36 CFR § 7.53 - Black Canyon of the Gunnison National Monument.
(1) During periods when snow depth prevents regular vehicular travel to the North Rim of the Monument, as determined by the superintendent, snowmobiling will be permitted on the graded, graveled North Rim Drive and parking areas from the north monument boundary to North Rim Campground and also to the Turnaround.
(2) On roads designated for snowmobile use, only that portion of the road or parking area intended for other motor vehicle use may be used by snowmobiles. Such roadway is available for snowmobile use only when there is sufficient snow cover and when these roads and parking areas are closed to all other motor vehicle use by the public. These routes will be marked by signs, snow poles, or other appropriate means. Snowmobile use outside designated routes is prohibited.