Winter monitoring reports from the 2008-09 season in Yellowstone National Park suggest more ways to reduce noise levels that are exceeding

standards and noted that a toll booth at the West Entrance didn't have its ventilation system working on the busiest day of the winter.

The draft reports cover noise and air pollution as well as animal reactions to winter visitors.

Overall, the reports show a decline in most areas monitored, in part because of an average decrease of 95 fewer over-snow vehicles from the previous winter.

During the winter season, 17,252 snowmobiles and 2,389 snow coaches entered the park.

Despite the decline from previous winters, the sound levels of older snowcoaches continued to exceed park thresholds, especially at higher speeds, even though snowmobiles were audible for longer periods.

Two-stroke snowmobiles used by park employees, concessionaires and contractors also topped the list for noisiest machines in the park.

Winter park tourists, by contrast, are required to ride quieter four-stroke machines.

The report suggested lowering the speed limit as a way to reduce noise levels in the park as well as educating snow machine operators.

The change to requiring guided snowmobile tours

in the park has led to

more concentrated travel on park roads, accord-

ing to monitoring of

wildlife-machine interactions.

The study's authors suggested establishing a 100-meter distance when

stopping near groups of wildlife as one way to

lessen impacts to the animals.

All three reports can be found online.

Comments or suggestions on the draft will be taken until Sept. 25 and can be e-mailed from the Web site or mailed to: Management Assistant, Yellowstone National Park, P.O. Box 168, Yellowstone National Park, WY 82190.