A Microsimulation-Based Stochastic Optimization Approach for Optimal Traffic Signal Design
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ORIGINAL ARTICLE
A Microsimulation‑Based Stochastic Optimization Approach for Optimal Traffic Signal Design Abdhul Khadhir1 · Lelitha Devi Vanajakshi1 · Ashish Bhaskar2 Received: 14 July 2019 / Accepted: 23 September 2020 / Published online: 6 October 2020 © Springer Nature Switzerland AG 2020
Abstract Arriving at optimal signal timing parameters to improve the efficiency of traffic flow has been one of the major challenges faced by traffic engineers. The choice of a robust optimization framework and an accurate traffic model plays a significant role in determining optimal signal timing parameters. Though traffic flow is intuitively stochastic, few studies incorporate stochasticity in their optimization framework for traffic signal design. This study proposes two simulation-based stochastic optimization algorithms—an evolutionary algorithm-based framework and a simultaneous perturbation stochastic approximation (SPSA) algorithm-based framework for the optimal signal design of an isolated intersection using a calibrated microsimulation environment with reasonable accuracy. A software-in-the loop approach is used to control the traffic signals in the microsimulation environment. SPSA is a gradient descent algorithm with a powerful approach for approximating the gradient with just two function evaluations per gradient approximation. To evaluate the performance of the two frameworks, the study optimizes the signal timings for a case study on an isolated intersection in an urban arterial in Chennai. On comparing the two algorithms, it is found that SPSA performed better and took 100 function evaluations less than that taken by GA. A better (near optimal) initial solution is found to yield a faster rate of convergence for both algorithms. As the proposed optimization framework incorporates the stochastic nature of traffic in the optimization algorithm, it can accommodate the temporal variations in traffic and thereby provide traffic engineers a robust signal control strategy for improving the efficiency of traffic flow. Keywords Stochastic optimization · Simultaneous perturbation stochastic approximation · Genetic algorithm · Microsimulation · Robust signal design · Mixed traffic conditions
Introduction Mobility of people and goods in a safe, reliable, and efficient manner is the primary goal of any transportation system. Though other modes of transportation are essential, road transport and thereby road network requires more attention * Abdhul Khadhir [email protected] Lelitha Devi Vanajakshi [email protected] Ashish Bhaskar [email protected] 1
Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, India
Science and Engineering Faculty, School of Civil and Environmental Engineering, Queensland University of Technology, Brisbane, QLD, Australia
2
than the other modes, as roads act as feeder systems to other modes and provide last mile connectivity. A major hurdle in providing a reliable and fast road transportation system is the delay incurred enroute. Intersections,
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