Urban mesoscopic credit control unit division method based on breadth search

Abstract

The invention relates to the field of urban traffic management and signal control, and discloses an urban mesoscopic credit control unit division method based on breadth search, which comprises the following steps: collecting traffic data in a road network, calculating an optimal signal timing scheme, and finely adjusting a signal period according to a downstream overflow risk; by calculating the coordination benefit of each steering, effective coordination steering is screened out, and a signal coordination trunk line is generated; generating a credit control unit by using a breadth search algorithm (BFS), and reasonably dividing the credit control unit into a single-point credit control unit, a trunk line credit control unit and a regional credit control unit; finally, by calculating the coordination direction and the phase difference, signal coordination and green wave passing are ensured, and a signal control scheme of a road network is optimized. According to the method, the traffic capacity of urban traffic can be improved, traffic congestion is reduced, and the overall traffic fluency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of urban traffic management and signal control, and specifically to a method for dividing medium-scale signal control units in a city based on breadth-first search. Background Art

[0002] Existing urban traffic signal control systems usually rely on fixed signal timing plans and lack real-time response and optimization for traffic flow changes and road network topologies. Most traditional signal control methods cannot dynamically adjust the signal cycle according to traffic demand changes, resulting in congestion problems during traffic peaks or special situations and reducing the traffic efficiency of the road network.

[0003] Most existing signal control systems rely on a single intersection signal timing plan and ignore the coordination between intersections and the overall traffic flow control of arterial roads. Especially when there are multiple intersections, the lack of effective green wave coordination strategies often results in poor traffic mobility and affects the overall traffic efficiency. The configuration of signal control systems often does not consider the synergistic effects between intersections, leading to frequent conflicts between signal units, wasting a large amount of passing time and further exacerbating traffic congestion.

[0004] In addition, the division of signal control units in existing technologies is relatively simple, mostly controlled by a single intersection as a unit, lacking consideration of the overall signal control capabilities of arterial roads and regions. When multiple intersecting arterial roads are in the same area, existing signal control systems often cannot effectively coordinate the signal timing of these intersecting arterial roads, resulting in signal interference and mutual influence between intersecting arterial roads and unable to fully utilize the potential of traffic flow.

[0005] Therefore, existing technologies lack an effective signal coordination and signal control unit division method, making it difficult to flexibly respond to traffic flow changes in complex road network structures, further restricting the traffic capacity and smoothness of urban traffic networks. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for dividing medium-scale signal control units in a city based on breadth-first search, which solves the problem that multiple intersection signals cannot be effectively coordinated in existing traffic signal control systems and optimizes the overall traffic capacity of the road network.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for dividing medium-scale signal control units in a city based on breadth-first search includes the following steps: Obtain multiple intersections in the road network and their traffic information; Calculate the optimal signal timing plan for each intersection based on the traffic information; Calculate the queuing length of vehicles waiting in the downstream sections of each intersection and adjust the release duration of this intersection based on the remaining passing capacity downstream. Calculate the coordination benefits for each turning direction, and select the turning directions with benefits greater than zero as coordination candidates; Expand the coordination path based on the breadth-first search algorithm to form a signal-coordinated arterial road; Divide the signal control units according to the arterial road topology relationship; Calculate the signal phase difference based on the main coordination direction of each arterial road to optimize the signal timing.

[0008] Preferably, the step of obtaining multiple intersections and their traffic information in the road network includes: Obtain intersection traffic demand, upstream and downstream topology of the intersection, signal control configuration of the intersection, and historical record data; Perform data fusion with the turning direction as the smallest granularity, and generate fields including intersection number, turning number, number of lanes, lane length, signal control phase number, actual intersection cycle, turning green ratio, actual turning flow rate and demand flow rate, upstream and downstream turns and corresponding flow ratios.

[0009] Preferably, the step of calculating the optimal signal timing plan for each intersection based on the traffic information includes: Calculate the optimal signal cycle according to the number of intersection phases, phase switching lost time, and saturation: where C(I) is the optimal signal cycle, N ph is the number of intersection phases, T loss is the single-phase switching lost time, and X(I) is the total intersection saturation; For each signal control phase, calculate its saturation: where X ph is the phase saturation, DR(T rep ) is the demand flow rate of the representative lane of the phase, and FR(T rep ) is the passing capacity of the representative lane of the phase, that is, the upper limit of the flow that the lane can pass under the current signal timing plan, that is, the lane saturation flow rate multiplied by the lane green ratio; Based on the phase saturation and the total intersection saturation, allocate the phase green ratio according to the equilibrium principle: where G(T) is the phase green ratio; According to the phase green ratio and the intersection cycle, calculate the green light time of each phase: T ph = G(T) × (C(I) - N ph × T loss ) where T ph is the phase green light time.

