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Traffic signal control machine classification
- Nov 30, 2018 -

Traffic signal control machine classification

A single point of control
Single intersection traffic signal control is the most basic form of traffic control, but also the basis of line control and surface control system. Its purpose is to eliminate or reduce the conflict points of traffic flow in all directions through reasonable signal allocation, and at the same time to minimize the total delay of vehicles and pedestrians. The traffic signal control mode of a single intersection is suitable for situations where the distance between adjacent signal engines is relatively long and the line control has little effect. Because the traffic demand of each phase changes significantly, the cycle length of the intersection and the independent control of green signal ratio are more effective than the line control. The traffic signal control of a single intersection is mainly divided into timing control, induction control and real adaptive control, among which timing control and induction control are the most basic traffic control methods. [2]

Line control
The coordinated control of urban trunk traffic signal on the intersections of the trunk traffic is a kind of line control. In the urban road network, intersections are very close, and the distance between two adjacent intersections is usually not enough to allow a small group of vehicles to evacuate completely. When the single point signal control is set at each intersection, vehicles often encounter red lights, stop and open on time, and the traffic is not smooth. In order to reduce the number of vehicle stops at each intersection and make the vehicles run smoothly on the main line, a coordinated control strategy for adjacent intersections of the main line was studied.
The original method of timing coordinated signals was based on the concept of green waves: when a train train is traveling on a main road with many intersections, coordinated control enables the vehicle to always arrive at the beginning of the green light when passing through the main intersections, so that it does not have to stop to pass through the intersections. Practice has proved that great benefits can be obtained by coordinating the signal timing between intersections. Main line traffic signal control can be divided into offline mode and online mode. In the offline mode, one main signal machine and several slave signals are set on the main trunk line, and the main signal machine sends synchronous signals to each slave signal machine. The slave signal machine allocates the red and green light start time and duration according to the phase difference and green signal ratio set in advance, so as to realize the green wave band control. Online control mode is computer by the city center to the main each intersection traffic signal coordinated control, the intersection traffic signal controller will detect the traffic flow information sent to the central computer, which according to the traffic flow on the main collected data is optimized, and then send the intersection traffic signal is red, the green light to control green wave band start signal. [2]

Regional control
Regional traffic signal control is also called online network control. The control object of the system is the traffic signal of all intersections in a certain area. All the traffic signals are linked together for coordinated control to minimize the total loss of each vehicle in the area when crossing the intersection. Regional control system is a modern traffic signal control system developed with the continuous development of traffic control theory and the wide application of communication, detection and computer technology in the field of traffic control.
From the perspective of control strategy, regional traffic control can be basically divided into two categories:
Timing surface control: this system USES the traffic flow history and current statistical data for offline optimization processing, and obtains the optimal signal timing scheme for multiple periods, which is stored in the controller to implement multi-period control for the entire area of traffic.
Inductive surface control: it is an "adaptive control system" that can adapt to the change of traffic volume.