Best case: "I don't seem to be making any progress going up." Worst case: "This is moving down way too fast! Aaaahhhhh!!!" -screamed by hundreds of people, man

Best case: "I don't seem to be making any progress going up." Worst case: "This is moving down way too fast! Aaaahhhhh!!!" -screamed by hundreds of people, many of which will die as they pile up at the bottom of the escalator. Now imagine the brakes failing on an escalator that leads down into a subway with an electrified rail.