Lighting and appearance. Signs shall not resemble, imitate, or approximate the shape, size, form, or color of railroad, traffic or other official signs, signals, or devices. Signs shall not obstruct or interfere with the effectiveness of railroad, traffic or other official signs, signals, or devices. Signs shall not 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. Signs shall not be placed so as to obstruct or interfere with traffic visibility, nor be lighted in such a way as to cause glare, objectionable distraction, or impair driver visibility upon public ways. Signs may be illuminated but nonflashing. Signs shall not be revolving or mechanically animated; however, information on time, temperature, reader-board, electronically or digitally generated sign fields may be cyclical or sequential. Signs in residential districts shall not be illuminated.