DES MOINES, Iowa — When she crashed on an all-terrain vehicle, Megan Cratsley was hurt so badly that doctors had to amputate much of her right arm, a life-altering surgery that launched the teenager on a personal mission to change New York traffic laws to protect other ATV riders.

The buzzy, open-air vehicles are supposed to be banned from roads in New York and many other states. But small communities across the nation are increasingly bending the rules under pressure from riders who want to go wherever they please, even though ATV manufacturers warn that the vehicles are unstable on flat terrain at high speed, and accidents on roads kill more than 300 riders each year.

The trend appalls public health officials and is opposed by the manufacturers.

“We’ve seen too many people die,” said Jen Kruzicke-Cratsley, Megan’s mother, who lives near Buffalo, New York, and joined in her daughter’s legislative efforts to make ATVs safer.

ATV enthusiasts acknowledge the vehicles can be dangerous if not driven properly, but they say the risks are overstated.

Thirty-five states allow local jurisdictions to authorize ATVs on some roads or road shoulders, according to a study by the Consumer Federation of American. While no one tracks how many local governments have offered ATVs access to local roads, the number is rising, as are ATV sales.

In Iowa, at least 17 counties allow all-terrain vehicles on public roads, and a state official said that number could climb to 30 counties by next fall. It’s a similar trend in Minnesota, where at least a dozen counties permit some ATVs on roads, and in Indiana, where about half of counties do so.

West Virginia and Montana allow ATV use on most roads other than highways. Utah lawmakers voted in 2015 to allow street-legal ATVs on the shoulders of all roads except interstate freeways.

In New York, ATVs are banned from public roads except for small stretches between off-road riding areas. Yet small communities often grant unrestricted access if riders demand it, said Peter Bauer, executive director of the group Protect the Adirondacks, which often fights such efforts.

ATV manufacturers say the vehicles are designed only for off-road use. Many models have a higher center of gravity than cars. That design allows them to roll easily across uneven ground but also makes them more likely to topple over at high speed. They also have low-pressure tires that can make handling difficult on paved, dirt or gravel roads.

Studies show that more than half of fatal ATV crashes happened on roads. From 2003 to 2013, that number ranged from a high of 377 road deaths in 2008 to 301 in 2003.

Charles Jennissen, an emergency room doctor at the University of Iowa hospital in Iowa City, has studied the issue and travels around the state to discourage officials from legalizing ATVs on public roads. He’s losing far more fights than he’s winning.

The biggest issue is speed, Jennissen said. The most powerful all-terrain vehicles can travel 80 or 90 mph, but it’s nearly impossible to reach these speeds except on roads, so riders race down rural lanes without realizing the risk.

“We see lots of accidents that are totally preventable,” Jennissen said. “It’s devastating to families and devastating to communities, and they don’t need to happen.”

Riders say manufacturers’ warnings are more about limiting liability than averting serious danger. They regard opening up public roads as a common-sense move that carries little risk and can spur desperately needed economic growth in rural areas by attracting riders and increasing vehicle sales.

Michael Rygh, who co-owns an ATV shop in Algona, Iowa, said a recent decision to open up Kossuth County roads to the vehicles has already boosted sales. He’s confident accidents will be rare.

In Iowa’s Louisa County, Tim Gerst said he had little trouble rounding up 400 signatures on a petition asking supervisors to permit ATVs on county roads. He acknowledges that people get hurt on the vehicles but insists “there’s nothing you can do in life that doesn’t carry risk.”

County supervisors are still studying the matter.

“I wish we didn’t have this decision to make,” Supervisor Randy Griffin said. “I’ll feel terrible if we do something and someone goes out and gets killed.”

Officials faced a similar choice last year in Lake County, Oregon, and opted to open up 700 miles of roads in the vast, sparely populated high plateau region.

County Economic Development Director Rob Thornton said the goal was to generate money from tourism and possibly convince some tourists to come back to stay. The scenic county of roughly 8,000 people has been hit hard by a decline in logging, and its remote location makes it hard to attract other industries.

The hope is to take advantage of the wide-open space by attracting riders not accustomed to so many miles of empty roads. Many people will “travel a long distance to come to a place they can ride,” Thornton said.

David Downing, who oversees ATV programs for the Iowa Department of Natural Resources, said the key to preventing accidents is education, not limiting access.

As long as riders receive proper training, Downing said, he doesn’t expect increased use of roads to result in more crashes. He acknowledged that riders who drive too fast can suddenly find themselves in trouble.

“It all comes down to how you operate them,” Downing said. “It will get you if you do something stupid.”

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