Expanding Stability Domains in Connected Vehicle Platoons: A Safety-Oriented Framework for Cooperative Control Parameter Optimization

Cooperative adaptive cruise control (CACC) has great potential to enhance the stability and safety of connected and automated vehicle (CAV) platoons. However, gaps remain in understanding how damping behavior and connectivity-enabled information flow jointly affect the relationship between platoon stability and collision risk. This study proposes a safety-oriented CACC framework that investigates the relationship between stability and collision risk under three damping states: underdamped, critically damped, and overdamped. Numerical simulations are performed on five-vehicle platoons with a fixed time headway (τ = 0.6 s) subjected to periodic disturbances. Additionally, varying connectivity weights are examined to evaluate the influence of vehicle-to-vehicle (V2V) communication on stability and safety. Safety performance is evaluated using multiple surrogate safety metrics, including deceleration rate to avoid crash (DRAC), rear-end collision risk index (RCRI), and time-to-collision (TTC). The results show that damping ratios within 1.0 to 1.2 provide favorable safety performance under fixed-headway conditions, while increased upstream information flow expands the stability domain and improves downstream safety margins. Additional sensitivity analyses on platoon size and communication delay further indicate that the proposed safety-oriented damping region is not restricted to the original five-vehicle setting, although delayed V2V information increases dynamic fluctuation and reveals a safety–smoothness tradeoff. These findings provide interpretable guidance for the design of robust and safety-oriented cooperative longitudinal control strategies for connected vehicle platoons.