NEW YORK - South Dakota, the state with the youngest licensed motorists, could cut fatal wrecks involving teens by more than half if it raises the minimum age to operate a vehicle and limits nighttime driving, an insurance group said Thursday.

The state, where a 14-year-old can get a learner’s permit, could reduce the rate of deadly crashes among drivers ages 15 to 17 by 63 percent by boosting the licensing age, prohibiting teens from driving after 8 p.m., and restricting passengers, according to an analysis by the Insurance Institute for Highway Safety. If such restrictions applied in all states, 500 fewer people would die in crashes each year, the organization said.

Motor-vehicle crashes killed 21 people and injured 1,135 in South Dakota this year through May 4, according to the state’s Department of Public Safety. In 2010, there were 140 such deaths, or 17.2 per 100,000 state residents, compared with a national rate of 10.7, according to the institute.