There are times when riding a snowmobile down the road in Yellowstone National Park can be particularly challenging. Times when it's 20 degrees below zero and the visor on your helmet ices up and when the goggles or sunglasses you were wise enough to wear under your helmet do as well.

I know this not because I have done it, but because I overheard some snowmobilers lamenting just those conditions during a break at the Madison Junction warming hut two winters ago. I had reached Madison Junction in a snowcoach, a warm, comfortable mode of transportation in which you don't need to scrape the frost from your glasses.

Which mode of travel is better?

That is a matter of opinion. Many visitors enjoy cruising through the park with their thighs wrapped around a snowmobile and the wind whistling through their helmets, others prefer sitting with friends and family in a warm, enclosed coach in which they can chat and immediately share wildlife sightings while listening to the driver/guide provide interpretation.

Which mode of travel is best for Yellowstone?

That is a decision about stewardship, and it can be rife with pitfalls, from those political in nature to those specific to how we are allowed to enjoy the national parks. In efforts over the past decade to make the decision, the professional judgment of the National Park Service has been stretched like a rope in a tug-of-war.

The agency's legal obligation to conserve Yellowstone and its resources, its scientific conclusions, and the tide of public comment have pulled in one direction. Politicians and political appointees have pulled in the other. But the question that goes begging in solving the winter-use dilemma in Yellowstone is this: If you cannot adhere to the Park Service's over-arcing mandate, to protect the resource unimpaired for the enjoyment of future generations, in the world's first national park, where in the National Park System can you?

The good news coming out of the public hearings that have been held since park officials first released their draft Environmental Impact Statement on the matter earlier this year is that Yellowstone Superintendent Dan Wenk has said time and again that the preferred alternative contained in that document will not be the preferred alternative in the final EIS. What remains to be seen is how it is altered.

Winter in the Upper Geyser Basin. Kurt Repanshek photo.

With the public comment period on the draft EIS coming to a close at midnight on Monday, July 18, we at the Traveler believe park officials need to make some serious tweaks to the document as they go about reviewing the comments.

Here are some places to start:

* Close Sylvan Pass In Winter

There is no good reason to keep the pass open in winter. Last winter, an average of three snowmobiles a day crossed the pass from the East Entrance. For that the park has budgeted $325,000 for efforts aimed at keeping the pass open. That math doesn't even make sense when the country isn't in economic straits.

And to keep the pass open, rangers use a World War II-era 105 mm howitzer to lob artillery rounds at 20 avalanche chutes that tower above the pass.

Not only does this practice go against the very grain of the National Park Service Organic Act, but it exposes rangers to unnecessary dangers. Nowhere else in the National Park System are "rangers ... doing this kind of avalanche hazard mitigation or where this type of work is performed for a transportation corridor that is primarily used  by over-snow vehicles," according to a panel of experts convened in 2007 to discuss avalanche control in Yellowstone.

Even during the highest winter-use seasons during the 1990s, over-snow traffic through the park's East Entrance and across Sylvan Pass accounted for less than 5 percent of the park's winter visitation, according to the DEIS.

How might closing the East Entrance to over-snow traffic affect the tax coffers of Cody, Wyoming, and its surrounding Park County?

According to economic studies contained in the DEIS, "Recent lodging and tax data for Fremont (Idaho) Park (Wyoming) counties indicate that declines in snowmobile entries into Yellowstone in particular, and in winter visitation in the park in general, have not detectably impacted the overall winter tourist economy in the counties as measured by monthly lodging tax collections. This is despite the fact that the economies of these counties are relatively small."

Part of the reason Park County is not greatly impacted, the report notes, is that it draws 41 percent of its lodging tax revenues in winter from the Mammoth Hot Springs Hotel, which you can't snowmobile to.

Old Faithful on a deeply sub-zero morning. Kurt Repanshek photo.

That the Park Service does not particularly like bombing within its parks was noted back in November 2008, when it decided that the Burlington Northern Santa Fe Railway could not use howitzers identical to those used in Yellowstone to control avalanche chutes on the southern flanks of Glacier National Park above their tracks.

Add to the cost and dangers of the Sylvan Pass avalanche control program the fact that the landscape being bombed in winter is used by the Canada lynx, a species already listed under the Endangered Species Act as threatened, and the wolverine, a species the U.S. Fish and Wildlife Service has said is a candidate species for listing, and you should raise your eyebrows higher over the propriety of this practice.

