A new survey finds that 19 percent of teens drive under the influence of alcohol, 15 percent drive after using marijuana, and 7 percent report driving under the influence of other drugs.

However, the annual Teens Today survey, sponsored by Students Against Destructive Decisions (SADD) and the Liberty Mutual insurance company, also found that teens whose parents set high expectations and impose serious consequences are less likely to drive while impaired. For example, 16 percent of teens who say there would be serious trouble at home reported driving drunk, compared to 29 percent of teens who said they would not face such consequences from their parents.

Boys (32 percent) were more likely than girls (25 percent) to have driven while impaired, the study found.

"It's quite encouraging to see that parental involvement can significantly improve teen driving statistics, a mission we've been committed to for some time now," said Liberty Mutual executive Paul Condrin. "And through this study, the type of parental involvement that works is clear -- parents need to know the laws and teen-driving rules of their state, set clear expectations with their teens about what safe driving is, and establish and enforce those consequences should those laws be broken or expectations not be met."

Good parenting also can cut down on car crashes, speeding, and distracted driving among teens, the study found. Suggested family rules for teen drivers include no friends in the car without an adult; no driving after 10 p.m.; no use of alcohol or other drugs; no distractions while driving, including eating, changing CDs, handling iPods and putting on makeup; and no cell phone use, including text messaging.