With the development of social economy, people pay more and more attention to urban traffic problems. Coordinating the relationship among people, vehicles and roads has become one of the important problems that traffic management departments need to solve. Urban traffic control system is a computer integrated management system for urban traffic data monitoring, traffic signal light control and traffic guidance, and it is the most important part of modern urban traffic monitoring and command system.

Different cities have different problems, but sex is a problem of mixed traffic. How to solve the mutual influence or mutual influence in mixed traffic flow at intersections is the key to solve the problem! With the development of urbanization in China, more and more emerging cities appear, making urban traffic an absolute major problem. At the same time, with the steady development of China's economy, the number of urban motor vehicles is increasing, people's living standards are improving day by day, and more and more cars are entering the homes of ordinary people.

In many big cities, such as Beijing, Shanghai and Nanjing, the traffic is overloaded. Coupled with the government's vigorous development of roads and taxis, there are more and more vehicles, which not only requires wider roads, but also requires the introduction of new traffic management models and traffic rules. Therefore, since the late 1980s, many cities have expanded and built urban roads, and in the initial stage of road construction, traffic conditions have been effectively improved. However, with the rapid growth of traffic volume and the lack of systematic research and control of roads, widening roads has not fully played its expected role. The characteristics of many intersections and intersections in urban roads also determine that the traffic conditions of urban roads are bound to be restricted by this road condition.

As a result, the disadvantages of the old traffic control system and people's higher and higher requirements have intensified the contradictions, making the traffic problems that were not prominent before put on the agenda. Therefore, how to use appropriate control methods, make full use of the expensive multi-lane urban roads, and alleviate the traffic congestion in urban areas has increasingly become the main problem that traffic management and urban planning departments urgently need to solve.

Due to the different shapes and scales of traffic intersections, the number of traffic lights and control requirements are different, and the complexity of control is also different. For this reason, relevant departments pay more and more attention to introducing automation and intelligent technologies into traffic management, such as "electronic police", adaptive traffic lights and expensive traffic command and control systems. With the development of economy and social progress, road traffic has increasingly become an important part of social activities. The ability to control traffic also reflects the country's ability to control the whole society from one side, so all countries attach great importance to strengthening the ability to control traffic by various high-tech means.

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This paper briefly introduces and analyzes the present situation of modern urban traffic control and management, and expounds the working principle of traffic light control system in combination with the actual situation of urban and rural traffic. This design introduces the application of PLC to realize the automatic control of traffic lights at intersections. By analyzing the control requirements of traffic lights, the hardware and software of PLC control system are designed. Experiments show that the system is simple, economical, reliable and has high practical value.