The Washington subway system is still being run in manual mode, and this time,
it looks like it prevented an accident. The details aren't clear, but it looks like a couple days ago the signaling system allowed two trains to get too close to each other. One was about to rear end a stopped train in a station and the driver engaged the emergency brake to prevent a crash. Some speed control system appeared to be malfunctioning and let the second train enter the station too fast.
This sucks.