 DTCS proposes a phased approach, with improvements to bus service (over the Dumbarton [Road] Bridge) to be implemented by 2020, diesel trains over the Dumbarton Rail Bridge to Union City by 2030, and finally electrification of the rail line by 2035, at a total estimated cost of $1.6 billion.This combined phasing contrasts with earlier DRC studies, which assumed that enhanced bus or rail service as mutually exclusive alternatives.In August 2018, SamTrans partnered with Cross Bay Transit Partners, a limited liability corporation formed by Facebook and the Plenary Group, to perform full environmental impact analyses and a fiscal impact analysis for the project or explore possible alternatives.