United States Department of Transportation
i
Testing and Evaluating the Effectiveness of Advanced Technologies for Work Zones in Nevada
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2008-08-30
[PDF-2.33 MB]
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION;NTL-SAFETY AND SECURITY-SAFETY AND SECURITY;
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Abstract:The objective of this study was to evaluate two advanced technologies for improving safety in work zones: 1) speed monitoring display and 2) automatic work zone information system. In the evaluation of the speed monitoring display (also called a speed trailer), different features of the speed trailer were tested: the size of the speed sign and flashing of the measured speed. In addition, the study also tested the performance of a second speed trailer in a work zone. Two test sites in the Las Vegas Area were chosen to test the speed trailer, one on a fully controlled access segment of Cr-215, a county principal arterial, and the other on I-15, a major Interstate highway. The basic scenarios tested at these two sites were (1) no new feature, 2) smaller sign, 3) bigger sign without flashing, 4) bigger sign with a fast flashing rate, and 5) bigger sign with a slow flashing rate. On Cr-215, an additional scenario for the warning message “Slow Down” was also included. To evaluate the performance of the tested systems, speed and vehicle classification data were collected using Nu-metrics detectors on Cr-215. On I-15, however, these data were collected using videos processed in house. Comparisons were made on the speeds collected in these scenarios. The comparisons were first made between a ‘before’ condition where a speed monitoring display was not deployed and an ‘after’ condition using one of the scenarios. From these comparisons, it can be seen whether these technology features were effective in reducing vehicle speeds. The speeds were compared later between different scenarios to identify the relative performance of the features. The comparisons considered different types of vehicles and whether they ran in free flow conditions. These comparisons were based on both the hypothesis testing method and regression modeling. The hypothesis tests were looking into whether average speeds and speeding rate changed significantly between scenarios. The regression modeling investigated the likelihood of speeding and the speed at which a vehicle would run. The results from these two methods supported each other, which was a way to vary the results of the tests conducted in this study. The evaluation of the automatic work zone information system was performed by first developing such a system. In this study, a simple automatic work zone information system was developed which consisted of video detection at two locations, line-of-sight radio frequency wireless communication, and one portable variable message sign. The system was tested on I-515 and evaluated from the perspectives of traffic diversion and speed reduction. The analysis used for evaluation was based only on hypothesis testing for traffic flow and speed.
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