[0010] Preferably, the steps of calculating the queuing length of the downstream section of each intersection and adjusting the green light time of this intersection based on the remaining passing capacity of the downstream section include: Calculate the queuing length of the downstream lane according to the flow difference of the downstream turns and the signal cycle: Wherein, L queue (D) is the queuing length of the downstream lane, DR(D) is the demand flow rate of the downstream turn, FR(D) is the actual flow rate of the downstream turn, C(D) is the signal cycle of the downstream intersection, and L std is the standard queuing vehicle spacing; Calculate the remaining lane capacity of the downstream section according to the total length of the downstream section, the queuing length, and the safety distance: L free (D) = L c (D) - L queue (D) - S safe Wherein, L free (D) is the remaining lane capacity of the downstream section, L c (D) is the lane length of the downstream section, and S safe is the safety distance of the exit lane; if the following conditions are met, it is determined that there is an overflow risk downstream: L free (D) < 0 Or L queue (D) ≥ L c (D) - S safe Calculate the maximum green light capacity of the downstream section based on the remaining lane length of the downstream section, that is, the maximum green light time allowed for this intersection to release: Wherein, G max (D) is the maximum green light capacity of the downstream section; T std is the headway time of the intersection saturation flow rate; Adjust the green light time of the corresponding phase of this intersection for the downstream turn with an overflow risk: T p ′ h = min(G max (D), T ph - S) + S Wherein, T p ′ h is the green light time of the corresponding phase of this intersection, T ph is the phase green light time, and S is the reserved buffer time; Recalculate the total cycle of the intersection according to the adjusted green time of each phase: C ′ (I) = ∑T p ′ h Where C ′ (I) is the adjusted signal cycle of the intersection.

[0011] Preferably, the step of calculating the coordination benefits of each turning direction and screening the turning directions with benefits greater than zero as coordination candidates includes: For each turning direction, if its demand flow rate is greater than the actual flow rate, it is determined that the turning direction is in an overflow state and does not participate in the green wave coordination; eliminate the overflow turning directions from all turning directions, and the remaining non-overflow turning directions form a coordination candidate set; For each candidate turning direction in the coordination candidate set, calculate its coordination benefit: Where FR(T) is the passing capacity of the turning direction in the optimal single-intersection plan, W coor (T) is the proportion of the coordinated flow of the turning direction, FR(I) is the total passing capacity of the intersection in the optimal single-intersection plan, N ph is the total number of signal phases of the intersection; Retain the turning directions with coordination benefits greater than zero and enter the final coordination candidate set.

[0012] Preferably, the step of expanding the coordination path based on the breadth-first search algorithm to form a signal coordination main line includes: step1: Initialize a new main line, including: (1) In the candidate turning direction set TurnSet valid , select the turning direction Turn max with the largest coordination benefit as the starting point of the main line and add it to the set of turning directions to be expanded TurnSet expand ; (2) Assign a unique identifier Corr id to the current main line; (3) Set the intersection relationship field INTER = null, indicating that the current main line does not intersect with other main lines; step2: Expand the main line step2.1. Select any turning direction Turn expand from TurnSet current ; step2.2. Perform coordination access verification on Turn current . If the following conditions are met, discard Turn current and return to step2.1: The current main line Corrid has intersected with other main lines; and Turn current intersects with other main lines; step2.3. Add Turn current to the current main line and label it as the main line coordinated turn Turn coor ; step2.4. If Turn current intersects with other main lines Corr i ′ d then update the current main line intersection relationship attribute: INTER = Corr i ′ d step2.5. Expand the upstream turn Turn current and the downstream turn Turn up of Turn down : Add Turn up and Turn down to the set of turns to be expanded TurnSet expand ; step2.6. Remove all turns in the phase where Turn valid is located from the candidate turn set TurnSet current ; step2.7. Repeat steps step2.1 to step2.7 until TurnSet expand is empty, and the generation of the current main line is completed; step3: Store the generated main line Corr id in the main line set. If the candidate turn set TurnSet valid is not empty, return to step1 to generate the next main line; otherwise, terminate the process.

[0013] Preferably, the step of dividing the signal control unit according to the main line topological relationship includes: Divide the signal control unit according to the main line topological structure, and the signal control unit includes: Single-point signal control unit: An independent intersection that does not belong to any main line; Main line signal control unit: A single non-crossing main line; Area signal control unit: A control area composed of multiple intersecting main lines; Merge the main lines according to the intersection situation to form an area signal control unit.

[0014] Preferably, the step of calculating the signal phase difference based on the main coordination direction of each main line includes: For the intersections within the signal control unit, select the coordinated turns of the arterial road intersections as the regional coordinated turns; Define the signal control phase where the coordinated turns are located as the coordinated phase of this intersection; Based on the travel time and queue length of the coordinated turns, calculate the phase difference: where L turn is the length of the turning section, V is the average travel speed of the section, T ph is the green light time of the phase, and W coor (T) is the proportion of the coordinated flow of the turn.

[0015] Preferably, the step of selecting the coordinated turns of the arterial road intersections as the regional coordinated turns for the intersections within the signal control unit includes: If the intersection belongs to two or more intersecting arterial roads, determine the main coordinated turns according to the priority of the arterial road generation order.

[0016] The present invention also provides a device for dividing urban mesoscopic signal control units based on breadth-first search, including: A data acquisition module, used to acquire intersection traffic information and calculate relevant traffic flow data; A single intersection signal optimization module, used to calculate the optimal signal timing plan for each intersection; A downstream overflow control module, used to adjust the release time of this intersection based on the downstream traffic capacity; A coordinated benefit calculation module, used to calculate the coordinated benefits of each turn and screen candidate turns; An arterial road generation module, used to expand the coordinated path by breadth-first search to form signal coordinated arterial roads; A signal control unit division module, used to divide signal control units; A coordinated direction and phase difference calculation module, used to calculate the coordinated direction and signal phase difference to achieve green wave coordinated control.

[0017] The present invention provides a method for dividing urban mesoscopic signal control units based on breadth-first search. It has the following beneficial effects: 1. By optimizing urban traffic signal control, the present invention realizes the coordination of intersection signals and green wave traffic, reducing traffic congestion. Through reasonable signal cycle and green light time allocation, traffic bottlenecks can be effectively avoided, and the traffic capacity of the entire urban road network can be improved.

[0018] 2. By effectively dividing the urban road network into signal control units based on the breadth-first search algorithm, the present invention can scientifically divide intersections into single-point signal control units, arterial road signal control units, and regional signal control units according to the traffic demands, topological structures, and intersection relationships of different intersections and arterial roads, so as to accurately control and optimize signal timing.

[0019] 3. The present invention effectively avoids the overflow risk of the downstream section by calculating the detention queue length of the downstream section and adjusting the signal timing. By adjusting the signal cycle and green light time, it can ensure the smoothness of the downstream section, reduce traffic congestion and queuing phenomena, and guarantee smooth traffic flow.

[0020] 4. The present invention ensures that only beneficial coordinated turns are selected for green wave coordination by calculating the coordinated benefits of each turn. By optimizing the arterial generation and expansion through the breadth-first search algorithm (BFS), the signal coordinated arterials can effectively cover multiple intersections and arterials, improving the coordination of the entire traffic network and optimizing the signal control scheme.

[0021] 5. The present invention can handle complex intersections and road network topologies, and reasonably plan the relationship between arterials and regional signal control units. By accurately recording and merging the intersection relationships of arterials, signal coordination of multiple intersecting arterials is achieved, thus avoiding the occurrence of deadlock phenomena and ensuring efficient coordination within the regional scope. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic flow chart of the method of the present invention; Figure 2 is a schematic flow chart of the method of the present invention; Figure 3 is a schematic structural diagram of the device of the present invention.

[0023] Among them, 10. Data acquisition module; 20. Single intersection signal optimization module; 30. Downstream overflow control module; 40. Coordinated benefit calculation module; 50. Arterial generation module; 60. Signal control unit division module; 70. Coordinated direction and phase difference calculation module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to the attached Figure 1 - attached Figure 2 , the present invention provides a method for dividing medium-scale signal control units in cities based on breadth-first search, which aims to optimize the urban traffic signal control system, improve the traffic flow efficiency, reduce the number of vehicle stops, and enhance the arterial coordination ability.

[0026] The present invention adopts the breadth-first search (BFS) algorithm to ensure the global optimality of the division of signal control units, and fully considers the intersection signal coordination relationship, the influence of queuing, the main line coordination requirement and the phase optimization strategy to achieve efficient green wave coordination control.

[0027] As Figure 1 shown, the method for dividing the medium-scale signal control units in the city based on breadth-first search may include the following steps: S1. Obtain multiple intersections in the road network and their traffic information; S2. Calculate the optimal signal timing plan for each intersection based on the traffic information; S3. Adjust the release duration of this intersection based on the remaining passing capacity downstream; S4. Calculate the coordination benefits of each turning direction, and select the turning directions with benefits greater than zero as coordination candidates; S5. Expand the coordination path based on the breadth-first search algorithm to form a signal coordination main line; S6. Divide the signal control units according to the main line topology relationship; S7. Calculate the signal phase difference based on the main coordination direction of each main line to optimize the signal timing.

[0028] The following is a detailed description of each step in the method of the present invention, and a comprehensive elaboration on the specific implementation principles, technical details and processes of each step is carried out.

[0029] For step S1, this step is used to collect and fuse the traffic data in the road network, providing the basic input for the subsequent division of signal control units and signal optimization. Through data association and calculation, a traffic feature data set with the turning direction as the smallest granularity is formed, including topological information, traffic demand, signal configuration information and traffic flow status.

[0030] First, collect the intersection traffic demand, the upstream and downstream topological relationships of the intersection, the intersection signal control configuration and historical record data. The data sources include fixed detection devices (such as geomagnetic detectors, video detectors), floating car data (FCD), manual survey data and signal control system logs. After the data is preprocessed, it is fused according to the turning granularity to form the following key fields: Intersection ID: A unique number is assigned to each intersection to identify the smallest control unit of the signal control unit. This number is used to define the intersection to which the turning direction belongs and establish the upstream and downstream topological relationships.

[0031] Movement ID: Each turn is assigned a unique number, which serves as the smallest perception unit for traffic state data fusion. The number consists of "intersection number + entrance lane group + target lane group" to ensure uniqueness.

[0032] Lane Count of Movement: Calculate the number of lanes included in the turn. For mixed lanes, convert according to the usage ratio of each type of vehicle: Where: N lanes (M) is the number of effective lanes included in the turn; W i is the mixed traffic ratio of the i-th type of lane (e.g., for a left-turn through lane, if the left-turn accounts for 40%, then W = 0.4); N i is the total number of the i-th type of lane.

[0033] Lane Length of Movement: Record the lane length involved in this turn and compare it with the queue length to evaluate the spillover risk. The conditions for queue spillover are as follows: When the queue length of this turn > the lane length of this turn, queue spillover may occur, affecting the signal optimization strategy.

[0034] Phase ID of Movement: Each turn corresponds to a main release phase in the signal control scheme. If a turn involves multiple phases, select its main release phase.

[0035] Actual Cycle Length: During the detection period, the signal cycle (seconds) of the intersection is defined as the time for the signal lights to execute once in the phase chain order.

[0036] This data can be used to calculate the green split of the turn, phase difference adjustment, etc.

