Effectiveness of Changeable Message Signs in Controlling Vehicle Speeds in Work Zones – Phase II

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 CMS 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 Phase II of the study are given.