Laramie, WY – More people rode snowmobiles in Yellowstone National Park this winter than in the past several years. But even the busiest day didn't approach the daily limit of 720 snowmobiles allowed in the park. On average, 299 snowmobiles entered the park between December and March 11th, when the winter season ended. Last year the average was 253. The busiest day this season was December 28th, when 542 snowmobiles entered. That's well below the daily limit of 720, that's been in place since 2004. It's the number the National Park Service is considering for a long-term rule, to reduce air pollution and noise in the park. All snowmobiles entering the park have to meet noise and pollution standards and all riders must be with a commercial guide.