New Report: Industry Making Dirtier Snowmobiles for Yellowstone National Park

Date:   July 17, 2012
Contact:   Kristen Brengel, NPCA, 202-454-3380 or
Ed Chen, NRDC, 202-289-2432

New Report: Industry Making Dirtier Snowmobiles for Yellowstone National Park

Why is the National Park Service Rewarding the Snowmobile Industry With a Proposal to Allow More Snowmobiles and Increased Emissions of Noxious Gasses in America’s Flagship National Park?

WASHINGTON, D.C. — University researchers and the National Park Service detail in a new report that snowmobiles made specifically for use in Yellowstone National Park have become dirtier. The trend contradicts the snowmobile industry’s repeated promises to make cleaner snowmobiles and keep unhealthy gasses such as carbon monoxide, benzene and formaldehyde from fouling the air of the country’s oldest national park.

The report explains that scientists tested 2011-model snowmobiles in Yellowstone and compared their emissions with 2006 models made by the same companies. One manufacturer’s newer snowmobile emitted over 20 times more carbon monoxide than its earlier model. Another company’s newer model had higher emissions of every exhaust gas sampled, including 5 times more hydrocarbons. The report concludes: “The model change in snowmobiles has not been a positive influence on air quality based on the emission data.”

Yellowstone officials posted the report on the park’s website the week after announcing a proposed plan to allow increased snowmobile use in the park.

The park’s superintendent, Dan Wenk said his proposal to allow up to 480 snowmobiles a day in Yellowstone, more than twice the average entries of recent winters, would make the park “cleaner and quieter.”

However, the National Park Service’s own Draft Supplemental Environmental Impact Statement contradicts that assertion. That document shows the proposed plan would increase snowmobile noise and pollution in Yellowstone National Park with significantly greater emissions of carbon monoxide and cancer-causing gasses such as formaldehyde and benzene.

Now in addition, the new emissions report reflects that while the park’s proposal is based on an expectation of snowmobiles becoming cleaner, snowmobiles have instead been getting dirtier.

“Rewarding a technology that is going backward and getting dirtier is the very opposite of stewardship that Americans expect and deserve in Yellowstone National Park,” said Tom Kiernan, President of the National Parks Conservation Association. “After 10 years of pledging to make major improvements to emissions and noise, the snowmobile industry has gone back on its promise to the National Park Service and the public.

The emissions study looked at “recent additions to the snowcoach fleet” and concluded: “emissions are generally lower for newer snowcoaches compared to mean values of the earlier fleet and especially compared to the older carbureted engine snowcoaches.” Indeed, specific data provided in the report show that current snowcoaches are up to 50 times cleaner than current models of “Best Available Technology” snowmobiles when the vehicles’ carbon monoxide emissions are calculated on a per-visitor basis. In per-visitor emissions of hydrocarbons and nitrogen oxides, the report shows snowcoaches are 2-5 times cleaner than snowmobiles. The report reflects that these air-quality advantages of snowcoaches are expected to become even more significant when Yellowstone requires all snowcoaches to utilize newer engines.  

“The National Park Service should make an immediate U-turn on this misguided policy. After all, the growing majority of Yellowstone Park’s visitors prefer multi-passenger snow coaches, which are demonstrably cleaner than snowmobiles, which are getting dirtier. Even park officials have acknowledged that,” said Chuck Clusen, Director, National Park Project at Natural Resources Defense Council. “The only obvious and responsible path forward is to facilitate the use of snow coaches, not snowmobiles.”

Yellowstone’s superintendent recently acknowledged that the snowmobile industry had not lived up to its promise to produce cleaner and quieter snowmobiles for the park and instead that machines had “gotten noisier and dirtier.”* The park has not posted results of recent noise tests yet.


* As far back as 2003, the National Park Service stated in regulations published in the Federal Register: “The NPS fully expects, and the industry has stated that, technological improvements will continue and that snowmobiles entering the parks will be even cleaner and quieter than the machines evaluated for the SEIS.” ( As early as 2005, Yellowstone officials began noting the snowmobile manufacturers’ failure to deliver cleaner and quieter snowmobiles to the park and production instead of noisier and dirtier snowmobiles. A 2005 PowerPoint presentation developed by Yellowstone staff summarized: “there have been no improvements in air or sound emissions since 4-strokes were introduced in 2001.” The new report posted on Yellowstone’s website thus confirms, more than a decade later, the extent of increased air emissions in park snowmobiles. Park officials have also said without offering details publicly that snowmobiles allowed to operate in the park have “continuously become louder” since Yellowstone first adopted its noise standards.


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