Abstract
A portable traffic signal (PTS) system is designed to move traffic through two-way rural highway work zones with one lane open to traffic. The primary objective of this study was to evaluate the use of PTS systems in conjunction with pilot car operations and to compare three conditions as means to control traffic at one-lane, two-way work zones: (a) flagging only, (b) PTS with flagger, and (c) PTS only. The measures of effectiveness were determined with respect to (a) red light running (RLR) violation percentages, (b) vehicle delay estimates, (c) queue lengths, and (d) green interval time. Comparisons of the operational parameters of average wait time, average queue length, and average green interval length indicated that all three conditions provided a similar level of operational efficiency. Percentages of RLR vehicles under the flagger-only, PTS-with-flagger, and PTS-only conditions were 1.1%, 1.3%, and 3.1%, respectively. A test of proportions indicated a significant difference in the number of violations between the three conditions. In addition, no significant difference was found in the number of RLR vehicles that followed an already-departed queue in the presence or the absence of a flagger. Furthermore, a significant difference was found in the number of vehicles that left the queue and the number of RLR vehicles that disregarded the traffic control under both conditions. These findings indicated more compliance when a flagger was present than when one was not. Results of an exploratory delay analysis indicated a 5% reduction in the total observed delay in the presence of a flagger.
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