Our Our Traffic Dangers Linked to Daylight Savings Time study examines how the spring transition to Daylight Savings Time (DST) affects motor vehicle accident risk across the United States.
Data from sources like the National Highway Traffic Safety Administration (NHTSA) and Current Biology show a sharp increase in fatal crashes immediately after the time change, especially in the morning and in western regions of time zones.
Sleep deprivation and circadian misalignment appear to be major factors in this heightened risk. Losing an hour of sleep can disrupt one’s sleep and lead to slower reaction times, reduced alertness, and more dangerous road conditions.
This study also explores the broader financial and public health effects of DST, including increased insurance claims and spikes in heart attacks. Unlike the spring transition, the fall return to Standard Time does not show the same adverse effects. As discussions on abolishing DST continue, these findings provide critical insights for future policy decisions.
DST Participation and Circadian Disruptions
Currently, 48 states, including Washington, DC, observe DST, while Arizona and Hawaii remain on standard time permanently. Every spring, most of the country loses an hour of sleep, disrupting natural circadian rhythms. This shift contributes to drowsiness and slower reaction times for both drivers and pedestrians.
According to data reviewed from NHTSA, between 2% and 20% of annual traffic deaths are linked to driver drowsiness. The spring DST transition intensifies this risk, making roads more dangerous in the days following the time change.
Morning commutes are especially hazardous, with fatal accident risk spiking by as much as 47% before noon in the first week. Several studies highlight how even a single lost hour of sleep can significantly impact alertness, increasing the likelihood of crashes.
Key Data Points
To illustrate the scope of the problem, here are the primary statistics we analyzed:
- Six percent increase in fatal traffic accidents: A 2020 Current Biology study analyzing over 700,000 car accidents from 1996 to 2017 found a 6% rise in fatal crashes during the first week after the spring DST transition.
- Eight percent spike on western edges of time zones: Our evaluation of data from Current Biology shows that people living on the western edge of a time zone see an even sharper climb, around 8%.
- Twenty–eight preventable fatal accidents annually: Our aggregated analysis suggests that doing away with DST could save about 28 lives each year.
- Morning hours are especially risky: Fatal accidents are notably higher in the early morning (4 AM–8 AM), when people who lose an hour may be sleep-deprived.
- Pedestrians at higher risk: Studies indicate a 68% increase in evening casualties for pedestrians. Darker afternoons coincide with peak walking times, reducing visibility and safety.
- The fall transition has no effect: Moving clocks back in autumn does not produce a comparable jump in crash fatalities.
We also observed that DST-related drowsiness can last up to a week, disrupting not only daily commutes but also the overall well-being of those forced to adjust to the sudden time change.
Impact on Public Health and Insurance
The consequences of circadian misalignment aren’t limited to the road. Various medical reports show a 24% rise in heart attacks on the Monday after we spring forward. This uptick in cardiovascular stress may relate to sudden changes in sleep patterns.
Similarly, our findings in a recent study of statistics from multiple sources suggest that insurance claims climb significantly the entire week after DST. These additional crash-related costs quickly accumulate, straining drivers and insurers alike.
Even pedestrians and cyclists pay a price. Reduced visibility in the evening and general fatigue can make roads especially dangerous, and the resulting accidents often lead to higher liability and medical insurance claims. In high-risk regions, rates may climb further, creating an economic burden that extends beyond individuals to the community at large.
Policy and Legislative Outlook
Legislative efforts to abolish DST or establish permanent Standard Time could help reduce fatal crashes. Permanent Standard Time aligns better with human circadian rhythms, preventing the sleep deficits that increase accident risk. States like Texas, Florida, and California have already proposed making this change, citing health and safety concerns.
Eliminating DST could also reduce the 5.7 additional fatal crashes per day that occur in the first week after the spring transition. Over the past 20 years, 626.9 fatal crashes during these workdays have been linked to DST-related fatigue.
Key findings supporting policy change include:
- 28 preventable fatalities per year if DST transitions were abolished.
- 47% increase in fatal crashes before noon in the first week of DST.
- 8% spike in fatal crashes in western regions of time zones compared to eastern regions.
- No significant increase in accidents after the fall transition to Standard Time.
If lawmakers need further motivation, the opportunity to prevent dozens of deaths each year should make this issue a priority.
Why It Matters Now
As of 2025, DST runs from March 9 to November 2. While a simple one-hour shift may seem minor, its effects can be deadly. Sleep deprivation and reduced visibility during peak travel times significantly increase the risk of fatal crashes.
Western regions of time zones experience an 8% higher fatal accident rate than other areas. This disparity suggests the need for policies that account for local sunrise and sunset times. Unlike the spring transition, the fall return to Standard Time does not show the same risks.
Rethinking DST could save lives, reduce health risks, and prevent financial burdens. The evidence points to a need for targeted changes that prioritize safety and well-being.
Creating Safer Roads by Rethinking DST
Daylight Savings Time is more than a twice-yearly inconvenience. Research shows that the spring transition causes a spike in fatal crashes, especially during morning commutes. This shift also affects public health, with a 24% increase in heart attacks and a surge in insurance claims.
The broader impact of DST extends beyond the roads. Disruptions to sleep cycles can lead to fatigue-related accidents, increased medical emergencies, and financial strain on individuals and communities. A Fort Worth car accident lawyer understands how these risks affect drivers and the legal challenges that follow.
Policymakers and community leaders should consider reforms that align timekeeping practices with human biology. Eliminating DST transitions could help save lives, prevent medical emergencies, and create safer roads.
