By the time his police cruiser tumbled to a halt in the underbrush beside the interstate in August, the young police officer had been flung clear of the car to his death, the same fate that had been suffered by 139 other officers nationwide who were ejected from their vehicles when not using a seat belt.

Although most state's laws require police to use seat belts, federal data show that only about half of them do, and over the past three decades, 19 percent of the officers killed in accidents were ejected from their vehicles.

"We've been told it's 'I want to be able to get out of the car quickly, it interferes with my gun or it interferes with my belt, it interferes with my driving.' All the wrong reasons," said Geoffrey Alpert, a University of South Carolina professor who has studied high-risk police activities for more than 25 years. "I can understand if you're pulling up to a scene and you undo your seat belt because you want to be able to get out quickly, but not when you're going 100 miles an hour on the freeway."

Prince George's County, Md., Police Officer Adrian Morris died of head injuries Aug. 20 after being thrown from his cruiser when it left Interstate 95 during the high-speed chase of a stolen car. His partner, Mike Risher, was buckled in the passenger seat. He was treated at and released from a hospital that day.

That incident came a week after a Fairfax County, Va., police officer whose name has not been released was involved in a fatal accident. A car swerved in front of his cruiser, striking it head-on. The car burst into flames, and its driver died. The officer was trapped, but he was pulled free and survived.

 "Thank God he had his seat belt on," said Capt. Susan Culin, who heads the county's traffic division. "He's very adamant that his seat belt saved his life."

Seat belts and air bags have made the high-risk pursuit of criminal suspects less deadly than it once was, but for more than a dozen years, traffic fatalities killed more police officers than bullets did. The trend was reversed last year, when the number killed by gunfire - 68 - was four more than the number who died in traffic incidents.

The question of when police should chase a fleeing suspect has been debated in public and law enforcement circles for years, leading most police departments to delineate their rules. Research has shown that 1 percent of chases end in a fatality and that an officer dies as the result of a pursuit every 11 weeks.

The National Highway Traffic Safety Administration determined that 139 officers died when ejected from their vehicles in crashes between 1980 and 2008 and that only 45 percent of the 733 officers who died in crashes during the period had their seat belts fastened.

By contrast, 84 percent of all American drivers use their seat belts, the NHTSA estimates.

In Prince George's County, the importance of officers using seat belts is stressed in the annual in-service training, a portion of which is devoted to safe driving, police said.

Kevin Davis, the county's assistant police chief, says the educational effort is essential to changing the way officers think about using their seat belts.

"You can change any policy and procedure that you want to change, reduce it to writing and stick it in your 400-500 page general order manual, but you're not making any headway unless you change the culture," Davis said.

He calls the three reasons most officers give for eschewing the seat belt - it gets tangled with their gun belt, it delays their exit from the car and it hampers their ability to dodge a bullet - "absolutely absurd."

"It's a bunch of garbage, and I just don't buy it," he said.

When officers get older, gain more experience and, particularly, when they start a family, they begin to see the wisdom of seat belt use, Davis said.

In addition to culture change, more training and new policies, Davis said the department plans to hold district commanders responsible for ensuring that their officers get the message.

"As long as it remains on their daily radar screen, we think that that will be half the battle in changing the culture about wearing seat belts in a police car," Davis said, adding that punishment for officers should be greater than the current written reprimand. "That, arguably, doesn't go far enough to modify someone's behavior."

Alpert said he has seen the influence of the Prince George's efforts.

"I was at the Prince George's County [police department] the other day, and there's a sign as you leave the parking lot, 'put on your seat belt on,' something to that effect," Alpert said. "They do have a policy. They're very concerned about it. But I've seen officers elsewhere wear their seat belt off the lot, then take if off and click it behind because they think they can do their jobs better" if they don't wear a seat belt.

Culin said Fairfax County police parking lots have similar signs. She said the department launched a buckle-up campaign after a visual survey found that 25 percent of officers were not wearing seat belts.

Even after an effort that included reminders at every shift roll call, she said 21 percent  "It's changing human behavior, and that's very difficult to do," she said. "It's something we have to keep harping about with the officers. It's a real issue. It's an issue here, and it's a pressing issue nationwide."

The roll call of officers who weren't wearing seat belts when they died in crashes includes Louisiana Deputy Sheriff Randall Benoit, 41, who was hit from behind this year on a state highway. Another local Louisiana officer, John Kendall, 64, was ejected from his cruiser four months earlier after he hit a pickup truck.

 The last officer to die in the line of duty in Prince George's before Morris, Thomas Jenson, was not wearing a seat belt in 2010 when his cruiser skidded on a patch of ice and hit a pole.

"A seat belt absolutely would have saved his life," Davis said.

That year, Houston officer Eydelman Mani, 30, was responding to a call at 60 mph when his patrol car hit a guardrail. A New Jersey officer, John Abraham, 37, died when his cruiser hit a utility pole in Teaneck.

An officer with the Bureau of Indian Affairs, Joshua Yazzie, 33, was hurled from his St. Louis Police Chief Dan Isom mandated strict enforcement of the department's seat belt requirement after two officers who weren't wearing them - Julius Moore, 23, and David Haynes, 27 - died in crashes within five months.

The events leading to Morris's death in Prince George's unfolded as things often do in routine police work. He and Risher were investigating a car break-in at a Laurel gas station when a silver Acura linked to the break-in passed by.

With overhead lights flashing, they pursued the car onto I-95. Chasing at high speed, Morris lost control of the cruiser and it tumbled into a ravine. He was thrown from the car and suffered fatal head injuries.

"I think he wasn't wearing his seat belt because of the excitement of the moment, of seeing a bad guy from a parking lot," Davis said. "He just forgot. From what I understand, he was a religious seat belt wearer."