Keeping daylight saving time (DST) year-round could provide more evening light, but a University of Washington study suggests it would also expose children to substantially darker mornings. The researchers estimate that permanent DST would create at least 2 billion additional trips to school before sunrise nationwide, potentially increasing pedestrian safety risks and reducing children’s exposure to morning sunlight.
Permanent daylight saving time could make billions of school trips darker
Debate over permanent daylight saving time is gaining momentum in Washington, D.C. This summer, the U.S. House of Representatives approved legislation that would eliminate the annual return to standard time in the fall. Nineteen states, including Washington, have already approved measures supporting the change; those measures would take effect in the states if the federal bill becomes law. The bill remains stalled in the Senate.
School start times have become a central concern. Permanent DST would shift winter sunrises about an hour later, producing darker mornings from November through March. Researchers at the University of Washington examined what that change could mean specifically for children traveling to school.
To estimate the impact, the researchers studied 14 of the 19 states that have approved permanent-DST measures. They combined school enrollment data, individual school start times and each school’s geographic coordinates to determine how often students would be at school or traveling there before sunrise. They then compared the projected number of trips under permanent DST with the current system, which switches between daylight saving time and standard time twice a year.
The analysis found a substantial increase. In Washington state alone, permanent DST would result in nearly 35 million additional trips to school in the dark. The researchers reported a similar pattern in 13 other states, with Georgia seeing the largest increase at about 71 million additional outings after dark.
Extrapolating the results nationally, the researchers calculated that permanent daylight saving time would increase the number of school trips made before sunrise by at least 2 billion compared with the current system.
Dark mornings could increase safety risks
The potential consequences go beyond an inconvenient commute. An analysis of U.S. traffic accident records found that fatal crashes involving school-age pedestrians are about twice as likely to occur in the dark before sunrise as they are after sunrise. The study was published in Current Biology on October 29.
“This law is called the Sunlight Protection Law because it gives us an extra hour of light at the end of the day, but that hour is taken away in the morning. You could call it the Sunlight Destruction Law,” said lead author Horacio de la Iglesia, a biology professor at the University of Washington. “These dark mornings will have an unfair impact on children who have to go to school at certain times. This is a very specific metric that anyone from any state or socio-economic background can relate to. No one wants their children to go to school in the dark.”
Why morning sunlight matters
Morning sunlight also helps regulate the body’s circadian clock, the internal timing system that influences sleep, mood, appetite and other functions. Too little bright light early in the day can make it more difficult to maintain these biological rhythms.
Because children generally follow fixed school schedules, dark mornings could prevent them from receiving sunlight at times that are important for their biological clocks.
“If you send children to school in the dark, you deprive them of the opportunity to see morning light,” said lead author Guadalupe Rodríguez Ferrante, a postdoctoral fellow in biology at the University of Washington. “We were asking, how much are these kids going to cost? We wanted to know the actual numbers, the actual number of kids based on the geographic location of each school.”
The researchers also identified communities likely to experience the greatest changes. Schools near the western borders of their time zones, including schools in Forks, Washington, would be especially affected because sunrise already occurs relatively late in those areas. Districts with early start times would also see larger increases in the number of students traveling to school in darkness.
Mississippi and Alabama illustrate the potential change. Schools in both states start before 8 a.m. on average. Under the current clock system, approximately 2 million school trips in each state take place in the dark. With permanent DST, that figure would rise to more than 20 million trips per state.
“Some school districts will have never experienced going to school in the dark under the current system, and when this passes, they will suddenly wake up to a new reality of children going to school in the dark,” Rodríguez Ferrante said. “Please note that we have used the actual start times listed for each school. Many schools offer breakfast, etc. before school starts, so children may arrive even earlier.”
Why the 2 billion estimate may be conservative
The researchers used detailed school information to calculate the change in 14 states, but estimating the national impact required broader assumptions. For the nationwide projection, they assumed that students typically leave home for school at around 8 a.m.
Since many children begin traveling earlier than that, the researchers believe the estimated increase of about 2 billion dark commutes could significantly understate the actual effect.
“Our estimates were that students would leave their homes around 8 a.m.,” Rodríguez Ferrante said. “It’s quite slow, so our calculations may be underestimating the actual numbers.”
The findings also raise questions about efforts to improve adolescent sleep by delaying high school start times. Adolescents’ biological clocks generally shift later than those of younger children and adults, making later school schedules beneficial. Permanently moving clocks forward could reduce some of those benefits by making morning light less available.
Starting school later could help compensate for darker mornings, but de la Iglesia said that change could affect families, workplaces and other daily schedules.
“I’ve heard the argument that, ‘If we have permanent DST, all we have to do is delay school start times to address these issues,’” de la Iglesia said. “Well, if you do that, you’re going to get to work late, and everything is going to be delayed. You’re going to finish work an hour later, and you’re going to miss out on the opportunity to enjoy the evening light. And essentially, we’re just recalibrating everyone to solar time, which by definition is standard time.”
The study highlights the central tradeoff in the debate over permanent daylight saving time. Eliminating seasonal clock changes would provide more evening sunlight during winter, but it would also reduce morning light, potentially affecting children’s safety, sleep and daily routines.
Additional study authors include high school student Daniel Chan and University of Washington undergraduate biology students Nirek Dasika, Alicia Nam, Jesse Lou, Navneet Tambor, Elena Curry Rivera, Viridian Cry and Michaela E. Romero.
Source: www.sciencedaily.com