The Police Chief is hereby empowered and authorized to designate or approve the erection of stop signs at such locations in a shopping center and upon any public grounds as he may believe necessary and desirable for the safe and efficient movement of vehicles and pedestrians subject to Council approval. The Police Chief is authorized to designate or approve the placing of appropriate devices, lines or marks upon the roadways, parking areas and sidewalks to indicate crosswalks, walkways and safety islands at such places in a shopping center or upon public grounds as he may believe necessary for the safe and efficient movement of pedestrians subject to Council approval. The Fire Chief is empowered and authorized to designate and approve fire lanes which shall be kept open and unobstructed at all times.