Keeping daylight saving time (DST) year-round would provide more evening light in winter, but a University of Washington study suggests it could also send at least 2 billion more school trips into the darkness before sunrise across the United States. The researchers warn that darker mornings could increase safety risks for children and reduce their exposure to morning sunlight, which helps regulate the body’s internal clock.
Permanent daylight saving time could darken school commutes
Debate over permanent DST is gaining momentum in Washington, D.C. This summer, the U.S. House of Representatives approved the Sunshine Protection Act, which would eliminate the need to return to standard time each 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, but the bill remains stalled in the Senate.
School start times are a major concern. Permanent DST would make winter sunrises occur an hour later, creating darker mornings from November through March. This would affect anyone traveling early in the day, but University of Washington researchers focused specifically on children traveling to school.
To estimate the impact, the researchers examined 14 of the 19 states that have approved permanent-DST measures. They combined school enrollment figures, individual school start times and geographic coordinates to determine how often students would be at school before sunrise. They then compared the projected number of trips under permanent DST with the number under the current system, in which clocks change twice a year.
The results showed a substantial increase. In Washington state alone, nearly 35 million additional school trips would take place in darkness under permanent DST. The researchers found similar patterns in the other 13 states, with Georgia seeing the largest increase at about 71 million additional outings after dark.
Extrapolating the results nationally, the researchers calculated that permanent DST would increase the number of school trips occurring before sunrise by at least 2 billion compared with the current system.
Dark mornings could increase risks for children
The consequences could extend beyond inconvenience. 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 on October 29 in the journal Current Biology.
“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 socioeconomic background can relate to. No one wants their children to go to school in the dark.”
Why morning sunlight matters
Morning darkness could also affect children’s health. Exposure to bright light early in the day helps synchronize the circadian clock, the body’s internal timing system that influences sleep, mood, appetite and other functions. Too little morning light can make it more difficult to maintain these biological rhythms.
Children who follow fixed school schedules may miss opportunities to receive sunlight at the time of day their bodies need it most.
“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 edges of time zones, including schools in Forks, Washington, could be especially affected because sunrise already occurs relatively late in those areas. Districts with early start times would likewise see a larger increase 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 darkness. If DST became permanent, that number 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 too low
The researchers used detailed school data to calculate changes in 14 states, but estimating the national impact required broader assumptions. For the nationwide projection, they assumed that students typically leave home at around 8 a.m.
Because many children begin traveling earlier than that, the researchers believe the projected increase of roughly 2 billion dark commutes could substantially underestimate the real impact.
“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.”
Potential effects on school schedules and sleep
The findings also raise questions about efforts to improve teenagers’ 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. The researchers argue that permanently moving clocks forward could undermine some of those benefits by making morning sunlight less accessible.
Starting school later could help compensate for darker mornings, but de la Iglesia said that change could affect families, workplaces and the rest of the day’s schedule.
“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 DST. Eliminating seasonal clock changes would preserve more evening light during winter, but it would do so at the expense of 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
