supervisors, who favored surface routes, but those were over the objections of Sunset residents, who preferred "the shorter and most direct [Duboce] route". Construction and opening Funds for test bores were set aside in June 1922 and the City Engineer's report, including detailed plans and estimated costs, were filed three months later in September. As planned, the tunnel would be long and would cost . The final route was not approved until April 6, 1925, due to "protracted political discussion." The contract for the Sunset Tunnel was awarded on May 10, 1926 for the low bid of , submitted by the Youdall Construction Company, who broke ground on the project on June 10, 1926. As designed, the Sunset Tunnel was long including approaches with a grade of 3%; inside, the width was and the vertical clearance was above the top of the rail. The total length of the two open cuts for the approaches was ; the tunnel was driven largely through serpentine rock. The tunnel was constructed using three drifts: a pilot drift at the crown, and two at the side walls. The pilot drift was accelerated in order to provide ventilation and to explore the geologic formations, and that crown drift was "holed-through" less than a year after groundbreaking, on March 11, 1927. Construction of the tunnel was completed on February 4, 1928 for a total cost of . After the tunnel was nearly complete, a contract was awarded to build the rail line, but work was halted under an injunction that lasted from October 1927 to May 1928. The tunnel was opened for revenue service on October 21, 1928 in a ceremony presided over by Mayor James Rolph. The new "N" line recorded the second-highest gross revenues of all streetcar lines shortly after opening. Both the Twin Peaks and Sunset tunnels were credited with spurring development in the Sunset District, with many of the homes built by Henry Doelger in the 1930s and 1940s. Intrusion Access to the tunnel is restricted to San Francisco Municipal Railway light rail trains only. Despite the access limitations, this tunnel is not well protected, and has been vandalized, copper cable has been stolen, and graffiti has been painted on the surfaces. From time to time, automobile drivers manage to drive their cars into the tunnel, including four separate incidents in February 2017 alone. Trackway Improvement Project The Sunset Tunnel Trackway Improvement