This online engineering PDH course provides key background information on three aspects of signalized intersections: user needs, geometric design, and traffic design and illumination. The intersection forms considered include signalized at-grade intersections and intersections with the potential for grade separation. The course provides a foundation of knowledge of signalized intersections that is useful as a learning tool for entry-level engineers and as a refresher for more experienced engineers. Topics: Human factors Intersection users Channelization Horizontal and vertical alignment Sight distance Pedestrian facilities Bicycle facilities Traffic signal control type and phasing Vehicle and pedestrian displays Traffic signal pole layout Traffic signal controller Detection devices Basic signal timing parameters Signing and pavement marking design Illumination design