How do escalators work?

An electric motor at the top of the escalator turns drive gears, which move two long chains connected to every step. The steps run on wheels along two sets of tracks, and the spacing between the tracks changes so the steps form a staircase on the incline but flatten out at the top and bottom for safe boarding. After passing the top, the steps flip underneath and travel back down in a continuous loop. A handrail, driven by the same system, moves at roughly the same speed as the steps. Safety features include comb plates at each end and emergency stop buttons.