The legislative authority of a city may create and abolish, by ordinance, a division of traffic engineering and safety within the department of public safety. The director of public safety of such city shall be the executive head of such division. He shall have all powers and duties connected with and incident to the appointment, regulation, and government of such division, and shall make such rules and regulations as he may deem necessary for the government and operation of the division. He shall keep a record of all his proceedings in connection with the administration of such division. A copy of such proceedings, when certified by him, shall be competent evidence in all courts. Such division may be staffed by traffic and safety engineers and such other employees as determined by the legislative authority.