Development of a tool for modeling snowmobile and snowcoach noise in Yellowstone and Grand Teton National Parks

The National Park Service (NPS) develops winter use plans for Yellowstone and Grand Teton National Parks to help manage the use of Over-Snow Vehicles (OSVs), such as snowmobiles and snowcoaches. The use and management of OSVs in the parks is an issue because of potential environmental impacts and because of actions by environmental, recreational, and commercial groups. The U.S. Department of Transportation, Research and Innovative Technology Administration, John A. Volpe National Transportation Systems Center (the Volpe Center) supported the NPS by modeling the acoustical environment in the parks associated with potential modeling alternatives as well as current and historical conditions. The modeling considered a number of alternatives for inclusion in the NPS’s winter use plans. These alternatives affect the type and number of OSVs that are allowed to operate in the parks and where they are allowed to travel. The acoustical modeling was performed by using the Federal Aviation Administration’s (FAA) Integrated Noise Model (INM), adapted for use with OSVs. INM adaptation included the development of an over-ground sound propagation model to account for propagation over snow-covered terrain. The Volpe Center also developed a new OSV noise database, which defined OSV noise as a function of speed and source-to-receiver distance, based on previously published OSV acoustical studies and winter 2005-2006 measurements. Vehicle types modeled included two- and four-stroke snowmobiles as well as two- and four-track snowcoaches.