Each year in the U.S., the shift in Daylight Saving Time (DST) impacts the daily lives of millions—students, pedestrians, professionals, emergency responders, heavy vehicle operators, and even wildlife. Whether you’re well-acquainted with the clock change or newly adjusting, we’re tackling a crucial question: Does DST increase risks on the road and contribute to accidents?

What is DST?

Daylight Saving Time, or DST, is the twice-yearly clock change where time is moved forward in spring and back in fall. This practice, observed across much of the United States, aims to extend daylight hours in the evening, resulting in darker mornings. While DST’s benefits are still debated, it impacts more than just our schedules—affecting sleep, health, productivity, and, as we’ll see, road safety.

The Origins of DST

The idea of DST can be traced to Benjamin Franklin’s 1784 satirical suggestion to wake earlier to conserve candles. In 1895, New Zealand scientist George Vernon Hudson formally proposed a two-hour shift, followed in 1905 by British builder William Willett, who advocated moving clocks forward in summer for longer daylight. Though Willett’s idea gained some traction, it wasn’t implemented in his lifetime. In the U.S., DST finally became standardized with the 1966 Uniform Time Act, which established federal oversight while allowing regional adjustments.

Is DST dangerous for drivers?

Short answer: Yes. On average, accidents increase by about 6% in the week following the shift to Daylight Saving Time (DST). Studies consistently show this rise in traffic incidents, particularly fatal ones, linked to factors such as sleep deprivation and disruptions to circadian rhythms

A) Sleep Deprivation & Health Factors

During DST, we lose an hour of sleep.

According to researchers at the University of Colorado Boulder, fatal car accidents in the United States increase by about six percent during the first workweek after the spring daylight saving adjustment.

In the second week following the change, the rate of fatal accidents starts to decline.

By the third week, accident rates return to their typical levels—though no fatality should be seen as “normal” (which is exactly the aim of Vision Zero).

Many people cope with the lost hour by skipping sleep, which impairs their driving ability. Sleep deprivation negatively affects reaction time, decision-making, and general alertness, increasing the likelihood of crashes. Alarmingly, spring daylight saving can also result in more afternoon accidents, even when there is more daylight, likely due to sleep loss.

Drowsy driving is a serious safety concern, and studies have shown that it can be as dangerous as driving under the influence of alcohol. A recent study discovered that people living in the western edges of time zones, such as Amarillo, Texas, and St. George, Utah, face an increased risk of fatal car crashes. Specifically, these individuals had an approximately 8% higher likelihood of being involved in fatal accidents. This heightened risk is partly due to the fact that they get around 19 minutes less sleep compared to those living in the eastern parts of their time zone, since the sun rises and sets later.

Chronic sleep deprivation, even caused by just an hour of lost sleep during Daylight Saving Time (DST), can lead to a surge in stress hormones that increase heart rate and blood pressure, as well as trigger inflammation. This disruption in sleep patterns worsens the body’s overall health, especially when the shift in time causes a misalignment between the body’s internal clock and the natural sun cycle. Dr. Nathaniel Watson, a neurology professor and sleep expert, explains that DST feels like a permanent form of jet lag for the entire population, as our biological and social clocks are out of sync. Research has shown that this misalignment has negative effects on both physical and mental well-being.

Health Issues

Losing an hour of sleep during the daylight saving time shift can indeed be jarring, and experts suggest several ways to mitigate the negative effects. According to sleep and depression specialists, the U.S. is facing an epidemic of sleep deprivation, which is worsened by the change in time.

Dr. Avery, an expert on seasonal affective disorder (SAD), explains that the time change exacerbates conditions like winter depression, as people with SAD experience significant struggles with their circadian rhythms. For those affected, the transition to daylight saving time means they’re waking up when their body is naturally at its lowest core temperature—around 5:30 a.m. This shift makes it harder for them to feel rested or alert. Research has shown that daylight saving time can lead to more heart attacks, strokes, and car accidents the day after the time change.

Interestingly, Dr. Avery mentions a failed experiment in Russia where permanent daylight saving time was implemented for three years. During this period, academic performance worsened, and people reported more severe symptoms of winter depression due to the lack of morning light, which is essential for regulating sleep cycles. As he notes, without the morning light to kickstart daily routines, people who are naturally more alert in the evening struggle to function.

B) Light Conditions

This past Sunday, November 3rd, clocks across Seattle and the entire coast were adjusted.

