36 CFR § 2.18 - Snowmobiles.
(a) Notwithstanding the definition of vehicle set forth in § 1.4 of this chapter, the provisions of §§ 4.4, 4.12, 4.13, 4.14, 4.20, 4.21, 4.22 and 4.23 of this chapter apply to the operation of a snowmobile.
(b) Except as otherwise provided in this section, the laws of the State in which the exterior boundaries of a park area or a portion thereof is located shall govern equipment standards and the operation of snowmobiles. Nonconflicting State laws are adopted as a part of these regulations.
(c) The use of snowmobiles is prohibited, except on designated routes and water surfaces that are used by motor vehicles or motorboats during other seasons. Routes and water surfaces designated for snowmobile use shall be promulgated as special regulations. Snowmobiles are prohibited except where designated and only when their use is consistent with the park's natural, cultural, scenic and aesthetic values, safety considerations, park management objectives, and will not disturb wildlife or damage park resources.
(d) The following are prohibited:
(1) Operating a snowmobile that makes excessive noise. Excessive noise for snowmobiles manufactured after July 1, 1975 is a level of total snowmobile noise that exceeds 78 decibels measured on the A-weighted scale measured at 50 feet. Snowmobiles manufactured between July 1, 1973 and July 1, 1975 shall not register more than 82 decibels on the A-weighted scale at 50 feet. Snowmobiles manufactured prior to July 1, 1973 shall not register more than 86 decibels on the A-weighted scale at 50 feet. All decibel measurements shall be based on snowmobile operation at or near full throttle.
(2) Operating a snowmobile without a lighted white headlamp and red taillight from one half-hour after sunset to one half-hour before sunrise, or when persons and vehicles are not clearly visible for a distance of 500 feet.
(3) Operating a snowmobile that does not have brakes in good working order.