Learning from Trajectories: How Heterogeneous CACC Platoons Affect the Traffic Flow in Highway Merging Area

Vehicle platoons equipped with cooperative adaptive cruise control (CACC) have the potential to improve traffic stability and reduce congestion. Existing CACC research lacks micro-level trajectory cluster observation regarding the impact of heterogeneous CACC platoons—comprising vehicles with different types and characteristics—on mixed traffic flow. This study implements a simulation framework that creates a realistic mixed traffic flow consisting of manual driving vehicles (HDVs) and heterogeneous CACC platoons on highway merging areas. By adjusting four influential factors: traffic volume, truck ratio, CACC market penetration rate (MPR), and CACC platoon size, a series of high-resolution trajectory data were obtained to analyze their influence on traffic flow characteristics. Subsequent analysis, using both quantitative statistical measures and visual demonstrations, revealed that higher traffic volumes and truck ratios lead to an expansion of congested areas. Whereas increasing the MPR of CACC platoons can alleviate this issue by reducing the overall oscillation level and actual traffic density, encouraging more vehicles to change lanes, thus blending clusters of high- and low-speed vehicles. However, the impact of increasing CACC Platoon size in a small range remains insignificant. This study can serve as a reference for investigating the mechanisms behind the impact of heterogeneous CACC platoons on the mixed traffic flow pattern.