[0037] Green Split of Movement: The proportion of green light time of the turn in the actual signal control: Where: T green (M) is the actual green light time (seconds) of this turn; C(I) is the intersection cycle (seconds).

[0038] Actual Flow Rate per Lane of Movement: Actual passing flow rate of this movement during the statistical period: Wherein: V pass (M) is the number of vehicles passing during the green light time; T std is the headway of the saturation flow rate at the intersection; T green (M) is the green light time (seconds).

[0039] Demand Flow Rate per Lane of Movement: When there is queuing and stagnation in this movement, calculate its demand flow rate: Wherein: Q init (M) is the number of vehicles queuing initially at the green light; C(I) is the intersection cycle (seconds).

[0040] When q demand (M) > q actual (M), it indicates that the traffic capacity of this movement is limited, and signal timing or coordination strategy needs to be adjusted.

[0041] Upstream Intersection of Movement: Determine the upstream intersection of this movement according to the topological relationship of the signal-controlled intersection. Generally, each movement corresponds to only one upstream intersection.

[0042] Upstream Movement of Movement: In the upstream intersection, determine the main source movement of this movement. If there are multiple possible sources in the upstream intersection, select the movement with the largest traffic contribution: M up (M) = arg max M ′ W coor (M ′ ) Wherein: M up (M) is the upstream main coordinated movement of this movement; W coor (M ′ ) is the traffic contribution ratio of the upstream movement.

[0043] Coordinated Flow Ratio of Movement: Calculate the flow ratio from the upstream movement in this movement: Where: Q coor (M) is the flow from the upstream coordinated movement; Q total (M) is the total flow of this movement.

[0044] This ratio is used for subsequent signal coordination calculations.

[0045] Downstream Intersection of Movement: Determine the downstream intersection of this movement according to the topological relationship of the signal-controlled intersections. Generally, there is only one.

[0046] Downstream Movement of Movement: In the downstream intersection, determine the main downstream movement of this movement. If there are multiple possible downstream movements, select the one with the largest flow contribution: M down (M) = arg max M′ W coor (M ′ ) Where: M down (M) is the main downstream coordinated movement of this movement.

[0047] This step completes the collection, fusion and calculation of data, providing the necessary input data for subsequent signal control unit division, arterial generation and signal optimization. The logical relationships between each field are as follows: The intersection number and movement number define the spatial topological relationship; Traffic flow data is used to evaluate the traffic capacity and coordination requirements; The upstream and downstream movement associations are used to calculate the coordination ratio to support signal optimization; The green ratio, flow and demand flow rate are used to judge the overflow risk and optimize the phase allocation.

[0048] After the data structure is reasonably organized, it will be passed as input to the subsequent steps for signal control unit division and signal optimization.

[0049] For step S2, based on the traffic demand at intersections, signal control phase information, and road capacity, the optimal signal cycle and green light time for each phase are calculated to optimize traffic efficiency.

[0050] First, calculate the optimal signal cycle based on the number of intersection phases, phase change loss time, and total saturation. The formula for the intersection cycle is as follows: Where: C(I) is the optimal signal cycle (seconds); N ph is the number of intersection phases; T loss is the single-phase change loss time (seconds); X(I) is the total saturation of the intersection (dimensionless value).

[0051] The intersection saturation is calculated by summing the saturations of each phase: Where: X ph is the saturation of a single phase.

[0052] For each signal control phase, calculate its saturation, defined as follows: Where: DR(T rep ) is the demand flow rate of the representative lane of the phase (vehicles / hour); FR(T rep ) is the saturation flow rate of the representative lane of the phase (vehicles / hour).

[0053] According to the equilibrium principle, calculate the green signal ratio of each phase: Where: G(T) is the green signal ratio of the phase (dimensionless value).

[0054] Finally, based on the green signal ratio of the phase and the signal cycle, calculate the green light time of each phase: T ph =G(T)×(C(I)-N ph ×T loss ) Where: T ph is the green light time of the phase (seconds).

[0055] The calculation logic of the above steps ensures that the signal cycle matches the traffic demand, improves the traffic capacity of the intersection, and reduces delays. The calculation results of the signal timing plan will be used for subsequent signal control unit division and signal coordination optimization.

[0056] For step S3, this step aims to judge whether there is an overflow risk by evaluating the queuing length of vehicles staying in the downstream section, and based on this, adjust the signal timing of this intersection to optimize the traffic efficiency and relieve the congestion in the downstream section.

[0057] First, calculate the queuing length of vehicles staying in the downstream lane. The calculation formula for the queuing length of vehicles staying is as follows: Where: L queue (D) is the queuing length of vehicles staying in the downstream lane (m); DR(D) is the demand flow rate of the downstream turning (vehicles / hour); FR(D) is the actual flow rate of the downstream turning (vehicles / hour); C(D) is the signal cycle of the downstream intersection (s); L std is the standard queuing vehicle spacing (m).

[0058] Next, calculate the remaining lane capacity of the downstream section. The calculation formula for the remaining lane capacity is as follows: L free (D) = L c (D) - L queue (D) - S safe Where: L free (D) is the remaining lane capacity of the downstream (m); L c (D) is the total lane length of the downstream section (m); L queue (D) is the queuing length of vehicles staying in the downstream lane (m); S safe is the safety distance of the exit lane (m).

[0059] If the following conditions are met, it is determined that there is an overflow risk downstream: L free (D) < 0 Or L queue (D) ≥ L c (D) - S safe Where: L free (D) is the remaining lane capacity of the downstream (m); L queue (D) is the length of the queue staying in the downstream lane (meters); L c (D) is the total length of the lanes in the downstream section (meters); S safe is the safety distance of the exit lane (meters).

