For the second time in a month, a mysterious power surge knocked out numerous BART cars Wednesday — puzzling agency officials who thought they had the problem under control the first time around, and making life miserable for commuters packed into shortened trains. BART was able to repair some of the 25 or so cars that lost their propulsion systems on the Pittsburg-Bay Point line, but not all of them — raising the likelihood that many trains will be short of cars for the Thursday morning commute.

BART engineers worked into the night trying to find an answer for what is becoming a major problem for the aging rail system. When the first round of problems began in late February, BART focused on a new electrical substation that had been installed a few months earlier near the Oakland end of the Transbay Tube. Wednesday’s problems, however, happened far from there — between the North Concord and Bay Point stations. READ MORE