Effectiveness of Dynamic Messaging on Driver Behavior for Late Merge Lane Road Closures

Efforts to improve safety and traffic flow through merge areas on high-volume/high-speed roadways have included early merge and late merge concepts and several studies of the effectiveness of these concepts have been conducted, many using Intelligent Transportation Systems for implementation. The Iowa Department of Transportation (Iowa DOT) planned to employ a system of dynamic message signs (DMS) to enhance standard temporary traffic control for lane closures and traffic merges at two bridge construction projects in western Iowa (Adair and Cass Counties) on I-80 during the 2008 construction season. This presentation will summarize efforts to evaluate the effectiveness of the DMS system implemented on I-80 by the Iowa DOT. The primary objective of the efforts was to examine driver merging actions. Data were collected over four weekends but only two yielded sufficient data for evaluation: one with two short periods of moderately impacted (transition) traffic flow and the other with an extended period of congestion flow. For both of these periods, a review of the data did not indicate a statistically significant impact on driver merging actions when the DMS messaging was activated as compared to free flow conditions with no messaging. Unforeseen difficulties with data collection efforts also adversely affected the ability to draw statistically significant conclusions on the project. Examples of such difficulties include personnel safety issues associated with the placement and retrieval of counting devices on a high-speed roadway, unsatisfactory equipment performance, and insufficient congestion to activate the DMS messaging hampered efforts.