Traffic signal control method and system for optimizing traffic flow

Abstract

The invention discloses a traffic signal control method and system for optimizing traffic flow, and relates to the field of traffic control, a plurality of intersection signal machines form a signal control subsystem of a designated area, and the method comprises the following steps: carrying out analog simulation by using traffic flow information of a key intersection in the designated area and an initial timing scheme; the saturation of the key intersection is obtained; on the basis of the saturation degree of the key intersection, optimizing the signal control period, the green time ratio and the phase difference of each intersection in the specified area to form a new timing scheme; the traffic flow information of the key intersection in the designated area and the new timing scheme are used for analog simulation until the optimal timing scheme is obtained, and the target of the optimal timing scheme is that traffic flow driving in all directions in the designated area is free of congestion and has continuity. The method can adapt to the characteristic of random change of traffic flow information, and the timing scheme of the selected intersection in the area is obtained through optimization calculation according to the current traffic flow information, so that the control efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of traffic control, and in particular to a traffic signal control method and system for optimizing vehicle flow. Background Art

[0002] With the rapid development of urban road traffic and the continuous improvement of urbanization level, transportation has become an indispensable and important part of people's economic life. It plays an increasingly important role in ensuring the normal operation of the social and economic system and daily life. As early as the 19th century, traffic participants began to study traffic signal control, using signal lights to direct vehicle traffic on the road and control the orderly entry and exit of vehicles. With the rapid development of transportation, people have put forward higher requirements for signal control.

[0003] The research and development of intelligent transportation and the shaping of models are being carried out on a large scale in my country. Various signal machine manufacturers have begun to study signal linkage coordination control systems with a large control range, and establish traffic simulation and models that simulate the traffic flow conditions of each intersection to solve the optimization problem of signal timing in traffic. Against the above background, major signal machine manufacturers in the industry have successively developed many signal control systems. For example, considering the convenience of selecting the control method, signal control is divided into single-point control, linear control and regional control. Here, single-point control is suitable for situations where the change in traffic demand in each phase is not significant, and the distance between adjacent signal machines is far, and effective line control cannot be achieved. Linear control is to connect several consecutive signal machines on a road to make a linkage, and make the driving vehicles smoother by reducing the number of stops of vehicles on the route. This method requires calculating a suitable phase difference based on the distance between adjacent intersections and the recommended speed. Regional control is to use centralized control of signal machines on a regional road network, which can be understood as regional control consisting of multiple linear controls. Although the above control methods have certain advantages, they cannot meet the signal control problems of today's urban traffic saturation flow conditions. Summary of the invention

[0004] In view of the above problems and technical requirements, the inventors have proposed a traffic signal control method and system for optimizing vehicle flow. The technical solution of the present invention is as follows:

[0005] In a first aspect, the present application provides a traffic signal control method for optimizing vehicle flow, where multiple intersection signals are combined into a signal control subsystem for a designated area, the method comprising the following steps:

[0006] Use the traffic flow information and initial timing plan of key intersections in the specified area to perform simulation and obtain the saturation of key intersections;

[0007] Based on the saturation of key intersections, the signal control cycle, green-to-signal ratio, and phase difference of each intersection in the specified area are optimized to form a new timing plan;

[0008] The traffic information of key intersections in the specified area and the new timing plan are used for simulation until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the specified area is uncongested and continuous.

[0009] A further technical solution is that the saturation of the key intersection is recorded as BH, and the expression is:

[0010]

[0011] Among them, l is the effective green light time for vehicles to pass through in one phase, and L is the green light time of the same phase set in the initial / optimized timing plan.

[0012] Its further technical solution is that l is obtained by calculating the traffic flow information of the key intersection, and the expression is:

[0013]

[0014] Among them, T j is the time when no vehicles pass during the green light period in a phase, t is the interval time between two adjacent vehicles passing the stop line during the green light period in a phase, n is the number of empty spaces in the queue corresponding to a phase, and i is the slope coefficient of the lane.

[0015] A further technical solution is to optimize the signal control cycle of each intersection in a specified area based on the saturation of key intersections, including:

[0016] Calculate the saturation of each phase of the key intersection within a signal control cycle, and take the average value as the selection threshold of the signal control cycle;

[0017] Set the maximum, minimum and average values ​​of the signal control cycle of the signal control subsystem;

[0018] For each intersection in the specified area,

[0019] When the saturation of the intersection is lower than the selection threshold, the signal control period of the intersection is selected between the average value and the minimum value of the signal control period, otherwise the signal control period of the intersection is selected between the maximum value and the average value of the signal control period.

