BART train operator Mike Granat came to the BART Board of Directors meeting Thursday with grim words for board members, warning that the transit agency’s much talked about “fleet of the future” train cars have a design flaw that could prove fatal.

Granat, a BART employee since 1990, initially appeared before to the board on July 25 to express his concerns, saying that the potential problem was not with the cars themselves but the way they were being put together.

BART riders are used to being able to easily walk from one train car to another, but some of the new cars—dubbed “D cars”—have special doors on one end that only the train operator can open with a key, since there’s a control booth on that end.

In an emergency, such as a fire, riders might not be able to evacuate a car without the help of the driver to unlock the door. Granat worries that the task of unlocking the specialized doors—twice if two D-cars happen to be facing each other—will prove difficult in a disaster.

And if the train operator is incapacitated or unable to reach the car in time, riders might not access the exit of that car.

Granat also worries that BART cops might not able to get into a car in an emergency.

“Someone will eventually die,” he predicted.

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At Thursday’s meeting, Granat spoke during public comment again, pointing out that a solution to the problem is already apparent: If BART only uses D cars at the ends of trains, instead of using them in the middle of trains, the danger disappears.

“What we’re really doing is testing equipment with passengers onboard, and I don’t think anybody here should feel comfortable about that,” he said.

Jusuf Nasir, also a BART operator, spoke after Granat, telling directors, “It’s an unsafe situation and it’s pretty scary for us. We’re being forced to choose between safety and our jobs.”

In response, BART spokesperson James Allison told the San Francisco Examiner, “We strongly believe our current practice is safe,” and dismissed Granat’s concerns.

BART board members seemed more invested in the warning, with Director Rebecca Saltzman asking BART staff why the board hadn’t been briefed about the D car designs after Granat’s July visit.

A larger hearing on the safety complaints is tentatively set for November.

Presently, BART has only one train composed of its new vehicles running on each line, but has purchased 775 of the new cars in all, with plans for hundreds more in the future.