Cooperative Overtaking and Adaptive Speed Limit in Connected Mixed Traffic: A Cellular Automaton Study of Bidirectional system

Connected vehicle (CV) technology offers the ability, through cooperative driving, to a potential improve of the heterogeneous traffic efficiency and safety. In this paper, an extended cellular automaton model is proposed to study the effect of connected vehicles (CVs) on the dynamics of cooperative overtaking along a two-lane bidirectional system under mixed traffic conditions composed of CVs and human-driven vehicles (HDVs). The proposed model incorporates vehicle-to-vehicle communication within a finite communication range D, allowing CVs to perform cooperative anticipation, speed harmonization, overtaking maneuvers coordination and an adaptive speed limit (ASL) strategy. Traffic performance is characterized using fundamental diagrams, overtaking frequency, and inter-lane velocity correlation. In addition, microscopic traffic conflict-risk indicators are introduced to quantify potentially dangerous rear-end (P RE ) and head-on (P HO ) configurations associated with longitudinal interactions and overtaking maneuvers, respectively. The results show that the communication range D emerges as an important control parameter governing the collective dynamics of the system. Short communication ranges favor efficient local coordination, leading to higher traffic flow and stronger inter-lane synchronization, whereas larger communication ranges improve longitudinal safety by reducing the rear-end conflict-risk indicator. However, extended communication ranges may simultaneously increase the head-on conflict-risk indicator during cooperative overtaking, revealing a trade-off between longitudinal and lateral safety. Within the investigated communication ranges, intermediate values provide a favorable compromise between traffic efficiency and the two conflict-risk indicators. Furthermore, the ASL strategy improves overall traffic performance by increasing throughput and reducing both rear-end and head-on conflict risks. These findings highlight the coupled roles of communication range and adaptive speed control in shaping the collective dynamics, efficiency, and safety of mixed connected traffic on bidirectional roads.