36 CFR § 1004.30 - Bicycles.
(a) The use of a bicycle is prohibited except on Presidio Trust roads, in parking areas and on routes designated for bicycle use; provided, however, that the Board may close any Presidio Trust road or parking area to bicycle use pursuant to the criteria and procedures of §§ 1001.5 and 1001.7 of this chapter. Routes may only be designated for bicycle use based on a written determination that such use is consistent with the protection of natural, scenic and aesthetic values, safety considerations and management objectives and will not disturb wildlife or the resources of the area administered by the Presidio Trust.
(1) Bicycle use is permitted on routes which have been designated by the Board as bicycle routes by the posting of signs, and as designated on maps which are available in the office of the Presidio Trust and other places convenient to the public.
(2) Bicycle speed limits are as follows:
(i) 15 miles per hour: Upon all designated routes within the area administered by the Presidio Trust.
(ii) 5 miles per hour: On blind curves and when passing other trail users.
(3) The following are prohibited:
(ii) Operating a bicycle on designated bicycle routes between sunset and sunrise without exhibiting on the bicycle or on the operator an activated white light that is visible from a distance of at least 500 feet to the front and with a red light or reflector visible from at least 200 feet to the rear.
(d) The following are prohibited:
(1) Possessing a bicycle in a wilderness area established by Federal statute.
(2) Operating a bicycle during periods of low visibility, or while traveling through a tunnel, or between sunset and sunrise, without exhibiting on the operator or bicycle a white light or reflector that is visible from a distance of at least 500 feet to the front and with a red light or reflector visible from at least 200 feet to the rear.