Buses may replace BART’s early morning trains during Transbay Tube retrofit

A westbound BART train enters the transbay tube in Oakland, Calif. on Friday, Feb. 16, 2018. BART officials will begin a study on the feasibility of a second tube under the bay. A westbound BART train enters the transbay tube in Oakland, Calif. on Friday, Feb. 16, 2018. BART officials will begin a study on the feasibility of a second tube under the bay. Photo: Paul Chinn / The Chronicle Buy photo Photo: Paul Chinn / The Chronicle Image 1 of / 19 Caption Close Buses may replace BART’s early morning trains during Transbay Tube retrofit 1 / 19 Back to Gallery

BART’s earliest morning riders will have to take buses to work instead of trains for as long as 3½ years while the agency makes the Transbay Tube more resistant to earthquakes, officials said Thursday.

The $276 million retrofit of the 3.6-mile-long connector between Oakland and San Francisco will require that BART start running weekday trains at 5 a.m. instead of 4 a.m., to give contractors the extra work time they’ll need to complete the job by 2022, BART officials said Thursday.

The additional work time will shave 4 months and $15 million off the job, said Tamar Allen, BART’s chief mechanical officer.

Rather than strand the 2,800 riders who typically ride the system between 4 and 5 a.m., transit agency staffers are suggesting that BART pay for buses that would either connect to AC Transit’s cross-bay service or run directly to San Francisco.

BART had hoped to start the Transbay Tube retrofit in September, but it may have to wait until February 2019 to give AC time to round up the extra buses and drivers, said Paul Oversier, BART’s assistant general manager for operations.

Most of BART’s predawn riders board at stations at or near the end of the line and travel to downtown San Francisco. Express bus rides from those stations to the Transbay Transit Center would take about 13 minutes less than trains that stop at all stations along the line, BART said. The agency hasn’t settled on a fare, but says it would be less than a train ride.

BART will draw up more detailed plans this summer after it completes studies of first-hour riders and negotiations with the transit agencies that will run the buses.

BART’s Board of Directors heard about the plans Thursday. It took no action, but several members indicated their support for the express buses.

“For a bunch of our riders, our express bus mitigation service is not just a mitigation, it’s a big improvement,” said Director Nick Josefowitz.