Nov. 4 (Bloomberg) -- The number of snowmobiles allowed in Yellowstone and Grand Teton national parks would be lowered by 39 percent following a judge's ruling that the vehicles dirty the air and displace wildlife.

The U.S. National Park Service proposed that 318 snowmobiles would be allowed in Yellowstone per day while 50 would be given access to Grand Teton. That's down from a combined 605 snowmobiles in a plan that was rejected by a federal judge in September.

The snowmobile cap released yesterday is part of an ongoing dispute about the number of the recreational vehicles allowed in the two popular Western parks. While the Bush administration pushed to increase snowmobile access, former President Bill Clinton tried to prohibit their use there altogether.

Environmentalists argue the machines pollute the air, disturb wildlife and are noisy. Snowmobile advocates say the ban will hurt business around the two national parks as enthusiasts instead would visit areas where there aren't restrictions.

The current park service proposal, which is subject to public comment until Nov. 17, would last until 2011 if adopted.

To contact the reporter on this story: Adam Satariano in San Francisco at asatariano1@bloomberg.net

Last Updated: November 4, 2008 13:50 EST