Lane departure warnings can be a good way to correct the frequent mistake among novice drivers of forgetting to use a turn signal, according to research by the Insurance Institute for Highway Safety. However, the study also determined that teen drivers were more likely to follow other vehicles too closely when a forward collision warning was activated.

In a partnership with the University of Michigan Transportation Research Institute and Honda, IIHS sought to determine how teen drivers would respond to warning systems and whether they could help influence safe driving habits. Forty Michigan high school students took part in the study; each driver was 16 or 17 years old and had been licensed for six to nine months.

Participants drove Honda Accords with crash avoidance technologies such as blind spot monitoring, curve speed warning, forward collision warning, and lane departure warning. The vehicles were also outfitted with sensors and cameras to record vehicle data and footage of driver behaviors.

Half of the drivers were in a control group that did not receive any warnings during a 14-week driving period. The other half had the warnings disabled for three weeks, received warnings for an eight-week period, and then drove for another three weeks with warnings disabled. The vehicle sensors continued to collect data on events that would have prompted a warning even if the system was disabled.

About 10,000 warnings were triggered during the 90,000 miles logged by the teen drivers on more than 15,000 trips during the study period. The vast majority of the alerts—73 percent—came from the lane departure warning system, which is activated if the driver crosses a lane marking without first indicating the maneuver with their turn signal.

Researchers found that lane departure warning and blind spot monitoring systems helped influence better driving behaviors. The number of changing lanes without signaling dropped by more than one-third when the lane departure warning system was activated. It increased again after the warning was deactivated, but the proportion of lane changes without signaling was down by about 75 percent compared to the initial three-week period without warnings.

Both the control and experimental groups showed a higher incidence of following vehicles too closely after the first three weeks of the study. IIHS says this behavior may be a result of the drivers becoming more comfortable with driving or with the vehicles used in the study. Researchers also posited that the drivers may have been more likely to ignore the forward collision warnings because they had a higher rate of false alerts than the lane departure warning or blind spot monitoring systems.

Eight percent of the alerts that occurred during the study period were issued by the forward collision warning system.

"We didn't find evidence of safety benefits from forward collision warning," said Jessica Jermakian, lead author of the study and a senior research engineer for IIHS. "During the treatment period, the teens actually spent more time following vehicles closely. Once the forward collision warning system was disabled, they backed off. This might indicate that the drivers were relying on the warning system to let them know when they should brake."

The study also looked at whether the warning systems had any effect on driver distraction. One concern with vehicle technology is that drivers will be more likely to do secondary tasks if warning systems are present, since the driver may believe that this reduces their chances of a crash caused by distraction.

IIHS says a previous study found that the teen drivers weren't any more or less likely to engage in distracting behaviors when warning systems were present. The most recent study also found no evidence that the drivers engaged in secondary behaviors more frequently when the warning systems were activated.