BILLINGS, Mont. (AP) – Environmental groups have filed a lawsuit over the National Park Service’s plan for allowing snowmobiles in Yellowstone National Park for the next three winters.

The environmentalists claim the government failed to take into account the effect that trails groomed for snowmobiles have on wildlife, particularly bison that travel the roads during the winter.

The lawsuit was filed last week in federal court in Washington, D.C., after the Park Service issued a “finding of no significant impact” for its winter snowmobile plans, an attorney said.

The environmental groups are asking the judge to prevent officials from implementing the plan and to stop trail grooming “in some or all of” Yellowstone until there is compliance with environmental laws and Park Service policies.

“The general rule is that, if you’re not sure about the impact of something, you don’t do it,” said Howard Crystal, an attorney for the groups that filed the suit.

A telephone message left Tuesday for a Yellowstone spokeswoman was not immediately returned.

Beginning this winter, the Park Service plans to allow up to 720 guided snowmobiles each day into Yellowstone and 140 snowmobiles, with no guiding requirement, in Grand Teton National Park and on a road connecting the parks. Nearly all snowmobiles will have to meet standards as cleaner, quieter machines.

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