The green button

To exit the door where I work, it's necessary to press a green button on the left wall of the door. There are signs posted at eye-height, messages saying "STOP! PRESS GREEN BUTTON ON LEFT!" on the actual bar of the door (top and side) as well as on the button itself. And for almost everyone except the frequenters, the first impulse is to push harder at the door--to try to force through it.