BART riders who have noticed brief stops on trips between Glen Park toward 24th St./Mission now know why: It's a safety precaution until a computer issue can be resolved.
"Basically, it's when the trackside computer, for some reason, cannot determine if there's a train in the section of the track for which it’s responsible," BART Chief Communications Officer Linton Johnson said. "As a failsafe mechanism, if a trackside computer isn’t sure there is a train in its segment it will show it is occupied until it can independently verify that the section is clear and safe. We call it a ‘false occupancy.' "
No other train can enter the segment of track in automatic mode until the false occupancy is cleared. In order to continue service through the area, trains must go into "road manual" mode to override the trackside computer -- creating a very brief, minor stop until the coast is clear
The phenomenon is sometimes incorrectly referred to as a "ghost train," although obviously there aren't any wraiths or phantoms involved.
"Why this is happening, we don't know yet," Johnson said. "We have all our resources at hand trying to figure it out. Hopefully, we will have it resolved soon. We're sorry for this minor inconvenience but hope everyone understands that it is in the interest of safety, which is our top priority."
The Glen Park stops for the false occupancy issue have typically been too brief to trigger the BART Service Advisory message (BSA), which is sent out on a threshold of when multiple trains are off schedule by 10 minutes or more. Read more information about BART Service Advisories.