The police department, through its officers:
   A.   Shall cause all signs, signals, parking meters and markings necessary to traffic controls provided for by enactments of the city council to be installed, marked and maintained in accordance with standards established by the state highway commission and nationally recognized traffic control standards (such as the "Manual On Uniform Traffic Control Devices" published by the U.S. bureau of public roads), and may cause to be placed and maintained additional and incidental traffic control devices necessary to regulate traffic under the provisions of this title or under state law, or to guide or warn traffic.
   B.   May trim or remove, or cause to be trimmed or removed, any tree, shrub or hedge which is within or extends over the street and interferes with the use of the sidewalk or roadway, or obstructs a driver's view of an intersection or traffic upon streets approaching an intersection, or otherwise constitutes a traffic hazard. Trees, shrubs and hedges shall be maintained at an unobstructed height of not less than eight feet (8') above the sidewalk and not less than thirteen and one-half feet (131/2') above the roadway. (1962 Code § 9-1-4)