The permittee shall give particular attention to facilitating the flow of vehicular and pedestrian traffic. Unless prior written approval is obtained from the director of public works, the permittee may not: (1) obstruct more than one-half of the area used by the vehicles; (2) obstruct any driveway for a period exceeding one hour, and; (3) obstruct the area between the curb (or the shoulder if there is no curb) and the right-of-way line in such a way as to create a hazardous path for pedestrians. The use of flagmen is mandatory where two-way vehicular traffic has less than twenty-four feet in which to pass. The permittee may be required to remove excavated material from the site of the encroachment as it is excavated rather than stockpiling it on the street when such removal is necessary to permit traffic to pass freely and safely. (Ord. No. 1201, § 2 (part).)