Impact of cooperative autonomous vehicle platooning on highway traffic efficiency and carbon emissions

Connected and automated vehicle (CAV) platooning is widely regarded as a key enabler of improved motorway efficiency, safety, and environmental performance. However, current evidence remains dispersed across heterogeneous experimental configurations, resulting in limited comparability and a scarcity of motorway-scale evaluations based on consistent performance metrics. This work develops a simulation-based, fully reproducible evaluation framework and applies it to Dublin’s M50 motorway to quantify safety efficiency trade-offs, environmental impacts, and incident resilience in mixed CAV and human-driven traffic. Five experimental scenarios are formulated to: (i) calibrate platoon-control aggressiveness and vehicle-following parameters for balanced safety and throughput; (ii) determine time-of-day-dependent CAV penetration thresholds; (iii) assess leadership effects by comparing mixed platoons led by lower-level CAV (CAV2) and higher-level CAV (CAV4); (iv) characterize powertrain-dependent traffic and emission responses for petrol, diesel, and battery-electric vehicles; and (v) evaluate resilience under a standardized multi-lane closure. Results indicate that a moderately aggressive combination of vehicle-type and control-policy settings reduces time-to-collision conflicts while increasing network throughput, that higher lead-vehicle automation improves platoon stability, and that platooning reduces post-incident recovery time and near-collision risk. The proposed framework establishes motorway-scale benchmarks and provides actionable guidance for platoon-control tuning, leader assignment, and environmentally informed operational planning under realistic CAV penetration levels. • SIMPLA platoon controller is integrated with SUMO for Dublin M50 motorway case study. • Effects of leader roles, time of day, and powertrain mix on CAV platooning are evaluated. • Maps time-dependent tipping points for optimal connected vehicle deployment. • Quantifies energy and emissions for petrol, diesel, and battery electric fleets. • Platooning improves efficiency, BEV energy savings, and resilience to lane closures.