Cooperative bus eco-approaching and lane-changing strategy in mixed connected and automated traffic environment

In mixed traffic environments, existing bus eco-approaching and lane-changing methods fail to adequately consider the uncontrollability of human-driven vehicles and their interactions with surrounding vehicles during lane changes, often leading to increased fuel consumption and emissions. To address this issue, this paper proposes a two-stage cooperative bus motion control model during lane-changing and approaching stops: the first stage finds the optimal positions and timings for bus lane changes in a mixed traffic environment; the second stage constructs a Model Predictive Control (MPC)-based cooperative lane change controller, which couples the lateral and longitudinal movements of buses. Using Lyapunov stability theory, the stability of this controller is demonstrated. A solution algorithm that integrates the Pontryagin Minimum Principle (PMP) and the Broyden–Fletcher–Goldfarb–Shanno Sequential Quadratic Programming (BFGS-SQP) method is proposed. The proposed model is tested on real-world cases with the Simulation of Urban Mobility (SUMO). The results show that, compared to traditional strategies, the cooperative strategy improves lane-changing efficiency by 14.95 %, reduces fuel consumption by 17.24 %, and increases traffic stability by 25.21 %. Under high-traffic conditions, the proposed strategy can significantly reduce lane-changing time by 25.18 %. The higher coefficient values in the objective function drive buses to adopt more proactive actions to quickly complete the space creation process. The results in a whole bus line show the proposed method increases the lane-changing success rate by 25.42 % and reduces the waiting time by 37.35 %.