Evaluation of Optimal Turns Configuration at Intersections in Urban Roads Network Based on Safety and Congestion indices using Non-dominated Sorting Genetic Algorithm-۲

Optimal turns configuration at intersections is a fundamental strategy in the pursuit of transportation network design problems. Most interventions implemented at intersections to manage traffic are typically assessed based on their localized impact at the specific node. However, a critical question arises: can any intervention at a single node be truly independent of the conditions and performance of other nodes within the transportation network? While point-based evaluation methods often produce limited and isolated outcomes, traffic dynamics within a network context evolve in a markedly different manner, where interdependencies render optimal solutions inherently multidimensional, and sensitive to broader system-wide interactions. This study proposes three novel approaches to address this challenge: (۱) the development of a comprehensive, network-based decision-making framework for managing turn movements; (۲) a conceptual shift from conventional link-based methodologies to node-centric patterns in network design; and (۳) the adoption of conflict indices as surrogate safety measures in place of traditional crash data, thereby facilitating a more integrated, proactive, and safety-oriented approach to urban transportation network planning. To operationalize these methodologies, a bi-level, multi-objective optimization framework is developed, integrating the NSGA-۲ algorithm for generating Pareto-optimal solutions and the TOPSIS method for decision-making support. The model formulation and optimization processes are grounded in empirical data collected from the urban road network of Dezful, Iran. The findings yield a diverse spectrum of optimal solutions, offering valuable insights for enhancing existing transportation systems and informing the strategic planning and design of future urban networks.