For years, federal regulators, doctors and the all-terrain vehicle industry have agreed: Children should not ride ATVs designed for adults.

But in most states, the practice is legal.

In Minnesota, lawmakers even dropped the age limit from 16 to 12 for driving adult ATVs, with a nod to safety: They require children to take a training class.

Across the country, thousands of children have been injured or killed riding ATVs, the majority on adult vehicles. But 40 states have laws and rules allowing children younger than 16 to drive ATVs designed for adults. Nineteen have no age limit. Some with age restrictions, including Minnesota, spend little effort trying to enforce them.

Minnesota state Rep. Tom Hackbarth, a Republican who co-sponsored the state’s current ATV regulations, contends that children will ride adult ATVs, regardless of the law or ATV warning labels. So Minnesota’s requirements for safety training and parental supervision are the best way to protect them.

“I’m not saying the manufacturers are wrong, but they shouldn’t be saying we’re wrong either,” Hackbarth said.

David Downing, manager of Iowa’s off-road vehicle program, said many children younger than 16 are fit to ride adult-sized ATVs. “What we have is a common-sense approach,’’ he said of Iowa’s regulations, which are similar to Minnesota’s. “We’re a farm state. We have big kids.”

But that approach clashes with mandates from the federal Consumer Product Safety Commission (CPSC), which regulates ATVs. Its view: Children younger than 16 are too impulsive and lack the physical strength and maturity to operate a powerful and sometimes unstable vehicle.

“I don’t see those states lowering the drinking age because some kids drink,” said Robert Adler, a CPSC commissioner. “I don’t see them lowering the age for tobacco because some kids smoke cigarettes. I don’t see them lowering the driving age because some kids play with their parents’ cars.”

By allowing children to drive adult-sized ATVs, states have left it to parents to determine when children can use the vehicles. But for some, that responsibility is confusing because they have to reconcile state law with manufacturer warning labels that children should never drive adult ATVs.

“It just doesn’t make any sense,” said Leann Bosma, whose 16-year-old nephew was killed while driving a Suzuki Eiger five years ago. Bosma, the mother of four children in Akeley, Minn., was surprised to learn it was legal for her 12-year-old to drive the family’s Arctic Cat 350.

“What do you do when the rules on the equipment say something that conflicts with the rules of the state?”

Some parents realize the gravity of their responsibility much too late.

“I won’t even ride on a four-wheeler anymore,” said Katie Hruby of East Grand Forks, Minn. She routinely allowed her 11-year-old son, Dylan, to ride a Polaris Trail Blazer at his grandparents’ house, where he was supervised and wore a helmet.

Four years ago, while his grandparents were cleaning up after supper, Dylan tried to jump over their driveway on the ATV. The machine flipped on top of him. He died before reaching the hospital.

“Accidents can happen right in front of you,” Hruby said. “And they can happen in a blink of an eye.”

Medical groups ask for bans

For nearly 30 years, federal regulators have challenged the ATV industry to better protect children from the dangers posed by off-road vehicles.

By 1987, injuries and deaths on three-wheel ATVs, which critics dub “rolling death machines,” had become a crisis.

At the request of the CPSC, the U.S. Justice Department sued five major ATV companies, accusing them of selling dangerous vehicles. To settle the case, the companies agreed to halt production of three-wheelers. The industry also agreed to warn buyers about the risks of riding ATVs and to create smaller machines for children.

The number of ATVs across the country has been rising since the early 1990s, reaching 10.7 million vehicles in 2011. Today’s ATVs are much larger and faster than the typical machine in the 1980s.

“They range from very powerful to insanely powerful,” said Mark Elrod, a Georgia engineer whose company has done work for several ATV makers.

In the past decade, 50 percent more children have died in ATV accidents than between 1982 and 1991. The rise in young deaths prompted several medical groups — including the American Academy of Pediatrics — to ask the federal government in 2002 to ban children younger than 16 from operating adult ATVs.

ATV manufacturers lobbied against the proposed ban, saying it would have “little if any practical effect,” records show. In a letter to the CPSC, the seven major ATV makers — including Polaris and Arctic Cat — argued that existing safety efforts, such as limitations on sales to minors, “have been effective in reducing the use of adult-size ATVs by children.”

ATV makers only support a ban at the state level, according to the Specialty Vehicle Institute of America, a trade group that advocates for manufacturers.

In late 2006, the CPSC voted 2 to 1 against the proposal to ban the vehicles for younger drivers, saying enforcement is a matter for the states.

“State legislatures are best equipped to decide under which circumstances children should use these machines,” Commissioner Nancy Nord wrote as part of the agency’s decision.

Rachel Weintraub, senior counsel at the Consumer Federation of America, said she believes the agency buckled to the industry pressure. “There has been a chronic inability of the agency to protect consumers and address the hazards posed by these vehicles,” Weintraub said.

