It is unlawful for any pedestrian to be in or upon any grade separation, except such grade separations as shall have pedestrian walks specifically designated or constructed thereon, provided that the provisions of this section shall not apply, in the event of an emergency, to persons employed to do work or labor upon such grade separation, or to members of the Police Department when engaged in law enforcement or traffic regulation. (Ord. 3262-NS § 7, 1952)