Effectiveness of changeable message signs in controlling vehicle speeds in work zones, phase 2 : final report

1998-01-01 00:00:000074816038555899Commonwealth of Virginia.1998Final reportPDFTech ReportVTRC 98-R10Accident exposureAutomobiles by typeBehaviorConstruction sitesDriversLengthMeasures of effectivenessRadarSpeed controlSpeedingTime durationTraffic speedVariable message signsWarning systemsWork zone traffic controlDurationEffectivenessExposureSpeed reductionVehicle typeVirginiaVirginia Transportation Research CouncilGarber, Nicholas J.Srinivasan, Srivatsan.Virginia Transportation Research CouncilVirginia. Dept. of TransportationUnited States. Federal Highway AdministrationNTL-HIGHWAY/ROAD TRANSPORTATION-Construction and MaintenanceNTL-INTELLIGENT TRANSPORTATION SYSTEMS-Roadway Operations and MaintenanceNTL-OPERATIONS AND TRAFFIC CONTROLS-OPERATIONS AND TRAFFIC CONTROLSNTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic FlowNTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic Control DevicesNTL-SAFETY AND SECURITY-Highway SafetyNTL-SAFETY AND SECURITY-Speed LimitsUS Transportation CollectionHighway work zones have been plagued with increasing numbers of accidents in recent years. Drivers' lack of compliance with speed restrictions within work zones has been cited as one of the major contributing factors to this trend. The conventional practice for regulating work zone speeds has been static signing procedures (using regulatory or advisory speed signs). It has been found that drivers do not slow down in response to these static control measures. A Changeable Message Sign (CMS) equipped with a radar unit can be used to display specific warning messages to speeding drivers. This offers a more dynamic speed control environment and therefore may prove to be more effective in influencing drivers to reduce their speeds. This report is the second phase of a longitudinal research study. The first phase of the project, conducted by Garber and Patel, examined the short term effectiveness of CMSs in reducing vehicle speeds in work zones. That research established that the CMS (with the radar unit) is more effective in reducing speeds in work zones than the standard Manual on Uniform Traffic Control Devices (MUTCD) signs. This study, while attempting to replicate the results obtained in Phase I of the project, concentrated on evaluating the effect of duration of exposure of the CMS with radar on its effectiveness in reducing speeds and influencing speed profiles in work zones. The impact of length of the work zone and vehicle type on speed reductions was also studied. Speed and volume data for the population and for speeding drivers were collected through automatic traffic counters and video cameras respectively at three work zones. These data were collected at the beginning, middle and end of each work zone, to study the behavior of high speed drivers in particular and to compute their average speed reduction in response to the warning message. The results of the study indicate that the duration of exposure of the CMS does not have a significant impact on speed characteristics and driver behavior. Therefore, the CMS continues to be effective in controlling speed in work zones for projects of long durations. It was also found that there were no distinctive differences among the different types of vehicles with regard to speed reduction. The study also established that in longer work zones, drivers who reduced their speed in response to the speed control effort frequently have a tendency to speed back up as they approach the end of the work zone. This indicated that very long work zones might warrant the installation of a second CMS to maintain speed reductions through the work zone