Signs shall not resemble, imitate, or approximate the shape, size, form, or color of railroad or traffic signs, signals, or devices. Signs shall not obstruct or interfere with the effectiveness of railroad or traffic signs, signals, or devices. No sign shall be erected, relocated, or maintained so as to prevent free ingress to or egress from any door, window, or fire escape; and no sign shall be attached to a standpipe or fire escape. No sign shall be placed so as to obstruct or interfere with traffic visibility.