Multiobjective Optimization of Signal Timings at a Displaced Left Turn: A Swarm Intelligence Approach

Fluctuations in speed and frequent stops at signalized intersections significantly increase fuel consumption and emissions. Focusing solely on optimizing vehicle performance measures may neglect pedestrian demands. A displaced left-turn intersection (DLT), with its alternative geometric layout and properly coordinated traffic signals, offers a promising solution to reduce stops and improve traffic flow smoothness and safety. This study proposes integrating an ecology-based performance index (EcoPI) to optimize traffic signal settings at DLT intersections. It defines a multiobjective optimization problem balancing ecological performance with pedestrian safety exposure (SE) and delays at DLT intersections. The study uses the bee colony optimization (BCO) technique, a swarm intelligence metaheuristic, to account for delays, stops, fuel consumption, and emissions. Overall, simulation results indicate that EcoPI outperforms the Federal Highway Administration (FHWA) solution in undersaturated (by 19.66%) and near-saturated traffic conditions (by 5.11%). These findings suggest that the methodology can support more balanced treatment of pedestrians at DLT intersections.