November 2nd, 2024: The official sunset in Seattle occurred at 17:49 p.m.
November 3rd, 2024: After the time adjustment, sunset in Seattle was at 16757 p.m

Spring daylight saving time also results in suddenly darker morning commutes for many people. On the following two dates in 2024:

March 8th, 2024: The official sunrise in Seattle occurred at 6:35 AM.
March 11th, 2024: The sunrise in Seattle happened at 7:29 AM.

Many citizens have all or part of their morning commute in the dark. While there are generally more accidents during daylight hours, darker mornings tend to increase the number of accidents per mile driven. This is primarily due to reduced visibility and the possible fatigue from the time change, making drivers more prone to errors, especially on less illuminated roads.

C) Deer Activity

In the United States, the issue of deer-vehicle collisions (commonly referred to as the “deer issue”) is an annual danger exacerbated by time shifts, which align with peak deer activity. Given the vast stretches of rural roads and highways that many people travel across, this becomes a recurring and dangerous situation. As the clock moves forward or backward, the overlap between human commutes and deer movements creates a risk that can be mitigated by permanent changes to daylight saving time.

Permanent DST would reduce deer-vehicle collisions, according to a University of Washington study:
- - Estimated 36,550 deer deaths could be prevented.
  - Estimated 33 human deaths and 2,054 injuries would be avoided.
  - $1.19 billion in costs would be saved each year.
  - 2.1 million deer-vehicle collisions occur annually in the U.S.
  - These collisions kill about 440 people and cause 59,000 injuries, totaling more than $10 billion in damages.
The relationship between human and deer activity:
- - Deer are most active around dawn and dusk, making these times high-risk for collisions.
  - Collisions are 14 times more frequent two hours after sunset than before.
  - Fall rut increases deer activity by up to 50%.

Impact of permanent standard time:
- - A shift to permanent standard time would increase deer-vehicle collisions by 73,660, with 66 more human deaths and 4,140 more injuries.
  - It would add $2.39 billion in costs.
  - Conversely, permanent DST would result in a 2.3% decrease in deer-vehicle collisions, reducing risks over the full year.

Deer-related risks:
- - In deer-populated areas, the risk of harming both wildlife and yourself is 14 times higher at night.

Pedestrian Crisis

According to research from the Arlington Insurance Institute for Highway Safety, the shift to Daylight Saving Time (DST) has mixed effects on vehicle crashes. The added daylight during the morning commute helps decrease vehicle crashes, but the twilight in the evening tends to increase accidents.

Sue Ferguson, a researcher for the Institute, highlights that switching to Standard Time results in more fatalities on the roads, which is why there are recommendations to extend DST and start it earlier in spring. A study suggests that over five years, around 900 fatal crashes could be avoided if DST were year-round. Of these, 727 would be pedestrian fatalities. Ferguson notes that extending DST by just one extra week in the fall and three in the spring could save an additional 250 lives during that period.

This information is based on studies conducted by the Insurance Institute for Highway Safety, illustrating how changes in time can significantly impact road safety, particularly for pedestrians.

What can help you sleep better and avoid traffic accidents?

To sleep better and reduce the risk of traffic accidents, consider the following strategies:

Gradually Adjust Your Sleep Schedule: Start going to bed 15 minutes earlier each night leading up to the time change (e.g., 2 a.m. during Daylight Saving Time). This helps your body adjust gradually, making it easier to adapt to the shift.
Use a Dawn Simulator: Consider using a dawn simulator or a progressive light alarm clock, which gradually simulates sunrise. This method helps regulate your circadian rhythm and improve sleep quality. Once awake, spending 20 minutes under a bright light box can further aid in resetting your body clock.
Maintain a Consistent Sleep Schedule: Aim to go to bed and wake up at the same time every day, including weekends. Consistency helps your body naturally align with its sleep-wake cycle, which can improve sleep and alertness.
Avoid Stimulants and Alcohol: Avoid caffeine for at least six hours before bedtime. Some people may need to stop even earlier. Additionally, limit alcohol consumption, and refrain from drinking for at least three hours before bed to ensure better sleep quality.
Exercise Regularly, But Not Before Bed: Regular exercise can improve sleep, but try to avoid intense physical activity close to bedtime, as it can make falling asleep more difficult by raising your heart rate.

By following these strategies, you can improve your sleep and reduce the chances of being involved in a traffic accident due to fatigue or sleep deprivation.

Does DST Make The Roads More Dangerous For Drivers and Pedestrians?