The Director of Public Safety is granted special power to prohibit commercial vehicles, other than those making deliveries to properties located on the street, from using any street which, in his opinion, has such a large child population as to substantially increase the chances of accidents involving motor vehicles on such street. A minimum child population average of at least 2.0 children under 18 years of age for each house on the street must be present before the Mayor can prohibit the street from being used by commercial vehicles, using the authority granted by this section.