Dynamic Late Lane Merge System at Freeway Construction Work Zones

Abstract

In normal work zones with lane closures, drivers do not merge at any one definite point, a situation thus often causing a sudden interruption in traffic flow and sometimes higher delay and longer queue. The Dynamic Late Lane Merge System (DLLMS) is used to specify a definite merge point, improve the flow of congested work zones, and reduce queue lengths in travel lanes. The DLLMS was implemented in Michigan on three freeway segments that were reduced from two lanes to one lane because of highway construction work zones. The DLLMS directed traffic to use both lanes (open and closed lanes) until the designated “merge point” (close to the taper) where traffic from each lane was instructed to take turns merging into the open lane. On the basis of travel time characteristics, merge locations, and throughput, the effectiveness of the DLLMS was evaluated as a part of this study. The before period data were not available; therefore, a conventional work zone merge system, located on eastbound I-94, was used as a control site for the westbound I-94 test site. Comparison of the I-94 control and test sites indicated that the presence of the DLLMS improved the flow of travel and increased the percentage of vehicles that merged at or near the designated taper location. Based on the expected travel time savings, at a $5/h value of time, the benefit-cost ratio will be greater than 1, indicating that the monetary benefits of the DLLMS outweigh the cost of the system.