Mixed Traffic Flow Characteristics and Energy Consumption in Highway Work Zone under a Connected and Automated Environment

Lane reductions in highway work zones often trigger merging conflicts and congestion, disrupting normal
traffic flow. By integrating the safety-distance-based car-following model, improved work-zone lane-changing rules, and connected and automated vehicles (CAV) platooning characteristics, this study develops a cellular automaton model for mixed traffic flow in a highway work zone under a connected and automated environment. Simulation results show that elevating the CAV penetration rate significantly improves capacity in work zone, with traffic flow increasing by over 50% at a penetration rate of 0.6 and above. The synergistic  effect of platooning becomes pronounced only at high penetration rates. Time-space diagrams of the work zone indicate that platooning mode is more effective than discrete CAV in alleviating congestion within the warning and upstream transition zone. Meanwhile, at low penetration rates, rising density worsens traffic flow stability, while the synergistic effect at high penetration rates suppresses the growth of traffic congestion ratio and velocity standard deviation, enhancing stability of high-density traffic flow. Furthermore, energy consumption is minimized with a penetration rate of at least 0.5 and platoon length of 4-6 vehicles. Increasing penetration rate effectively reduces PM emissions, but its marginal emission reduction benefit diminishes gradually (greatest in low penetration ranges). Blindly increasing penetration rate and enlarging platoon length lead to a rebound in energy consumption due to frequent velocity changes in high-density sections.