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A new plan affecting oversnow vehicles at Yellowstone National Park is nearing final approval, and conservation groups, which typically have been critical of winter access in the wildlife refuge, mostly are pleased.

The National Park Service on Thursday issued a Record of Decision for the Yellowstone Winter Use Plan/Supplemental Environmental Impact Statement, setting the stage for a new access management system in the world's first national park.

The park service must complete final steps before the regulations can be implemented. Officials expect the plan to be published in the Federal Register this fall.

The upcoming winter will be a "transition" year. Rules used for the past four winters will remain the same this winter.

The plan does not specify a maximum number of vehicles allowed into the park on a daily basis starting with the 2014-15 winter. Access management instead will be defined by "transportation events," which are defined as one snow coach or a group of up to 10 snowmobiles.

"This winter use plan is the product of hundreds of hours of public involvement, is based on sound science and is a different approach to winter use management," Yellowstone National Park Superintendent Dan Wenk Wenk said Thursday in a prepared statement. It provides "mechanisms to make the park cleaner and quieter than ever before authorized, allow greater flexibility for commercial tour operators, reward oversnow vehicle innovations and technologies and permit increases in visitation."

A National Park Service release said commercial tour operators will be able to use their allocated "transportation events" for snowmobiles, snowcoaches or a mix of both as long as no more than 50 of the authorized 110 daily events involve snowmobiles. By relying on user demand to determine the best mix of oversnow vehicle (OSV) use and focusing on the impacts of OSV use on park resources, the transportation-event concept protects park resources and allows appropriate access.

"We just got the document and we will continue to study it, but when you look at the trend over the years, this is absolutely going in the right direction," Caroline Byrd, executive director of the Greater Yellowstone Coalition, said Thursday. "We will keep an eye on things, but we give the park service a lot of credit. Things will be moving at a much slower pace in Yellowstone in the winter. That's a good thing for the wildlife and the visitor experience."

The 2014-15 plan also allows for one entry a day per entrance for a noncommercially guided group of up to five snowmobiles and will continue to allow for OSV use on the East Entrance road over Sylvan Pass.

Conservation groups including the Greater Yellowstone Coalition, National Parks Conservation Association, Winter Wildlands Alliance, Sierra Club and Natural Resources Defense Council supported the proposed plan in February but expressed some concerns.

They worried snowmobile groups may be allowed into the park without professional guides. Wenk said this was an effort to replicate other nonguided recreational opportunities on federal lands across the country.

"Required guiding in many ways has solved the wildlife harassment issues," Wenk said in February. "But this plan recognizes that some people want to go without a guide. If you and a group of four others with Best Available Technology [BAT] compliant machines took a training course and met with a ranger, you could enter the park without a guide. This is similar to private trips allowed on many of the rivers."

The groups also took exception with the National Park Service's proposal to continue allowing motorized travel on the East Entrance road and over Sylvan Pass.

The groups say the effort to keep the East Entrance road open and safe from possible avalanches is too expensive, $125,000 annually according to the release, for the low number of visitors that use the access. There were 110 visitors in 2011-12.

They say avalanche control on Sylvan Pass is dangerous for park employees and intrusive on sensitive wildlife such as wolverines and lynx due to the use of artillery shelling.

Twitter: @BrettPrettyman