Safety evaluation of mixed traffic flow with truck platoons equipped with (cooperative) adaptive cruise control, stochastic human-driven cars and trucks on port freeways

Abstract

This study examines the operational safety levels of a novel, complex traffic flow mixed with truck platoons equipped with (cooperative) adaptive cruise control, known as TPs-(C)ACC (referred to as TPs), as well as traditional human-driven cars (HDCs) and trucks (HDTs) in various scenarios on port freeways. The stochastic behavior of human drivers in car-following situations is captured using the stochastic intelligent driver model (SIDM). In contrast, the car-following behaviors of TPs are modeled using the Adaptive Cruise Control (ACC) and Cooperative Adaptive Cruise Control (CACC) models, respectively. Surrogate safety measures (SSMs) are employed to evaluate the safety performance of the mixed traffic flow. The experimental findings demonstrate that, all else being equal, the oscillation of the mixed traffic flow considered in this study diminishes as the penetration rate and lengths of TPs increase, respectively. The safety levels of the mixed traffic flow would be improved with longer TPs but deteriorate with higher total traffic flow rates. For a given CACC intra-platoon headway, larger headways of ACC truck leaders are advantageous to enhancing the safety levels of the mixed traffic flow. However, for TPs with a shorter headway of leading trucks, higher penetrations of TPs with shorter platoon lengths would worsen the safety levels of the mixed traffic flow. When considering a fixed combination of penetration rates, replacing an ACC truck leader with a CACC truck leader improves the safety of the mixed flow, while the incremental effects of lengthening the TPs on enhancing the safety levels diminish. A mixed flow with longer TPs is more susceptible to the stochastic behavior of human drivers.