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HAYWARD — BART riders hoping for relief from trains packed beyond capacity will have to wait until after the New Year, officials said Thursday.

The agency is in the process of replacing its 669 train cars with 775 new ones, a $2.6 billion effort to upgrade an aging fleet, add capacity throughout the system and improve passengers’ experience with quieter, more reliable cars.

BART’s first 10-car test train failed a key safety inspection in early November when it was unable to recognize the train’s length and opened the doors on only three of the 10 cars. Independent of that incident, the train doors did not open automatically at one station and the train operator was unable to open them manually, BART said in a letter sent earlier this month to state regulators explaining the failures.

BART made some hardware and software changes to solve the problems, including adding a manual switch for operators to indicate the train’s length and adding redundancy in the software so the doors open when they should. In its letter to state regulators, BART officials said the train cars, despite not performing as intended, at least failed in a way that would not endanger passengers.

“In both cases, the equipment responded as designed, and, in fact, demonstrated that the built-in vital systems remained intact, functioned as intended and automatically disallowed any condition that might compromise passenger safety,” read the unsigned letter to the California Public Utilities Commission, the agency overseeing the rollout of BART’s new cars.

Now, the agency is ready for a re-do, said BART spokesman Chris Filippi.

“We’re currently working with the CPUC to set up a date and time for that test, but a date has not yet been set,” he said. “An estimate for when the new trains will go into service will be based on the test run and when the CPUC is available.”

In addition to problems with the cars doors, Filippi said BART identified an issue with its public address system, which has since been resolved. He, along with colleagues in BART’s communications team and key staff involved in testing the new cars, did not respond to questions about any other issues the agency may be working through to bring the new cars on board.

The lack of transparency during the testing process has been frustrating, said several member’s of BART’s governing board, who, along with the public, have been largely left in the dark in recent weeks about the status of the new cars. Board Director Debora Allen said the agency’s refusal to be forthcoming about obstacles it’s working through reinforces the perception BART has something to hide.

“It should be public knowledge what the process is,” she said. “The public has a right to know. These are public funds.”

Newly-elected president of the BART board, Robert Raburn, said staff is just focused on fixing any glitches before the new trains start carrying passengers.

“We’re focused on getting it right,” he said.

Even if everyone wishes the new cars were in service “yesterday,” ensuring they are safe and won’t need major retrofits are the top priorities, said Director Rebecca Saltzman.

“That’s why the testing process has taken a lot of time; we want to make sure the trains are safe — that’s the first priority — and they work well and aren’t having to go back for service or back for other changes,” she said. “We appreciate our riders staying patient, and we know it’s frustrating because the trains are crowded.”

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26-story housing highrise eyed in downtown San Jose BART needs the new cars to accommodate an anticipated increase in riders that will come with the expected May opening of the Antioch extension and the Berryessa and Milpitas stations, expected in June. The Santa Clara Valley Transportation Authority (VTA), which is constructing the stations in the South Bay, bought 60 new BART cars as part of the initial 10-mile extension into Silicon Valley.

The VTA doesn’t expect the delays in the new cars to jeopardize the stations’ opening, which will add an estimated 23,000 daily trips, said VTA spokeswoman Brandi Childress. Service will ramp up and cars will be phased in over time, she said.

BART now has 18 new cars — not including the first 10-car test train — at its test track in Hayward, Filippi said. Two more have left Bombardier’s Plattsburgh, New York, plant and are en route to California, he said.