Improving Contraflow Left-Turn Lane Design at Signalized Intersections to Decrease Traffic

Contraflow left-turn lanes (CLL) are designed for increasing left-turn capacity and have been increasingly implemented at signalized intersections. Professor Yi Qi will introduce this innovative intersection design and the signal timing and geometric design required for its implementation. She will share a systematic method for determining CLL length and signal timing, and a case study for evaluating the operational benefits of redesigning a real-world CLL intersection using these recommendations, which resulted in decreased average traffic delay, vehicle travel time, and queue length. Professor Qi will also discuss an innovative signal timing strategy, Counterclockwise Split Phasing (CSP) signal timing, for implementing CLLs at signalized intersections with split phasing (SIWSPs.) She’ll share the results of a traffic simulation-based case study which indicate that by using the proposed CSP signal timing plan, CLLs can be implemented at SIWSP to significantly reduce traffic congestion caused by high left-turn demand at this type of intersection.

Dr. Yi Qi is the Chair of the Transportation Studies Department and a professor at Texas Southern University. Dr. Yi Qi is a very productive scholar who has directed more than 20 external foundered projects sponsored by various federal and local governments and has more than 50 journal publications, and numerous conference proceeding papers and technical report publications. Her research areas include transportation safety analysis, traffic signal operation, intersection geometric design, and GIS-based transportation system performance analysis. Dr. Qi is a nationally recognized scholar and serves as a member of numerous committees of national and international organizations. She received her M.S. and Ph.D. degrees in transportation planning and engineering from the Polytechnic University of New York (New York University Tandon School of Engineering) in 2002. In addition, she has a B.S. in mathematics and an M.S. in probability and statistics from East China Normal University (ECNU) in China.