Design of Lane Merges at Rural Freeway Construction Work Zones

Practices for the design and control of work zone traffic control configurations have evolved over time to reflect safer and more efficient management practices. However, they are also recognized as areas of frequent vehicle conflicts that can cause congestion and safety problems. In this research, a new design has been developed that could lessen some of these detrimental effects. This new concept, known as the “joint merge,” simultaneously merges two lanes into one. The key feature of the design is its two-sided taper in which the two adjacent lanes approaching a lane reduction are simultaneously tapered into a single lane with neither lane having a priority. This is theorized to influence drivers into merging in a smooth alternating pattern. To evaluate its operational effects, the joint merge was examined in a work zone in Louisiana and compared to an manual on uniform traffic control devices (MUTCD) conventional merge configuration at the same site. Lane-specific volume and vehicle speeds were collected in the field and the two designs were compared using Analysis of Variance (ANOVA) and T-test statistical procedures. Overall, the joint merge was found to increase the efficiency of the closed lane and encourage the use of both lanes into the work zone entrance. It was also found that the number of lane changes during low and high-volume periods decreased when the joint merge configuration was used. While no conclusive findings could be made relative to its specific effect on capacity, video recordings and lane usage data suggested that the joint merge strategy was understood and well received by most drivers.