Identification of Potential Enhancements for Work Zone Safety in Alabama

The objective of this report is to evaluate the effectiveness of police presence and double fine signs to reduce speed in work zones in Alabama and to measure the actual speed and time headway of vehicles in work zones and upstream of work zones. This report monitored a total of 254,841 vehicles for speed and time headway at five Interstate work zone locations where four different types of road work was proceeding. Research methods included a literature search, live field data collection with cameras equipped with Machine Vision Processing (MVP), and data analysis.
The report finds that level of service is reduced when vehicles enter the work zone. Police presence is the most effective method of reducing speed in work zones. The standard deviation of the speed of vehicles also increases as they enter the work zone. Time headway decreases from the non-work zone case to work zone cases, which helps explain why misjudging stopping sight distance/following too close is the most frequent cause of crashes in work zones in Alabama.
The researchers recommend that ALDOT review its method of setting work zone speed limits in light of new recommendations in the 2000 MUTCD. They also affirm that reducing speed using police presence is the most effective method in use in Alabama.