36 C.F.R. § 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.
(b) Designated bicycle routes. The use of a bicycle is permitted in non-developed areas, as follows:
1. (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. (2) Bicycle speed limits are as follows:
  1. (i) 15 miles per hour: Upon all designated routes within the area administered by the Presidio Trust.
  2. (ii) 5 miles per hour: On blind curves and when passing other trail users.
3. (3) The following are prohibited:
  1. (i) The possession of a bicycle on routes not designated as open to bicycle use.
  2. (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.
(c) A person operating a bicycle is subject to all sections of this part that apply to an operator of a motor vehicle, except §§ 1004.4, 1004.10, 1004.11 and 1004.14.
(d) The following are prohibited:
1. (1) Possessing a bicycle in a wilderness area established by Federal statute.
2. (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.
3. (3) Operating a bicycle abreast of another bicycle except where authorized by the Executive Director.
4. (4) Operating a bicycle while consuming an alcoholic beverage or carrying in hand an open container of an alcoholic beverage.