Joint Optimization of Multi-Port Berth Allocation and Ship Lock Scheduling in River–Sea Direct Transport

River–sea direct transport systems emerging along the Pinglu Canal connect coastal and inland port clusters through shared lock facilities. When berth and lock resources are planned independently, uneven port workloads, mismatched vessel flows, and avoidable waiting may arise. This study formulates a coordinated scheduling problem for a multi-port–lock network operating under direct transshipment. The mixed-integer programming model jointly determines port assignment, berth service sequences, lockage plans, and vessel placement within lock chambers, while balancing lock-operation expenditure against the port dwell time of seagoing and river vessels. To address large instances, a hierarchical iterative collaborative optimization algorithm (HICOA) is developed. Its iterative mechanism exchanges information between berth and lock decisions, and a packing heuristic and adaptive large neighborhood search are applied to the associated subproblems. Computational results show that HICOA recovers the optimum for small instances and produces feasible solutions efficiently when CPLEX is constrained by a 5-h time limit. Compared with independent scheduling, coordinated optimization reduces total port time by up to 55.69%. The sensitivity analysis further indicates that river-vessel arrival dispersion and berth distribution across ports materially influence system performance.