Construction of BART’s next extension into Silicon Valley is on track to be completed by the end of the year, but the transit system may not have enough rail cars to fully serve the two new stations it will serve.

BART has ordered new cars to expand and replace its existing fleet, but it needs at least 30 to 40 more cars to serve the extension. Its contract with Canadian rail manufacturer Bombardier calls for 35 cars to be delivered by the end of the year. So far, BART has received just 10, and problems discovered during testing have already led to delays in delivering the rest of the cars.

Meanwhile, work on the 10-mile, two-station extension from the newly opened Warm Springs/South Fremont station to the Berryessa neighborhood of San Jose is at least three months ahead of schedule. Work is 94 percent complete on the extension that was originally expected to open in spring 2018, said Stacey Hendler Ross, a spokeswoman for the Santa Clara Valley Transportation Authority.

VTA, as it is known in the South Bay, is building and paying for the extension then turning it over to BART to operate. But the combination of speedy construction and a delay in rail car deliveries could spell trouble.

“It is going to be close,” said Paul Oversier, BART’s assistant general manager for operations. “But we think we can count on it.”

Whether BART riders can count on it as well remains to be seen. BART already struggles to keep to its schedules with a current fleet of 669 rail cars, some more than 40 years old. And delivery of even the first 10 new cars was problematic.

The transit system already suffers from a car shortage, as anyone who’s crowded onto a packed BART train knows. During a typical commute, BART doesn’t have the ability to run trains with as many cars as it needs. And it can’t even come close to the dream of running 10-car trains, the maximum length, on all lines during the busiest times of day. Without enough cars, passengers are left to stand aboard overcrowded trains — or wait on platforms for the next train that has room to crowd aboard.

The lack of rail cars has prompted BART’s decision to limit service to the Warm Springs station. The result is that some riders have to transfer on trains to or from Warm Springs.

“We just need more cars,” said Robert Raburn, a BART director from Oakland.

Bombardier is under contract with BART to deliver 775 new rail cars within five years. As the cars are delivered, they’ll be added to BART’s existing fleet, which will be slowly retired. The new rail cars will be used throughout the system, not just on the new extension.

The first 10 of the new cars arrived five months late. They’ve been undergoing rigorous testing in BART’s Hayward yard and throughout the system in the early mornings to find and fix problems before BART officially accepts them and Bombardier fires up the production line at its Plattsburgh, N.Y., plant for the remainder of the cars.

BART officials said they hope to give the go-ahead in June and put the new cars to work.

Under its agreement, Bombardier is scheduled to deliver 25 more cars by the end of 2017. Original plans called for 60 cars but troubles discovered during testing of the cars that had been delivered caused BART and Bombardier to extend the tests before the go-ahead to the manufacturer for more new cars.

Back to Gallery BART extension to San Jose on track, but new cars delayed 3 1 of 3 Photo: Michael Macor, The Chronicle 2 of 3 Photo: Michael Macor, The Chronicle 3 of 3 Photo: Michael Macor, The Chronicle





Since the tests began last spring, BART has discovered a number of problems, including the failure of an on-board electrical system that powers lights, air conditioning, heating and part of a braking system. That problem was fixed but more glitches, mainly with software, have emerged repeatedly.

Among those problems are issues related to train control and propulsion, including getting the new cars to stop within 1 foot of the black boarding marks on station platforms. Existing cars have a 3-foot margin.

BART spokesman Jim Allison said software fixes are time-consuming because programming changes need to be made, tested in a lab, tested on the train, then tested on a train in operation. Once one software glitch is fixed, another is often found, he said.

The new BART cars are also overweight. It doesn’t affect how they operate, Oversier said, but does exceed standards in the contract and could accelerate wear and tear on the system. Solving the weight problem could mean the loss of some features that make the trains heavier: extra arm rests, stronger window frames, thicker seat cushions. Or BART could increase the weight limit.

According to Oversier, specifications allow the cars to weigh 64,500 pounds empty and 100,000 pounds carrying a crush load of passengers. The cars meet the fully loaded threshold, he said, but are 1,000 to 1,500 pounds too heavy when empty.

BART officials have been testing the 10 rail cars early in the morning after regular service is shut down. Testing has been going well, Oversier said, and should soon move to daylight hours. Test trains will run between scheduled trains, and aren’t yet allowed to carry passengers. But that could happen by June, BART spokeswoman Alicia Trost said.

At that point, Bombardier will start producing cars at a faster pace. While fewer new cars will arrive this year than first planned, more will come in 2018. By the end of that year, BART should have 166 new rail cars. Delivery of the new BART cars is scheduled to continue through 2022 with at least 341 cars in service in 2019, 529 at the end of 2020 and 721 at the end of 2021. All of the remaining cars are scheduled to arrive in 2022.

As BART has been meticulously testing its new rail cars, the Santa Clara Valley Transportation Authority has been ahead of schedule building the first phase of what it has labeled “Silicon Valley BART.” The extension will head south from Warm Springs/South Fremont to stations in Milpitas and Berryessa in East San Jose.

Ross, the VTA spokeswoman, said she was not aware that a shortage of rail cars could affect the start of BART to and from San Jose.

“It’s their show once we finish the lines and stations,” she said.

Allison said that BART and VTA hold regular meetings to discuss the progress of the extension and how to coordinate plans for starting service. But he said he doesn’t know if the matter of having enough rail cars has been discussed.

In any event, Allison said, it’s too early to start making contingency plans.

Bombardier spokeswoman Maryanne Roberts said BART can count on having all 35 cars by the end of the year.

Oversier said he, too, is optimistic that BART will have enough cars.

“We’ll be ready,” he said.

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan