Intersection traffic signal control method and device

Abstract

The invention discloses an intersection traffic signal control method and device. The method comprises the following steps: performing formation on vehicles in the upstream direction of a target intersection; the intersection is divided into an upstream flow direction and a downstream flow direction of the intersection by taking the initial position of the downstream road section as a boundary; calculating a time supersaturation index and a space supersaturation index of each vehicle formation in the upstream direction and the downstream direction in the target intersection; and according to the time supersaturation index and the space supersaturation index of each vehicle formation in the upstream flow direction and the downstream flow direction in the target intersection, controlling traffic lights in the upstream flow direction and / or the downstream flow direction of the target intersection. According to the technical scheme provided by the invention, the oversaturation state of the intersection can be relieved in a more targeted manner, the negative influence of oversaturation is reduced, and the operation efficiency of a traffic system is improved.

Description

Technical Field

[0001] The present application relates to the field of traffic control, and more specifically, to a method and device for controlling traffic signals at intersections. Background Art

[0002] With the acceleration of urbanization, traffic congestion is becoming increasingly serious, especially during peak hours, when urban roads are often oversaturated, resulting in reduced traffic flow efficiency.

[0003] Existing technologies primarily rely on cross-sectional detectors, such as geomagnetic coils, to identify and control traffic flow conditions. However, these methods suffer from limited detection accuracy and an inability to fully identify the causes and stages of oversaturation. Furthermore, existing technologies exhibit significant limitations when handling complex traffic situations, such as traffic flow fluctuations during special events or extreme weather conditions.

[0004] Therefore, how to design an intersection traffic signal control solution to meet the needs of urban smart transportation has become a problem that needs to be solved in this field. Summary of the Invention

[0005] In view of this, in a first aspect, the present application proposes a method for controlling traffic signals at an intersection, comprising:

[0006] The vehicles flowing upstream of the target intersection are platooned; the intersection is divided into an upstream flow direction and a downstream flow direction of the intersection by taking the initial position of the downstream road section as the boundary;

[0007] Calculating the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the upstream direction and the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the target intersection;

[0008] Traffic lights in the upstream and / or downstream directions of the target intersection are controlled according to the time oversaturation index and space oversaturation index of the upstream flow direction and the time oversaturation index and space oversaturation index of the downstream flow direction of each vehicle formation in the target intersection.

[0009] Preferably, platooning the vehicles flowing upstream of the target intersection includes:

[0010] Calculating the interval time between each following vehicle and the preceding vehicle in the same lane in the upstream direction of the target intersection;

[0011] If the interval between the rear vehicle and the front vehicle in the same lane is less than the preset value, the rear vehicle will be incorporated into the formation corresponding to the front vehicle;

[0012] If the interval between the rear vehicle and the front vehicle in the same lane is not less than the preset value, the rear vehicle will be set as the first vehicle in the new formation.

[0013] More preferably, the method further comprises:

[0014] In the upstream flow direction of the target intersection, the headway between vehicles is calculated based on the positions and instantaneous speeds of the preceding and following vehicles adjacent to each other in the same lane;

[0015] The interval time between the rear vehicle and the front vehicle in the same lane is obtained according to the headway between the vehicles and the instantaneous speed of the corresponding rear vehicle.

[0016] Preferably, the calculation expression of the time supersaturation index is:

[0017]

[0018] Where TOSI represents the temporal supersaturation index; g e represents the effective green light time; Acc represents the total number of vehicles in the queue; i represents the vehicle number; h s,i Indicates the distance between the front of the i-th vehicle and the rear of the preceding vehicle; s is an identifier; the TOSI, g e 、Acc、h s,i Corresponding to the same signal phase.

[0019] More preferably, the method further comprises:

[0020] The number of vehicles queued in the current vehicle formation is added to the number of vehicles queued in the corresponding next vehicle formation to obtain the total number of vehicles queued.

[0021] More preferably, the method further comprises:

[0022] The number of vehicles in the queue in the current vehicle formation is calculated based on the duration of the yellow light, the position of the stop line, and the position and speed of the queued vehicles.

[0023] More preferably, the method further comprises:

[0024] determining whether a distance between a position of a rear vehicle in a queued vehicle formation and a position of a front vehicle in a next queued vehicle formation is not greater than a distance threshold;

[0025] If not, the number of vehicles queued in the next vehicle formation is obtained according to the number of vehicles in the next vehicle formation;

[0026] If it is greater than, the number of vehicles queued in the next vehicle formation is equal to 0; or

[0027] Determining whether the spatial average speed of the next vehicle formation is not greater than a speed threshold;

[0028] If not, the number of vehicles queued in the next vehicle formation is obtained according to the number of vehicles in the next vehicle formation;

[0029] If it is greater, the number of queuing vehicles in the next vehicle formation is equal to 0.

[0030] Preferably, the method further includes:

[0031] Calculating the spatial oversaturation index according to the detector pulse conditions collected by the stop line detector within a statistical period.

[0032] More preferably, calculating the spatial oversaturation index according to the detector pulse conditions collected by the stop line detector within a statistical period includes:

[0033] If N up = N down ≠ 0 and UP1 > DOWN1, then

[0034]

[0035] If N up = N down ≠ 0 and UP1 < DOWN1, then

[0036]

[0037] If N up = N down + 1, then

[0038]

[0039] t1 = max[0, t - UP i - t occ ;

[0040] If N up = N down - 1, then

[0041] <00D0315>

[0042] t0 = max[0, DOWN0 - (t - T) - t occ ;

[0043] If N <D000016>= N down = 0, or

[0044] N' up = 0 ≠ N' down F or

[0045] N' up ≠ 0 and N' down ≠ 0 and UP' i' < DOWN' j' then

[0046] SOSI=0;

[0047] If N' up ≠0 and N' down =0, or

[0048] N' up ≠0 and N' down ≠0 and UP' i' >DOWN' j' ,

[0049] Then SOSI=1;

[0050] UP={t1,t2,…,t i};

[0051] DOWN={t1,t2,…,t j};

[0052] UP′={t′1,t′2,…,t′ i'};

[0053] DOWN'={t'1,t'2,…,t' j'};

[0054] Where SOSI represents the spatial supersaturation index; T represents the time from the onset of the green light to the end of the yellow light within a signal control cycle; t represents the time at the end of time period T; t0 represents the time that the last vehicle that overflowed from the downstream intersection in the previous signal control cycle occupied the stop line detector in the current signal control cycle; t1 represents the time that the vehicle that stopped at the stop line detector due to overflow obstruction occupied the stop line detector at the end of the yellow light within a signal control cycle; t occ Indicates the time duration that a vehicle normally takes to pass through the stop line detector; DOWN indicates the pulse response time sequence of the falling edge of a detector corresponding to the flow direction within a statistical time period; UP indicates the pulse response time sequence of the rising edge of a detector corresponding to the flow direction within a statistical time period; UP' indicates the pulse response time sequence of all rising edges counted before the current signal control cycle; DOWN' indicates the pulse response time sequence of all falling edges counted before the current signal control cycle; UP n and DOWN n They represent the time corresponding to the nth rising edge or the nth falling edge in the time period T of a signal control cycle; UP1 and DOWN1 represent the time corresponding to the first rising edge and the first falling edge in the time period T of a signal control cycle; UP -1 and DOWN -1They represent the time corresponding to the last rising edge and the last falling edge in the time period T of a signal control cycle respectively; DOWN0 represents the time corresponding to the last falling edge in the time period T of the previous signal control cycle; UP i Indicates the time corresponding to the i-th rising edge within the time period T of a signal control cycle; UP' i' and DOWN' j' Respectively represent the time corresponding to the i'th rising edge or j'th falling edge before the current signal control cycle; N up Indicates the number of rising edges in a signal control cycle, N down Indicates the number of falling edges in a signal control cycle; N' up Indicates the number of all rising edges before the current signal control cycle; N' down Indicates the number of all falling edges before the current signal control cycle; i, j, and n are identification symbols, i, j, i', and j' respectively represent the number of rising edges and falling edges in the corresponding time series, and n is an index variable.

[0055] Further preferably, the detection range of the stop line detector needs to meet the following requirements:

[0056] When a vehicle formation is in a queue state in the upstream flow direction, the first vehicle in the queue activates the detector, and the head position of subsequent vehicles other than the first vehicle cannot activate the detector;

[0057] When the vehicle formation is in a dissipating state in the upstream flow and when the rear end of the leading vehicle leaves the detection area, the position of the front end of the following vehicle cannot be determined.

[0058] Preferably, controlling the traffic lights in the upstream and / or downstream directions of the target intersection according to the time oversaturation index and the space oversaturation index of the upstream flow direction and the time oversaturation index and the space oversaturation index of the downstream flow direction of each vehicle formation in the target intersection includes:

[0059] If the value of the temporal supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the temporal supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the traffic signal control scheme for the upstream flow direction and the downstream flow direction of the target intersection is maintained;

[0060] If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the upstream green light of the target intersection is turned on earlier or turned off later;

[0061] If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the green light downstream of the target intersection is turned on earlier or the green light downstream is turned off later;

[0062] If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the green light downstream of the target intersection is turned on earlier or the green light downstream is turned off later;

[0063] If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the upstream green light of the target intersection is turned off later and the downstream green light is turned on earlier;

[0064] If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, the green lights upstream and downstream of the target intersection will be turned off later.

[0065] Preferably, after platooning the vehicles flowing upstream of the target intersection, the method further comprises:

[0066] Determine the supersaturation stage status of each vehicle formation in the upstream and downstream directions at the target intersection;

[0067] According to the supersaturation stage status of each vehicle formation in the upstream flow direction and the downstream flow direction of the target intersection, the traffic lights in the upstream flow direction and / or the downstream flow direction of the target intersection are controlled.

[0068] More preferably, the method further comprises:

[0069] According to the number of vehicles flowing upstream at the end of the green light Effective green light time g e,k , saturated headway h s , calculate the number of supersaturation events; where

[0070] if Then the number of supersaturation events increases by 1;

[0071] The supersaturation stage state is determined according to the number of occurrences of the supersaturation events and the time supersaturation index.

[0072] Preferably, before platooning the vehicles flowing upstream of the target intersection, the method further comprises:

[0073] Identify the key flows in the critical path that cause congestion;

[0074] The target intersection is determined according to the key flow direction, and is used to control the traffic lights in the upstream flow direction and / or downstream flow direction of the target intersection according to the time oversaturation index and space oversaturation index of each vehicle formation in the upstream flow direction, as well as the time oversaturation index and space oversaturation index of the downstream flow direction.

[0075] Further preferably, determining the key flow direction in the key path causing congestion includes:

[0076] determining a supersaturation severity value for a target flow direction, a maximum supersaturation severity value for a flow direction upstream of the target flow direction, and a maximum supersaturation severity value for a flow direction downstream of the target flow direction;

[0077] Determining a supersaturation severity value of a current path according to the supersaturation severity value of the target flow direction, a maximum supersaturation severity value of a flow direction upstream of the target flow direction, and a maximum supersaturation severity value of a flow direction downstream of the target flow direction;

[0078] The path with the largest oversaturation severity value in the region is set as the critical path causing congestion;

[0079] Setting the flow direction of each flow in the critical path to the critical flow direction;

[0080] The calculation expression of the oversaturation severity value is:

[0081] SVRT Movement =TOSI×(1+SOSI+thpt Ge ×N max +μ);

[0082] Among them, SVRT Movement Indicates the severity of supersaturation in the flow direction; TOSI indicates the temporal supersaturation index; SOSI indicates the spatial supersaturation index; thpt Ge Indicates the throughput rate during the green light period; μ indicates the correction coefficient; N max Indicates the maximum number of vehicles flowing in a direction within a signal control cycle.

[0083] In a second aspect, an embodiment of the present invention further provides an intersection traffic signal control device, comprising:

[0084] A platooning module is configured to platoon vehicles flowing upstream of a target intersection; the intersection is divided into an upstream flow direction and a downstream flow direction of the intersection by an initial position of a downstream road segment;

[0085] a calculation module configured to calculate a temporal oversaturation index and a spatial oversaturation index of each vehicle formation in the target intersection in an upstream flow direction, and a temporal oversaturation index and a spatial oversaturation index of each vehicle formation in a downstream flow direction;

[0086] The control module is configured to control the traffic lights in the upstream and / or downstream directions of the target intersection based on the time oversaturation index and space oversaturation index of each vehicle formation in the upstream direction and the time oversaturation index and space oversaturation index of the downstream direction in the target intersection.

[0087] The intersection traffic signal control method provided by the present application first forms a formation of vehicles flowing upstream of a target intersection, quantifies the degree of oversaturation of the target flow in time and space dimensions, and then controls the traffic lights in the upstream and / or downstream directions of the target intersection based on the time oversaturation index and space oversaturation index of each vehicle formation in the upstream and downstream directions of the target intersection, so that the present application can more specifically alleviate the oversaturation state of the intersection, reduce the negative impact of oversaturation, and improve the operating efficiency of the traffic system.

[0088] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] The accompanying drawings, which constitute part of this application, are used to provide a further understanding of the application, and the exemplary embodiments of the application and their descriptions are used to explain the application. In the accompanying drawings:

[0090] Figure 1 A flowchart of a traffic signal control method for an intersection according to a preferred embodiment of the present invention;

[0091] Figure 2 A spatiotemporal diagram of the running trajectories of vehicles stranded in a queue according to a preferred embodiment of the application;

[0092] Figure 3 A spatiotemporal diagram of vehicle trajectory during overflow at the downstream intersection according to the preferred embodiment of the application;

[0093] Figure 4 A schematic diagram of vehicle formation division according to a preferred embodiment of the application;

[0094] Figure 5 A schematic diagram of the layout of a stop line detector according to a preferred embodiment of the present invention;

[0095] Figure 6A schematic diagram of a pulse waveform of a detector in case 1 of a preferred embodiment of the present invention;

[0096] Figure 7 A schematic diagram of a pulse waveform of a detector in case 2 of a preferred embodiment of the present invention;

[0097] Figure 8 A schematic diagram of the pulse waveform of a three-time detector in the case of a preferred embodiment of the application;

[0098] Figure 9 A schematic diagram of the pulse waveform of a four-hour detector in the case of a preferred embodiment of the application;

[0099] Figure 10 A schematic diagram of a pulse waveform of a detector in case five of the preferred embodiment of the present invention;

[0100] Figure 11 A schematic diagram of a pulse waveform of a detector in case six of the preferred embodiment of the application;

[0101] Figure 12 A schematic diagram of a simulated road network design for the preferred implementation scheme of the application;

[0102] Figure 13 A schematic diagram of traffic flow changes in the key direction of westbound straight traffic during other observation periods for applying for the preferred implementation method;

[0103] Figure 14 This is a schematic diagram of the supersaturation stage identification result of the preferred embodiment of the application;

[0104] Figure 15 This is a schematic diagram of the analysis results of the causes of supersaturation according to the preferred embodiment of the application;

[0105] Figure 16 A schematic diagram of the supersaturation stage, key path, and flow output results of the preferred embodiment of the application;

[0106] Figure 17 A schematic diagram of a curve showing a change in total delay at a target intersection under different control methods in the preferred embodiment of the application;

[0107] Figure 18 This is a schematic diagram of an intersection traffic signal control device according to a preferred embodiment of the application. DETAILED DESCRIPTION

[0108] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. To better understand the present application, the terms involved in the present application are first explained:

[0109] Temporal Oversaturation Severity Index (TOSI):

[0110] like Figure 2 As shown in the spatiotemporal diagram of vehicle trajectories in the figure, the horizontal axis represents time, the vertical axis represents the distance of vehicles on the road section, and different colors are used to represent the corresponding vehicle speeds. If the vehicles queuing in the flow direction are not completely cleared at the end of the green light, the stranded vehicles will need to use the green light time of the next cycle to pass through the intersection. At this time, a stranded queue appears at the intersection, which means that the flow direction is considered to be in a state of oversaturation in the time dimension. These stranded queues need to be dissipated using the green light time of the subsequent cycle. The ratio of the green light time used by this part to the green light time provided by this phase can be used as an indicator to quantify the oversaturation in the time dimension, namely, TOSI.

[0111] Typically, TOSI values ​​range from 0% to 100%. When TOSI = 100%, all green time in that phase is used to dissipate the backlog queue, resulting in temporal oversaturation of the flow direction. If the arrival rate of subsequent vehicles remains constant or even increases, the backlog queue will continue to grow. At this point, when the TOSI value exceeds 100%, the backlog vehicles in the queue cannot be fully dissipated during the next green time, resulting in a secondary queue.

[0112] The TOSI value directly indicates how much additional green time is needed to dissipate the queue. TOSI is related to the phase difference between the target intersection and its upstream intersection. If the upstream queue at the target intersection is released too early or the phase difference is not set properly, a significant TOSI value may be obtained.

[0113] Spatial Oversaturation Severity Index (SOSI):

[0114] like Figure 3 As shown in the spatiotemporal diagram of vehicle trajectories, when overflow occurs at the downstream intersection, these overflowing vehicles block the movement space of upstream vehicles in the spatial dimension. This prevents vehicles at the upstream intersection from passing smoothly even if they have the right of way during the green light period, rendering some of the upstream green light time "unusable." The ratio of this "unusable" green light time to the green light time provided during this phase can be used as a quantifiable indicator of oversaturation in the spatial dimension, namely, the SOSI.

[0115] Typically, SOSI ranges from 0% to 100%. When SOSI = 100%, it means that due to congestion at the downstream intersection, all green light time in that phase is wasted, and all vehicles cannot move to the downstream intersection, resulting in oversaturation in space.

[0116] SOSI = 100% and TOSI = 100% correspond to two distinct situations. When TOSI = 100% and the downstream still has a certain amount of traffic capacity, increasing the green time for upstream traffic can effectively alleviate congestion at the upstream intersection. When SOSI = 100%, no additional green time should be allocated to this phase to avoid spreading congestion or even forming a deadlock.

[0117] The SOSI value indicates the additional green light duration required to relieve congestion at the downstream intersection, ensuring that vehicles at the upstream intersection can continue to pass during the green light period without being affected by overflow at the downstream intersection. The SOSI is also affected by the phase difference between the upstream and downstream intersections. Therefore, when formulating traffic control methods for oversaturated conditions, the traffic conditions at both upstream and downstream intersections should be comprehensively considered to achieve the desired control objectives.

[0118] Signal control cycle: refers to the time interval required to complete a complete signal change in a traffic signal control system.

[0119] Signal phase: Within a signal control cycle, one or several traffic flows receive exactly the same signal light color display at any moment. The continuous sequence in which they receive different light colors (green, yellow, all red) is called a signal phase.

[0120] Effective Green Time: The time used to serve traffic flow is called Effective Green Time. The effective green time for a phase is the sum of the actual green time displayed and the interval time, minus the total lost time for that phase. The effective green time for a cycle is the cycle duration minus the total lost time within that cycle.

[0121] Vehicle platooning: refers to the formation of vehicles on the road into one or more platoons based on their position and speed. Each vehicle platoon has its own formation speed and density.

[0122] Stop line detectors: These devices are used in the transportation field to detect vehicle stoppages, as well as their position and speed, at stop lines at intersections. They typically use geomagnetic induction coils. In scenarios using millimeter-wave and lidar detectors, position calibration can be used to achieve similar results to geomagnetic coil detectors.

[0123] Rising edge, falling edge: In the field of transportation, especially in the application of stop line detectors, rising edge and falling edge refer to the signal changes generated when a vehicle passes through an induction coil or other type of detector. The rising edge (RisingEdge) refers to the moment when the vehicle enters the detection area (for example, passing the induction coil at the stop line), causing the output signal of the detector to jump from a low level to a high level. This change usually indicates that a vehicle has entered the detection range and can be used to trigger certain actions, such as extending the green light time to allow the vehicle to pass through the intersection. The falling edge (FallingEdge) refers to the moment when the vehicle leaves the detection area, causing the output signal of the detector to return from a high level to a low level. This indicates that the vehicle has left the detection range and can be used to confirm that the vehicle has passed or to end the corresponding timing operation.

[0124] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0125] like Figure 1 As shown, the intersection traffic signal control method provided by this embodiment includes steps 110-130:

[0126] Step 110, platooning the vehicles flowing upstream of the target intersection;

[0127] Specifically, the intersection is divided into upstream and downstream flows, using the initial position of the downstream road section as the boundary. That is, even if a vehicle passes the stop line but has not yet entered the downstream entrance, it still belongs to the upstream flow. This application platoons the discrete vehicles in the upstream flow of the target intersection, which is beneficial for dividing parking queues and driving queues of different speeds, and improving the utilization rate of green light time during traffic signal control. Analyzing the movement of vehicles and platoons can provide a basis for subsequent quantification of the degree of oversaturation of the target flow in time and space dimensions.

[0128] It is understandable that if an upstream flow includes multiple lanes, vehicles in each lane need to be platooned.

[0129] The process of platooning vehicles upstream of the target intersection begins by calculating the headway between the vehicles in the upstream direction of the target intersection based on the positions and instantaneous speeds of the adjacent leading and following vehicles in the same lane. This headway is the distance between the front of the following vehicle and the rear of the corresponding preceding vehicle. Next, based on the headway and the instantaneous speed of the following vehicle, the interval between the following vehicle and the preceding vehicle in the same lane is calculated. If the interval between the following vehicle and the preceding vehicle in the same lane is less than a preset value, the following vehicle is incorporated into the corresponding platoon. If the interval between the following vehicle and the preceding vehicle in the same lane is not less than the preset value, the following vehicle is designated as the first vehicle in the new platoon.

[0130] In a specific embodiment, the position of vehicle n in a lane is recorded as y, starting from the stop line and counting upstream. n , the position of the vehicle behind vehicle n is recorded as y n-1 , the instantaneous speed of vehicle n is v n , then the headway Δy of vehicle n n Satisfies expression (1):

[0131] Δy n =y n -y n-1 (1);

[0132] Consecutive vehicles with similar distances can be divided into a formation, and the gap time GapTime is used as a parameter to quantify whether the distance is close. If the instantaneous speed of a vehicle n allows it to catch up with the preceding formation within the GapTime, it can be considered to belong to the same vehicle formation as the preceding vehicle. In other words, the condition for belonging to the same vehicle formation as the preceding vehicle should satisfy the following expression (2):

[0133]

[0134] Among them, t φ The preset time threshold should not be set too large and can be close to the unit green delay. Here, the unit green delay can be understood as: a fixed increment of the green light time of a certain phase preset to meet real-time traffic needs. Preferably, t φ Set to 3.5 seconds.

[0135] Assume that the vehicles on the lane can be divided into m vehicle formations, and a single vehicle can also form a formation. Figure 4 In the vehicle formation division scenario shown in the figure, the vehicle formation is the set Groups = {Group1, Group2, ..., Group m}, where a formation m with n vehicles is denoted as Group m ={y1,y2,…,y nIf there is a car in the lane, then Group1 must be {y1}.

[0136] Assume that the formation of the jth car in front of the nth car is Group i ={y1,y2,…,y j}, then the formation membership of the vehicle is determined as shown in expression (3):

[0137]

[0138] That is, when the nth vehicle belongs to the front formation (GapTime n ≤t φ ), then add it to its set (y n ∈Group i ), if it does not belong to (GapTime n >t φ ), then the vehicle becomes the first vehicle of the new formation (y n ∈Group i+1 ={y n}).

[0139] In addition, the mth vehicle group Group m ={y1,y2,…,y n} as a whole, and the number of vehicles in a formation m is N v,m , the length of each car is length veh , then the head position of the formation is y1 and the tail position is y n +length veh Vehicle formation length Group length,m For example, expression (4):

[0140]

[0141] Where m is the serial number of the vehicle formation, and i is the number of vehicles in the formation. m ={y1,y2,…,y n} or Group i ={y1,y2,…,y j} are all used to express that a certain fleet includes certain vehicles. The subscripts of Group and y (i.e., m and i, n and j) have the same mathematical meaning, but the values ​​they represent may be different.

[0142] Since the vehicle formation is compressible in space, let the minimum safe distance between vehicles be length safe , then when all vehicles maintain the minimum safety distance, that is, satisfy Δy n =lengthsafe , we can get the minimum length of the formation Group queue,m , that is, the queue length of the formation, which is calculated by expression (5):

[0143] Group queue,m =N v,m ×(length veh +length safe ) (5)

[0144] Assume there are n vehicles in formation m, and the speed of the nth vehicle is v n Apply to use the spatial average speed as the speed of the vehicle group velocity,m , unit is (km / h), the calculation method is as shown in expression (6):

[0145]

[0146] In formula (6), i is the index variable used to traverse the vehicles in the formation, representing the i-th vehicle in the formation m, v i represents the speed of the i-th vehicle.

[0147] When there is v n =0, we can know from the above formula

[0148] The known length of the fleet is Group length,m , then the fleet density Group density,m , the unit is (pcu / km), and the calculation method is as follows:

[0149]

[0150] Step 120 , calculating the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the upstream direction and the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the target intersection in the downstream direction;

[0151] Specifically, when controlling traffic signals at intersections, the present application needs to comprehensively consider the time oversaturation index and space oversaturation index of the upstream flow direction, as well as the time oversaturation index and space oversaturation index of the downstream flow direction, so as to target the traffic lights for the upstream and / or downstream flow directions of the intersection.

[0152] Based on this, the present application provides a method for calculating the temporal supersaturation index and the spatial supersaturation index. It can be understood that the temporal supersaturation index and the spatial supersaturation index in the present application correspond to the temporal supersaturation index and the spatial supersaturation index at a certain signal phase.

[0153] Regarding the time supersaturation index, in a specific embodiment, the calculation expression of the time supersaturation index is as shown in formula (8):

[0154]

[0155] Where TOSI represents the temporal supersaturation index; g e represents the effective green light time; Acc represents the total number of vehicles in the queue, that is, the total number of vehicles that fail to pass the stop line within the detection range of the corresponding flow direction during the green light time of a phase, which can also be understood as the number of remaining vehicles in the queue; i represents the vehicle number; h s,i Indicates the distance between the front of the i-th vehicle and the rear of the preceding vehicle; s is an identification symbol, which is the same as h s Together they express headway; among them, TOSI, g e 、Acc、h s,i Corresponding to the same signal phase.

[0156] As can be seen from the above expression, the value of Acc will have a very large impact on the calculation of TOSI, so the value of Acc needs to be as accurate as possible. In this regard, the calculation expression for the total number of queued vehicles Acc proposed in this application is as follows:

[0157] Acc=Acc'+Acc” (9)

[0158] Among them, Acc' represents the number of vehicles in the current vehicle formation, and Acc" represents the number of vehicles in the next vehicle formation. That is, if there is a vehicle formation Group m , the vehicle formation has n vehicles. At the end of the yellow light, the total number of vehicles that fail to pass the stop line and need to stop and wait is Acc'. m Another vehicle formation Group behind m+1 , the vehicle formation has k vehicles. At the end of the yellow light, these vehicles will merge into the front formation Group m The total number of vehicles is Acc".

[0159] That is, the present application not only considers the vehicles queued in the current vehicle formation, but also considers the vehicles that may merge into the queue in the next vehicle formation.

[0160] Based on this, this application also calculates the number of queued vehicles in the current vehicle formation based on the length of the yellow light, the position of the stop line, and the position and speed of the queued vehicles.

[0161] In a specific embodiment, the current vehicle formation Group m The speed set corresponding to each vehicle is V = {v1,v2,…,vi}, the calculation expression of Acc' is as follows:

[0162]

[0163] Where j represents the remaining vehicles that failed to pass the stop line and stopped in line; y j Indicates the position of the remaining vehicles that failed to pass the stop line and stopped in line; v j Indicates the speed of the remaining vehicles that failed to pass the stop line and stopped in line; yelllow Indicates the duration of the yellow light; y stp Indicates the stop line position.

[0164] Moreover, due to the discreteness of traffic flow in some cases, it is necessary to further analyze the traffic flow according to Group m+1 Zhongshouche and Group m The distance between the last workshop and the Group m+1 The average speed of the Group m+1 Whether the vehicle in the queue belongs to the remaining vehicles in the queue. That is:

[0165] Determine whether the distance between the last vehicle in the queued vehicle formation and the first vehicle in the next vehicle formation is not greater than a distance threshold; if not, determine the number of vehicles queued in the next vehicle formation based on the number of vehicles in the next vehicle formation; if greater, determine the number of vehicles queued in the next vehicle formation equal to 0. Alternatively, determine whether the spatial average speed of the next vehicle formation is not greater than a speed threshold; if not, determine the number of vehicles queued in the next vehicle formation based on the number of vehicles in the next vehicle formation; if greater, determine the number of vehicles queued in the next vehicle formation equal to 0.

[0166] In a specific embodiment, the specific calculation expression of Acc" is as shown in formulas (11) and (12):

[0167] When either of the following two conditions is met:

[0168]

[0169] Group m+1 The k vehicles in will merge into the front convoy and become the vehicles that fail to pass the stop line and stop when the green light of this phase ends. At this time, they are recorded as:

[0170] Acc”=k (12)

[0171] Among them, y n Indicates the current vehicle formation Group m The last car in Group m There are n cars); y n+1Indicates the next vehicle formation Group m+1 The position of the first car in Group m+1 There are k cars); L GAP Indicates the minimum distance threshold of the formation; if y n+1 -y n ≤L GAP , Group m+1 Can merge into the front group m ; Indicates the spatial average speed threshold, which can be set according to the actual situation of the road space. Represents a vehicle formation Group m+1 The spatial average speed of Group m+1 Can also merge into the front team Group m .

[0172] For the spatial supersaturation index, the calculation method of SOSI proposed in this application uses the data collected by the stop line detector to calculate. Figure 5 Under the different vehicle driving conditions shown, the layout of the stop line detector, that is, the detection range of the stop line detector must meet the following requirements:

[0173] When the vehicle formation is in a queue state in the upstream flow direction, the first vehicle in the queue activates the detector, and the head position of the subsequent vehicles other than the first vehicle cannot activate the detector, which is specifically manifested as satisfying expression (13):

[0174] z 1,0 <y1<z 1,1 <y2 (13)

[0175] When the vehicle formation is in a dissipated state in the upstream flow direction and the tail of the leading vehicle leaves the detection area, the detector is in an activated state when the front of the following vehicle is in an unavailable position, specifically satisfying expression (14):

[0176] y1 <z 1,0 <z 1,1 <y2 (14)

[0177] The two ends of the detection area of ​​the stop line detector are the upstream detection limit and the downstream detection limit, respectively. 1,0 represents the downstream detection limit, z 1,1 represents the upstream detection limit, y1 represents the front position of the leading vehicle in the vehicle formation, and y2 represents the front position of the leading vehicle in the vehicle formation.

[0178] Using the detector layout described above, the spatial supersaturation index (SOSI) can be calculated based on the detector pulses collected by the stop line detectors during the statistical period, depending on the vehicle arrival and parking conditions. The SOSI calculation method for each case is as follows:

[0179] In the following formulas (15)-(21), we have:

[0180] When the subscript value is -1, it indicates the last element in the corresponding sequence set;

[0181] SOSI stands for spatial supersaturation index;

[0182] T represents the time from the moment the green light turns on to the moment the yellow light turns off within a signal control cycle; t represents the time at the end of time period T; t0 represents the time that the last vehicle that overflowed from the downstream intersection during the previous signal control cycle occupied the stop line detector during the current signal control cycle; t1 represents the time that a vehicle that stopped at the stop line detector due to overflow obstruction at the end of the yellow light within a signal control cycle occupied the stop line detector; t occ Indicates the time it takes for a vehicle to pass through the stop line detector normally;

[0183] UP represents the pulse response time sequence of the rising edge of a detector on the corresponding flow direction (lane) within a statistical time period, and DOWN represents the pulse response time sequence of the falling edge of a detector on the corresponding flow direction (lane) within a statistical time period; the above two statistical time periods can be set according to statistical needs and can include multiple signal control cycles; UP' represents the time sequence of all rising edge pulse responses before the current signal control cycle; DOWN' represents the time sequence of all falling edge pulse responses before the current signal control cycle; UP n and DOWN n They represent the time corresponding to the nth rising edge or the nth falling edge in the time period T of a signal control cycle; UP1 and DOWN1 represent the time corresponding to the first rising edge and the first falling edge in the time period T of a signal control cycle; UP -1 and DOWN -1 They represent the time corresponding to the last rising edge and the last falling edge of the time period T of a signal control cycle respectively; DOWN0 represents the time corresponding to the last falling edge in the statistical time period T of the previous signal control cycle; UP i Indicates the time corresponding to the i-th rising edge within the time period T of a signal control cycle; UP' i' and DOWN' j' Respectively represent the time corresponding to the i'th rising edge or j'th falling edge before the current signal control cycle;

[0184] N up represents the number of rising edges within a signal control period, N down represents the number of falling edges within a signal control period; N' up represents the number of all rising edges before the current signal control period; N' down represents the number of all falling edges before the current signal control period;

[0185] i, j, n are identification symbols used for marking; i, j, i' and j' respectively represent the number of rising and falling edges in the corresponding time series, and n is an index variable. And there is

[0186] UP = {t1, t2, …, t i}

[0187] DOWN = {t1, t2, …, t j}

[0188] UP′ = {t′1, t′2, …, t′ i'}

[0189] DOWN' = {t'1, t'2, …, t' j'}

[0190] The first case:

[0191] If N up = N down ≠ 0 and UP1 > DOWN1, this case is as shown in Figure 6 , indicating that there is a vehicle parked in the detection area before the green light turns on, keeping the detector activated, and the vehicle drives out of the detection area after the green light turns on. Before the green light ends, another vehicle enters the detection area, but this vehicle does not leave the detection area until the red light turns on. Then the calculation expressions of SOSI are as shown in Eqs. (15), (16)

[0192]

[0193]

[0194] The second case:

[0195] If N up = N down ≠ 0 and UP1 < DOWN1, this case is as shown in Figure 7 , indicating that there is no vehicle in the detection area before the green light turns on, and vehicles enter the detection area after the green light turns on. And before the red light turns on, all vehicles that enter the detection area can drive out of the detection area. Then the calculation expression of SOSI is as shown in Eq. (17):

[0196]

[0197] The third case:

[0198] If N up =N down +1, if the situation Figure 8 As shown in Figure 1, there are no vehicles in the detection area before the green light turns on, and vehicles enter the detection area only after the green light turns on. Before the red light turns on, a certain vehicle (which may also be the first vehicle to enter the detection area after the green light turns on) fails to enter the detection area, causing the detector to be in an active state. The calculation expressions of SOSI are as follows:

[0199]

[0200] t1=max[0,t-UP i -t occ ] (19)

[0201] The fourth case:

[0202] If N up =N down -1, the situation is as follows Figure 9 As shown, it means that before the green light turns on, a vehicle is parked in the detection area, keeping the detector active. After the green light turns on, the vehicle leaves the detection area. Before the green light ends, if there are vehicles entering the detection area, all vehicles entering the detection area can leave the detection area (or after the first vehicle leaves, no other vehicles enter the detection area). The calculation expressions of SOSI are as follows:

[0203]

[0204] t0=max[0,DOWN0-(tT)-t occ ] (twenty one)

[0205] In the fifth and sixth cases, if N up =N down = 0, and the detector is in the active state before the statistical period. Figure 10 As shown; if N up =N down = 0, and the detector is in an inactive state before the statistical period. Figure 11 As shown. In the above two cases, SOSI calculation needs to be considered in combination with the rising and falling edge responses of the previous cycle statistics. Assume that the time series of all rising and falling edge pulse responses before the statistical cycle are UP'={t'1,t'2,…,t' i'} and DOWN'={t'1,t'2,…,t' j'},but:

[0206] If N up =N down =0, or

[0207] N' up =0≠N' down ,or

[0208] N' up ≠0 and N' down ≠0 and UP' i' <DOWN' j' ,

[0209] Then SOSI=0.

[0210] If N' up ≠0 and N' down =0, or

[0211] N' up ≠0 and N' down ≠0 and UP' i' >DOWN' j' ,

[0212] Then SOSI=1.

[0213] It should also be noted here that, whether it is the physical implementation in the actual circuit or the idealized mathematical model, the rising edge and falling edge times in the same cycle must be strictly different.

[0214] The calculation method of the temporal oversaturation index and the spatial oversaturation index has been introduced above. The temporal oversaturation index and the spatial oversaturation index of each vehicle formation in the upstream and downstream directions at the target intersection can be calculated based on this method for use in step 130.

[0215] Step 130 , controlling the traffic lights in the upstream and / or downstream directions of the target intersection according to the time oversaturation index and space oversaturation index of each vehicle formation in the upstream direction, and the time oversaturation index and space oversaturation index of the downstream direction.

[0216] Specifically, whether the TOSI and SOSI values ​​are greater than zero indicates whether oversaturation exists in the corresponding flow direction. Furthermore, depending on whether temporal and / or spatial oversaturation exists in the upstream or downstream flow direction, different traffic signal control methods for the upstream and / or downstream flows at the target intersection are applied.

[0217] In a specific embodiment, for TOSI and SOSI values ​​greater than 0 and equal to 0, this application considers the following six cases:

[0218] First case:

[0219] If the value of the temporal oversaturation index TOSI of the upstream flow of the vehicle formation is equal to 0, the value of the spatial oversaturation index SOSI of the upstream flow of the vehicle formation is equal to 0, the value of the temporal oversaturation index TOSI of the downstream flow of the vehicle formation is equal to 0, and the value of the spatial oversaturation index SOSI of the downstream flow of the vehicle formation is equal to 0, it means that the target intersection is not oversaturated in time and space. In this case, the traffic signal control plan for the upstream and downstream flows of the target intersection can be maintained, and no new traffic control measures are needed for the time being.

[0220] Second case:

[0221] If the time supersaturation index TOSI of the upstream flow direction of the vehicle formation is greater than 0, the spatial supersaturation index SOSI of the upstream flow direction of the vehicle formation is equal to 0, the time supersaturation index TOSI of the downstream flow direction of the vehicle formation is equal to 0, and the spatial supersaturation index SOSI of the downstream flow direction of the vehicle formation is equal to 0, then it means that a queue has appeared in the upstream flow direction of the target intersection, and since no other supersaturation phenomenon has occurred in other flow directions, the queue in the upstream flow direction should be eliminated first at this time, and the upstream green light of the target intersection should be turned on earlier or turned off later.

[0222] Furthermore, based on the original green light duration, increasing the green light time Δt required to dissipate these vehicles can effectively alleviate the oversaturation in this flow direction. The calculation expression of Δt is as shown in formula (22):

[0223] Δt=TOSI×G i (twenty two)

[0224] Among them, G i Indicates the original green light duration of phase i.

[0225] When these vehicles enter the downstream intersection, they may be diverted to multiple different directions. Because traffic flow is discrete, if a coordinated phase needs to be designed between the upstream and downstream intersections, Δt cannot be directly applied to the green light time of the coordinated phase at the downstream intersection.

[0226] If the above-mentioned method of directly increasing the green light duration at the end of the green light ("late green light off") is adopted, it will lead to an increase in the cycle length. In order to minimize the disruption of the coordination relationship between upstream and downstream, when oversaturation has just occurred or is not very serious and there is no sign of spreading, priority should be given to allocating part of the green light time in the phase corresponding to the flow direction with starvation to the flow direction that needs to increase the green light duration.

[0227] When green light starvation occurs in multiple phases, the green light duration of the phase with starvation before the phase to be overtime is added to the phase to be overtime.

[0228] If the required additional green light duration Δt is greater than the sum of all available hungry green light durations ∑t starvation , it means that the oversaturation state of the intersection is approaching or in the development and spread stage. At this time, after fully utilizing the green light time of the hungry phase, the remaining green light time should be increased to the original green light time.

[0229] The third case:

[0230] If the value of the time supersaturation index TOSI of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index SOSI of the upstream flow direction of the vehicle formation is greater than 0, the value of the time supersaturation index TOSI of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index SOSI of the downstream flow direction of the vehicle formation is equal to 0, then it means that the accumulated queue in the downstream flow direction of the target intersection overflows to the upstream intersection and hinders the passage of vehicles at the upstream intersection. In addition, there is a accumulated queue in the downstream flow direction at the end of the green light, but there is no accumulated queue in the upstream flow direction at the end of the green light. The downstream green light of the target intersection should be turned on earlier or turned off later.

[0231] Furthermore, in this case, the traffic bottleneck is located in a certain flow direction at the downstream intersection. At this time, priority should be given to increasing the throughput of the road network so that vehicles at the downstream intersection can exit the road network as quickly as possible. In this application, vehicles exiting the downstream intersection are equivalent to exiting the road network, so the traffic load generated by these vehicles at other intersections is no longer considered.

[0232] At this time, the “late green light upstream” approach will cause vehicles to queue further upstream, so the “early green light downstream” approach can be adopted. The increased green light duration Δt = SOSI × G i Due to overflow at the downstream intersection, even if the green light time is increased, downstream traffic may still be delayed and queued when the green light ends. This situation requires further optimization in subsequent cycles.

[0233] Of course, in this case, the "green light is turned off later" method can be adopted to further determine the green light extension time based on the corresponding detected vehicle formation situation.

[0234] The fourth case:

[0235] If the temporal oversaturation index (TOSI) of the upstream flow direction is equal to 0, the spatial oversaturation index (SOSI) of the upstream flow direction is equal to 0, the temporal oversaturation index (TOSI) of the downstream flow direction is greater than 0, and the spatial oversaturation index (SOSI) of the downstream flow direction is equal to 0, then a queue has formed in one direction downstream of the target intersection. The remaining directions are not oversaturated, so eliminating the queue in that direction should be prioritized. The green light downstream of the target intersection should be illuminated earlier or removed later.

[0236] Furthermore, the signal control method in this case is the same as the third case mentioned above, and in the case discussed in this application, there is no need to consider the impact of these queued vehicles on other intersections after they exit the road network. It is sufficient to increase the green light time by using the "green light off later" or "green light on earlier" method.

[0237] However, if the TOSI value of the downstream direction is too large and there is excessive traffic in the upstream direction (no backlog has formed upstream), the risk of overflow caused by excessive backlog in the downstream direction needs to be considered. To avoid overflow, the green light extension time should be further determined based on the corresponding detected vehicle formation.

[0238] The fifth case:

[0239] If the temporal oversaturation index (TOSI) of the upstream flow direction of the vehicle formation is greater than 0, the spatial oversaturation index (SOSI) of the upstream flow direction of the vehicle formation is equal to 0, and the temporal oversaturation index (TOSI) of the downstream flow direction of the vehicle formation is greater than 0, and the spatial oversaturation index (SOSI) of the downstream flow direction of the vehicle formation is equal to 0, then this indicates that there are traffic congestion and queues at both the target intersection and its downstream intersection, but there is no overflow in these two traffic directions. In this case, while ensuring that there is no overflow in the downstream flow direction, the upstream traffic congestion and queues should be eliminated as much as possible, and the upstream green light at the target intersection should be turned off later and the downstream green light should be turned on earlier.

[0240] Furthermore, the traffic bottleneck in this case is in the downstream direction. If the upstream flow is released before the downstream flow has dissipated, the risk of overflow will increase. Therefore, releasing the downstream flow should be prioritized over the upstream flow, that is, adopting a "late green light cut-off" approach for the upstream flow and an "early green light on" approach for the downstream flow.

[0241] If both flows extend the green light time Δt=TOSI×G i (i.e. the “green light and late cut-off” approach is adopted), and the downstream flow needs to be extended for a longer time to avoid delays and queues.

[0242] The relationship between the physical space of the downstream entrance and the phase difference between upstream and downstream flows should be considered. If the physical space of the downstream entrance can accommodate the subsequent arrival of upstream vehicles without causing serious delays, queues, or even overflow, the downstream flow can adopt a "late green light off" approach. Otherwise, a "early green light on" approach should be adopted to avoid overflow.

[0243] If oversaturation is still in the initial stage and the queuing situation in the downstream flow has not become serious, a part of the green light time in the hungry phase of the downstream intersection can be taken out to extend the green light time of the downstream oversaturated flow, and the cycle length should not be changed as much as possible; when oversaturation is already in the development and spread stage, the queuing situation in the upstream is more serious. At this time, after fully utilizing the green light time in the hungry phase of the downstream intersection, the remaining green light time should be added to the original green light time to increase the throughput of the road network and control the aggravation and spread of oversaturation at the intersection.

[0244] The sixth case:

[0245] If the time supersaturation index TOSI of the upstream flow direction of the vehicle formation is greater than 0, the spatial supersaturation index SOSI of the upstream flow direction of the vehicle formation is greater than 0, the time supersaturation index TOSI of the downstream flow direction of the vehicle formation is greater than 0, and the spatial supersaturation index SOSI of the downstream flow direction of the vehicle formation is equal to 0, it means that a certain flow direction at the target intersection is affected by the overflow of a certain flow direction at the downstream intersection and cannot pass through the intersection during the green light period. In this case, the traffic bottleneck is located in a certain flow direction at the downstream intersection. At this time, the overflow vehicles in the downstream flow direction should be eliminated first, and the green lights upstream and downstream of the target intersection should be delayed.

[0246] Furthermore, when overflow occurs in the downstream flow direction, if the upstream flow directions continue to allow vehicles to enter the downstream section, the degree of oversaturation will be aggravated and spread. In this case, restrictive measures should be taken in the upstream flow direction, and the downstream flow direction should be released first. i , so that some vehicles leave the road network before allowing vehicles in the upstream direction to pass. At this time, both upstream and downstream directions adopt the "green light late off" method, and their respective green light time is extended on the original basis by Δt=TOSI×G i .

[0247] However, this may result in an increase in queues in the upstream direction when the green light comes on or a delayed queue when the green light ends. At this time, the green light extension time should be further determined based on the corresponding detected vehicle formation, and the "green light late cut-off" measure should be taken for the upstream direction to avoid delayed queues.

[0248] However, due to the large number of vehicles in the downstream flow, even with the above measures, it may not be possible to completely clear the backlog queue within a single cycle. After one cycle of optimization, backlog queues may still exist. This situation requires further optimization in subsequent cycles.

[0249] If upstream traffic flows adopt a "late green light" policy and the green light duration is not increased, traffic may be delayed or queued at upstream intersections. Increasing the green light duration will alter the coordination between upstream and downstream intersections. To maximize coordination, when oversaturation is developing or dissipating, the green light duration of the hungry phase should be used to extend the green light duration of the demand phase. When oversaturation is developing, increasing the cycle time, thereby increasing the green light duration of each phase, can be prioritized.

[0250] The above content mentions the oversaturation stage. In this regard, the present application also proposes a method for determining the oversaturation stage, including steps 310-320:

[0251] Step 310: Based on the number of vehicles flowing upstream at the end of the green light Effective green light time g e,k , saturated headway h s , calculate the number of supersaturation events; if Then the number of supersaturation events increases by 1;

[0252] Specifically, when the traffic volume input from the upstream intersection of the target intersection to the upstream direction of the target intersection exceeds the dissipation capacity of the upstream direction of the target intersection for several consecutive cycles, the input traffic volume will not be effectively dissipated within the green light time of several consecutive cycles, which manifests as continuous and significant TOSI. At this time, the degree of oversaturation begins to intensify.

[0253] When the traffic volume flowing upstream of the target intersection begins to decrease, the vehicles flowing upstream of the target intersection gradually dissipate. Although a continuous TOSI value still exists at this point, it has dropped significantly compared to the previous TOSI. The oversaturation in the flow direction is now in the dissipation stage.

[0254] Note g,end is the time when the green light ends, and the number of vehicles flowing upstream from the target intersection is when When it is considered that there are too many vehicles in the flow direction and they cannot be completely cleared within the green light time of the next cycle, Recorded as an event That is, if The supersaturation event The number of occurrences increases by 1;

[0255] Step 320 : Determine the oversaturation stage state according to the number of oversaturation events and the time oversaturation index.

[0256] Specifically, set an acceptable If the current TOSI value exceeds The value of , then it is considered that the current TOSI is high. Preferably, It can be specifically set to 35%.

[0257] At this time, according to t g,end Three features of the flow direction k at the moment: TOSI value, number of vehicles in the flow direction event Whether it occurs multiple times in a continuous cycle can be used to determine the stage of the supersaturation state.

[0258] In a specific embodiment, if two or more events occur within four signal cycles, This judgement event If it occurs multiple times in a continuous cycle, the corresponding supersaturation stage states are shown in Table 1, where the supersaturation stage states of "development" and "occurrence" can be equivalent to the "queuing stage" mentioned above.

[0259]

[0260] Table 1

[0261] Based on the above-mentioned method for determining the oversaturation stage, the present application can, after platooning the vehicles flowing upstream of the target intersection, determine the oversaturation stage status of each vehicle formation in the upstream and downstream directions of the target intersection. Then, based on the oversaturation stage status of each vehicle formation in the upstream and downstream directions of the target intersection, control the traffic lights in the upstream and / or downstream directions of the target intersection. Obviously, when the oversaturation stage status is in the "developing" or "occurring" state, the green light duration can be appropriately increased. Conversely, when the oversaturation stage status is in the "dissipating" state, the green light duration can be appropriately reduced.

[0262] Of course, the oversaturation stage state, the time oversaturation index, and the space oversaturation index can be used as reference values ​​together or individually as reference values ​​to provide decision-making references for controlling traffic lights.

[0263] In addition, although the TOSI / SOSI value of a flow direction reflects the degree of supersaturation of that flow direction, it cannot directly reflect the criticality of that flow direction in the path. Therefore, in some preferred embodiments, before platooning the vehicles flowing in the upstream direction of the target intersection, the present application also needs to determine the key flow directions in the critical path that causes congestion, and then determine the target intersection based on the key flow directions. This is used to subsequently control the traffic lights in the upstream and / or downstream directions of the target intersection based on the temporal supersaturation index and spatial supersaturation index of each vehicle formation in the upstream and downstream directions of the target intersection.

[0264] In this regard, the present application also proposes a method for determining a key flow direction in a key path causing congestion, including steps 410-440:

[0265] Step 410 , determining a supersaturation severity value of a target flow direction, a maximum supersaturation severity value of a flow direction upstream of the target flow direction, and a maximum supersaturation severity value of a flow direction downstream of the target flow direction;

[0266] Specifically, oversaturation can be caused by three factors: excessive traffic volume, overflow from the widening section, and overflow from downstream intersections. When traffic in a given direction is excessive, that direction needs to be optimized by adjusting the green-to-signal ratio of the corresponding signal phase. When the oversaturation of a given direction is caused by overflow from the widening section, the signal phase that needs to be adjusted should be that of the signal corresponding to other directions. For example, if the straight-ahead flow is blocked by overflow from the left-turning direction, the green-to-signal ratio of the left-turn phase (the proportion of time available for vehicle traffic within a traffic light cycle) should be adjusted.

[0267] Therefore, this application introduces a correction factor μ. This correction factor is designed to make a flow direction exhibit different levels of oversaturation severity under different oversaturation causes, thereby better distinguishing the criticality of each flow direction in the oversaturation scenario. The value of μ can be determined based on the actual conditions at the intersection in actual applications. In this application, μ is specifically set to 1 or 0.5. A value of 1 corresponds to excessive traffic volume, while a value of 0.5 corresponds to overflow at the downstream intersection.

[0268] Taking into account SOSI, the throughput in the flow direction, and the causes of oversaturation, the calculation expressions for the oversaturation severity value in this application are as follows:

[0269] SVRT Movement =TOSI×(1+SOSI+thpt Ge ×N max +μ) (23)

[0270] thpt Ge =∑q opt,t,k / ∑q ipt,t,k (twenty four)

[0271] Among them, q ipt,t,k ,q opt,t,k They represent the number of vehicles entering and leaving the road section of direction k at time t, and there are 0 <t<G e ; G e Indicates the effective green light time of the flow direction in a signal cycle; SVRT Movement Indicates the severity of supersaturation in the flow direction. TOSI indicates the temporal supersaturation index; SOSI indicates the spatial supersaturation index; thpt Ge Indicates the throughput rate during the green light period; μ indicates the correction coefficient; Nmax Indicates the maximum number of vehicles flowing in a direction within a signal control cycle.

[0272] According to the above formulas (23) and (24), the supersaturation severity value of the target flow direction, the supersaturation severity values ​​of all upstream flow directions of the target flow direction, and the supersaturation severity values ​​of all downstream flow directions of the target flow direction can be calculated, and the maximum supersaturation severity value (max(SVRT)) of all upstream flow directions of the target flow direction can be found. UP,movement ) and the maximum supersaturation severity value max(SVRT) corresponding to all downstream flows DOWN,moveement ), if there is no upstream and downstream flow direction, then the flow direction cannot form a complete path, and the criticality of the incomplete path in the intersection is 0.

[0273] Step 420 , determining a supersaturation severity value of the current path based on the supersaturation severity value of the target flow direction, the maximum supersaturation severity value of the flow direction upstream of the target flow direction, and the maximum supersaturation severity value of the flow direction downstream of the target flow direction;

[0274] Specifically, this application calculates the severity of oversaturation SVRT of a certain path according to the following formula (25): Route :

[0275] SVRT Route =SVRT Movement +max(SVRT UP,movement )+max(SVRT DOWN,movement ) (25)

[0276] Step 430 , setting the path with the largest oversaturation severity value in the area as the critical path causing congestion;

[0277] Specifically, after determining the severity of oversaturation of all paths in the area, the maximum severity value of oversaturation of the path max(SVRT Route ) Identify the critical paths in the area that cause congestion.

[0278] Step 440, setting the flow direction of each flow in the critical path as a critical flow direction;

[0279] Specifically, the SVRT corresponding to the critical path that will cause congestion Movement 、max(SVRT UP,movement ) and max(SVRT DOWN,movement ) is the key flow direction that constitutes the critical path.

[0280] The intersection traffic signal control method provided by the present application first forms a formation of vehicles flowing upstream of a target intersection, quantifies the degree of oversaturation of the target flow in time and space dimensions, and then controls the traffic lights in the upstream and / or downstream directions of the target intersection based on the time oversaturation index and space oversaturation index of each vehicle formation in the upstream and downstream directions of the target intersection, so that the present application can more specifically alleviate the oversaturation state of the intersection, reduce the negative impact of oversaturation, and improve the operating efficiency of the traffic system.

[0281] Example:

[0282] Through secondary development of VISSIM (a simulation software), the simulation realizes the analysis of intersection oversaturation state and signal control decision-making in actual traffic application scenarios.

[0283] 1. Build an oversaturated simulation road network in VISSIM and define simulation parameters and configurations;

[0284] In the embodiment, there is Figure 12 Among the five intersections shown, Intersection 0 is the target intersection, and the traffic conditions in its westward straight flow direction are mainly studied.

[0285] 2. A vehicle platooning model is established based on the position and speed of the vehicles, and the oversaturation evaluation indicators TOSI and SOSI are calculated based on the model.

[0286] Figure 13 Figure 2 shows the traffic flow changes in the key westbound through direction during other observation periods. Throughout the simulation, TOSI and SOSI progressed from low to high and then back to low again. Their levels and trends were consistent with the traffic conditions corresponding to the spatiotemporal graph of vehicle motion trajectories and the vehicle platooning graph, as well as the simulation design. This experiment effectively validated the accuracy of the proposed method for quantifying oversaturation levels based on vehicle platooning under regional detection conditions.

[0287] 3. Identify the stage of oversaturation based on the calculated TOSI, SOSI, and changes in traffic volume in the road network. Establish a vehicle abnormal queue identification model based on the vehicle position and speed to identify the vehicle queue situation and determine the cause of oversaturation based on this.

[0288] During the entire simulation process, the TOSI and the trend of the number of vehicles in the flow direction are shown in the figure below. Figure 14 The experiments effectively verified the accuracy of the proposed method for identifying the oversaturation stage under regional detection conditions.

[0289] During the entire simulation phase, the target flow direction oversaturation intensified development stage was intercepted for analysis. According to the oversaturation cause analysis method proposed in this paper, the moment when an abnormal parking queue exists is represented by a yellow line, and the opposite is represented by a gray line. When an abnormal queue appears, if the conditions for determining abnormality at the next moment are the same, it is represented by a gray line (i.e., t i+1 The judgment of abnormal parking queue is compared with t i When the time changes, it is highlighted with yellow lines). Figure 15 It can be clearly observed that no matter the overflow of the queue comes from the downstream intersection or the widening section, it can be effectively marked, which is in line with the experimental expectations.

[0290] 4. Based on the calculated TOSI, SOSI and changes in throughput in each flow direction, a criticality evaluation model is established, and based on this model, the critical paths and critical flow directions are identified.

[0291] In the simulation process, the critical path identification method proposed in this paper is used to output the critical path results as follows: Figure 16 The output format of each line is: [simulation timestamp (seconds)-supersaturation stage-{target key flow direction, upstream flow direction of target key flow direction, downstream flow direction of target key flow direction}]. The identification results are consistent with the expectations of the experimental design.

[0292] 5. According to the different oversaturated traffic conditions corresponding to the calculated TOSI and SOSI, the traffic control strategy under the oversaturated state is implemented, the traffic signal control under the oversaturated state is performed on each key flow direction in the critical path, and the traffic operation condition is optimized.

[0293] from Figure 17 From the changes in the blue curve in the graph, it can be seen that the oversaturation traffic control method proposed in this paper effectively delays the aggravation of oversaturation, shortens the duration of oversaturation, and accelerates the dissipation speed of oversaturation compared with the fixed timing and full-sensing control strategies, and achieves the expected control goals at different stages of oversaturation.

[0294] In a second aspect, the present application also provides an intersection traffic signal control device for implementing the above-mentioned intersection traffic signal control method, such as Figure 18 As shown, the device includes:

[0295] The platooning module 510 is configured to platoon the vehicles flowing upstream of the target intersection; the intersection is divided into an upstream flow and a downstream flow of the intersection by an initial position of the downstream road segment;

[0296] The calculation module 520 is configured to calculate the temporal oversaturation index and the spatial oversaturation index of each vehicle formation in the upstream flow direction and the downstream flow direction at the target intersection;

[0297] The control module 530 is configured to control the traffic lights in the upstream and / or downstream directions of the target intersection according to the time supersaturation index and the spatial supersaturation index of each vehicle formation in the upstream and downstream directions of the target intersection.

[0298] Other preferred embodiments of the intersection traffic signal control device disclosed in this application and the technical effects that can be achieved are the same as those of the above-mentioned intersection traffic signal control method, and will not be repeated here.

[0299] The preferred embodiments of the present application are described in detail above. However, the present application is not limited to the specific details of the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0300] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0301] In addition, the various embodiments of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for controlling traffic signals at an intersection, characterized in that: The method comprises: The vehicles flowing upstream of the target intersection are platooned; the intersection is divided into an upstream flow direction and a downstream flow direction of the intersection by taking the initial position of the downstream road section as the boundary; Calculating the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the upstream direction and the temporal oversaturation index and spatial oversaturation index of each vehicle formation in the target intersection; Traffic lights in the upstream and / or downstream directions of the target intersection are controlled according to the time oversaturation index and space oversaturation index of the upstream flow direction and the time oversaturation index and space oversaturation index of the downstream flow direction of each vehicle formation in the target intersection.

2. The method according to claim 1, characterized in that The vehicles flowing upstream of the target intersection are platooned, including: Calculating the interval time between each following vehicle and the preceding vehicle in the same lane in the upstream direction of the target intersection; If the interval between the rear vehicle and the front vehicle in the same lane is less than the preset value, the rear vehicle will be incorporated into the formation corresponding to the front vehicle; If the interval between the rear vehicle and the front vehicle in the same lane is not less than the preset value, the rear vehicle will be set as the first vehicle in the new formation.

3. The method according to claim 2, characterized in that The method further comprises: In the upstream flow direction of the target intersection, the headway between vehicles is calculated based on the positions and instantaneous speeds of the preceding and following vehicles adjacent to each other in the same lane; The interval time between the rear vehicle and the front vehicle in the same lane is obtained according to the headway between the vehicles and the instantaneous speed of the corresponding rear vehicle.

4. The method according to claim 1, wherein The calculation expression of the time supersaturation index is: Where TOSI represents the temporal supersaturation index; g e represents the effective green light time; Acc represents the total number of vehicles in the queue; i represents the vehicle number; h s,i represents the distance between the front of the i-th vehicle and the rear of the preceding vehicle; s is an identifier; the TOSI, ge, Acc, h s,i Corresponding to the same signal phase.

