Yesterday, 09:15 PM
They are, in a sense. There are mechanisms for tripping the emergency brakes. There are trips every so many hundreds of feet in the NYC subways. When a train passes one, an arm swings upward. When the train goes beyond a certain distance, the arm resets to the lowered position. But if while the arm is up another train passes over it, which would only happen if that train is following too closely, said arm will impact with an arm on the truck of the train which is attached to the emergency brake system, tripping it and thereby engaging the brakes and bringing the train to a stop.
In addition, there is a device called a "dead man switch" that function such that if perchance the motorman were to suddenly drop dead, the corpse would let go of at least one of the two or three levers that must be engaged in order that the throttle will function properly. The train then slows to a halt, thus averting any disaster such as that captioned in this thread.
Trains are pretty heavily monitored. I know that mainline freight trains are very heavily monitored in real time and motormen/engineers can get into very hot water for breaking the rules such as over-speed going into corners, and so forth. Their positions and speeds are very carefully monitored these days. Whatever the cause, I'd bet money I do not have that the watchers knew what was happening as it was happening. This could, therefore, get very interesting.