No person shall place anything on public sidewalks, streets, or places, that will obstruct public traffic. Such obstruction is, however, permissible in case of loading or unloading of articles, where no court or yard is available. In such cases, as little inconvenience as possible shall be caused to traffic, and the said articles must be removed without unreasonable delay. Carts, as well as handcarts shall not be unduly delayed upon public streets, roads or places, for the purpose of loading or unloading without the special permission of the police authorities.