Long wait times have become a regular occurrence on BART amid this winter’s wet weather, and now we have some answers as to why.

KNTV found that the new “Fleet of the Future” trains have a braking problem, and that glitch has been exacerbated by the storms in recent months. New cars make up about half of BART’s fleet.

Apparently, BART data from ​​September through December of 2022 shows rain accounted for nine of BART’s ten worst delays, according to KNTV.

The issue is how the new cars’ brakes respond to wet conditions. BART spokesman Jim Allison told the outlet that the new BART trains have sensors that detect when their wheels slide or spin too quickly, which they do on wet rails. This in turn triggers the train’s emergency “fail-safe” brakes, so they can safely stop at the next station. But that can make all the wheels on the train go “flat,” because the new fleet’s braking system automatically applies to all the wheels at once. The old trains reportedly didn’t have this full automatic wheel control system which creates this issue.

The braking causes uneven wear-and-tear to the wheels, which can mean entire trains need to be repaired, spending days to weeks in the shop.

To try to solve this, BART has been reducing speeds on above-ground parts of its system on rainy days, also leading to delays and not fully fixing the flat issue. Allison admitted to KNTV that the new Fleet is less than perfect and said a long-term fix may take a decade.

The agency is urging riders to check its website and social media accounts for updates on service delays and to plan accordingly.

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Image via BART.