It is unlawful for any person to make any excavation in any street, alley, sidewalk or public way of the city without a permit therefor or to leave any excavation, building material, vehicle, stones, bricks, other materials or obstructions in or on any street, alley, sidewalk or public way in the city during the course of any work, unless the same be protected by barricades at all times or in the nighttime unless the excavation, building materials or obstruction is guarded with red lanterns or flares, sufficient in number and so located as to guard and warn vehicles and passers-by of the extent and danger of such excavation or obstruction. Such lights shall be lighted before dark and left burning during the nighttime; provided, that it shall be the duty of any officer or any employee of the city having charge of any of the foregoing work, to place suitable warning signs and barricades to guard the public against injury and in the nighttime to keep and maintain a sufficient number of warning lights as in the case of other persons; provided further, that the director of public works is authorized to direct the placing of any barricade, warning sign or lights herein required, and he may, if the public safety requires it, during the progress of any such work, close off the public street or sidewalk or any portion thereof to prevent public use of the same; provided further, that any person holding a permit to cut streets or sidewalks shall not be released from any obligation to barricade, light or otherwise guard or warn vehicles or passers-by of the extent and danger of the excavation until forty-eight (48) hours after notification has been given to the director of public works, Saturdays, Sundays and holidays excepted, that the excavation is ready for backfill and/or surface replacement. (Prior code § 14-206)