"Escalators at the 34th Street-Herald Square and Roosevelt Island stations in Manhattan and the Jamaica-Van Wyck and Jamaica Center-Parsons/Archer stations in Queens were to begin operating at variable speed, as part of a pilot program to save energy and reduce wear and tear.
According to signs posted by the authority, each escalator was equipped with an infrared motion sensor that " ‘sees' customers approaching and ‘tells' the escalator to speed up." The escalators are supposed to slow to just 15 feet per minute when no one is on them, from the normal speed of 100 feet per minute. When someone steps on, the escalators should accelerate gradually to the full speed over a few seconds.
Late in the day, officials acknowledged that only 22 of the 35 escalators at the four stations were working as intended."