• July 15, 2019

    WSU research paper sees success in Transportation Research Part B: Methodological

    After more than two years of dedicated work, WSU Civil and Environmental Engineering Assistant Professor, Ali Hajbabaie, and Graduate Research Assistant, Rasool Mohebifard, got their paper accepted, published, and downloaded more times than most in Transportation Research Part B: Methodological last winter. 

    Their piece, titled, “Optimal network-level traffic signal control: A benders decomposition-base solution algorithm,” focuses on the network-level traffic signal timing optimization problem and explores the ways in which it can be solved.

    The problem is expressed as a Mixed-Integer Nonlinear Program (MINLP), which is based on the Cell Transmission Model (CTM). This allows it to consider closed-form constraints and capture the fundamental flow-density diagram, ultimately getting rid of the flow holding-back problem.

    The MINLP is then divided into an Integer Program (IP), or the “master problem”, and new MINLP, otherwise known as the “primal problem”, using a solution algorithm based off of the Benders decomposition technique. 

    The image above compares the runtimes of solving the primal problem versus the master problem. 

    Some of the research highlights include: 

    • “Formulating a signal timing optimization program with explicit representation of the cell transmission model flow-density diagram to avoid the flow holding-back problem.
    • “Developing an algorithm based on the Benders decomposition technique to convert the original MINLP to an IP and several CTM simulation runs. 
    • “Providing the optimality, convergence, and feasibility properties of the solution technique.
    • “Developing a dual estimation algorithm for the MINLP to generate Benders cuts with a simulation-based approach.” (Mohebifard & Hajbabaie, 2019). 

    To view the complete paper, click here.