A recent report from the US Department of Transportation suggests that starting high school at a later time of day could reduce the number of motor vehicle crashes experienced by teenage drivers due to the sleep needs of adolescents.
Data was collected from two jurisdictions that had pushed the start time of their high schools significantly back — including Forsyth County, North Carolina and Fayette County, Kentucky. Researchers then looked to see whether there was also a drop in the crash rate among 16 and 17-year old drivers in those areas. Comparable data was collected from other counties that did not change their start time in an effort to control for conflicting factors.
The report, "School Start Times and Teenage Driver Motor Vehicle Crashes," found some evidence that a change to the start time did in fact help to reduce the number of crashes for Forsyth County, although no such evidence was found for Fayette County.
Driving while sleepy or tired has been found to result in a decrease in alertness, delayed reaction times, an inability to notice emergency situations, and in some cases, the driver could possibly fall asleep while behind the wheel. While it is difficult to obtain accurate data on car crashes, the NHTSA's Crashworthiness Data System (CDS) found close to 4% of car crashes between 2000 and 2003 involved drivers who were either tired or had fallen asleep.
Previous research on the topic found that drivers under the age of 25 were responsible for the majority of drowsy driving accidents in North Carolina. However, more recent research found that those under the age of 21, who make up around 6% of the entire licensed driving population, accounted for 20% of drowsy driving crashes. The authors suggest that this could be due in part to a connection between driving experience and hazard perception, pointing to evidence from a separate study which found experienced drivers are less likely to observe hazards if they are tired or less experienced behind the wheel.
The also discussed the changes to the circadian rhythm that occur during adolescence, which researchers say cause teenagers to fall asleep at a later time than they did when they were younger. Due to this "sleep phase shift," the National Sleep Foundation suggests teenagers need to sleep in the early morning hours when high schools typically begin for the day.
Despite new technologies and social media changing how teenagers spend their time in recent years, with 5th and 6th graders reporting activities such as watching television and surfing the internet as reasons for their sleep deprivation, 10th-12th graders point to early school start times and academic pressures among their contributing factors.
Researchers suggest that a policy change, which they say can be done at the local level, to change the start time of high schools would help to reduce the number of car crashes involving teenage drivers. They point to a study performed in southeastern Virginia that found a 29% reduction in crash rates among 16-18 year-olds in a county that had a start time 80 minutes later than a separate county that was also observed.