Obedience to Traffic Control Signals

21462.  The driver of any vehicle, the person in charge of any animal, any pedestrian, and the motorman of any streetcar shall obey the instructions of any official traffic signal applicable to him and placed as provided by law, unless otherwise directed by a police or traffic officer or when it is necessary for the purpose of avoiding a collision or in case of other emergency, subject to the exemptions granted by Section 21055.