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 Syst