Photos of cars on freeway, speeding sign

Freeway Management and Operations Handbook

Description of Figure 4-2: "Temperature" Diagram of Traffic Flow Conditions

This graph is shown as a color-coded contour map. It is labeled "Traffic Profile, General Purpose Lanes". On the left side of the graph, a contour map is shown of westbound traffic. In the middle of the graph, a vertical depiction of the Route 520 corridor is shown. On the right side of the graph, a contour map is shown of eastbound traffic. Each contour map shows the location along the corridor on the vertical axis and the time of day on the horizontal axis, ranging from 0 AM to 12 PM. The area formed by these time and space axes are colored as follows:

  • Green: uncongested, near speed limit
  • Yellow: restricted movement, but near the speed limit
  • Red: more heavily congested (45–55 mph)
  • Blue: extremely congested.