5. The method according to claim 4, characterized in that The method further comprises: The number of queued vehicles in the current vehicle formation is added to the number of queued vehicles in the corresponding next vehicle formation to obtain the total number of queued vehicles.

6. The method according to claim 5, characterized in that The method further comprises: The number of vehicles in the queue in the current vehicle formation is calculated based on the duration of the yellow light, the position of the stop line, and the position and speed of the queued vehicles.

7. The method according to claim 5, characterized in that The method further comprises: determining whether a distance between a position of a rear vehicle in a queued vehicle formation and a position of a front vehicle in a next queued vehicle formation is not greater than a distance threshold; If not, the number of vehicles queued in the next vehicle formation is obtained according to the number of vehicles in the next vehicle formation; If it is greater than, the number of vehicles queued in the next vehicle formation is equal to 0; or Determining whether the spatial average speed of the next vehicle formation is not greater than a speed threshold; If not, the number of vehicles queued in the next vehicle formation is obtained according to the number of vehicles in the next vehicle formation; If it is greater, the number of vehicles queued in the next vehicle formation is equal to 0.

8. The method according to claim 1, characterized in that The method further comprises: The spatial supersaturation index is calculated according to the detector pulse conditions collected by the stop line detector within a statistical period.

9. The method according to claim 8, characterized in that The spatial supersaturation index is calculated according to the detector pulse conditions collected by the stop line detector within the statistical period, including: If N up =N down ≠0 and UP1>DOWN1, then If N up = N down ≠ 0 and UP1 < DOWN1, then If N up =N down +1, then t1=max[0,t-UP i -t occ ]; If N up =N down -1, then t0=max[0,DOWN0-(t-T)-t occ ]; If N up =N down =0, or N' up =0≠N' down ,or N' up ≠0 and N' down ≠0 and UP' i' <DOWN' j' ,but SOSI=0; If N' up ≠0 and N' down =0, or N' up ≠0 and N' down ≠0 and UP' i' >DOWN' j' , Then SOSI=1; UP={t1,t2,…,ti}; DOWN={t1,t2,…,tj}; UP'={t'1,t'2,…,t' i' }; DOWN'={t'1,t'2,…,t' j' }; Where SOSI represents the spatial supersaturation index; T represents the time from the onset of the green light to the end of the yellow light within a signal control cycle; t represents the time at the end of time period T; t0 represents the time that the last vehicle that overflowed from the downstream intersection in the previous signal control cycle occupied the stop line detector in the current signal control cycle; t1 represents the time that the vehicle that stopped at the stop line detector due to overflow obstruction occupied the stop line detector at the end of the yellow light within a signal control cycle; t occ Indicates the time duration that a vehicle normally takes to pass through the stop line detector; DOWN indicates the pulse response time sequence of the falling edge of a detector corresponding to the flow direction within a statistical time period; UP indicates the pulse response time sequence of the rising edge of a detector corresponding to the flow direction within a statistical time period; UP' indicates the pulse response time sequence of all rising edges counted before the current signal control cycle; DOWN' indicates the pulse response time sequence of all falling edges counted before the current signal control cycle; UP n and DOWN n They represent the time corresponding to the nth rising edge or the nth falling edge in the time period T of a signal control cycle; UP1 and DOWN1 represent the time corresponding to the first rising edge and the first falling edge in the time period T of a signal control cycle; UP -1 and DOWN -1 They represent the time corresponding to the last rising edge and the last falling edge in the time period T of a signal control cycle respectively; DOWN0 represents the time corresponding to the last falling edge in the time period T of the previous signal control cycle; UP i Indicates the time corresponding to the i-th rising edge within the time period T of a signal control cycle; UP' i' and DOWN' j' Respectively represent the time corresponding to the i'th rising edge or j'th falling edge before the current signal control cycle; N up Indicates the number of rising edges in a signal control cycle, N down Indicates the number of falling edges in a signal control cycle; N' up Indicates the number of all rising edges before the current signal control cycle; N' down Indicates the number of all falling edges before the current signal control cycle; i, j, and n are identification symbols, i, j, i', and j' respectively represent the number of rising edges and falling edges in the corresponding time series, and n is an index variable.

10. The method according to claim 9, characterized in that The detection range of the stop line detector must meet the following requirements: When a vehicle formation is in a queue state in the upstream flow direction, the first vehicle in the queue activates the detector, and the head position of subsequent vehicles other than the first vehicle cannot activate the detector; When the vehicle formation is in a dissipating state in the upstream flow and when the rear end of the leading vehicle leaves the detection area, the position of the front end of the following vehicle cannot be determined.

11. The method according to claim 1, wherein Controlling traffic lights in the upstream direction and / or downstream direction of the target intersection according to the time oversaturation index and the space oversaturation index of each vehicle formation in the upstream direction and the time oversaturation index and the space oversaturation index of the downstream direction of the target intersection, including: If the value of the temporal supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the temporal supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the traffic signal control scheme for the upstream flow direction and the downstream flow direction of the target intersection is maintained; If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the upstream green light of the target intersection is turned on earlier or turned off later; If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the green light downstream of the target intersection is turned on earlier or the green light downstream is turned off later; If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the green light downstream of the target intersection is turned on earlier or the green light downstream is turned off later; If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is equal to 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, then the upstream green light of the target intersection is turned off later and the downstream green light is turned on earlier; If the value of the time supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the spatial supersaturation index of the upstream flow direction of the vehicle formation is greater than 0, the value of the time supersaturation index of the downstream flow direction of the vehicle formation is greater than 0, and the value of the spatial supersaturation index of the downstream flow direction of the vehicle formation is equal to 0, the green lights upstream and downstream of the target intersection will be turned off later.

12. The method according to claim 1, characterized in that After platooning the vehicles flowing upstream of the target intersection, the method further includes: Determine the supersaturation stage status of each vehicle formation in the upstream and downstream directions at the target intersection; According to the supersaturation stage status of each vehicle formation in the upstream flow direction and the downstream flow direction of the target intersection, the traffic lights in the upstream flow direction and / or the downstream flow direction of the target intersection are controlled.

13. The method according to claim 12, characterized in that The method further comprises: According to the number of vehicles flowing upstream at the end of the green light Effective green light time g e,k , saturated headway h s , calculate the number of supersaturation events; where if Then the number of supersaturation events increases by 1; The supersaturation stage state is determined according to the number of occurrences of the supersaturation events and the time supersaturation index.

14. The method according to claim 1, wherein Before platooning the vehicles flowing upstream of the target intersection, the method further includes: Identify the key flows in the critical path that cause congestion; The target intersection is determined according to the key flow direction, and is used to control the traffic lights in the upstream flow direction and / or downstream flow direction of the target intersection according to the time oversaturation index and space oversaturation index of each vehicle formation in the upstream flow direction, as well as the time oversaturation index and space oversaturation index of the downstream flow direction.

15. The method according to claim 14, characterized in that Identify key flows in the critical path that cause congestion, including: determining a supersaturation severity value for a target flow direction, a maximum supersaturation severity value for a flow direction upstream of the target flow direction, and a maximum supersaturation severity value for a flow direction downstream of the target flow direction; Determining a supersaturation severity value of the path according to the supersaturation severity value of the target flow direction, the maximum supersaturation severity value of the flow direction upstream of the target flow direction, and the maximum supersaturation severity value of the flow direction downstream of the target flow direction; The path with the largest oversaturation severity value in the region is set as the critical path causing congestion; Setting the flow direction of each flow in the critical path to the critical flow direction; The calculation expression of the oversaturation severity value is: SVRT Movement =TRUE×(1+SOSI+thpt Ge ×N max +μ); Among them, SVRT Movement Indicates the severity of supersaturation in the flow direction; TOSI indicates the temporal supersaturation index; SOSI indicates the spatial supersaturation index; thpt Ge Indicates the throughput rate during the green light period; μ indicates the correction coefficient; N max Indicates the maximum number of vehicles flowing in a direction within a signal control cycle.

16. A traffic signal control device for an intersection, characterized in that: The device comprises: A platooning module is configured to platoon vehicles flowing upstream of a target intersection; the intersection is divided into an upstream flow direction and a downstream flow direction of the intersection by an initial position of a downstream road segment; a calculation module configured to calculate a temporal oversaturation index and a spatial oversaturation index of each vehicle formation in the target intersection in an upstream flow direction, and a temporal oversaturation index and a spatial oversaturation index of each vehicle formation in a downstream flow direction; The control module is configured to control the traffic lights in the upstream and / or downstream directions of the target intersection based on the time oversaturation index and space oversaturation index of each vehicle formation in the upstream direction and the time oversaturation index and space oversaturation index of the downstream direction in the target intersection.

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