Welcome to our new website. St. Louis County is dedicated to improving your experience.


Intersections present special challenges to traffic safety and efficiency.  They contain conflicts between many vehicles. The Public Works Department is working to provide the best intersection designs and control.

Traffic Signals

Traffic signals, also known as traffic lights, are electronic traffic control devices that assign right-of-way to vehicles entering an intersection. Traffic signals use indications (lights) to indicate the right-of-way to drivers and pedestrians.


A roundabout is a type of circular intersection designed to keep traffic moving safely and efficiently. A roundabout is not the same as a neighborhood traffic circle or large rotary. Some features that are unique to roundabouts include a large central island, counterclockwise traffic flow, splitter islands on the approaches to the roundabout, and traffic entering a roundabout must yield to traffic in the roundabout circulatory lane.

J-Turn (Reduced Conflict Intersection)

A J-Turn, or reduced conflict intersection, is a u-turn type intersection installed on divided highways (expressways). A J-Turn requires vehicles on the side street intending to cross a divided highway or make a left turn onto the divided highway to use the u-turns installed in the divided highway median. Vehicles on the divided highway can still make a left turn or right turn at the intersection as normal.

Continuous Green-T Intersection

A continuous green-T intersection is an intersection that is controlled by a traffic signal but allows one direction of traffic on the major road to have continuous traffic flow. The continuous green-T provides similar traffic operational benefits to a grade-separated interchange, but at a significantly reduced cost.