Steven Acheson, an Iraq War veteran, at his apartment in Platteville, Wis., May 3, 2013. (Andy Manis/For The Washington Post)

For men and women who have fought in the country’s wars in Iraq and Afghanistan, death behind the wheel is becoming another lethal aftereffect of combat.

After they leave military service, veterans of the two wars have a 75 percent higher rate of fatal motor vehicle accidents than do civilians. Troops still in uniform have a higher risk of crashing their cars in the months immediately after returning from deployment than in the months immediately before. People who have had multiple tours in combat zones are at highest risk for traffic accidents.

The phenomenon has been revealed by various pieces of evidence — research as well as observations of service members, veterans and counselors.

The most common explanation is that troops bring back driving habits that were lifesaving in war zones but are dangerous on America’s roads. They include racing through intersections, straddling lanes, swerving on bridges and, for some, not wearing seat belts because they hinder a rapid escape.

That’s probably not the whole story, however. Post-traumatic stress disorder (PTSD), suffered by thousands of veterans, increases aggressive driving. Drunken driving and thrill-seeking also are more common after combat, according to a few studies and the testimony of many veterans.

Steven Acheson drives his car around Platteville, Wis., May 3, 2013. (Andy Manis/For The Washington Post)

If further research supports the observations, motor vehicle crashes will join suicide and interpersonal violence as a fatal, if indirect, consequence of the war on terrorism.

Motor vehicle crashes have long been a serious problem in the military. From 1999 through 2012, a period spanning peacetime and the two wars, as many active-duty military personnel died in noncombat motor vehicle crashes both on and off duty (4,423) as were killed in the Iraq war (4,409).

“Before suicides became the leading cause of non-battle injuries, motor vehicle injuries were,” said Bruce H. Jones, a physician and epidemiologist who heads the Army’s injury prevention program at Aberdeen Proving Ground, in Maryland.

War, however, worsens the problem.

Men who served in the wars in Iraq or Afghanistan have a 76 percent higher rate of dying in vehicle crashes, and women a 43 percent higher rate, than people in the general population, according to an unpublished study by Han K. Kang, an epidemiologist with the Department of Veterans Affairs. The same phenomenon was seen in Persian Gulf War veterans and took five years to dissipate.

Fatal motorcycle crashes in particular spiked during the wars. They accounted for 14 percent of military traffic deaths in 2001, but 38 percent in 2008. The absolute rate of motorcycle deaths also tripled over that period.

“A lot of people come home and buy a motorcycle to have that adrenaline rush again,” said Steven Acheson, 27, a former forward observer in the Army and an engineering student in Wisconsin.

He spent time at Fort Stewart in Georgia, where the post put vehicles from fatal crashes on display as a form of warning. “There was once six or seven completely mangled motorcycles out in front of the gate,” Acheson recalled.

One of the best pieces of evidence that combat raises a person’s risk for car crashes comes from an in-house study by USAA, an insurance company in San Antonio that covers thousands of military personnel.

The company offers a reduced-price insurance premium if vehicles are stored securely during deployment. Almost all of the company’s active-duty customers opt for it. As a consequence, USAA has before-and-after records for 171,000 deployments to Iraq and Afghanistan.

Troops had more at-fault accidents in the six months after their return from deployment than in the six months before they left. The increase was highest for people in the Army (23 percent) and in the enlisted ranks (22 percent).

Tellingly, there was a “dose­-response relationship” between deployment and risk. Troops with three deployments had 36 percent more accidents, compared with 27 percent more in the twice-deployed and 12 percent in people deployed only once.

But the problem isn’t just a carry-over of habits.

One-quarter of the Iraq and Afghanistan veterans enrolled in a 60-day residential treatment program for PTSD in California said they drove after drinking. One-fifth said they used seat belts “less than sometimes,” in part because they get in the way of a rapid escape from a vehicle.

“Failure to adapt the unique combat driving behaviors used in the current conflicts cannot be the only explanation for deployment-related risky driving behavior and excess . . . mortality,” wrote Mark A. Zamorski, a Canadian military physician, and Amanda M. Kelley, a civilian U.S. Army psychologist, in a report to NATO on the subject.

