From the Missing Link-

Take Shattuck Ave. south to Center St,
Go Right. on Center St. 1 block to Milvia,
Go Left on Milvia 1 block to Allston Way
Go Right on Allston Way to the City Corp Yard and continue along side the basketball courts and jog to the right to pick up Allston Way again. Continue all the way down to 4th St,
Go Right on 4th St. 1 block to Addison,
Go Left on Addison to Aquatic Park then bear right to get onto bike path leading over the I-80 Pedestrian/Bike bridge,
At the West end of the bridge go Left onto the Bay Trail,
Cross University Ave. and continue North on Bay Trail
At Gilman St. there is a sign that says Bay Trail End, go left past parking lot, then right to go to Golden Gate Fields.
Go up the little hill and stay all the way to your left to go around the GGF clubhouse and to the massive parking lot, there are exits along the North fenced border of the parking lot. Exit through the gate and go right to get onto the bike path across the street from the parking lot and take a Left at the intersection (Trail is signed at this point).
After about 1 mile the BayTrail splits before Central Ave. Continue straight rather than Left, and cross Central Ave. and Rydin to the NorthEast corner of the intersection where the trail continues North.
After crossing the bridge bear Left to follow trail around Marina Bay development and the Richmond Marina. Turnaround point.