Example Organizational Objective #2 – Presentation of Findings

Using the data and the database outputs, the analyst develops a scatter plot of the RCTs for all lane-blocking incidents, color codes the data points by number of lanes blocked, and shows the average for each category (figure below).

As would be expected, the more lanes that are blocked, the longer the average RCT. For incidents that blocked 1 lane, the RCTs are clustered around the average RCT of 25 minutes. For incidents that blocked 2 lanes, the RCTs are more dispersed and show some overlap with the RCTs for both 1- and 3-lane incidents. The RCTs for 3-lane incidents also overlap somewhat with the RCTs for incidents blocking 4 or more lanes, and there appears to be even more dispersion in the RCTs for 3-lane incidents. There were only eight incidents that blocked 4 or more lanes in the database, with an average RCT of 139 minutes.

The figure below could be compared to the scatter plot of the ICTs for all freeway incidents in Organizational Objective #1 (click here to view scatter plot) . While that scatter plot shows ICTs and includes all freeway incidents, the two plots look very similar.

Roadway Clearance Times by Lanes BlockedRoadway Clearance Time by Number of Lanes Blocked

Next, the analyst creates a graph with the frequency distributions for each category and a graph with the cumulative distributions for each category, which are shown in the two figures below, respectively.

The first figure below shows that 45 percent on one-lane incidents are cleared from the roadway in 20-29 minutes. The sharp peak of the frequency distribution of RCTs for one-lane incidents shows there is little variability in clearing the roadway during these incidents.

The frequency distributions of RCTs for two-and three-lane incidents are less peaked and a little wider, showing more variability in clearing the roadway during two- and three-lane incidents as compared to one-lane incidents. A few outliers can also be seen for the three-lane incidents. There were only nine incidents that blocked four or more lanes.

Examining the cumulative distributions in the second figure below, it can be seen that for all one-lane incidents, the roadway was cleared in under 60 minutes; for all two-lane incidents, the roadway was cleared in under 90 minutes; and for all but two of the three-lane incidents, the roadway was cleared in under 130 minutes. The nine incidents that blocked four or more lanes ranged from an RCT of 89 minutes to an RCT of 209 minutes.

Frequency Distribution of RCTs by Number of Lanes Blocked Frequency Distribution of RCTs by Number of Lanes Blocked

Distribution of RCTs by Number of Lanes Blocked Distribution of RCTs by Number of Lanes Blocked