Police Enforcement Strategies and Speed Reduction in Work Zones

Highway work zone safety is a nationwide concern and it will likely draw ever increasing attention as the number of highways that require renovation or maintenance increases. In an effort to improve work zone safety now and in the future, the Indiana Department of Transportation (INDOT) recently established a special fund for work zone speed enforcement and further commissioned the authors of this study to help them achieve the maximum safety benefits within their budget constraint. A previous study by the authors modeled the crash frequency in Indiana work zones with various features, which provided the potential for safety improvement. In this study, the focus is on evaluating the effectiveness of police enforcement strategies in reducing driving speed in work zones. These results will eventually be included in a comprehensive method for optimizing enforcement strategies and resource allocation to improve work zone safety. Different combinations of stationary police enforcement, with or without supplemental variable message signs (VMS), were evaluated in six work zone sites. The authors conducted data collection using experiment design techniques and multilevel linear modeling for the data analysis with the goal of finding the best way to estimate the effectiveness of enforcement strategies. The developed statistical model allows predicting speed reduction as a function of police enforcement elements and roadway characteristics. The results indicate that spreading enforcement resources among multiple work zones is a good strategy instead of concentrating enforcement on a smaller number of work zones. Furthermore, adding VMS with relevant messages about enforcement greatly increases the effectiveness of the enforcement program.