## 2 Origins and Development of Traffic Control Systems  
Although technologies and measures for controlling traffic flow based on traffic signals date back over a century, traffic coordination control involving multiple traffic signals originated in the 1950s-1960s with the offline multi-period control system proposed by the UK's Transport Research Laboratory, which embedded optimized signal timing based on survey data into signal controllers. However, such control systems struggled to adapt to dynamic traffic conditions and diverse dynamic demands, and regenerating control schemes required extensive traffic surveys each time, proving time-consuming, labor-intensive, and costly. Traffic signals at each road intersection regulate the right-of-way (phases), duration (green time length), and cycle time for each approach and movement direction, controlling pedestrian, bicycle, and motor vehicle traffic flows. Furthermore, by coordinating the green onset time differences (offsets, green wave bands) between upstream and downstream signals at two or multiple intersections, coordinated control of multiple intersections is achieved. To further implement system control for an entire city, traffic engineers commonly divide the road network into several zones (sub-area division) for inter-zone coordinated control. Therefore, achieving integrated optimization and dynamic optimization control for an entire city represents an extremely complex systems engineering challenge, requiring not only dynamic and precise understanding of the entire road network's traffic conditions and trends but also comprehensive traffic facilities and orderly traffic flow as a foundation. While electronic, information, and computer technologies are necessary, the more critical and core element should be specialized traffic control technology based on traffic engineering expertise. With the rapid development of computer and electronic technologies, the 1970s witnessed the gradual development of Australia's SCATS (Sydney Coordinated Adaptive Traffic System; a dynamic plan selection control system based on detector-collected data) and the UK's SCOOT system (Split Cycle Offset Optimization Technique; a dynamic prediction optimization control system based on detector-collected data). Subsequently emerging systems from Italy, the United States, Germany, Japan, and other countries share fundamentally similar control principles. In the mid-1980s, China established the \"Urban Traffic Real-time Adaptive Control System\" project as a major national \"Seventh Five-Year Plan\" scientific and technological research initiative. This joint research project, undertaken by Tongji University (system design and core models and algorithms), the 28 th Research Institute of the Ministry of Electronics Industry (system platform and signal controllers), the Traffic Management Research Institute of the Ministry of Public Security (project management), and the Nanjing Traffic Police Detachment (project implementation), was implemented in Nanjing. This represented the first systematic independent development of a traffic control system byChinese researchers, laying the foundation for China's subsequent traffic control technology research and development. The project achieved recognition as a major scientific and technological breakthrough during the \"Seventh Five-Year Plan\" period [9]. Although the \"Seventh Five-Year Plan\" scientific and technological research achieved significant results in traffic control systems, due to the need for improved commercialization, traffic control systems in China's major cities still predominantly relied on imported systems: Beijing imported SCOOT systems; Shanghai, Tianjin, and others imported SCATS; Shenzhen imported Japan's Kyosan system; Wuhan imported a Spanish system; and Jinan and Xi'an imported American systems.