How escalator safety mechanisms work — and why they cause machines to stop

Technicians at U.N. headquarters inspect the escalator that stalled as President Trump and First Lady Melania Trump rode it Tuesday on Thursday, Sept. 25.

President Trump called his escalator mishap at the United Nations "sabotage." The U.N. says the White House team triggered a safety mechanism. We asked two people who work on escalators to explain.

(Image credit: Ted Shaffrey)