YELLOWSTONE NATIONAL PARK, Wyo. (AP) — The National Park Service is about to publish the final version of its new regulation for snowmobiles and snow coaches in Yellowstone National Park.

The new rule is set for publication in the Federal Register on Wednesday.

Park officials have been working on the new rule for several years. The goal is to allow winter access to Yellowstone while controlling the environmental side effects of having snow machines in the park.

The latest version of the winter use plan doesn't strictly limit numbers of snowmobiles and snow coaches. Instead, planning focuses on "transportation events." A transportation event is defined as one snow coach or a group of up to 10 snowmobiles.

The new rule will take effect starting in the winter of 2014-2015.