* Do Away With The Sliding Scale For Over-Snow Vehicle Numbers

This approach makes visiting the park a bit more problematic for visitors. As outlined in the draft EIS, Yellowstone's managers would drape a patchwork of priorities and quotas across the winter calendar.

On some days visitors would find the park placing emphasis on allowing higher levels of motorized traffic with a lower level of resource protection; on others (a much smaller number of days in the proposed plan) visitors would experience less noise and disruption because less overall traffic would be allowed and the vehicle mix would tip toward multi-passenger snowcoaches rather than one- and two-person snowmobiles.

Beyond visitors having to juggle their calendars to mesh with the sliding scale (and hope for snowy weather to coincide), sticking with the preferred alternative in the DEIS could lead to a maximum 28,852 over-snow vehicles in the park during the 90-day winter season.

That total would surpass the levels of snowmobiles and snowcoaches seen entering the park during the winters of 2003-04 (24,481 vehicles), 2004-05 (20,565) and 2005-06 (24,379), the years monitored by Dr. P.J. White, a Yellowstone wildlife biologist, and his colleagues to measure wildlife impacts. In that study, the biologists recommended that over-snow vehicle levels be kept "at or below those observed during our study."

Going with the park's preferred alternative also could lead to a noisier Yellowstone, as the DEIS notes that under Alternative 7, "Cumulative impacts to soundscapes would be longterm, moderate and adverse."

* Give Yellowstone the Best Possible Protection

Perhaps the best choice for Yellowstone's environment and resources would be simply to ban over-snow travel in the park. Take a page from Glacier or Yosemite national parks, which don't try to keep either the Going-to-the-Sun Road or the Tioga Road open in winter -- for any vehicles, wheeled or over-snow -- because of the extreme conditions and hazards.

The Old Faithful Inn is shuttered in winter. Kurt Repanshek photo.

But plowing only the roads from Mammoth Hot Springs to Cooke City, Montana, so Cooke City and Silver Gate residents could get out and banning all other travel in the park's interior, would no doubt be an overly tough sell after all these years of winter use in Yellowstone.

The next best thing would be to minimize as much as possible the impacts that continued winter-use brings, and that can be accomplished by relying solely on snowcoaches to ferry visitors around Yellowstone's snowbound interior.

Reversing decades of practice is never easy. Nor is protecting the world's first national park. At odds is an individual's preferred form of recreation, and telling people what they can and can't do is never popular.

But Yellowstone's resources -- its thermal features, soundscapes, clean water and air, its wildlife -- are incomparable. Shouldn't they be protected as such?

While snowmobile manufacturers in 2005 were put on notice by the National Park Service that strides in reducing noise and pollution from snowmobiles were expected to be made, their record has been uneven.

In some cases, while there were initial reductions achieved in noise under the "best available technology" requirements, numbers have begun to reverse. Some models approved for use in the park have become louder than those approved in earlier seasons and their hydrocarbon emissions have increased.

But a snowcoach-only approach to navigating Yellowstone in winter would require that the Park Service insist that only best available technology snowcoaches be used. Already, according to the park's DEIS, cleaner snowcoaches exist than some of those being used in the park.

Cleaner emitting snowcoaches than the present vehicles being used in the park have been demonstrated by the Bombardier snowcoaches outfitted with modern engines with pollutant controls and catalytic converters. A BAT for snowcoaches should be possible and would lead to a reduction in emissions.

When the Environmental Protection Agency wrote to the Park Service at the outset of this winter-use environmental study, it said: "...we expect marked environmental performance improvements as older snowcoaches are replaced by today's engines and emission-control technology."

With snowcoaches being capable of carrying a dozen or more visitors at a time, phasing out snowmobiles would lead to fewer over-snow vehicles needed to meet demand, and, as a result, fewer impacts on the park's resources. Relying entirely on BAT snowcoaches would negate the need for playing the numbers game with sliding scales, would be more reliable and comfortable for park visitors in Yellowstone's highly variable temperatures and snow conditions, and would be healthier for the ecosystem.

The Park Service has the authority under its Organic Act to come down on such a decision.

Let's hope it does.