Integrated optimization of lane assignment and signal timing for freeway ramp-surface intersections based on flexible lane-changing restrictions

Frequent lane-changing at freeway ramp–surface street intersections causes weaving conflicts, queue spillback and safety risks. This study proposes an integrated optimization model based on flexible lane-changing restrictions to coordinate lane assignment, signal timing and admissible target-lane sets. Unlike rigid isolation or unrestricted lane-changing, the model establishes a source–destination–lane matching mechanism that selectively permits or restricts lane-changing according to traffic source, target movement and feasible weaving space. A mixed-integer linear programming model is developed with constraints on phase structure, lane configuration, flow equilibrium, weaving volume and capacity. VISSIM and SSAM are used to evaluate operational efficiency and safety at a ramp-connected intersection. Results show that the proposed model reduces average delay by 29.4%, average queue length by 42.1% and total conflicts by 54.07% compared with the status quo. Sensitivity analysis further confirms its robustness under varying demand levels.