[0020] Its further technical solution is to optimize the green signal ratio of each intersection in the specified area based on the saturation of key intersections, including:

[0021] Prepare multiple green-to-signal ratio schemes for each intersection, each of which specifies the order and duration of green lights in each phase;

[0022] In each signal control cycle, multiple green-to-signal ratio schemes are compared, and a green-to-signal ratio scheme is selected based on the principle that the saturation of each phase at the intersection is equal or relatively close;

[0023] If the same green-to-signal ratio scheme is selected continuously in the two most recent signal control cycles, the green-to-signal ratio scheme will be used as the execution scheme for the next signal control cycle.

[0024] Its further technical solution is that the method further comprises:

[0025] The signal control cycle and green-to-signal ratio of each intersection in the specified area are optimized simultaneously. The green light time of each phase at each intersection is adjusted based on the optimization results to determine the proportion of the green light time of each phase to the length of a signal control cycle.

[0026] A further technical solution is to optimize the phase difference of each intersection in a specified area based on the saturation of key intersections, including:

[0027] For two or more selected intersections that make periodic changes in a designated area, multiple phase difference schemes are prepared for them;

[0028] In each signal control cycle, a corresponding phase difference scheme is selected based on the optimization result of the signal control cycle of the selected intersection;

[0029] Determine the green light release time of adjacent intersections in the same direction, and adjust the green light timing of upstream and downstream intersections according to the saturation of the selected intersection, so as to obtain the phase difference adjustment strategy of the entire specified area.

[0030] A further technical solution is to select a corresponding phase difference solution based on the optimization result of the signal control period of the selected intersection, including:

[0031] When the optimized signal control period of the selected intersection is the same as the minimum value of the signal control period set by the signal control subsystem, a scheme with a phase difference of 0 is selected;

[0032] When the signal control period after optimization at the selected intersection is between the average value of the signal control period set by the signal control subsystem and the first threshold, a phase difference scheme of the first range value is selected;

[0033] When the signal control period after optimization at the selected intersection is between the average value of the signal control period set by the signal control subsystem and the second threshold, selecting a phase difference scheme of the second range value;

[0034] When the signal control period after optimization at the selected intersection is between the second threshold value and the third threshold value of the signal control period set by the signal control subsystem, a phase difference scheme with a third range value is selected;

[0035] Among them, the first range value, the second range value, and the third range value of the phase difference increase successively and do not overlap with each other; the first threshold is less than the average value of the signal control period and greater than the minimum value of the signal control period; the average value of the signal control period, the second threshold, and the third threshold increase successively, and the second threshold and the third threshold are both less than the maximum value of the signal control period.

[0036] In a second aspect, the present application further provides a traffic signal control system for optimizing traffic flow, comprising a signal control subsystem of a designated area composed of a plurality of intersection signals, the signal control subsystem comprising:

[0037] The simulation module is used to simulate the traffic flow information and initial timing plan of key intersections in the specified area and obtain the saturation of key intersections;

[0038] The optimization module is used to optimize the signal control cycle, green-to-signal ratio, and phase difference of each intersection in the specified area based on the saturation of key intersections to form a new timing plan;

[0039] The simulation module is also used to use the traffic information of key intersections in the specified area and the new timing plan to simulate until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the specified area is congestion-free and continuous.

[0040] The beneficial technical effects of the present invention are:

[0041] The traffic signal control method and system for optimizing traffic flow proposed in this application obtains saturation by simulating the traffic flow information and initial timing plan of key intersections, and uses saturation as the target value for optimization control to optimize the signal control cycle, green-to-signal ratio, and phase difference of each intersection, thereby forming a new timing plan, which is simulated again to obtain the best timing plan through continuous iteration. This method can adapt to the characteristics of random changes in traffic flow information, and optimize the timing plan for selected intersections in the area based on the current traffic flow information. The subsystems in each area are relatively independent and do not interfere with each other. There is a certain coordination relationship between the subsystem and the area. With the real-time changes in traffic conditions, the areas can be controlled separately or recombined according to needs.

