Twice a year, most Americans adjust their clocks for Daylight Saving Time (DST). While “falling back” in autumn is often welcomed, the “spring forward” transition in March can have a surprising – and dangerous – side effect: an increase in car accidents.
So, are there really more crashes during Daylight Saving Time? Research suggests the answer is yes – especially in the days immediately following the spring time change.
What the Research Shows
Multiple studies have found a measurable rise in serious crashes after the clocks move forward.
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A widely cited study found a 6% increase in fatal car accidents during the workweek following the spring DST shift
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This translates to roughly 28 additional traffic fatalities each year in the United States
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The increase is most noticeable in the morning commute hours, when drivers are adjusting to lost sleep
These findings have been supported by research published in scientific journals and reported by sources like Insurance Institute for Highway Safety and academic studies available through National Institutes of Health.
Why Does “Spring Forward” Increase Accident Risk?
The main culprit isn’t darkness or traffic – it’s sleep disruption. When clocks move forward by one hou, most people lose sleep. Even just one hour can have meaningful effects on the body and brain.
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Sleep Deprivation. Driving while sleep-deprived can be comparable to driving under the influence in terms of reduced cognitive performance.
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Disrupted Circadian Rhythms. Your body runs on an internal clock known as the circadian rhythm. This biological mismatch is a key reason accident rates spike right after the time change.
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Increased Fatigue During Commutes. The morning commute is where the danger is most pronounced. Drivers are adjusting to less sleep, Roads are often busier during weekday mornings, and Reduced daylight in early mornings (right after the shift) can also play a role.
What About the Fall Time Change?
Interestingly, the opposite shift – when clocks “fall back” – does not show the same increase in fatal crashes. In fact:
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Gaining an extra hour of sleep can slightly reduce fatigue-related accidents
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Some studies suggest improved safety outcomes, particularly in the short term
However, darker evenings in the fall can increase risks for pedestrians, even if driver fatigue is reduced.
How Long Does the Risk Last?
The increased crash risk is typically short-lived but significant.
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The biggest spike in accidents occurs during the first workweek after DST begins
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Most people adjust within a few days to a week
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However, even temporary increases can result in dozens of preventable fatalities nationwide
In Summary
Yes – there are more car accidents during Daylight Saving Time, particularly after the spring “forward” shift.
A combination of sleep deprivation, disrupted circadian rhythms, and fatigue leads to a measurable increase in fatal crashes, with studies showing a 6% rise and dozens of additional deaths each year.
While the time change may seem minor, its impact on driver safety is very real.
