ARLINGTON, VA — Teenage drivers' cell phone use edged higher in North Carolina after the state enacted a cell phone ban for young drivers, according to a new study from the Insurance Institute for Highway Safety.

This is the case even though young drivers and their parents said they strongly support the restrictions. Parents and teens alike believe the ban on hand-held and hands-free phone use isn't being enforced. Researchers concluded that North Carolina's law isn't reducing teen drivers' cell phone use.

The two-part study coupled researchers' observations of teenage drivers with telephone surveys of teens and their parents in the first evaluation of a cell phone law for young drivers. North Carolina's ban for drivers younger than age 18 is part of the state's graduated licensing system.

Just one to two months prior to the ban's Dec. 1, 2006, start, 11 percent of teen drivers were observed using cell phones as they left school in the afternoon. About five months after the ban took effect, almost 12 percent of teen drivers were observed using phones. Most drivers were using hand-helds. Nine percent were holding phones to their ears, while fewer than 1 percent were using hands-free devices. About 2 percent were observed dialing or texting. Cell phone use remained steady at about 13 percent at comparison sites in South Carolina, where teen driver cell phone use isn't restricted.

"Most young drivers comply with graduated licensing restrictions such as limits on nighttime driving and passengers, even when enforcement is low," said Anne McCartt, the institute's senior vice president for research and an author of the study. "The hope in North Carolina was that the same would hold true for cell phone use, but this wasn't the case. Teen drivers' cell phone use actually increased a little. Parents play a big role in compliance with graduated licensing rules. Limiting phone use may be tougher for them since many want their teens to carry phones."

When surveyed after the cell phone restrictions took effect, teenage drivers were more likely than parents to say they knew about the ban. Only 39 percent of parents said they were aware of the cell phone law, compared with 64 percent of teen drivers.

Support for the ban was greater among parents (95 percent) than teens (74 percent). Eighty-eight percent of parents said that they restrict their teenage drivers' cell phone use, though only 66 percent of teenagers reported such parental limits. About half of the teenagers surveyed after the law took effect admitted they had used their phones, if they had driven, on the day prior to the interview.

Most parents and teen drivers agreed that police officers weren't looking for cell phone violators. Seventy-one percent of teens and 60 percent of parents reported that enforcement was rare or nonexistent. Only 22 percent of teenagers and 13 percent of parents surveyed believed the law was being enforced fairly often or a lot.

"Cell phone bans for teen drivers are difficult to enforce," McCartt noted. "Drivers with phones to their ears aren't hard to spot, but it's nearly impossible for police officers to see hands-free devices or correctly guess how old drivers are." Absent some better way to enforce them, "cell phone bans for teenage drivers aren't effective, based on what we saw in North Carolina," McCartt added.

In both North Carolina and South Carolina, observed cell phone use was significantly higher among girls than among boys and higher when teens drove alone in vehicles rather than with friends. For example, 13 percent of female drivers and 9 percent of males were observed using cell phones in North Carolina before the law. Cell phone use was 14 percent among solo drivers and 8 percent among teens with one passenger. More SUV drivers than car drivers were viewed using phones.

Phone bans for young drivers are becoming commonplace as concerns mount about the contribution of distractions to teens' elevated crash risk. Seventeen states and the District of Columbia restrict both hand-held and hands-free phone use by young drivers. Six states and the District of Columbia bar all drivers from using hand-helds.

For a state-by-state list of cell phone laws, visit www.iihs.org.