Most states are making it easier for children to ride adult ATVS. Many have rules similar to Minnesota’s, which requires children 12 and older to complete safety training to ride an adult ATV on public trails. Widely supported by ATV riding clubs, the rules sailed through the Legislature with no public opposition, state records show.

State Sen. David Tomassoni, a DFLer who co-sponsored the Minnesota bill, said state guidelines aren’t the problem. “I would venture to say that parents with ATVs are allowing their kids to drive under conditions that they shouldn’t.”

‘Heartbreaking’ losses of children

For many parents, allowing a child to ride an ATV has brought grief and guilt.

Three years ago, Brandy Sutton was stunned when she learned that one of her son’s friends, Jack Capko, was killed on an ATV just 7 miles from his home in Swanville, Minn. She decided it was time for a change.

“I specifically told my ex-husband: ‘You keep my son off ATVs. It could happen to him,’ ” recalled Sutton. “[He] pretty much said, ‘If you don’t like what you see, close your eyes. Everything is fine.’ ’’

Loren Sutton said he thought his son Gavin was ready. “I was riding four-wheelers when I was 8 and 9 years old,” he said.

Last November, 10-year-old Gavin was cruising around his father’s 40-acre spread on a Yamaha Grizzly. He had to stop for a fallen tree and tried backing up along the slope of a ravine. The machine tipped over, pinning Gavin underneath. He died the next day.

“Am I blaming myself? What do you think? I wish he was here,” Loren Sutton said.

Maryrose Capko, Jack’s mother, said she isn’t second-guessing herself. Jack had been driving ATVs on their farm in Little Falls since he was 7. He could ride the vehicle only from the house to the barn. His older brother rode, too.

“They didn’t see them as toys,” Capko said. “They saw them as transportation.”

In November 2011, she told Jack he would have to do chores instead of hockey practice after he damaged the family’s new loader. Jack stormed out of the house and jumped on the family’s Kawasaki Prairie 360. He zipped down the driveway, but when he tried turning, the machine flipped, landing on his chest.

Capko regrets letting her son leave the house angry that day, but she doesn’t think it was a mistake to let him ride ATVs.

“If Jack were here today, would I let him drive a four-wheeler? Yes,” she said, adding that she’s not sure she would give the same advice to other parents.

Adler of the CPSC said it’s heartbreaking to talk to such parents. “The majority of these accidents are utterly predictable and foreseeable and avoidable.”

Despite the risks, certified to ride

On a Saturday morning this summer, more than 20 children drove a deafening collection of all-terrain vehicles around the Dakota County Fairgrounds.

The machines carried the names of the top ATV manufacturers — Polaris, Arctic Cat, Yamaha among them. And all but one carried the same warning: “Never operate this ATV if you are under age 16.”

But the children, 11 to 15, were being certified to operate vehicles that manufacturers insist are too dangerous for them.

Each year, about 2,700 children younger than 16 complete safety training in Minnesota, a relatively small percentage of the state’s young ATV riders. Of the 139 accidents involving young drivers reviewed by the Star Tribune, just 17 had gone through safety training, state records show.

Training can reduce the risk of ATV injuries by half, according to the CPSC, but it emphasizes that training can’t compensate for the challenges facing underage riders.

Neriah Farmer of Faribault brought his two sons to the class because he wanted them to address “bad riding habits,” and because one had been warned for driving on state trails without safety certification. His 11-year-old was training on a Yamaha YFZ 450, an ATV that can go 80 miles per hour.

“They don’t make a faster machine than that one,” Farmer said.

Before the training began, instructor Jay Peterson gathered the children, then pulled out a piece of paper: “This is a list of fatalities in Minnesota, and it’s not fun to read.”

He described how children and adults were killed making basic mistakes while driving ATVs. For the next three hours, he drilled the students on driving fundamentals — emergency stopping, hand signaling, equipment checks. The trainees navigated a pylon-lined obstacle course and practiced turning their machines on a steep hill.

They were quizzed on how they would handle various riding situations, such as hitting a patch of ice.

This is the sort of initiative that George Radke, president of the ATV Association of Minnesota, has supported for years. The group lobbied against age restrictions and pushed for the safety training program.

A few months after Radke’s 14-year-old son, Andrew, took the training class, he went on an ATV ride with some friends. It was a January night in 2004, and the roads in Anoka County were slippery. Andrew zoomed ahead on his father’s Honda 400, lost control and slammed into a tree. He died before he reached the hospital.

“It wasn’t the ATV that killed my son, it was my son’s own bad decision,” Radke said.

Radke worries when he sees some children struggling to operate an adult ATV. Yet, he maintains that families should make their own decisions.

“If I had never brought ATVs into the house, my son would still be alive today,” Radke said. “But that’s all ‘could have, would have, should have.’ ”

Next: Part 3: State to state, ATV rules are all over the map

Go to Part 1: ATV thrills drive child injuries, deaths

Go to Part 4: New push for changes to ATV design

Go to Part 5: Dangerous terrain: ATVs and open roads