Most of the walk buttons at NYC intersections serve no purpose. They are "placebo buttons" and do not make a walk signal occur faster. Any benefit from them is only imagined. Most of the buttons scattered through the city, mainly outside of Manhattan, are relics of the 1970's, before computers began tightly choreographing traffic signal patterns on major arteries. They were installed at a time when traffic was much lighter, said Michael Primeggia, deputy commissioner of traffic operations for the city's Transportation Department.