All of the likely mechanisms . . . could be mediated by distress or mental disorders,” they wrote.

‘You’re scaring me’

Todd Nelson was an Army logistician riding in the front seat of a Toyota Land Cruiser in Kabul in August 2007 when a car in an adjoining lane blew up. He lost his right eye, broke both jaws and had burns on 18 percent of his body surface. He’s had 43 operations under general anesthesia.

When he was finally well enough to get back on the road, he drove for several months before his wife “made a comment about how aggressive I was being. She said, ‘You’re scaring me,’ ” Nelson, 40, recalled recently.

He sped. He hated letting cars get in front of him. He swerved whenever he saw a vehicle with a low-hanging rear end suggesting a heavy load. “Hey, I drove much worse than this over there and nothing happened,” he says he told himself.

In hindsight, he says, he’s embarrassed at how unaware he was. Of his wife, he says, “It was very patient of her to wait that long to tell me.”

Nelson, who works in the recruiting department of USAA, broke the habit on his own.

He timed how long it took him to drive to college each day in San Antonio and proved to himself that going the speed limit added little time to the trip. He made a game of counting the number of cars he would let merge on the way in and the way back. After a month, he said, he was back to driving pretty normally. He now goes out of his way to talk about it to other veterans.

“I think we probably suffer with this more than we like to admit.”

Acheson, the Wisconsin veteran, agrees.

He spent 11 months driving a colonel around the Sadr City district of Baghdad in an ­up-
armored Humvee in 2006. He drove courteously. “It was kind of our colonel’s motto when we were out there — ‘Show people respect,’ ” he said.

He escaped injury. But he developed a habit of merciless attention to the road — noticing every curb line repainted or jersey barrier moved — that he’s never really lost.

“When I see a vehicle on the side of the road, it puts me on edge,” said Acheson, a senior at the University of Wisconsin at Platteville. “I am constantly scanning. If I see a bag blow across the road a mile up, I say, ‘What is that?’ ”

He has occasional — and unaccountable — moments of panic behind the wheel.

Three years ago, he went to Long Island to visit an Army friend whose father was dying in hospice care. He helped carry the man’s body out of the house. Driving home, he was overcome by dread and anxiety. Somewhere in Indiana, in the middle of the day, he stopped, rented a motel room, called his mother and spent a sleepless night.

He thinks drinking and driving is a largely unacknowledged part of the car-accident problem.

“It’s just everywhere,” he said. “You just survived the war, so what do you mean I can’t drive drunk? If I can drive and shoot out my window, I can drive drunk. It’s that kind of mentality I saw a lot of soldiers taking.”

Training materials

The military is beginning to pay attention to the particular risks facing — and needs of — Iraq and Afghanistan veterans who resume driving when they get home.

The Army gives out a brochure called “Post-Combat Driving: The American Road” that includes data from a survey that an occupational therapist at the University of Minnesota, Erica B. Stern, conducted with deployed and non-deployed reservists. (Forty-nine percent of returning troops said they were anxious when cars approached quickly; 25 percent said they had driven through stop signs in the previous month.) The publication has tips on how to increase self-control; one is to tape a drawing by one’s child to the dashboard.

VA has new training materials for clinicians advising them to talk about driving with veterans of Iraq and Afghanistan, some of whom are enrolling in the department’s driver-rehabilitation programs offered at 40 VA medical centers across the country, which have traditionally been used by people with physical disabilities.

The VA hospital in Palo Alto, Calif., is conducting a study aimed at identifying the best techniques for relieving driving anxiety while on the road.

Veterans drive hour-long trips near the medical center that incorporate their “triggers” — underpasses, bridges, construction sites, busy intersections. Their pulse and breathing are monitored.

When they feel panic, they pull over and try various self-calming techniques.

“We’ve had a lot more trouble recruiting participants than we expected,” said Steven Woodward, a VA psychologist running the study. “Why? I wish we knew.”

Getting permission for the study from scientific review boards wasn’t easy. There haven’t been any disasters so far. Woodward hopes one day to extend it to an even more overlooked group — returning veterans who aren’t yet confident enough to resume driving.