Agency to release latest Yellowstone winter plan

The new proposal will undergo more public review before a final decision is made.

If the plan goes through, it will take effect in the 2014-15 winter season. Next winter's season would operate under the current limits of up to 318 snowmobiles and 78 snow coaches.

Yellowstone Superintendent Dan Wenk said the new proposal is unique because it's based on the number of "transportation events" and not the actual numbers of snow machines. A transportation event is initially defined as either one snow coach or on average a group of seven snowmobiles.

The idea is to keep snow machines in groups, making it easier to control the overall noise and air pollution in the park and allow flexibility on the number of machines allowed to operate in the park.

"By the fact that we're basing this on the number of events and not the number of vehicles, it requires packaging of traffic which we think benefits greatly wildlife and natural soundscapes," Wenk said. "By packaging traffic we believe that we will be less impactful on the natural environment, and noise and air pollution testing will continue in the park to ensure that we stay within the requirements that we have."

Under the concept, the park can allow up to 480 snowmobiles plus 60 multi-passenger snow coaches on busy weekends, but the snowmobile groups cannot average more than seven snowmobiles over the entire season. Most of the snowmobile groups must be guided, but the Park Service would allow one non-commercially guided group of up to five snowmobiles to enter each of the park's four entrances each day.

Jack Welch, a leader of the snowmobile advocacy groups called the Yellowstone Task Force and the Blue Ribbon Coalition, said snowmobile guides like the package concept.

"The bottom line is, they're able to run their business in such a manner that they can accommodate more people on certain days and average it out over the season," Welch said.