Door Issues 101
The doors on the trains all have safety sensors on them to tell the train computer if it's ok to move the train. We all know although they resemble elevator doors it's obvious they are not. These safety measures re-assure us that nobody will be sucked out mid flight.
When there is a problem, all the train operator sees on their "Dashboard" is a little light that says "Door Open"
Say it's Sunday afternoon on a four car train and this happens. The next train to this location is 20 minutes away.
The T/O radios central and reports the event and that they are now stopped. Central considers this for a moment and says go check it out. The T/O has about 19 minutes to find 1 defective door out of 6 if at the platform or 12 if on main line. The T/O is in the first car so we eliminate it from the suspects because they can usually see problems in the first unit without leaving the cab.
It's safe to assume that a T/O can find, lock out the door, apply door not working stickers and return to the cab within 10 minutes.
It's Monday evening and the same thing happens during commute and it's an 9 car train in downtown San Francisco.
The T/O radios central and without pause central says you're out of service sweep your train.(of Passengers)
It is way faster to take a train out of service than to have that train tie up the whole system causing a big delay. Don't forget the flood of people coming down the stairs.
Yes, it is a bitch to have to get off and fight for a seat again but the 10 trains behind this one are stll close to being on time. This is why there are different circumstances affecting the way to handle the same problem.
BART would rather have 1,000 people complain than 300,000