Mo. Rev. Stat. § 300.020

The traffic division with such aid as may be rendered by other members of the police department shall enforce the street traffic regulations of the city and all of the state vehicle laws applicable to street traffic in the city, to make arrests for traffic violations, to investigate accidents and to cooperate with the city traffic engineer and other officers of the city in the administration of the traffic laws and in developing ways and means to improve traffic conditions, and to carry out those duties specially imposed upon the division by this ordinance and the traffic ordinances of the city.