Left-turn phasing selection considering vehicle to vehicle and vehicle to pedestrian conflicts

Left-turning vehicle movement at signalized intersections with permissive left-turn phases creates safety concerns due to the higher chance of conflict with opposing-through vehi-cles and pedestrians. In this research, a simulation-based study was conducted to evaluate pedestrians' impact on traffic conflicts between left-turning vehicles and opposing-through vehicles (V-V conflicts) as well as traffic conflicts between left-turning vehicles and pe-destrians (V-P conflicts) in the permissive left-turn phasing scenario. Intersections with different opposing-through volumes, left-turn volumes, number of opposing-through lanes, and pedestrian volumes were modeled in VISSIM, a traffic micro-simulator. The surrogate safety assessment model (SSAM) was used to estimate the number of V-V and V-P conflicts. The effect of pedestrian presence on V-V and V-P conflicts was evaluated using simulation scenarios with and without pedestrian presence. Simulation results revealed that pedestrian presence increased both V-V and V-P conflicts. As pedestrian presence increased the total number of traffic conflicts, permissive left-turn phasing processed fewer left-turn vehicles to maintain the same level of intersection safety with pedestrian presence compared to the no-pedestrian scenario. Since current left-turn phasing decision guidelines do not consider the impacts of pedestrian presence, this research quantified pedestrian-influenced and pedestrian-involved left-turn traffic conflicts to determine appropriate left-turn signal phasing decisions to ensure safe and efficient crossing of pe-destrians and vehicles at signalized intersections. This simulation-based study's findings can be beneficial in the decision making of left-turn phasing selection as the before-after intersection safety performance analysis by collecting field data often resources intensive.(c) 2023 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).