Office of Operations
21st Century Operations Using 21st Century Technologies

A Methodology and Case Study: Evaluating the Benefits and Costs of Implementing Automated Traffic Signal Performance

Long Description for Figure 6. Illustration. Example of states and event data

The figure is a bar chart or bar diagram of sorts, with six bars running horizontally from left to right. The horizontal distance represents the cycle length of a traffic signal, where typical cycle lengths in the U.S. are between 60 seconds and 150 seconds. Although the duration of the cycle length is not indicated on this figure, a cycle length of 100 seconds is assumed for an easier upcoming explanation of the six bars. The first horizontal bar is titled “Phase 2 Active”. According to the illustration, Phase 2 is active from approximately time equals 40 seconds until time equals 80 seconds, resulting in a 40-second phase duration. A good contrast to this is the sixth horizontal bar, which is titled “Detector 2”. Although the illustration implies that Detector 2 is on for approximately 40 seconds, similar to the duration of Phase 2, the detector is on at a different time during the signal cycle (i.e., from approximately time equals 20 seconds until time equals 60 seconds). The second horizontal bar is titled “Phase 2 Green Active”, where the illustration implies that Phase 2 displays green on the traffic signal from approximately time equals 40 seconds until time equals 74 seconds. The third horizontal bar is titled “Phase 2 Yellow Active”, where the illustration implies that Phase 2 displays yellow on the traffic signal from approximately time equals 74 seconds until time equals 78 seconds. The fourth horizontal bar is titled “Phase 2 Red Active”, where the illustration implies that Phase 2 displays red on the traffic signal from approximately time equals 78 seconds until time equals 80 seconds. The fifth horizontal bar is titled “Detector 1”. Unlike the other bars, the illustration implies that Detector 1 is on not once, but twice during the signal cycle (i.e., time 10 seconds to 40 seconds, and then again from time 50 seconds to 60 seconds).