## 8 Conclusions and Discussion
### Conclusions of the Review
Related research can not only contribute to the innovative development of theoretical frameworks for new heterogeneous traffic flows on urban roads but also provide key support for countermeasures to urban road new heterogeneous traffic flow control problems and the development of next-generation traffic control systems. In conclusion, this study is oriented toward the new heterogeneous traffic flow environment composed of human-driven vehicles, intelligent connected vehicles, and even autonomous vehicles that will coexist for a long time. This heterogeneous coexistence paradigm is supported by recent traffic flow research. [PERSON] et al. [81] developed mathematical frameworks demonstrating that mixed HDV-CAV traffic networks require fundamentally different control strategies compared to homogeneous flows, while [PERSON] et al. [82] empirically validated through car-following experiments that heterogeneous traffic exhibits distinct behavioral patterns that significantly impact system stability and capacity utilization at varying penetration rates. Through analyzing their basic characteristics and collaborative mechanisms, it establishes collaborative control theories and methods under new heterogeneous traffic environments and realizes collaborative control of new heterogeneous traffic flows oriented toward typical scenarios and application cases. Research on this issue has significant implications for deepening understanding and recognizing future new heterogeneous traffic flows, enhancing new heterogeneous traffic flow management and control capabilities, and advancing the development of intelligent connected vehicle collaborative control technologies oriented toward traffic efficiency in new heterogeneous traffic flows. Y.W. : Conceptualization, Methodology, Writing--Original Draft, Investigation, Writing--Review and Editing. X.Y. : Conceptualization, Methodology, Supervision, Writing--Review and Editing. All authors have read and agreed to the published version of the manuscript. This study is supported by the National Natural Science Foundation of China (General Program), Research on Basic Problem of Vehicle-Infrastructure Cooperative Traffic Control for Special Vehicles (52472350), The China Postdoctoral Science Foundation, Cooperative Optimization on Right-of-Way at Signalized Intersections in Heterogeneous traffic Environment (2022M712410), and Guangxi Major Science and Technology Special Subproject, Reutilization of Pinglu Canal Cross-Line Bridges and Optimization of Traffic Organization (2023 AA14006). Not applicable. All authors are grateful for the resources provided by the Intelligent Transportation System Research Center of Tongji University. The authors declare that there is no conflict of interest regarding the publication of this paper. The following abbreviations are used in this manuscript:  
A2C Advantage Actor-Critic  
ADP Approximate Dynamic Programming  
AIM Autonomous Intersection Management  
ASC Actuated Signal Control  
CAV Connected and Automated Vehicle  
CBFs Control Barrier Functions  
CACCu Cooperative Adaptive Cruise Control with unconnected vehicles  
CACC Cooperative Adaptive Cruise Control