As mass-transit technologies go, trains are among the oldest. The basics of trains running on tracks date back to sometime in the very early 1800s. In that light, it feels kind of surprising when a modern train breaks down, though it probably shouldn't: wear and tear, gremlins and bugaboos... they creep into all human efforts, given enough time.
Today I experienced a train breakdown that didn't stop it from being "drivable," but was still significant enough that it stopped and commuters had to transfer to another train. I'm not honestly sure what the issue/failure was, but I gather it was some sort of pedestrian-related safety system thing.
Whatever it was, it amounted to a 5 to 10 minute delay. Nothing major, though I had to wait for the next bus at the train station, having missed my connection by a scant few minutes.