When her 20-year-old son is driving and his cellphone rings or receives a text message, Maureen Friar says she speaks up.

“I say, ‘You don’t need to get it, you don’t need to get it.’ ”

When she’s driving and her phone buzzes, she doesn’t always follow her own advice.

“In all honesty, I’ve probably modeled bad behavior,” says the consultant from Arlington County. “So it’s a classic case of do as I say, not as I do.”

The parent as role model is not new to highway safety. In decades past, research showed that the parents who disdained seat belts or drove after drinking influenced the behavior of their teenage children to disregard those risks.

In an online survey of 1,300 teen drivers with cellphones, scheduled for release Monday, the youths said that even though their parents may warn them against it, they think adult drivers send text messages “all the time.”

A sizable proportion of the teens in the study also admitted to engaging in the same dangerous practice. About the same number who said they saw their parents do it admitted to doing it themselves.

The new data — released as part of an effort by AT&T to combat distracted driving — conform with some of the work done by the Pew Research Center, which conducted surveys and focus groups two years ago with teenagers about smartphones.

“Often it was the parent who was engaging in dangerous behavior that the teens themselves thought was crazy,” said Amanda Lenhart, who directs Pew’s research on teens, children and families. “We heard from some teens who said, ‘My dad does it or my mom does it, but they do it in a safe way.’ Other teens would say things like, ‘It’s crazy, it totally freaks me out.’ ”

But just as with adults, research has shown that many teens who acknowledge the danger of smartphone use by other drivers admit that they do it themselves. Cellphone use by novice drivers has been banned in the District and 31 states, including Maryland and Virginia. Nevertheless, distracted driving was cited as a possible factor by the Governors Highway Safety Association this month when it sounded the alarm that teen highway deaths appeared to be creeping up after years of decline.

There is now a growing body of research that can be expected to find its way into the arsenal of arguments used by advocates who want state legislatures to ban drivers from all forms of mobile-device use behind the wheel.

Both U.S. Transportation Secretary Ray LaHood and the National Transportation Safety Board are pushing for laws against texting and cellphone use while driving. But state lawmakers have moved cautiously for fear of backlash from a population thoroughly wedded to iPhones, Androids and Blackberrys.

That they pose a risk, however, is evident to almost any observant driver and has been catalogued in dozens of studies and surveys. The National Safety Council estimates that a quarter of all crashes are the result of distracted driving.

Smartphone use is particularly widespread and dangerous among teenagers, for whom auto crashes are the leading cause of death. Today, more than two-thirds of people younger than 25 have a smartphone.

Martha and Eric Karandy have experienced the evolution of cellphone use from the parental perspective. Their daughter, Bernadette, is 24. Son Conrad is 15 and three months away from getting a learner’s permit to drive.

“When Bernadette was 16, kids were just starting to get their cellphones and they weren’t really texting, it was mostly just talking,” said Martha Karandy, who lives in Annapolis. “We told her: Don’t do it. It’s a bigger concern with Conrad, because he’s grown up with it. Texting with him is just second nature.”

Karandy said she has abided by an Oprah Winfrey pledge she took two years ago not to deal with text messages or e-mails while driving.

“I try not to even be on the phone in the car. Sometimes I am, but I try not to do it around Conrad,” she said. “Conrad is much more of a risk taker than Bernadette. I’m nervous about it, and I probably will look into apps or different things to make sure that the phone is not activated in the car.”

A study by the National Highway Traffic Safety Administration last month found that 13 percent of drivers ages 18 to 20 in crashes admitted they were talking or texting on mobile devices. Among drivers of all ages, that number dropped by more than half.

About 20 percent of young drivers said sending e-mails or text messages did not affect their driving performance. Forty-four percent of drivers between 18 and 20 and 49 percent of those between 21 and 24 said they sent texts and e-mails, the NHTSA study said.

“With adolescents there’s an element of risk taking that in some ways is age appropriate,” Lenhart said, adding that teens whose friends have been in crashes often are outspoken against smartphone use. “There was also a subset of very nonchalant teenagers who were like: ‘I can do it in a safe way. I think I’m a good enough driver so this isn’t a problem.’ ”

Friar agreed: “Especially teenage boys think there’s an invincibility.”

The sample of teen drivers in the AT&T-sponsored study said they expect to receive a reply to a text or an e-mail within five minutes, an incentive for those who are driving to regularly check their smartphone. Sometimes, Lenhart said, that may be for fear of missing a parent’s message.

“We do hear from kids who talk about the fact that their parents require them to respond as a part of their freedom,” Lenhart said. “So, for some teens there was a sense of urgency, particularly if they felt a parent would be concerned or angry if they didn’t respond.”

“If I knew Bernadette was driving to her boyfriend’s or something, I wouldn’t call her during that period of time because I didn’t want her to answer the phone,” Karandy said.