any notable increases of motor vehicles fatalities, and discovered the week immediately after springing forward by one hour was associated with a six percent increase in fatalities.

The spike in motor vehicle fatalities following the “spring forward” is believed to be due to a combination of factors including sleep deprivation and circadian misalignment, which is a disruption of the cardiac rhythm that regulates sleep-wake cycles.

The data indicated most fatalities following the spring forward adjustment were in the morning, which could be attributed to the adjustment period drivers require to become comfortable with driving in darker conditions.

Researchers indicated no significant increases in motor vehicle fatalities were found in relation to springing forward evening hours, nor were any noted for rewinding the clocks.

According to the National Highway Traffic Safety Administration (NHTSA), drowsy driving causes approximately 4 million automobile crashes annually, resulting in about 6,000 fatalities. In addition to the lives lost, drowsy driving is anticipated to cost the nation an estimated $109 billion each year.

Drowsy driving has consistently been one of the nation’s largest contributing factors to motor vehicle crashes and fatalities, with the American Automobile Association (AAA) previously reporting drowsy driving increases a person’s risk of being involved in an auto accident. The organization has also found numerous similarities between drowsy driving and drunk driving such as impaired attention, impaired mental processing, judgment and decision making.

Late last year, the American Academy of Sleep Medicine (AASM) released the results of a survey and found 45% of adults admitted to driving drowsy, which may place themselves and others on U.S. roadways at risk.

AASM polled more than 2,000 participants on whether they have ever driven drowsy, highlighting the widespread problem of drivers operating motor vehicles while they may be too tired to effectively avoid a crash.