The environmental coalition said that off-road vehicles are used in 56 of the 108 large national parks it surveyed.
Environmental groups have complained that off-road traffic poses hazards to hikers, causes erosion on hillsides and is often harmful to plants and animals.
A new study raises the possibility that off-road activities increase the spread of the deadly hantavirus in mice that live near such popular recreation areas.
In mid-December, a federal appeals court in Washington ruled that off-road tires from China could not be subjected to the anti-subsidy taxes the Commerce Department had tried to impose.
The American Alpine Institute, a climbing school and guide service in Bellingham, Wash., estimates that off-road skiing, as it might be called, is growing three to five times faster than the traditional downhill sport.
The commission's statistics show that off-road motorcycle use accounted for more than 39,000 injuries that required emergency room treatment in 1998, a figure that rose to 47,400 in 1999.
Mr. Kratzke said that he was studying a requirement that off-road tires and possibly heavy-duty tires meet the same standards as car tires, and that all of these tires pass a test of at least 100 miles an hour.
It is noted that off-road crashes were not included in any of the national police accident reporting systems.
A judge agreed, determining that off-road vehicles are a "major contributor to the problem".
Off-road motorcycle circuits should be considered to be an appropriate form of reclamation of closed quarries, sandpits and claypits, considering that off-road motorcycles can potentially be used as a management tool to block the afforestation of habitats formed at post-industrial sites.
As with that off-roader, the box works seamlessly, slipping among its multitude of ratios without calling undue attention to itself.