[0042] The advantage of this system is that it coordinates and controls each area while adopting the specific traffic flow conditions of each intersection for comprehensive control, thereby improving the efficiency of control. In addition, the system does not require a large amount of equipment, has low investment, and is easy to implement, which is suitable for traffic signal control in most cities in China. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of the traffic signal control method for optimizing vehicle flow provided in this application. DETAILED DESCRIPTION

[0044] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0045] Please refer to Figure 1 As shown, in one embodiment of the present application, a traffic signal control method for optimizing vehicle flow is provided. In the method, multiple intersection signals are combined into a signal control subsystem of a designated area. The method uses the signal control subsystem as a basic control unit, and specifically includes the following contents:

[0046] Step 1: Use the traffic flow information and initial timing plan of the key intersections in the specified area to perform simulation and obtain the saturation of the key intersections. The traffic flow information of the key intersections can be obtained by setting a traffic flow detector on each entrance lane of each intersection / intersection to obtain real-time traffic flow information and the actual passing rate of vehicles passing the lane stop line during the green light. The detector can be a coil, a video device or a radar-visual integrated machine. In this embodiment, a radar-visual integrated machine is used, and its detection range covers 150 meters behind the lane stop line.

[0047] The saturation can be calculated using a formula, which is expressed as the ratio of the effective green light time for vehicles to pass through in a phase (i.e., the green light time actually used for vehicles to pass through, excluding the loss time when the signal changes) to the green light display time of the phase set in the timing plan. The saturation is denoted as BH, and the expression is:

[0048]

[0049] Among them, l is the effective green light time for vehicles to pass through in a phase, and L is the green light time of the same phase set in the initial / optimized timing plan. Here l can be calculated from the traffic flow information of key intersections, and the expression is:

[0050]

[0051] Where: T j is the time when no vehicles pass during the green light period in a phase; t is the time between two adjacent vehicles passing the stop line during the green light period in a phase; n is the number of gaps between two adjacent vehicles in the queue corresponding to a phase; i is the slope coefficient of the lane. These parameters can be measured by the traffic detector.

[0052] Step 2: Based on the saturation of key intersections, optimize the signal control cycle, green-to-signal ratio, and phase difference of each intersection in the specified area to form a new timing plan. In this step, the signal control cycle, green-to-signal ratio, and phase difference are optimized and adjusted as interacting parameters. The method used in the adjustment process is based on traffic flow and saturation. The specific optimization methods for each parameter are introduced below:

[0053] The signal control cycle refers to the time required for a signal to complete a complete change. For periodic signals, this cycle is repeatable and variable. The method for optimizing the signal control cycle of each intersection in a specified area includes: firstly calculating the saturation of each phase of the key intersection within a signal control cycle, and taking the average as the selection threshold of the signal control cycle. Setting the maximum value Z of the signal control cycle of the signal control subsystem max , minimum value Z min and the mean value Z s For each intersection in the specified area, when the saturation of the intersection is lower than the selection threshold, the selection range of the signal control cycle of the intersection is limited to the average value of the signal control cycle Z s and the minimum value Z min Between and including Z min When the saturation of the intersection is not lower than the selection threshold, the selection range of the signal control cycle of the intersection is within the maximum value Z of the signal control cycle. max and mean value Z s Between and including Z max and Z s .

[0054] The green-to-signal ratio refers to the proportion of time available for vehicle traffic within a signal control cycle, that is, the ratio of the effective green light time of the current phase to the cycle length. The method for optimizing the green-to-signal ratio of each intersection in a specified area includes: preparing multiple green-to-signal ratio schemes for each intersection in advance, each green-to-signal ratio scheme specifies the order and duration of the green lights in each phase, and the green light time and order of different green-to-signal ratio schemes may be different. The selection of the green-to-signal ratio scheme must be made once in each signal control cycle. The specific implementation plan is as follows: In each signal control cycle, multiple green-to-signal ratio schemes are compared, and a green-to-signal ratio scheme is selected based on the principle that the saturation of each phase of the intersection is equal or relatively close. If the same green-to-signal ratio scheme is selected continuously in the two most recent signal control cycles, the green-to-signal ratio scheme will be used as the execution plan for the next signal control cycle.

[0055] Optionally, in this embodiment, the signal control cycle and green-to-red ratio of each intersection in the specified area are optimized simultaneously, and the green light time of each phase of each intersection is adjusted based on the optimization results to determine the proportion of the green light time of each phase to the length of a signal control cycle. As the signal control cycle is adjusted, the traffic light time of each phase also changes accordingly.

