National Park Service Winter Access Act

National Park Service Winter Access Act - Continues the use of snowmobiles in specified National Park System (NPS) units where such activity occurred or was authorized as of January 1, 2000. Restricts the use to levels of no less than the average wintertime use and activity over the last three winters.

Authorizes the Secretary of the Interior: (1) under certain conditions, to address or avert significant environmental impacts in a particular unit or portion thereof, to restrict such use down to a level that is no less than 50 percent below the three year average; and (2) to prohibit such use within all NPS units not listed in this Act.

Requires: (1) the Environmental Protection Agency to promulgate final national standards governing emissions by snowmobiles; (2) the National Park Service, in conjunction with the Society of Automotive Engineers, to set noise standards for snowmobile use in the NPS; and (3) the Service to propose revised regulations and management plans to govern such use, based on results of new comprehensive studies.