Entrance to Alameda County Shoreline Trail on the East Bay side of the Dumbarton Bridge.
Access to Shoreline Trail from the south is through a Caltrans maintenance area hidden underneath the Dumbarton Bridge where Marshlands Road from Newark deadends at the Dumbarton fishing pier. The unpaved dirt trail, which is open only during daylight hours, goes north along the top of a salt pond levee. Google Maps shows Shoreline Trail as a bike trail, though bikeability might be tough in the winter when the levee top becomes a goopy mud pit. The packed mud is ridable when dry even with road bikes, though the trail surface can be rutted and bumpy.
From the Dumbarton Bridge, Shoreline goes north to the Alameda Creek Region Trail. It also provides access to Coyote Hills Regional Park via another levee path — the “No Name” Trail. Though Google Maps does not show a direct connection from No Name to Coyote Hills, the connection is there and is shown on the ABAG South Bay trail map [PDF].
Shoreline Trail is part of the 500 mile San Francisco Bay Trail that will someday ring the entire San Francisco Bay and San Pablo Bay shores. When complete, this continuous trail will connect the shoreline of all nine Bay Area counties, link 47 cities, and cross the major toll bridges in the region. To date, approximately 290 miles of the alignment—over half the Bay Trail’s ultimate length—have been completed.