Marin Singletrack Law
10.05.020 Bicycles. No person shall operate any bicycle or similar vehicle within parks except upon paved roads, fire protection roads, designated bicycle pathways or public roads not signed against such use. Furthermore, no person shall operate or possess any bicycle or similar vehicle elsewhere within parks, including trails, unless signed specifically to permit such operation. (Ord. 3235 § 2 (part), 1996)
http://www.co.marin.ca.us/depts/PK/main/pos/parkrules.cfm#43
10.05.040 Speed limits. No person shall operate any land vehicle, including bicycles, at speeds in excess of fifteen miles per hour within parks, unless otherwise posted. No vehicle shall be operated at a speed greater than is reasonable for safe operation, nor in any manner which may endanger the safety of others or the protection of facilities and environmental resources. (Ord. 3235 § 2 (part), 1996)
http://www.co.marin.ca.us/depts/PK/main/pos/parkrules.cfm#50
BICYCLES ON OPEN SPACE
The District maintains approximately 70 miles of fire protection roads and service roads exceeding eight feet in width which are open to bicycle use. The Open Space District Code specifies that bicyclists must operate their vehicles at speeds which do not exceed 15 miles per hour and reduce their speed to 5 miles per hour when approaching blind turns or passing others using open space lands. Bicycles are not permitted "off-road" or on "single-track" trails. The District road network offers a variety of open space experiences, from expansive and panoramic views of the bay area to intimate and unique environments. Bicyclists are encouraged to explore the diverse opportunities available on open space lands.
http://www.co.marin.ca.us/depts/PK/main/MCOSD/os_about_rulesnregulations.asp
9.05.020 Bicycles. No person shall operate any bicycle or similar vehicle on lands managed by the department except upon paved roads, fire protection roads, designated bicycle pathways or public roads not signed against such use. Furthermore, no person shall operate or possess any bicycle or similar vehicle elsewhere on lands managed by the department, including trails, unless signed specifically to permit such operation. (Ord. 3235 § 2 (part), 1996)
http://www.co.marin.ca.us/depts/BS/Main/BOSagmn/ordinances/ord-3418.pdf
10.05.040 Speed limits. No person shall operate any land vehicle, including bicycles, at speeds in excess of fifteen miles per hour within parks, unless otherwise posted. No vehicle shall be operated at a speed greater than is reasonable for safe operation, nor in any manner which may endanger the safety of others or the protection of facilities and environmental resources. (Ord. 3235 § 2 (part), 1996)
http://www.co.marin.ca.us/depts/BS/Main/BOSagmn/ordinances/ord-3418.pdf