Whenever special pedestrian control signals exhibiting the words "Walk" or "Don't Walk" are in place such signals shall indicate as follows:
(a) Walk. While the "Walk" indication is illuminated, pedestrians facing such signal may proceed across the roadway in the direction of the signal, and shall be given the right- of-way by the drivers of all vehicles.
(b) Don't Walk. While the "Don't Walk" indication is illuminated, either steady or flashing, no pedestrian shall start to cross the roadway in the direction of the signal, but any pedestrian who has partly completed his crossing during the "Walk" indication shall proceed to a sidewalk.
(M.C. 1963, § 20.109.)