Permanent daylight saving time would move school travel into the dark for millions of children
Keeping daylight saving time in place all year would do more than preserve lighter evenings. It would push winter sunrise an hour later and send a large share of U.S. children to school before dawn, especially in states where morning schedules already run early. New analysis from the University of Washington estimates at least 2 billion additional school commutes in darkness if the United States adopted permanent daylight saving time nationwide. That is not an abstract timekeeping change. It is a daily exposure shift affecting children’s travel safety, morning light exposure, and the timing of family routines across the country.
The study focused on 14 states that have already approved permanent daylight saving time measures, then used school enrollment, start times, and geographic coordinates to estimate how often students would leave home before sunrise. Washington state alone would add nearly 35 million dark school trips. Georgia would see the largest increase among the states examined, with about 71 million additional commutes in darkness. Across Mississippi and Alabama, where many schools begin before 8 a.m., the change would be especially stark: each state already has about 2 million dark school trips under the current system, and permanent daylight saving time would push that figure beyond 20 million.
One sentence captures the practical effect: mornings would get darker for children almost everywhere.
Road safety risk rises when sunrise disappears from the morning commute
The strongest public safety concern is pedestrian injury. Traffic collision records in the United States show that fatal crashes involving school-aged pedestrians were roughly twice as likely during dark mornings as after sunrise. That pattern fits what is known about visibility, driver reaction time, and the vulnerability of children crossing streets near schools, bus stops, and neighborhood intersections. Morning darkness reduces the margin for error for drivers and pedestrians alike, and children are often moving through traffic when attention is still waking up on both sides of the street.
The risk is not evenly distributed. Communities near the western edge of time zones would be hit harder because sunrise already arrives later there. Forks, Washington, is one example singled out in the analysis, but the same logic applies broadly to districts that already operate with early bell times. Schools that offer breakfast or other preclass activities may expose children to even earlier departures than the official start time suggests, which means the real burden could exceed the modeled estimates.
Horacio de la Iglesia, senior author and professor of biology at the University of Washington, framed the policy choice in blunt terms: an extra hour of evening light comes directly at the expense of morning light. For families weighing school safety, that tradeoff is immediate and visible at the curb.
Morning light is a biological signal, not a luxury
The consequences go beyond traffic. Morning sunlight is one of the most powerful cues for the circadian clock, the internal timing system that helps regulate sleep, mood, appetite, and daily physiological rhythms. When the body receives bright light early in the day, the clock is reinforced and aligned more cleanly with the external day-night cycle. Remove that cue, and the system can drift.
For children, whose schedules are already constrained by fixed school start times, the loss of morning daylight matters in a different way than it does for adults who may have flexible work hours. A child sent out before sunrise loses a predictable opportunity for light exposure at a biologically useful time. That matters especially in winter months, when the school day begins before the sun reaches the horizon in many parts of the country.
Guadalupe Rodríguez Ferrante, the study’s lead author and a postdoctoral researcher in biology at the University of Washington, emphasized the need for concrete numbers rather than vague concern. The analysis did exactly that by translating the policy debate into school-level commute counts. The question is not whether children might be affected. The question is how many morning exposures would shift into darkness, and where those changes would fall most heavily.
The national total may still be conservative
The estimate of at least 2 billion additional dark commutes may understate the true effect. For the nationwide projection, the researchers assumed students would generally leave for school around 8 a.m., a relatively late departure for many districts. Because many children leave earlier than that, especially where breakfast programs or early buses are common, the real number of dark trips could be higher.
The modeling also intersects with another current policy debate: later high school start times. Delaying adolescent school start times is often discussed as a way to better match teenagers’ later biological rhythms. Permanent daylight saving time could complicate that effort by making the early morning even darker, reducing the daylight benefit that later start times are meant to preserve. If districts respond by shifting schedules later still, the effects could spill into work hours, after-school logistics, and household timing across entire communities.
De la Iglesia drew a straight line from school timing to social timing. Pushing children later can force workplaces later as well, because school drop-off, commute patterns, and parent schedules are linked. The result would not be a simple swap of one clock setting for another. It would be a broad reordering of daily life around the sun.
School policies, sleep biology, and the real cost of a clock change
This study lands in the middle of a long-running policy fight. The U.S. House has already approved legislation that would eliminate the annual return to standard time, and 19 states have approved measures supporting permanent daylight saving time if federal law allows it. The Senate has stalled on the issue, and school start times have become one of the central objections.
From a clinical perspective, the analysis is useful because it ties policy to measurable exposures rather than ideology. Morning light exposure is a biological input. Pedestrian darkness is a safety condition. School start time is the bridge between them. Permanent daylight saving time would stretch evening daylight farther into the day, but the tradeoff would be paid in darker mornings when children are most likely to be on the road.
Published in Current Biology on October 29, the study does not resolve the policy argument by itself. It does, however, make the burden more concrete: millions of children would spend more mornings walking, biking, waiting, or riding to school in the dark, and the heaviest effects would fall on districts already operating early or sitting near the western edge of a time zone. Any decision to lock the country into permanent daylight saving time would need to account for those safety and circadian costs, not just the appeal of brighter evenings.