Table of Contents

8.1.4 Recovery from Flow Breakdown

Whilst the mechanism for flow breakdown follows the general pattern described in the fundamental diagram, the recovery from flow breakdown follows a different phenomenon generally known as the hysteresis of traffic flow. As observed by Brilon, Geistefeldt and Regler (2005), after flow breakdown all recoveries to fluent traffic passed through synchronised flow (the transient state) and involved much lower traffic volumes than the preceding breakdown as shown in the examples in Figure 8.5.

Figure 8.5: Two typical patterns of traffic dynamics during breakdown and recovery

Source: Brilon, Geistefeldt and Regler (2005).

Traffic flow breakdown and recovery observed on Melbourne’s freeways exhibit similar characteristics. An example that shows the path of flow breakdown and recovery is provided in the speed-flow graphs in Figure 8.6. The lower flows on recovery illustrate that a motorway not only experiences lost productivity during flow breakdown but also throughout the flow recovery period.

Figure 8.6: Example of speed-flow diagram during flow breakdown and recovery

Flow breakdown

Flow recovery

Source: VicRoads (2013).