بخشی از مقاله (انگلیسی)
The imminent emergence of connected and autonomous vehicles (CAVs) highlights the need for preparing the road infrastructure for traffic flows mixed with CAVs and human-driven vehicles. A dedicated lane (DL) for CAVs is one of the practical and potential ways to upgrade the road infrastructure for the mixed traffic.
This paper proposes a theoretical method to discuss the influence of implementing a CAV DL policy on the freeway traffic efficiency. In detail, the impact was measured by capacity and throughput. The calculation methods of these efficiency measurements under different CAV DL policies were proposed.
Numerical experiments were conducted under various compositions of CAV DL policies and traffic conditions. More specifically, the relationship between the traffic conditions (i.e., traffic demand, market penetration rate (MPR) of CAVs, platoon intensity of CAVs, willingness of CAVs using the CAV DL) and the CAV DL policies (i.e., lane configuration, DL access control policy) were discussed.
Results and Conclusion
The results have led to some interesting findings, including the critical values of MPR that are valuable to guide an appropriate implementation of a CAV DL policy under a specific traffic condition.
Connected and Autonomous Vehicles (CAVs) are expected to bring benefits to traffic efficiency, safety, and energy-saving [1, 2]. And there will be a long transition period with the coexistence of CAVs and Human-driven Vehicles (HVs). This mixed traffic condition is one of the major challenges in future traffic because of its complexity. For instance, CAVs might have six automation levels identified by the Society of Automotive Engineers (SAE), which results in different driving behaviors. The unpredictable human driving behavior could cause confusion and potentially unsafe situations to the CAVs. As a result, the expected outstanding performance of CAVs might be affected, especially with a low market penetration rate (MPR) . It urges some appropriate and effective management or control strategies for the mixed traffic condition.
Conclusions and future works
This study presents a review of the “state-of-the-art” studies on CAV DL policy under the mixed traffic condition as well as the headway distributions of the mixed traffic. And then, the detailed CAV DL policies and the headway-based theoretical methods evaluating the traffic efficiency are proposed. The discussions based on several numerical experiments give some insights into the relationship between traffic efficiency measures and various conditions (traffic conditions and DL policies). As a final observation, it seems when the MPR of CAVs on a freeway segment is low (e.g., below 50%), the implementation of CAV DL does not have a significant positive impact on traffic efficiency. At this condition, if a DL policy is required, the ‘mandatory use’ is recommended compared with the ‘optional use’, especially when CAVs use the safe driving mode. When MPR of CAVs grows to a high value (e.g., larger than 80%), the ‘optional use’ policy performs better instead. All in all, distributing one lane as a DL is enough as a beginning stage of DL implementation.