[0060] If the conditions for spillover risk are met, then calculate the maximum green light capacity of the downstream section as the maximum green light time limit for this intersection. The calculation formula for the maximum green light capacity is as follows: Where: G max (D) is the maximum green light capacity of the downstream (seconds); L free (D) is the capacity of the spare lanes in the downstream (meters); L std is the standard spacing between queuing vehicles (meters).

[0061] For the downstream turns with spillover risk, adjust the green light time of the corresponding phase at this intersection. The calculation formula is as follows: T p ′ h = min(G max (D), T ph - S) + S Where: T p ′ h is the adjusted green light time of the phase (seconds); G max (D) is the maximum green light capacity of the downstream (seconds); T ph is the original green light time of the phase (seconds); S is the reserved buffer time (seconds), which can be set to 10 seconds.

[0062] Finally, according to the adjusted green light time of the phase, recalculate the signal cycle of the intersection. The calculation formula is as follows: C ′ (I) = ∑T p ′ h Where: C ′ (I) is the adjusted signal cycle of the intersection (seconds); T p ′ h is the adjusted green light time of the phase (seconds).

[0063] Through the above calculation process, the signal timing at the intersection can be adjusted to reduce the risk of spillover on the downstream road section and improve traffic fluency. The adjustment of the signal cycle and green light time effectively optimizes the signal control at the intersection and avoids serious spillover congestion on the downstream road section.

[0064] For step S4, this step is used to evaluate the coordinated benefits of the intersection turns. By judging the overflow of each turn, the non-overflowing turns are screened out, their coordinated benefits are calculated, and the turns with benefits greater than zero are screened out as coordination candidates.

[0065] First, for each turn, if its demand flow rate DR(T) is greater than the actual flow rate FR(T), it is determined that the turn is in an overflow state and cannot participate in the green wave coordination. The determination condition for the overflow turn is as follows: DR(T)>FR(T) Where: DR(T) is the demand flow rate of the turn (vehicles / hour); FR(T) is the actual flow rate of the turn (vehicles / hour).

[0066] If the turn is in an overflow state, the turn is removed from the coordination candidate set, and the remaining non-overflowing turns form a new coordination candidate set.

[0067] Next, for each turn in the coordination candidate set, its coordination benefit R coor (T) is calculated. The calculation formula for the coordination benefit is as follows: Where: R coor (T) is the coordination benefit of the turn; FR(T) is the passing capacity of the turn in the optimal single intersection plan (vehicles / hour); W coor (T) is the proportion of the coordinated flow of the turn (dimensionless value); FR(I) is the total passing capacity of the intersection in the optimal single intersection plan (vehicles / hour); N ph is the number of phases in the intersection signal cycle.

[0068] After calculating the coordination benefit of each turn, the turns with benefits greater than zero are screened out as the final coordination candidate set. These coordinated candidate turns have good coordination benefits and can achieve higher passing efficiency in the green wave coordination plan.

[0069] Finally, through screening and optimization, all turns with positive coordination benefits are retained as candidates for the final coordination plan. The coordination benefits of these turns help improve traffic flow, optimize signal timing, achieve green wave passing, and enhance the passing capacity of intersections.

[0070] For step S5, in this step, the coordination path is extended through the breadth-first search algorithm (BFS) to form a signal coordination trunk line and optimize the signal timing plan. The specific steps are as follows: Step1: Initialize the new trunk line. The initialization process includes the following: 1. From the candidate turn set TurnSet valid select the turn Turn max with the largest coordination benefit as the starting point of the trunk line and add it to the turn set TurnSet expand to be expanded.

[0071] 2. Assign a unique identifier Corr id to the current trunk line.

[0072] 3. Initialize the intersection relationship field INTER of the trunk line to null, indicating that the current trunk line does not intersect with other trunk lines.

[0073] Step2: Start the trunk line expansion process: 2.1. Select any turn Turn expand from the turn set TurnSet current .

[0074] 2.2. Perform a deadlock loop judgment on Turn current . If the following conditions are met, discard Turn current and return to step 2.1: The current trunk line Corr id has already intersected with other trunk lines; and Turn current belongs to the coordinated turns of other trunk lines.

[0075] 2.3. Add Turn current to the current trunk line and mark it as the trunk line coordinated turn Turn coor .

[0076] 2.4. If Turn current intersects with other trunk lines Corr i ′ d i INTER = Corr i ′ d where: Corr id is the identifier of the current main line; Corr i ′ d are the identifiers of the intersecting main lines; INTER is the intersection relationship field, representing the intersection of the current main line and other main lines.

[0077] 2.5. Turn upstream to Turn current and downstream to Turn up are extended, and Turn down and Turn up and Turn down are added to the set TurnSet to be extended expand .

[0078] 2.6. Remove all the turns in the stage where Turn valid is located from the candidate turn set TurnSet current .

[0079] 2.7. Repeat steps 2.1 to 2.7 until TurnSet expand is empty, and the generation of the current main line is completed.

[0080] Step 3: Store the generated main line Corr id into the main line set. If the candidate turn set TurnSet valid is not empty, return to Step 1 to generate the next main line; otherwise, terminate the process.

[0081] Through this step, the process of generating signal - coordinated main lines based on the breadth - first search algorithm can be realized, optimizing the signal timing at intersections and improving the coordination and traffic flow efficiency.

[0082] For step S6, this step divides the signal control units according to the topological relationship of the main lines. The signal control unit is a set of intersections that can independently perform green - wave coordination. The types of signal control units include: single - point signal control unit, main - line signal control unit, and area signal control unit. The specific steps are as follows: First, define the types of signal control units. The signal control units are divided according to the topological relationship of the main lines, mainly including the following types: Single - point signal control unit: During the generation of the main line, the intersections that are not assigned to any main line are single - point signal control units. That is, these intersections do not participate in the coordination of any main line and are controlled by signals independently.

[0083] Arterial signal control unit: If a certain arterial does not intersect with other arterials, then this arterial forms an independent arterial signal control unit. This type of signal control unit contains an arterial that does not intersect with other arterials and can independently perform green wave coordination.

[0084] Area signal control unit: When multiple arterials intersect to form an area, multiple arterials form an area signal control unit. Due to the intersection relationship between arterials, the area signal control unit may contain multiple intersecting arterials, and these arterials cannot perform green wave coordination as independent signal control units. This area signal control unit needs to be merged according to the intersection situation of the arterials to form a coordinated signal control area.

[0085] Next, merge the arterials according to the intersection situation to form an area signal control unit. The specific operation steps are as follows: Record of intersection relationship of arterials: According to the INTER attribute of each arterial, record the intersection relationship between arterials. The INTER attribute indicates the intersection situation of an arterial with other arterials. If two arterials have an intersection point, record this intersection information in their intersection relationship.

[0086] Merge of arterials: When there is an intersection relationship between arterials, according to the information of the INTER attribute, merge these intersecting arterials into an area signal control unit. The area signal control unit formed by multiple intersecting arterials can coordinate its signal cycle and perform green wave control.

[0087] Division of signal control units: After merging, the remaining non-intersecting arterials continue to be used as arterial signal control units, and individual intersections are divided into single-point signal control units. The finally formed signal control units include: single-point signal control units, arterial signal control units, and area signal control units.

[0088] As Figure 2 shown, according to the intersection relationship recorded by the INTER attribute of the arterials, associate the arterials to generate an area.

[0089] Through this step, the intersection set can be divided into different types of signal control units according to the topological relationship of the arterials. Each signal control unit independently performs green wave coordination according to its type, thereby improving the overall traffic flow.

[0090] For step S7, this step is used to determine the coordination direction and phase difference of each intersection within the signal control unit, and calculate the phase difference based on the travel time and queue length of the coordinated turns. The specific steps are as follows: First, determine the coordinated turns. For the intersections within the signal control unit, select the coordinated turns of the arterial intersections as the area coordinated turns. If an intersection belongs to two or more intersecting arterials, select the coordinated turns of the arterial with a higher priority as the main coordinated turns of the core coordinated intersection. By default, the arterial generated first has a higher priority, that is, the arterial with a smaller arterial number has a higher priority.

[0091] Next, define the coordination phase. The coordination turn to the current signal control phase is defined as the coordination phase of this intersection. This phase corresponds to the coordinated signal phase in the intersection signal control plan, indicating the coordinated signal control plan for this intersection.

[0092] Then, calculate the coordination phase difference. The coordination phase difference is the phase difference of the coordination turn, reflecting the phase difference between different turns. The calculation formula is as follows: Where: Δφ is the phase difference of the coordination turn (seconds); L turn is the length of the turning section (meters); V is the average driving speed of the turning section (meters / second); T ph is the green light time of this phase (seconds); W coor (T) is the proportion of the coordinated flow of the turn (dimensionless value).

[0093] The calculation of the coordination phase difference is based on the length of the turning section, the driving speed, the green light time, and the proportion of the coordinated flow of this turn. This phase difference can be used to adjust the signal timing to ensure signal coordination and green wave passing between different signal control units.

[0094] Through this step, the signal coordination of each intersection within the signal control unit can be optimized, the traffic conflicts between different intersections can be reduced, and the traffic smoothness can be improved.

[0095] Generally speaking, the present invention proposes a method for dividing the urban mesoscopic signal control unit based on breadth-first search, aiming to optimize urban traffic signal control and improve traffic smoothness. The following is the overall process of this method: 1. Obtain traffic information: Collect the traffic demand, upstream and downstream topological relationships, signal configuration information, and historical traffic flow data of each intersection in the road network. Collect data through fixed detection equipment, floating car data, and manual surveys, and preprocess it into traffic characteristics that can be used for subsequent analysis.

[0096] 2. Calculate the optimal signal timing plan for intersections: According to the traffic demand, signal control phase, and road capacity of each intersection, calculate the optimal signal cycle of the intersection. Based on factors such as the number of phases, phase switching loss time, and phase saturation, determine the signal cycle of the intersection and allocate the green ratio to optimize the signal control strategy.

[0097] 3. Adjust the signal timing of intersections to avoid downstream overflow: Judge whether there is an overflow risk by calculating the queuing length of the downstream section. If an overflow occurs in the downstream section, adjust the signal timing of the intersection based on the available lane length and the maximum green light capacity to reduce the overflow pressure downstream and optimize the green wave coordination.

[0098] 4. Calculate the coordination benefits of each intersection and screen the coordination candidates: Calculate the coordination benefits of each intersection and eliminate the overflowing turns. For the non-overflowing turns, calculate their coordination benefits and screen out the turns with benefits greater than zero as the candidate turns for subsequent signal coordination.

