Does Daylight Saving Time Cause Auto Accidents?

(shotbydave / Getty Images)

Each March, 48 of the 50 states shift their clocks an hour forward to daylight saving time (DST). The change officially happens at 2 a.m. on the second Sunday in March, and remains in place until the first Sunday in November. In essence, the clock shift takes an hour of daylight away from the morning and gives it to the evening.

Studies suggest that it also costs lives, particularly during the first several days after the nation “springs forward” an hour. A 2014 study by the University of Colorado Boulder shows a spike in fatal automobile collisions during the six days following the shift, and pins the cause as “shifting ambient light reallocates fatalities within a day, while sleep deprivation caused by the spring transition increases risk.”

In short, it takes drivers nearly a week to adjust to the darker morning commutes, but the main cause is that at the same time they are less alert due to the sleep deprivation caused by the loss of an hour of sleep.

Austin C. Smith, who authored the study, contends that there were 302 traffic fatalities attributable to daylight saving time over the 10-year sample period. That’s a 6.3 percent increase in fatalities over the six days following the time change.

Data from Canada’s Manitoba Public Insurance in 2014 showed a 20 percent increase in crashes on the Monday following the start of daylight saving time compared to all other Mondays in 2014. However, the small sample size of the study and lack of information about other variables, such as weather, makes it hard to draw concrete conclusions from the Canadian study.

Some studies suggest that transitioning to year-round daylight saving time would create a small but significant reduction in pedestrian and motor vehicle occupant fatalities in the United States. A study by Rutgers University professors Douglas Coate and Sara Markowitz concludes that pedestrian fatalities would be reduced by 171 per year, while motor vehicle occupant fatalities would be reduced by 195 per year if year-round DST was implemented.

On the opposite side of that argument is the National Parent Teacher Association (PTA), which lobbied against the 2007 expansion of daylight saving time due to safety concerns with children traveling to school in the dark.

History of Daylight Saving Time                                       

It is Benjamin Franklin who is often credited with the concept of daylight saving time. He viewed it as a way to maximize the work that could be achieved in the daylight. Alas, Franklin’s idea was never taken seriously, and there wouldn’t have been an easy way to implement it during his era anyway.

Daylight saving time, as we now know it, was devised as a way to save energy used in lighting. It was employed in both World Wars I and II, and its implementation was standardized nationwide in 1966, though it allows states to opt-out.

Before Congress stepped in, communities were allowed to choose DST or not, and at one point, even the Twin Cities, Minneapolis and St. Paul, Minnesota, were on different clocks. It was chaos for bus companies and airlines, so the federal government stepped in with a common start and stop date. Plus, they eliminated local issues by disallowing individual cities and counties from choosing to use daylight saving time or not. It’s now decided on a state-by-state basis. Only Arizona, Hawaii, and some U.S. overseas territories don’t follow the annual shifts to DST and back.

The underlying reason for the adoption and expansion of daylight saving time as an energy saving strategy is now being questioned, with studies indicating that it might have the opposite effect as once thought. Much of the energy used in the evening is now used for air conditioning, rather than lighting (which is becoming more efficient). If you extend evening daylight hours, home air conditioners have to run longer, consuming copious amounts of energy.

So, How Can You Stay Safe?

The answer is simple, go to bed early on the night of the time change, get plenty of sleep, and remain vigilant of fatigued drivers for the next several days. Pay particular attention to trucks, as their drivers may not work traditional hours, and may not have had the weekend to adjust to the time change. Statistically speaking, there's another benefit to going to bed early on Saturday night – you’ll avoid the hours that you’re more likely to be killed by a drunk driver.