[0056] Phase difference refers to the time difference between the phases released in the same direction of two or more signal intersections with periodic changes. The method for optimizing the phase difference of each intersection in the specified area includes: for two or more selected intersections with periodic changes in the specified area, multiple phase difference schemes need to be prepared in advance. Two situations are considered when preparing the scheme, one is the existence of air defense phenomenon, and the other is the problem of import channel overflow. In addition, the phase difference must be selected for each signal control cycle. The specific implementation plan is as follows: In each signal control cycle, the corresponding phase difference scheme is selected based on the optimization result of the signal control cycle of the selected intersection. Determine the green light release time of the same direction of adjacent intersections, and adjust the green light timing of the upstream and downstream intersections according to the saturation of the selected intersection, so as to obtain the phase difference adjustment strategy of the entire specified area. For example, when the saturation of the selected intersection is large, the green light timing of its upstream and downstream intersections can be set longer, and some traffic can be shared by releasing the upstream and downstream intersections.

[0057] The corresponding phase difference scheme is selected based on the optimization result of the signal control cycle of the selected intersection. Specifically, the phase difference scheme includes: 1) when the signal control cycle after optimization of the selected intersection is equal to the minimum value Z of the signal control cycle set by the signal control subsystem; min If the phase difference is the same, the solution with a phase difference of 0 is selected. 2) When the optimized signal control period of the selected intersection is the average value Z of the signal control period set by the signal control subsystem s and the first threshold value, and includes the first threshold value, the phase difference scheme of the first range value is selected. 3) When the signal control period after optimization of the selected intersection is within the average value Z of the signal control period set by the signal control subsystem s and the second threshold, including Z s 4) When the signal control period after optimization of the selected intersection is between the second threshold and the third threshold of the signal control period set by the signal control subsystem, and includes the third threshold, the phase difference scheme of the third range value is selected. The above setting values ​​are stipulated as follows: the first range value, the second range value, and the third range value of the phase difference are successively larger and do not overlap; the first threshold is less than Z s , and greater than Z min ; Z s , the second threshold, and the third threshold increase in sequence, and the second threshold and the third threshold are both less than Z max .

[0058] In this embodiment, the first range value of the phase difference is set between 0 and 15, the second range value is set between 15 and 45, and the third range value is greater than 45. The first threshold value is Z s -15, the second threshold is Z s +15, the third threshold is Z s +45.

[0059] Optionally, for each direction's entrance, the number of vehicles that can be released and the saturation of the entrance when the corresponding phase difference scheme is executed must be calculated respectively. In this way, the number of vehicles that can pass through each entrance can be given, so that the release strategy can be better adjusted to make the method more scientific.

[0060] Step 3: Use the traffic information of key intersections in the specified area and the new timing plan to perform simulation, and re-execute the optimization method of step 2 until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the specified area is uncongested and continuous.

[0061] Based on the same inventive concept, another embodiment of the present application provides a traffic signal control system for optimizing traffic flow, including a signal control subsystem of a designated area composed of multiple intersection signals, and the subsystem includes a simulation module and an optimization module. The simulation module is used to use the traffic information and initial timing plan of the key intersections in the designated area to perform simulations and obtain the saturation of the key intersections. The simulation module is also used to use the traffic information and new timing plan of the key intersections in the designated area to perform simulations until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the designated area is congestion-free and continuous. The optimization module is used to optimize the signal control cycle, green-to-signal ratio, and phase difference of each intersection in the designated area based on the saturation of the key intersections to form a new timing plan.

[0062] It should be noted that the implementation solution provided by this subsystem is similar to the implementation solution recorded in the above-mentioned traffic signal control method for optimizing traffic flow. Therefore, the specific limitations in each module embodiment can be found in the above limitations on the method and will not be repeated here.

[0063] The above is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A traffic signal control method for optimizing vehicle flow, which combines multiple intersection signals into a signal control subsystem for a designated area, characterized in that: The method comprises: Use the traffic flow information and initial timing plan of key intersections in the specified area to perform simulation and obtain the saturation of key intersections; Based on the saturation of the key intersections, the signal control cycle, green-to-signal ratio, and phase difference of each intersection in the specified area are optimized to form a new timing plan; The traffic information of key intersections in the specified area and the new timing plan are used for simulation until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the specified area is uncongested and continuous.

2. The traffic signal control method for optimizing vehicle flow according to claim 1, characterized in that: The saturation of the critical intersection is recorded as BH, and the expression is: Among them, l is the effective green light time for vehicles to pass through in one phase, and L is the green light time of the same phase set in the initial / optimized timing plan.

