These days when a teenage driver can’t keep it between the white lines, text messaging and cellphone chatting often seem to be the culprit. Drinking also is a common cause, but authorities are worried about another factor: Kids may be stoned on marijuana.

New data compiled by Students Against Destructive Decisions (SADD) and the insurance industry indicates that pot smoking is up among teens, and use is higher among high school kids than it has been in three decades.

Nineteen percent of teens said they’d driving a vehicle while stoned, according to a survey done by SADD and Liberty Mutual Insurance.

The information released Wednesday comes a week after the Governors Highway Safety Association reported teen highway fatalities increased in the first half of 2011, reversing an eight-year downward trend and contradicting data that showed overall fatalities continued to decrease.

About a third people who die during their teenage years in the United States are killed in vehicle accidents, the single leading cause of teenage death.

SADD and Liberty Mutual have surveyed teens about their driving habits for a dozen years.

Responses collected last year showed that the number of teens who believe smoking pot distracts their focus on driving declined by 8 percent. More than one-third said marijuana use causes no distraction to their driving. And 19 percent of teens who say they have driven after drinking believe alcohol doesn’t result in distraction.

“What keeps me up at night is that this data reflects a dangerous trend toward the acceptance of marijuana and other substances compared to our study of teens conducted just two years ago,” said Stephen Wallace, senior adviser for policy, research and education at SADD.

Most teens said, however, that they would stop driving after smoking or drinking if their passengers asked them to, and almost as many said they would speak up if they were passengers in a car driven by someone who was impaired.

“Teens are faced with potentially destructive decisions every day and don’t always make the best ones,” said Dave Melton, a driving safety expert with Liberty Mutual Insurance and managing director of global safety. “It’s our job as mentors, parents, role models or friends to effectively communicate with them to ensure they are armed with the right information and aware of the dangers of marijuana and other substances, especially while driving.”

The survey of teen drivers began with four teenage focus groups, followed by questioning of 2,294 11th- and 12th-grade students from 28 high schools nationwide. The poll was done by ORC International, which said the results had a margin of error of 2.02 percent.