It shall be the duty of the police department to enforce the street traffic regulations of this city and the state vehicle laws and regulations applicable to street traffic in this city, to make arrests for traffic violations, to investigate accidents, and to cooperate with other officers of the city in the administration of the traffic laws and regulations and in developing ways and means to improve traffic conditions, and to carry out those duties specially imposed upon said department by this title and any other traffic ordinances of this city.
(Code 1962 § 19-2(a))
Officers of the police department or such persons authorized by the chief of police or his designee to perform crossing guard or traffic direction duties are authorized to direct all traffic and pedestrians by voice, hand, or signal as conditions may require, notwithstanding the provisions of the traffic laws, regulations, and ordinances. A driver of a vehicle or a pedestrian may not fail to obey a lawful order or direction of a police officer, firefighter, crossing guard, or other authorized person directing traffic.
(Code 1962 § 19-2(b); Ord. 1393 § 1, 1998; Ord. 1504 § 1, 2004)
Officers of the fire department, when at the scene of a fire, may direct or assist the police in directing traffic thereat or in the immediate vicinity.
(Code 1962 § 19-2(c))
(a) 
The traffic authority of the city is empowered to make regulations necessary to make effective the provisions of the traffic ordinances of this city and to make and enforce temporary or experimental regulations to cover emergencies or special conditions. No such temporary or experimental regulation shall remain in effect for more than 90 days.
(b) 
The traffic authority may have traffic control devices tested under actual conditions of traffic.
(Code 1962 § 19-3)