The trail through the Cal Park Hill Tunnel offers a quick, smooth ride through the hill that separates San Rafael from the ferry terminal in Larkspur and southern Marin County. As part of the 70-mile SMART Pathway, the trail will share the tunnel with the SMART commuter trains when they start running.
The original tunnel was constructed in 1884 as part of the Northwestern Pacific line that carried freight and passengers to Tiburon and Sausalito. The tunnel was then expanded in 1924 to allow for double tracking and an electrified passenger trail. Freight continued to run on the line until the late 1970s, when Marin County purchased the corridor for future passenger rail and trail use. Due to deterioration, unstable rock and fires, the north and south sections of the tunnel both collapsed in the 1980s.
To reconstruct the tunnel, all the wood timbers had to be removed and replaced with steel arches that were then encased in shotcrete embedded with small steel fibers to increase flexibility. The new tunnel will also accommodate the SMART commuter rail line, and the trail will be walled off from the rail line to prevent trail users from accessing the tracks. The trail will have a separate ventilation system from the train track, which will have diesel engines running on the line.
The path can be accessed from the Larkspur Landing Shopping Center on the tunnel's south side, and off of Andersen Drive in San Rafael on its north end.