The state traffic laws regulating the speed of vehicles shall be applicable upon all streets within the city, except that the city may by ordinance declare and determine upon the basis of engineering and traffic investigation that certain speed regulations shall be applicable upon specified streets or in certain areas, in which event it shall be unlawful for any person to drive a vehicle at a speed in excess of any speed so declared when signs are in place giving notice thereof, but no city ordinance shall regulate the speed of vehicles upon controlled access highways of the state.
§ 300.205, RSMo