Representing traffic and transit interactions in multimodal transportation networks is essential for obtaining link travel times and transit operating conditions. Achieving a consistent equilibrium between traffic and transit networks is important because inaccurate representation of modal interactions may lead to unreliable evaluations of multimodal transportation strategies. However, existing static traffic and transit assignment approaches often rely on predefined or sequential interaction procedures, where the convergence of traffic and transit states is not explicitly assessed. As a result, these approaches may require unnecessary iterations or terminate before achieving consistent network conditions.
This study develops a convergence-based link-level traffic and transit assignment framework that iteratively exchanges information between traffic and transit assignment models until a convergence criterion is satisfied. The proposed approach incorporates transit-generated passenger car equivalent flows into traffic assignment and updates transit operating characteristics, including travel time, dwell time, and headway, based on revised traffic conditions.
The proposed framework converged in both case studies and demonstrated that traffic and transit interactions vary across link types and operational conditions. The results indicate that transit operations can influence network conditions beyond transit-served links. Sensitivity analyses further confirm the robustness of the proposed convergence procedure under different transit supply and demand conditions, with the private vehicle network showing greater sensitivity to public transport demand on lower-demand lines and dwell time playing a more influential role on higher-demand lines.
The proposed approach provides a computationally efficient, link-level framework that can support transportation planners in more accurate evaluation of multimodal infrastructure and operational strategies.