Credit: Darrow Montgomery

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If I get on a Metro escalator going up (particularly a long one), and I lean with my right arm on the handrail, before too long, the handrail will have moved too far too fast, I’ll be off-kilter, and I’ll have to scoot my arm backwards before I can lounge again. This is always the case. Why?

It’s not just Metro. As a safety measure, all escalators in the United States are required to have handrails that keep pace with the steps. While they’re supposed to sync with the steps, the handrail is actually on a different gear system. That means that escalators, especially older ones like those in Metrorail stations, can fall out of sync. The longer the escalator is, the more time the handrails have to de-sync. Newer models, according to the Schindler Elevator Corp., have special sensors that prevent this from happening.