The Dumbarton Rail Corridor is a proposed transbay passenger rail line which would reuse the right-of-way that was initially constructed from 1907–1910 as the Dumbarton Cut-off. The Dumbarton Cut-off includes the first structure to span San Francisco Bay, the 1910 Dumbarton Rail Bridge, although the vintage Cut-off bridges would likely be replaced prior to activating new passenger service. Dumbarton Rail Corridor would provide service between Union City in the East Bay (where passengers could connect with BART, ACE and Capitol Corridor trains) and Menlo Park on the Peninsula, with train service continuing to both San Francisco and San José along the existing Caltrain tracks. It has been in the planning stages since 1988, and would be the first above-ground transbay rail line since Key System electric trains stopped running on the lower deck of the Bay Bridge in 1958, and the first new transbay crossing of any kind since the completion of the Transbay Tube in 1974. Route description The Dumbarton Rail Corridor service, as proposed in 2006, would provide six westbound trains originating from the Union City BART station, rebuilt as an intermodal station; after crossing the rebuilt Dumbarton Cut-off bridges, the trains would join the existing Peninsula Corridor (Caltrain) line south of the existing Redwood City station. Three trains would proceed north to San Francisco and three trains would proceed south to San Jose. In the afternoon, the six trains would return from San Francisco and San Jose to Union City. The initial service offering would not include reverse commute (west-to-east in the mornings and east-to-west in the afternoons), mid-day, evening, or weekend trains. Hayward to Centerville (Segments G/F) Part of the Dumbarton Rail Corridor plans include a new connection between the Oakland subdivision (running generally north–south) and the Centerville line (running generally east–west) near Shinn Street, east of the Fremont Centerville station. Trains originating in Union City would enter the Shinn connection, turning right from southbound to westbound, and pass under the BART tracks before joining the Centerville line. Freight traffic would be rerouted from the Oakland subdivision to the parallel Niles subdivision, slightly to the east. Other proposed improvements included a proposed fourteen-span bridge over Alameda Creek to separate freight and passenger traffic. Use of this segment would require acquisition of the right-of-way from Union Pacific. Capitol Corridor trains would be rerouted to the Oakland subdivision to share service at the Union City intermodal station. A