U.S. researchers say that starting classes an hour later each morning may significantly reduce the risk of car accidents.

The scientists compared sleep times and auto accident rates among high school students in Kansas before and after the schools delayed class start times by one hour.

Before the change, the local high schools began classes at 7:30 a.m. After the change, the start was moved forward to 8:30 a.m. The later start time meant that the students got more sleep. The study’s authors analyzed surveys taken before and after the change was operated, and found that where only 35% of students got at least eight hours of sleep before the change, afterwards this increased to 50%. The percentage of students getting at least nine hours went up from about 6% to more than 10%.

It was also found that the students reduced weekend “catch-up sleep” as well, as the average went down from around to hours to just one hour.

But the main change is that investigators found significantly reduced motor vehicle accident rates among high-school students after the change. The rate dropped by almost 16 percent in the area. Meanwhile accident rates across the state for teens increased by roughly 8 percent.

Study author Barbara Phillips, M.D., director of the UK Healthcare Good Samaritan Sleep Center in Lexington, Kentucky found surprising the practice of high schools continuing to set start times early, despite it impairing learning, attendance and student driving safety.

The study was published in the online edition of the Journal of Clinical Sleep Medicine on December 15, 2008.