As ridership has grown nationwide, hundreds of children have been killed riding all-terrain vehicles built for adults. The Star Tribune published a five-part series in November 2014 examining how the industry, government and families have failed to heed the warnings about risks that off-road vehicles pose to children.

Part Two: States shun federal ATV age limits

Owen Farmer, 11, of Faribault, Minn., drove through an obstacle course, shifting his body weight to compensate for the hill, during a training session

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.

Part Three: ATV regulations are all over the map

Four-year-old Nina Haley, of San Francisco, rode an ATV on her own while her mother, Stacy Situ, watched from a nearby ATV at the Oceano Dunes State V

Some have imposed tough laws for children to ride, but others leave age minimum open.

Massachusetts has nation's toughest ATV law

In Massachusetts: Warden Nate Cristofori is responsible for patrolling the activity of off-road vehicles around his town.

– The showroom at Pilgrim Power Sports is sparse if you’re looking for an all-terrain vehicle. Only three new ATVs are on…

Part Four: ATV design changes could reduce injuries

Some call for added features, but the industry says riders who follow the warnings already in place will be safe.

Part Five: Dangerous terrain: ATVs and open roads in Minnesota

No surface is more dangerous for ATVs than pavement, many road safety authorities say. But across the country, more local and state governments are allowing all-terrain vehicles to be driven on paved roads.

Live Chat Replay: Our Q&A on regulating ATVs

The Star Tribune just completed a series about the missed warnings and risks of off-road vehicles that frequently injure or kill children. Read a chat conducted by the series reporter.