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208 Big Data Analytics for Connected Vehicles and Smart Cities Practical Applications and Concepts for Transportation Data Analytics 209

Revised Approach—Traffic Turbulence Analysis

The team identified that a traffic turbulence analysis would be a more appropri-
ate approach to the evaluation of VSLs. The analysis was also focused on the
end of the bottleneck within the zone of influence but beyond the bottleneck.
To facilitate the analysis a revised bottleneck speed profile template was created
as illustrated in Figure 10.8.
Like Figure 10.4, the vertical axis of the graph in Figure 10.8 represents
traffic speed in miles per hour, averaged over one-minute time increments. The
horizontal axis represents distance, with the arrow indicating the direction of
travel for the traffic. The rightmost black dot on Figure 10.8 indicates the be-
ginning of the bottleneck. This is the point at which the speed of the traffic
drops below 60% of the reference speed. The leftmost black dot represents
the end, or the point at which traffic climbs through 60% of reference speed.
The gray shaded area in the center of the diagram represents bottleneck condi-
tions where the traffic speed has dropped below 60% and has not yet recovered
back to 60% of reference speed. The area to the right of the box represents
pre-bottleneck traffic speed, and the area to the left of the box represents post
bottleneck traffic speed. The bottleneck is defined as the width of the gray box.
Along the bottom of the graph in Figure 10.8, a series of boxes is arrayed
to represent the TMC segments of the freeway. The two rightmost white boxes
are labeled TMC PRB (pre-bottleneck). The small gray boxes under the large
gray box are labeled TMCB (bottleneck).

Figure 10.8 Modified bottleneck template with zone of influence segments at the end of the
queue.