36 C.F.R. § 212.51 : Parks, Forests, and Public Property — FOREST SERVICE, DEPARTMENT OF AGRICULTURE — TRAVEL MANAGEMENT — DESIGNATION OF ROADS, TRAILS, AND AREAS FOR MOTOR VEHICLE USE — Designation of roads, trails, and areas

(a) General. Motor vehicle use on National Forest System roads, on National Forest System trails, and in areas on National Forest System lands shall be designated by vehicle class and, if appropriate, by time of year by the responsible official on administrative units or Ranger Districts of the National Forest System, provided that the following vehicles and uses are exempted from these designations:
(1) Aircraft;
(2) Watercraft;
(3) Over-snow vehicles (see §212.81 );
(4) Limited administrative use by the Forest Service;
(5) Use of any fire, military, emergency, or law enforcement vehicle for emergency purposes;
(6) Authorized use of any combat or combat support vehicle for national defense purposes;
(7) Law enforcement response to violations of law, including pursuit; and
(8) Motor vehicle use that is specifically authorized under a written authorization issued under Federal law or regulations.
(b) Motor vehicle use for dispersed camping or big game retrieval . In designating routes, the responsible official may include in the designation the limited use of motor vehicles within a specified distance of certain forest roads or trails where motor vehicle use is allowed, and if appropriate within specified time periods, solely for the purposes of dispersed camping or retrieval of a downed big game animal by an individual who has legally taken that animal.

36 C.F.R. § 212.51

70 FR 68288, 11/9/2005, as amended at 73 FR 74613, 12/9/2008