At places where large numbers of people and vehicles are to gather or have gathered, nothing in this Title shall be construed to prevent any police officer from prohibiting any person from parking any vehicle upon or using any street or sidewalk, or from prohibiting any pedestrian from using any street or sidewalk, and said police officer shall have authority to direct the parking of vehicles in any reasonable manner, way or direction; and it is hereby declared to be unlawful for any person to fail to promptly obey the said police officer’s order, signal or command, regardless of any other provision of this Title.