In this lecture the flow of traffic under traffic interruptions is studied. Traffic interruptions are collectively a general situation used to denote conditions where a stream of traffic flowing under certain conditions of speed and density meets another stream flowing under some other condition of speed and density. For example, if traffic flowing at high speed meets another stream flowing at a greater density and lower speed, the former traffic stream will face a traffic interruption. There are various ramifications of such interruptions on traffic flow and these are discussed in the next section on shock waves. Within this general description of traffic interruptions, two kinds of traffic interruptions are of special interest. These are the interruptions that take place at signalized and unsignalized intersections.

In this section, there are three subsections; the first studies shock waves. The second and third study the traffic flow at signalized and unsignalized intersections, respectively.