National Park Service officials will allow 318 snowmobiles and 78 snow coaches a day in Yellowstone National Park during the next two winters.

Officials announced the two-year plan during a teleconference Thursday. The interim rule will be in effect this winter and the next while the Park Service works on a permanent winter travel plan for Yellowstone.

This year’s winter season begins Dec. 15 and lasts until March 15. The plan will keep the East Entrance and Sylvan Pass open through the use of avalanche control from Dec. 22 to March 1.

Yellowstone spokesman Al Nash defended the decision to go down to 318 of the cleanest-running machines a day.

“We have allowed up to 720 guided, best available snowmobiles in the park the past five winters,” he said. “Our use certainly hasn’t been anywhere near that.”

Nash said the average daily snowmobile use during the past three winters was 266 snowmobiles and 33 snow coaches a day, with a peak of 557 snowmobiles and 60 snow coaches.

“If you look at the last three winters, about 25 percent of the days would exceed the new 318 limit,” he said.

The majority of those days occur during the Christmas/New Year’s, Martin Luther King Jr. Day, and Presidents Day holidays, he said. 

For the South Entrance, the plan would allow 114 snowmobiles and 13 snow coaches a day divided among 12 companies with permits to operate in the park. During the past three winters, roughly 32 percent of the days exceeded 114 snowmobiles at the South Entrance, which serves visitors from Grand Teton National Park and Jackson Hole.

Wyoming politicians criticized the interim plan.

Wyoming Gov. Dave Freudenthal said the rule is “simply not acceptable.”

“It extends even further the policy of the National Park Service to limit access to the public’s lands,” Freudenthal said in a release. “It had been our hope that the Park Service would at least compromise and allow us more than 318 people on those days which were considered high business or high traffic days, namely Christmas, New Year’s and Presidents Day.”

The Wyoming congressional delegation, U.S. Sens. Mike Enzi and John Barrasso and Rep. Cynthia Lummis, also advocated for more machines.

“This decision ignores the primary mission of our national parks,” Barrasso said in a release. “The administration’s proposal will limit public access and harm our local communities. Putting limits on public access is not required by law and is not backed by science. The administration has put politics ahead of management by limiting public access to our parks.”

A Park Service directive, however, puts protecting resources above motorized recreational use in parks.

Patricia Dowd, Yellowstone program manager for the National Parks Conservation Association, said the science clearly shows that snow coaches, not snowmobiles, are the best way to protect Yellowstone’s natural resources.

“For the past 10 years, the National Park Service and the Environmental Protection Agency have studied the impacts snowmobile use has on visitor experience, Yellowstone’s air quality and wildlife,” she said. “Repeatedly, [National Park Service] and EPA studies have determined that even at 250 snowmobiles per day, visitor experience, wildlife and air quality are impacted.”

“So, yes, 318 snowmobiles per day is too high,” she said.