Families snowmobiling in Yellowstone National Park this winter will not have to pay a separate entrance fee for each snow machine they ride into the park, according to Wyoming's congressional delegation.

Under a change adopted by the National Park Service, families entering Yellowstone with several snowmobiles will be charged just $10 - the same entrance fee they would pay in the summer if they entered the park in one car.However, any two people on a snowmobile who are not part of a larger family group would pay the per-person fee of $4 each, the congressional delegation said. Families are defined by the Park Service as a person's spouse, children and parents, the congressmen said.

The change announced by Sens. Malcolm Wallop, Alan Simpson and Rep. Dick Cheney, all Republicans, is the result of comments from Wyoming snowmobilers who said it would be unfair to charge them the same fee they would pay to drive into Yellowstone during the summer.

"A family of six on three snow machines shouldn't have to pay $30 to enter in the winter time, when it would cost only $10 in the summer," the delegation said, asking the Park Service to change the entrance fee scale.

The new rules apply to all parks charging entrance fees and to motorcycles and mopeds in the summer as well as snowmobiles in the winter, the delegation said in a joint release.

Grand Teton National Park south of Yellowstone does not charge a winter entrance fee, but snowmobilers must buy a $5 permit for access to the park for an entire winter.