3. The traffic signal control method for optimizing vehicle flow according to claim 2, characterized in that: The l is obtained by calculating the traffic flow information of the key intersection, and the expression is: Among them, T j is the time when no vehicles pass during the green light period in a phase, t is the interval time between two adjacent vehicles passing the stop line during the green light period in a phase, n is the number of empty spaces in the queue corresponding to a phase, and i is the slope coefficient of the lane.

4. The traffic signal control method for optimizing vehicle flow according to claim 1, characterized in that: Based on the saturation of the key intersections, the signal control period of each intersection in the designated area is optimized, including: Calculate the saturation of each phase of the key intersection within a signal control cycle, and take the average value as the selection threshold of the signal control cycle; Setting the maximum value, minimum value and average value of the signal control period of the signal control subsystem; For each intersection in the specified area, When the saturation of the intersection is lower than the selection threshold, the signal control period of the intersection is selected between the average value and the minimum value of the signal control period, otherwise the signal control period of the intersection is selected between the maximum value and the average value of the signal control period.

5. The traffic signal control method for optimizing vehicle flow according to claim 1, characterized in that: Based on the saturation of the key intersections, the green-signal ratio of each intersection in the specified area is optimized, including: Prepare multiple green-to-signal ratio schemes for each intersection, each of which specifies the order and duration of green lights in each phase; In each signal control cycle, multiple green-to-signal ratio schemes are compared, and a green-to-signal ratio scheme is selected based on the principle that the saturation of each phase at the intersection is equal or relatively close; If the same green-to-signal ratio scheme is selected continuously in the two most recent signal control cycles, the green-to-signal ratio scheme will be used as the execution scheme for the next signal control cycle.

6. The traffic signal control method for optimizing vehicle flow according to claim 4 or 5, characterized in that: The method further comprises: The signal control cycle and green-to-signal ratio of each intersection in the specified area are optimized simultaneously. The green light time of each phase at each intersection is adjusted based on the optimization results to determine the proportion of the green light time of each phase to the length of a signal control cycle.

7. The traffic signal control method for optimizing vehicle flow according to claim 1, characterized in that: Based on the saturation of the key intersections, the phase difference of each intersection in the specified area is optimized, including: For two or more selected intersections that make periodic changes in a designated area, multiple phase difference schemes are prepared for them; In each signal control cycle, a corresponding phase difference scheme is selected based on the optimization result of the signal control cycle of the selected intersection; Determine the green light release time of adjacent intersections in the same direction, and adjust the green light timing of upstream and downstream intersections according to the saturation of the selected intersection, so as to obtain the phase difference adjustment strategy of the entire specified area.

8. The traffic signal control method for optimizing vehicle flow according to claim 7, characterized in that: The selecting a corresponding phase difference scheme based on the optimization result of the signal control period of the selected intersection includes: When the optimized signal control period of the selected intersection is the same as the minimum value of the signal control period set by the signal control subsystem, a scheme with a phase difference of 0 is selected; When the signal control period after optimization at the selected intersection is between the average value of the signal control period set by the signal control subsystem and the first threshold, selecting a phase difference scheme with a first range value; When the signal control period after optimization at the selected intersection is between the average value of the signal control period set by the signal control subsystem and the second threshold, selecting a phase difference scheme with a second range value; When the signal control period after optimization at the selected intersection is between the second threshold value and the third threshold value of the signal control period set by the signal control subsystem, a phase difference scheme of a third range value is selected; Among them, the first range value, the second range value, and the third range value of the phase difference increase successively and do not overlap with each other; the first threshold is less than the average value of the signal control period and greater than the minimum value of the signal control period; the average value of the signal control period, the second threshold, and the third threshold increase successively, and the second threshold and the third threshold are both less than the maximum value of the signal control period.

9. A traffic signal control system for optimizing vehicle flow, comprising a signal control subsystem for a designated area composed of a plurality of intersection signals, characterized in that: The signal control subsystem comprises: The simulation module is used to simulate the traffic flow information and initial timing plan of key intersections in the specified area and obtain the saturation of key intersections; An optimization module, for optimizing the signal control cycle, green-to-signal ratio, and phase difference of each intersection in a specified area based on the saturation of the key intersection, to form a new timing plan; The simulation module is also used to use the traffic information of key intersections in the specified area and the new timing plan to perform simulation until the best timing plan is obtained. The goal of the best timing plan is to ensure that traffic in all directions in the specified area is congestion-free and continuous.

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