How Escalator Steps Turn Around and Return

Pick one step on this escalator. We will mark it orange and follow it all the way around. It climbs toward the upper floor, meets the steps in front of it, and seems to disappear beneath the landing. Where did it go? The step has not folded into the floor. It is still moving inside the machine. First, look beneath the metal tread. This is one solid step with a tread you stand on and a face that fills the gap to the next step. On either side, an axle connects the step to a moving chain. A second pair of rollers sits farther back on the step. Those rollers have their own guide tracks. The chain moves the step forward. The two sets of wheels and tracks control where its two ends go. Along the slope, the tracks are separated in a way that keeps the tread level while the step climbs. Look at the marked step beside its neighbors. Their treads are level, even though the whole line of steps rises. The steps do not grow taller. Their positions change relative to one another as they follow the sloping path. Now follow the marked step toward the top. The guide paths change shape. The rise between neighboring treads gets smaller until several steps travel across the landing at nearly the same height. That makes a flat place to step off. The narrow grooves on the treads pass beneath the fixed comb at the edge of the floor. The comb stays put. The step keeps moving underneath it. We can remove part of the side cover in the animation and keep following that same orange mark. Past the comb, the step is hidden from passengers, but both chains and both roller paths continue into the upper end of the frame. The step travels around the turnaround as a whole. It does not shrink, dissolve, or leave the chain. On the far side of the curve, its tread faces downward. From outside, there is no sign of it. From this cutaway, you can see it returning below the steps that are carrying people upward. This is why there are two kinds of guide path. The chain side wheels follow the route pulled by the drive. The other rollers follow a separate route. Their changing positions set the step's angle as it levels out, turns over, and later becomes a usable step again. The curved rail shapes shown here make that relationship easier to see. They are a teaching view, not a measurement of every Otis rail. The marked step now travels down through the hidden return space. Its tread is upside down, so the phrase step stay level no longer describes this part of the trip. The passenger side and the return side are two parts of one continuous loop. At the lower end, the chain and guide tracks bend around again. The step turns right side up, comes out beneath the lower landing, and lines up with the other steps before entering the slope. Here is the complete route in one view. Up the passenger side, flat across the top, around behind the landing, down the hidden return, then around the bottom, and back into view. It is the very same orange step. The motor keeps the chains moving. The guide tracks make the step behave like a stair where people ride, and like a returning carrier where they cannot see it. That is where the steps go when they disappear at the top.