Work on the eastern trestle approaches was nearly complete by the end of 1907, but it was the foundation for the steel structure over the San Francisco Bay that posed the greatest challenge, due to the rushing current and marshy land approaches.
Tracks were laid from Niles to Dumbarton starting in late 1906, and on the opposite side of the Bay, tracks were laid between Redwood City and the western bridge approach in 1908.

The Dumbarton Cut-off rail line includes a second swing bridge to the east of the Dumbarton Rail Bridge, spanning Newark Slough.
The Newark Slough bridge was complete by May 1908.

The bridge was initially anticipated to be completed in mid-1907, then March 1909, but it was not completed and opened until June 1910, providing San Francisco with a more direct transcontinental rail link for freight and passenger service, avoiding detours through Santa Clara and San Jose.
Just prior to its opening, the San Francisco Call described the existing Southern Pacific passenger rail station at Third and Townsend as "notoriously inadequate," calling for a new or relocated station closer to Market Street.
One of the conditions imposed on Southern Pacific in granting the construction permit was the Cut-off would be open to all railroad companies, although as the owner, Southern Pacific would be allowed to charge a toll.
Work on the eastern trestle approaches was nearly complete by the end of 1907, but it was the foundation for the steel structure over the San Francisco Bay that posed the greatest challenge, due to the rushing current and marshy land approaches. Tracks were laid from Niles to Dumbarton starting in late 1906, and on the opposite side of the Bay, tracks were laid between Redwood City and the western bridge approach in 1908.
The Dumbarton Cut-off rail line includes a second swing bridge to the east of the Dumbarton Rail Bridge, spanning Newark Slough. The Newark Slough bridge was complete by May 1908.
The bridge was initially anticipated to be completed in mid-1907, then March 1909, but it was not completed and opened until June 1910, providing San Francisco with a more direct transcontinental rail link for freight and passenger service, avoiding detours through Santa Clara and San Jose. Just prior to its opening, the San Francisco Call described the existing Southern Pacific passenger rail station at Third and Townsend as "notoriously inadequate," calling for a new or relocated station closer to Market Street. One of the conditions imposed on Southern Pacific in granting the construction permit was the Cut-off would be open to all railroad companies, although as the owner, Southern Pacific would be allowed to charge a toll.
Dumbarton Rail Bridge