For you parents who might have suspected that teen drivers tend to take far more risks and drive more dangerously when they have friends in the car, a new federal study shows that your hunch is probably correct.

And for you teens who feel that Maine’s prohibition on new drivers carrying passengers for the first six months after getting a license is an unfair and unnecessary restriction – sorry, but the evidence would seem to suggest otherwise.

The new study, conducted by researchers from the National Institute of Child Health and Human Development, reveals that risk-taking behind the wheel is greatest when teenage drivers of either sex are accompanied by teenage passengers, especially boys. Monitors stationed a quarter- to a half-mile from the parking lots of 10 high schools in suburban Washington, D.C., determined that fully a quarter of all teenage drivers they saw with a male passenger in the car exceeded the speed limit by at last 15 miles an hour. Of those boys who were observed driving dangerously, one in every five had a male passenger riding shotgun in the car. Only one in 20 of the reckless drivers had a girl in the car, however.

About 15 percent of teenage boys overall and 13 percent of teenage girls were spotted driving dangerously, with speeding and tailgating high on the list of offenses. The researchers determined that teenage boys tended to become slightly more careful drivers when carrying female passengers, while teenage girls tended to take more risks when they were accompanied by either male or female passengers.

“The most surprising finding is that females would have a moderating effect on male teen driving,” the study’s lead researcher told the Washington Post.

Researchers, who tracked the driving habits of about 470 teens and compared them with a sizeable sample of adult drivers, admit that future studies are needed to determine why it is male passengers seem to bring out the worst in teen drivers. They speculate that teen drivers, especially boys, feel a macho kind of urge to show off and to drive less prudently when they have males in the passenger seat. Another theory is that the male passengers exert peer pressure on their friends to drive more dangerously.

Whatever the reasons, researchers say, the study points out the need for parents to always be mindful when their teenagers are driving around with their pals in the car.

It also points out that Maine lawmakers were ahead of the safety curve when they wisely adopted a three-tiered graduated drivers license system a couple of years ago. Under the revised system, new drivers who have completed a six-month learning-permit period under adult supervision are allowed to take a road test to earn an intermediate license. For the next six months, before they can earn an unrestricted license, drivers are banned from carrying any passengers other than adults. They can’t use cell phones while driving, either, and are prohibited from driving between midnight and 5 a.m.

While it’s impossible to legislate away all of the hazards of teen driving, Maine’s sensible license restrictions are a good first step in reducing some of the risks that rookie drivers face while gaining critical experience and maturity behind the wheel.