For many teens across the United States, it’s a momentous occasion to get a driver’s license. With it, they’ll be able to come and go from their homes whenever they see fit — as long as Mom and Dad allow it — and they’ll get a taste of independence, too. But there are risks as well. Every time a teenager gets behind the wheel, they’re putting themselves at risk of death; seven teens aged 16 to 19 die every day from motor vehicle accidents. New research, however, sheds light on the effectiveness of tighter teen driver restrictions in Massachusetts.

“We know that teenaged drivers are more vulnerable to performance impairment due to sleep deprivation than older people,” said lead author Dr. Shantha Rajaratnam, associated neuroscientist in the Division of Sleep and Circadian Disorders at Brigham Women’s Hospital, in a statement. “Our research shows that restricting unsupervised nighttime driving until age 18 years, with significant penalties for violating the law, contributed to a significant reduction in the crash rate in junior operators, and importantly, reduced crashes that occurred at night, and those that caused serious injury.”

Specifically, the researchers found there was a 40 percent drop in crashes leading to death or incapacitating injury after the restrictions were enacted, when compared to before. Overall, crash rates decreased by 19 percent after the laws were enacted, while nighttime crash rates fell 29 percent.

These changes were largely due to stricter penalties for driving alone at night — between 11 p.m. and 5 a.m. — when a teen driver is supposed to be accompanied by someone aged 20 and up with a driver’s license. For example, teens are no longer given a $35 ticket for their first offense; they get their licenses suspended for 60 days. Subsequent offenses are no longer penalized with tickets either, but longer license suspensions instead.

The study used data from police-reported crashes in Massachusetts that resulted in property damage of over $1,000 or personal injury between March 2006 and March 2012. They looked at both nighttime and daytime crash rates before and after the stricter laws were implemented in 2007, and updated the number of teens with licenses each year.

Some states, such as New York, Connecticut, and Virginia, have already implemented stricter penalties like those in Massachusetts. Other states have similar laws, though they tend to be more lenient. With a consistent 40 percent reduction in crash rates over five years, the current study suggests stricter restrictions could save more teen lives. The most common causes of teen motor vehicle crashes include speeding, drowsiness, not using seatbelts, nighttime driving, and distracted driving.

Source: Rajaratnam S, Czeisler C, et al. Health Affairs. 2015.