Mysterious BART short circuit adds to beleaguered system’s headaches

In the latest problem to vex BART and its riders, an electrical “flashover” early Friday morning — a short circuit on the third rail — sparked a day full of detours and delays as trains were first halted and then had to roll slowly along a critical stretch of track in San Francisco.

Hoping to get the Bay Area’s backbone transit system back on track, BART is asking voters to approve a $3.5 billion bond measure to repair and modernize its infrastructure.

BART resumed service through the area at 6:50 a.m., first having trains in both directions share a single track, then using both tracks but operating under manual control at reduced speeds below 27 mph.

A series of still-mysterious power surges in April knocked scores of cars out of service — and caused major service interruptions between the North Concord and Pittsburg/Bay Point stations — before disappearing as suddenly as they started.

In January, after a gun killing on a BART train that remains unsolved, The Chronicle revealed that the vast majority of security cameras in BART trains are either decoys or don’t work.

Responding to public outcry, BART soon announced it would outfit all train cars with at least four operating cameras.

The flames were quickly extinguished but not before damaging cables that are part of the automatic train control system, sending signals between trains and the control center.