Teenage drivers are more likely to speed or tailgate if there are male teenagers along for the ride.

A new study shows that both male and female teenage drivers take more risks if there is a teenage male passenger in the front seat, but female passengers may have a soothing effect on male drivers.

Researchers found teenage boys were less likely to tailgate or exceed the speed limit if a teenage girl was sitting in the passenger's seat.

"The findings indicate that teen risky driving increases in the presence of teen passengers, particularly male teen passengers," Duane Alexander, MD, director of the National Institute of Child Health and Human Development, which conducted the study, says in a news release.

"But more important, the finding should remind teens -- and the adults who care about them -- that they need to drive safely, regardless of who is in the passenger seat."

More States Giving Teen Drivers the Yellow Light

Teen Driving Worsens With Company

Researchers say previous studies have shown that crash rates for 16- and 17-year-old drivers are higher when there are other teenagers in the car, but it's unclear why this is so.

In the study, published in an online edition of Accident Analysis and Prevention, researchers monitored teen driving habits with and without fellow teenagers in the car.

Researchers observed teens leaving 10 Washington-area high school parking lots and then monitored their driving habits at a nearby location using video equipment.

The results showed that teens drove an average of 1.3 miles per hour faster and allowed .17 seconds less headway (about 10 feet traveling at 40 miles an hour) between them and the car in front of them than others.

Parents Can Foster Safe Teen Drivers

Male Passengers Pose Higher Risk

Researchers found male and female teenage drivers were most likely to speed and tailgate if there was a male passenger in the car. For example, a quarter of teenage drivers exceeded the speed limit by at least 15 miles an hour when a teenage male was in the car.

Other findings of the study include:Teenage males allowed longer headways in the presence of female passengers. Teenage females were slightly more likely to tailgate if there was a female passenger in the car.

Overall, researchers found that of the nearly 15% of teen males who engaged in some form of risky driving, such as driving 15 or more miles above the speed limit or allowing less than one second of headway between them and the car ahead, almost 22% had a male teen passenger in the car. But less than 6% of teen male drivers displayed risky driving habits in the presence of a female passenger.

Among the 13% of teenage girls who showed risky driving, nearly 13% had a male teen passenger and 16% had a female passenger.

The study didn't look at why teenage drivers take more risks with other teens in the car, but researchers say teenage passengers may distract the driver or change the driver's attitude or emotion in ways that aren't yet clear.

Teen Drivers More Likely to Wreck

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Simons-Morton, B. Accident Analysis and Prevention, online advance publication, 2005. News release, National Institutes of Health.