Montgomery County high school students soon will get a new public safety message: When crossing the street, keep your cellphone down and your head up.

The campaign, titled “YOLO: You Only Live Once,” is aimed at the problem of “distracted walking” — when pedestrians have their noses buried in their cellphones while crossing the street.

Images that will make the rounds of Montgomery high schools include photos of teenagers with black tire tread marks across their faces and messages such as, “If you text, you’re next,” and “Smart phones can make you do stupid things.”

Montgomery officials said the problem surfaced locally in October 2012, when 15-year-old Christina Morris-Ward died after being hit by a car two blocks from Seneca Valley High School in Germantown as she looked down at her cellphone. Before then, officials said, much of the focus was on distracted driving.

“Christina’s death was a wake-up call for me and my peers, that we had to do more and that distracted crossing was a problem that needed to be addressed,” said Montgomery police Capt. Thomas Didone, director of the department’s traffic division.

About half of students ages 15 to 19 say they use a cellphone when walking to school, according to the Safe Kids Worldwide advocacy group.

Montgomery police have stepped up enforcement of pedestrians crossing outside the crosswalk and drivers not yielding to pedestrians, Didone said, but police can’t crack down on distracted walking in the same way because crossing the street while wearing headphones or engrossed in a cellphone isn’t illegal.

Didone compared the campaign to raise public awareness — it was developed by Montgomery’s transportation department — to those launched years ago against drunken driving. They, too, included polished marketing and involved schools, parents, police, government officials, the media and the community, he said.

County officials said adults also need to serve as good role models by not using their cellphones while driving or crossing the street and should reach out to teens they see doing so. Drivers and pedestrians also need to make sure they make eye contact with each other rather then being distracted by music or a video game, Didone said.

The campaign was launched at Seneca Valley, where Christina would have graduated this spring. The school has its own safety campaign urging students to wear brighter colors, especially during the darker winter months, use reflective material on their backpacks and take their earbuds out when crossing the street.

Christina’s mother, Gwendolyn Ward, said she wants drivers to be more careful and for teens to take more responsibility for their safety.

“I don’t think they think it could be them, just like I don’t think my daughter thought it could be her,” Ward said. “I want kids to know this is for real.”