@hawkeye10,
Here is an example of how things can go wrong due to no human fault.
There was a mile long freight train one night that broke apart and due to two factors the train let 30 cars sitting on the main line without anybody knowing about it for more then an hour.
First no caboose was available so the train needed to leave the yard with all the crew riding the engine.
Next the nice fail safe air brakes did not engage to stop the train once the train had broken apart due to the air hose having a kink so the air pressure did not drop enough to cause the reserve tanks to engage the brakes on the rest of the cars.
I was manning the yard that night when the crew reported that somewhere and somehow they had lost 30 freight cars that they was support to drop off at.....Sorry it been too many decades I forgot the siding they was suppose to place the missing cars at.
Paul the Train Master was not happy when I woke him up over the matter that I do remember.
Trains brakes do not always work as they are suppose to.