(a) The Director of Public Safety and Service is hereby authorized to place and maintain traffic control devices upon any street or highway under his jurisdiction as are necessary to effectuate the provisions of this Traffic Code, or to regulate, warn or guide traffic, and such other traffic control devices as are required by ordinance: or as he shall deem necessary for the proper control of traffic. The Director shall determine the location, timing and coordination of such traffic control devices upon the basis of an applicable engineering or traffic investigation and shall consider the following:
(1) The maximum safety and protection of vehicular and pedestrian traffic from physical injury or property damage.
(2) The existing and potential traffic movement, volume and conditions.
(3) The location and frequency of accidents, including studies of remedial measures.
(4) The recommendations of the Police and Fire Chiefs.
(5) The acceleration of transportation of persons and property by vehicles so as to expedite travel and promote public safety.
(6) The convenience and welfare of the general public in parking, standing, loading and unloading, and the use of the streets as affecting business concerns and places of assembly.
(7) Economy in the expenditure of money.
(b) No provision of any ordinance or rule or regulation for which traffic control devices are required shall be effective until signs, signals, markings or other devices giving notice of such provision are posted or placed upon or at the entrance to the street or part thereof affected, as may be most appropriate, so that in a proper position they are sufficiently legible to be seen by an ordinarily observant person.