Most snowmobile enthusiasts spend most of their day riding behind multiple machines, and are frequently exposed to dozens of machines at rest stops, entrance stations, and gas stations. In the areas where snowmobiles congregate, and along busy trails, dangerous carbon monoxide levels exist. After repeated complaints from park employees stationed at snowmobile entrance booths, the National Park Service tested carbon monoxide levels. The levels were higher than carbon monoxide levels found in Los Angeles and Denver - two of the country's smoggiest cities While the NPS acted to protect rangers by fully enclosing Yellowstone's entrance booths and some gas stations attendants have begun wearing breathing filters, most people exposed to dangerous emissions levels from snowmobiles remain unaware of the problem. Snowmobiles enable the average American to have access to the parks.
Snowmobiles limit park access to a wealthy few.
One day of snowmobile use costs as much as nearly ten days of renting snowshoes or cross-country skis.