That's why a federal judge was right to strike down a plan by the National Park Service to increase their numbers in the park. To do so, the judge ruled, violates the law that protects park resources and ignores the Park Service's own scientific studies on the machines' impacts.

In recent winters, the Park Service has allowed about 260 snowmobiles (sorry, Sarah) into the park each day. It proposed to rev up that number to 540.

That's simply too many. Biologists have recommended that the policy go in the other direction, reducing or capping the number of snowmobiles. As the judge noted, "According to the NPS's own data, the [plan for 540 snowmobiles] will increase air pollution, exceed the use levels recommended by NPS biologists to protect wildlife, and cause major adverse impacts to the natural soundscape in Yellowstone."

For years, environmentalists have argued, rightly, that substituting snow coaches for snowmobiles still enables people to enjoy the park in winter while reducing the adverse impact on air, water quality and wildlife. Snow coaches are tracked buses that carry up to 20 people. It's like the difference between private cars and mass transit.

Sure, snow coaches don't provide the high-speed thrill and independence of snowmobiles, but in other ways they enhance the visitor experience. Guides provide commentary on the snow coach rides, and people can share conversations about the park and what they are seeing.

Visitors rued the passing of private automobiles in Zion National Park, but now that the shuttle system is a tradition there, many folks prefer it to the bad old days of traffic jams.

The battle over snowmobiles in Yellowstone has consumed a decade and four environmental studies. The park is quieter now than in the days in the 1990s when up to 1,400 snowmobiles a day swarmed through park gates and rangers had to wear gas masks to protect themselves from the exhaust fumes.

The transition to snow coaches is well under way. Rather than raising snowmobile numbers, it's time to phase them out for good. Whatever you call them.