MINNEAPOLIS — A law meant to prevent new drivers from dying on the roads seems to be working.

Five years after the Minnesota Legislature imposed the restrictions on teenagers’ licenses, the number of fatalities in crashes involving teen drivers has been cut in half.

The rules prohibit teens from driving between midnight and 5 a.m. for their first six months and limit the number of teenage passengers they can carry.

Injuries are down, too, since the rules took effect in August 2008. The average rate of personal injury crashes involving 16- and 17-year-old drivers fell by nearly a third during the full four calendar years after the law’s start compared with the four previous years, according to data from the Minnesota Department of Public Safety.

“The provisions we’ve put in place are working,” said Rep. Kim Norton, DFL-Rochester, one of the bill’s chief authors. “But when you look at the data, you find that there are still some gaps.”

The rules fall below recommendations from the Insurance Institute for Highway Safety, which estimates that Minnesota could further reduce fatal crashes by 44 percent by raising the age for a learner’s permit to 16 from 15 and not allowing teens to drive after 8 p.m., among other things.

State officials are testing a voluntary 90-minute class aimed at parents of teenagers. They’ve reached 250 parents across Minnesota so far.

“Folks, if you think that your teen driver, who’s a really good driver, if you don’t think their behavior changes when you are not in the car, wake up,” Gordy Pehrson, a coordinator for the Office of Traffic Safety, said during a class last week in Chaska.

Pehrson ran through the nighttime driving restrictions and the limits on passengers younger than 20. A teen is allowed just one teenage rider for the first six months and three for the next six months unless accompanied by a parent or guardian. There’s an exception for passengers younger than 20 who are members of the driver’s immediate family.

“You can make stricter rules,” Pehrson told the parents.

He said not allowing a single teenage passenger and setting an earlier curfew are some examples.

“If we went with what really works, what the data shows us, we’d start at about 9 o’clock at night,” he said.

At a traffic safety conference next month, Dr. Leslie Seymour of the Minnesota Department of Health will address the question: Do graduated driver’s licenses work?

Her answer: Yes. “But possibly not in the manner it was intended to,” Seymour said.

The law has taken teens off the road, her research suggests, but it probably has not improved their driving skills.

While the number of crashes involving teenage drivers has fallen faster than for other age groups, the crash rate for teens has actually increased when taking the total miles traveled into account, according to the research. So while teens are crashing less, the miles they’re traveling are deadlier.