[0099] 5. Generate the signal coordination main lines: Use the breadth-first search algorithm to select the one with the maximum coordination benefit from the candidate turns to generate the signal coordination main lines. According to the topological relationship of the main lines, handle the intersections between the main lines to generate independent main lines and regional signal control units. Expand the main lines and merge the main lines according to the intersection relationship to generate regional signal control units.

[0100] 6. Divide the signal control units: Divide the road network into different signal control units according to the topological structure of the main lines. It includes single-point signal control units, main-line signal control units, and regional signal control units. The single-point signal control unit is an independent intersection, the main-line signal control unit is a non-crossing main line, and the regional signal control unit is composed of multiple intersecting main lines.

[0101] 7. Determine the coordination direction and phase difference of the signal control units: Determine the coordinated turns within the signal control unit and calculate the phase difference based on the travel time and queuing length of the turns. The coordinated phase difference is calculated based on the length of the turning section, the section travel speed, and the green light time to ensure signal coordination and green wave passing between different intersections.

[0102] 8. Output the result of the signal control unit division: Finally, output the optimized signal control unit division plan, which provides effective support for urban traffic signal control, ensures the implementation of the green wave coordination plan, and improves traffic fluency.

[0103] Through the method of the present invention, intelligent signal control of each intersection in the urban traffic network can be realized, the distribution of the signal cycle and green light time can be optimized, the passing capacity of the intersection can be improved, traffic congestion can be reduced, and traffic fluency can be enhanced. By reasonably dividing the signal control units, the conflicts between different signal control units can be reduced, the green wave coordination effect can be improved, and ultimately the efficient scheduling and optimization of traffic can be achieved.

[0104] The medium-scale urban signal control unit division device based on breadth-first search described below can be correspondingly referred to the medium-scale urban signal control unit division method based on breadth-first search described above.

[0105] Please refer to the appendixFigure 3 , the present invention also provides an urban mesoscopic signal control unit division device based on breadth-first search, including: A data acquisition module 10, configured to acquire intersection traffic information and calculate relevant traffic flow data; A single intersection signal optimization module 20, configured to calculate the optimal signal timing plan for each intersection; A downstream overflow control module 30, configured to adjust the release time of this intersection based on the downstream traffic capacity; A coordination benefit calculation module 40, configured to calculate the coordination benefits of each turning direction and screen candidate turning directions; A main line generation module 50, configured to expand the coordination path by breadth-first search to form a signal coordination main line; A signal control unit division module 60, configured to divide signal control units; A coordination direction and phase difference calculation module 70, configured to calculate the coordination direction and signal phase difference to achieve green wave coordination control.

[0106] This device can be used to execute the above method, and its principle and technical effects are similar, which will not be elaborated here.

[0107] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for dividing urban mesoscopic signal control units based on breadth search, characterized in that: The following steps are involved: Get multiple intersections and their traffic information in the road network; Calculating an optimal signal timing scheme for each intersection based on the traffic information; Calculate the length of the queue at the downstream section of each intersection and adjust the release time of the intersection based on the remaining traffic capacity downstream; Calculate the coordination benefit of each turn, and select the turns with benefits greater than zero as coordination candidates; Expand the coordination path based on the breadth search algorithm to form a signal coordination trunk line; Divide the signal control unit according to the trunk line topology relationship; The signal phase difference is calculated based on the main coordination direction of each trunk line to optimize the signal timing.

2. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of obtaining multiple intersections in the road network and their traffic information comprises: Obtain intersection traffic demand, intersection upstream and downstream topology, intersection signal control configuration and historical record data; Data fusion is performed with turns as the smallest granularity to generate fields including intersection number, turn number, number of lanes, lane length, signal control stage number, actual intersection cycle, turn green-signal ratio, actual turn flow rate and demand flow rate, upstream and downstream turns, and corresponding flow ratios.

3. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of calculating the optimal signal timing scheme for each intersection based on the traffic information comprises: Calculate the optimal signal cycle based on the number of intersection stages, stage switching loss time and saturation: Among them, C(I) is the optimal signal period, N ph is the number of intersection stages, T loss is the single-stage switching loss time, X(I) is the total saturation of the intersection; For each signal control stage, calculate its saturation: Among them, X ph is the stage saturation, DR(T rep ) is the demand flow rate of the representative lane in the stage, FR(T rep ) is the capacity of the representative lane at the stage, that is, the upper limit of the flow rate that can pass through the lane under the current signal timing scheme, that is, the lane saturation flow rate multiplied by the lane green signal ratio; Based on the stage saturation and the total saturation of the intersection, the green-signal ratio of each stage is allocated according to the principle of balance: Among them, G(T) is the green-to-signal ratio of the stage; According to the green-to-signal ratio and intersection cycle, the green light time of each stage is calculated: T ph =G(T)×(C(I)-N ph ×T loss ) Among them, T ph Green light time for the stage.

4. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of calculating the length of the detention queue at the downstream section of each intersection and adjusting the release time of the intersection based on the downstream remaining traffic capacity includes: According to the flow difference of the downstream turn and the signal cycle, the queue length of the downstream lane is calculated: Among them, L queue (D) is the queue length of the downstream lane, DR(D) is the demand flow rate of the downstream turn, FR(D) is the actual flow rate of the downstream turn, C(D) is the signal cycle of the downstream intersection, L std The standard queuing vehicle spacing; Calculate the capacity of the downstream free lanes based on the total length of the downstream road section, the length of the stranded queue and the safety distance: L free (D)=L c (D)-L queue (D)-S safe Among them, L free (D) is the downstream free lane capacity, L c (D) is the lane length of the downstream section, S safe is the safe distance of the exit channel; if the following conditions are met, it is determined that there is an overflow risk downstream: L free (D)<0 or L queue (D)≥L c (D)-S safe Based on the length of the downstream free lane, calculate the downstream maximum green light capacity, that is, the maximum green light time allowed for this intersection: Among them, G max (D) is the maximum green light capacity of the downstream, T std is the headway time of the intersection saturation flow rate; For downstream turns with overflow risks, adjust the green light time at the corresponding stage of the intersection: T p ′ h =min(G max (D),T ph -S)+S Among them, T p ′ h is the green light time of the corresponding stage at this intersection, T ph is the green light time of the stage, and S is the reserved buffer time; Recalculate the total intersection cycle based on the adjusted phase green light time: C ′ (I)=∑T p ′ h Among them, C ′ (I) Adjusted intersection signal cycle.

5. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of calculating the coordination benefit of each turn and selecting the turn with benefit greater than zero as the coordination candidate includes: For each turn, if its required flow rate is greater than the actual flow rate, the turn is determined to be in an overflow state and does not participate in the green wave coordination; the overflow turns are removed from all turns, and the remaining non-overflow turns form a coordination candidate set; For each candidate turn in the coordination candidate set, calculate its coordination benefit: Among them, FR(T) is the turning capacity in the optimal single intersection solution, W coor (T) is the proportion of coordinated flow in turning, FR(I) is the total traffic capacity of the intersection in the optimal single intersection solution, N ph is the total number of signal stages at the intersection; The turns with coordination benefits greater than zero are retained and enter the final coordination candidate set.

6. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of expanding the coordination path based on the breadth search algorithm to form a signal coordination trunk line includes: Step 1: Initialize the Shinkansen, including: (1) In the candidate turn set TurnSet valid In the process, choose the turn with the largest coordination benefit. max As the starting point of the trunk line, add the turn set to be expanded TurnSet expand ; (2) Assign a unique identifier Corr to the current trunk line id ; (3) Setting the intersection relation field INTER of the trunk line to null indicates that the current trunk line does not intersect with other trunk lines; Step 2: Trunk expansion Step 2.1, from TurnSet expand Select any turn current ; Step 2.2: Turn current Perform coordination access verification. If the following conditions are met, Turn is discarded. current And return to step 2.1: Current Main Line Corr id It has intersected with other trunk lines; And Turn current Intersection with other trunk lines; step2.3, Turn current Join the current trunk line and mark it as the trunk line coordinated turn coor ; step2.4, if Turn current Corr with other trunk lines i ′ d If they intersect, update the current trunk intersection relationship attributes: INTER=Corr i ′ d step2.5, turn current Upstream Turn up and downstream turn down To expand: Turn up and Turn down Add to the set to be expanded TurnSet expand ; Step 2.6, from candidate to set TurnSet valid Remove Turn current All turns in the current stage; step2.7, repeat steps step2.1 to step2.7 until TurnSet expand If it is empty, the current trunk generation is completed; Step 3: Generate the trunk line Corr id Stored in the trunk set, if the candidate turn set TurnSet valid If it is not empty, return to step 1 and generate the next trunk line; otherwise, terminate the process.

7. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of dividing the signal control unit according to the trunk line topology relationship comprises: The signal control unit is divided according to the trunk topology structure, and the signal control unit includes: Single-point signal control unit: independent intersection, not belonging to any trunk line; Trunk signal control unit: a single trunk line without crossing; Regional signal control unit: a control area consisting of multiple cross trunk lines; The trunk lines are merged according to the intersection situation to form a regional signal control unit.

8. The method for dividing city meso-level signal control units based on breadth search according to claim 1, characterized in that: The step of calculating the signal phase difference based on the main coordination direction of each trunk line includes: For the intersections within the signal control unit, the coordinated turn at the trunk intersection is selected as the regional coordinated turn; The signal control phase of the coordinated turn is defined as the coordination phase of the intersection; Based on the travel time and queue length of the coordinated turn, the phase difference is calculated: Among them, L turn is the length of the turning section, V is the average speed of the section, T ph is the green light time of the stage, W coor (T) is the proportion of coordinated flow that is turned.

9. The method for dividing city meso-level signal control units based on breadth search according to claim 8, characterized in that: The step of selecting the coordinated turning at the trunk intersection as the regional coordinated turning for the intersection in the signal control unit includes: If the intersection belongs to two or more intersecting trunk roads, the main coordinated turn is determined by the priority of the trunk road generation order.

10. A device for dividing city mesoscopic signal control units based on breadth search, used to execute the city mesoscopic signal control unit division method based on breadth search according to any one of claims 1 to 9, characterized in that: include: A data acquisition module is used to obtain intersection traffic information and calculate relevant flow data; Single intersection signal optimization module, used to calculate the optimal signal timing plan for each intersection; Downstream overflow control module, used to adjust the release time of this intersection based on downstream traffic capacity; A coordination benefit calculation module is used to calculate the coordination benefit of each turn and screen candidate turns; A trunk generation module, used for expanding the coordination path by using breadth search to form a signal coordination trunk; A signal control unit division module, used to divide the signal control unit; The coordination direction and phase difference calculation module is used to calculate the coordination direction and signal phase difference to achieve green wave coordinated control.

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