Pedestrians step off sidewalk corner staircases onto the platform, which precesses according to simple gyroscopic motion. Set the spinning weight going such that precession is counterclockwise when viewed from above. Pedestrians get off when they reach the raised platform of the sidewalk at the other side.
The rotational energy of the spinning weight on the gyroscope arm will decrease with friction, so electric motors are built into the arm to maintain angular velocity. A balancing mass capable of moving closer or farther from the gyroscope's center could ensure a relatively consistent angular velocity of precession by moving closer or farther from the center of the traffic intersection (i.e. lengthening or shortening the moment arm).-- Ketchupybread, Dec 14 2008random, halfbakery