A passive lane-changing behavior model for connected vehicle platoons was developed from the perspective of cooperative optimization of platoon behavior aiming at the issue of significant speed fluctuations and low traffic efficiency in freeway work zones. The Plexe-SUMO simulation platform was employed, and algorithms for platoon generation and lane-changing choices were designed, thereby enabling the generation and simulation of platoon behavior. Different traffic flow conditions were considered, and the impact of platoon size adjustments on the enhancement of traffic efficiency in work zones was analyzed, culminating in the quest for an optimal platoon organization structure. The experimental results show that small platoons of less than 4 pcu are more suitable in medium and low-volume states (less than 900 pcu/h). Larger platoon sizes (greater than 6 pcu) improved passing efficiency as volume increases, especially in high-volume states. An ideal platoon size of 2 pcu was found when the single-lane volume was less than 1100 pcu/h in the experimental scenario, while a platoon size between 6 and 8 pcu was ideal for high volume states. There exists an optimal platoon size in work zones under different traffic flow conditions, allowing the roadway capacity to reach its maximum efficiency.