Study finds permanent daylight saving time would add 2 billion dark school commutes a year

A new analysis published in Current Biology estimates that switching the United States to permanent daylight saving time would send American schoolchildren out the door before sunrise more than 2 billion additional times a year, reviving a safety debate that helped kill an earlier version of the policy five decades ago. The study, led by researchers at the University of Washington, arrives as Congress weighs legislation that would end the twice-yearly clock change for good and keep the country on daylight time year-round.

What the researchers found

The team, led by postdoctoral researcher Guadalupe Rodríguez Ferrante and senior author Horacio de la Iglesia, a UW professor of biology, examined start times, enrollment and locations for more than 16,000 public schools across 14 states, covering roughly 8.6 million children. They modeled three scenarios: the current system of switching clocks twice a year, permanent standard time and permanent daylight saving time, then calculated how many school mornings in each scenario would begin before sunrise.

Across the 14 states alone, permanent daylight saving time would add about 356 million dark-morning commutes a year compared with the status quo. Extrapolated nationally, assuming an 8 a.m. start time that the authors say likely understates the true effect, the increase comes to at least 2 billion additional dark commutes annually. Washington state would see nearly 35 million more; Georgia, the hardest-hit state in the study, would see about 71 million more. Communities toward the western edge of their time zones and districts with early first bells were affected most.

Reading the crash data

To gauge the stakes, the researchers paired the commute modeling with a decade of federal traffic-safety records, examining more than 10,000 fatal crashes that occurred on school-year mornings between 7 and 8:30 a.m. from 2015 through 2024. Crashes that happened before sunrise were 77 percent more likely to involve a pedestrian than crashes after sunrise, and for children between the ages of 5 and 18, the odds of a pedestrian being involved more than doubled in the dark. The authors are careful to note that the study is not an experiment and cannot say precisely how many additional crashes a switch to permanent daylight saving time would cause; it establishes an association between darkness and pedestrian risk, not a forecast of deaths.

A fight Congress has had before

The research lands in the middle of a live legislative fight. The House of Representatives passed the Sunshine Protection Act by a 308-117 vote in July, and 19 states, including Washington, have already enacted trigger laws that would move them to permanent daylight saving time automatically if federal law allows it. The bill has not received a Senate vote, and leadership has given no timetable for one. Sen. Tom Cotton of Arkansas has been among the holdouts, arguing that locking the country into daylight saving time would push winter sunrises to an unreasonably late hour, a concern the UW researchers' commute data now puts a number on: communities at the western edges of their time zones would see winter sunrise pushed close to, or past, 8 a.m., leaving students waiting for buses well into what is now the morning rush.

The United States has tried this before. Congress imposed permanent daylight saving time in January 1974 amid the energy crisis, but reversed course within months after a string of child pedestrian deaths in dark morning hours turned public opinion against the law. Standard time, which the country reverted to on Nov. 1, now governs the clocks again until the question resurfaces with the next change in March.

Who stands to be affected

Rodríguez Ferrante said the burden of a change would not fall evenly. School districts that currently schedule later start times, she noted, "probably never experience a dark commute under the current system" and would be newly exposed if daylight saving time became permanent. Public health researchers who reviewed the findings separately have pointed out that lower-income children are likely to be disproportionately affected, since they are more likely to walk, bike or take public transit to school and are more likely to arrive early for subsidized breakfast programs.

"Nobody wants their kids to go to school in the dark," said Horacio de la Iglesia, the study's senior author, who argued that the bill's name is misleading because the additional evening daylight it promises comes directly at the expense of morning light.

De la Iglesia also pushed back on a commonly proposed fix: delaying school start times to compensate. Pushing start times later, he argued, would not resolve the mismatch, because work schedules and evening activities would simply shift later as well, effectively re-creating the same solar misalignment the country already experiences for part of the year under daylight saving time.

Emergency physicians who were not involved in the research have largely echoed that assessment. Leana Wen, an emergency physician and clinical associate professor at George Washington University, told CNN that "visibility is a major factor" in pedestrian crashes and described the study's findings as a plausible safety concern rather than a definitive forecast, since actual crash counts depend on local traffic patterns, street lighting and how quickly drivers adjust to months of earlier darkness. Coverage of the paper summarized by the medical news outlet News-Medical.net noted that the research adds to a body of circadian-biology literature arguing that morning light exposure, not just total daylight, shapes alertness, mood and the timing of the body's internal clock.

What comes next

The Senate has set no timetable for taking up the House-passed bill, and President Trump has repeatedly urged senators from both parties to clear it, calling it an issue that could unite Republicans, Democrats and independents. Sleep researchers and several medical organizations have for years argued for the opposite fix, permanent standard time, saying it better matches the body's internal clock to the sun and avoids the darker winter mornings a shift to daylight saving time would lock in. Unless the Senate acts, the 19 states with trigger laws remain bound to the twice-yearly clock change that resumed on Nov. 1, with the next shift, back to daylight saving time, scheduled for March. The UW analysis covered only 14 of those 19 states, using listed school start times rather than actual bus routes or walking paths, which is why the authors describe their 2 billion figure as a conservative floor rather than a precise national count.