Improved NEMA phase control method based on traffic state of physical area of intersection

Abstract

The invention belongs to the technical field of intelligent traffic, and particularly relates to an improved NEMA phase control method based on the traffic state of a physical area of an intersection. Comprising the steps of obtaining intersection channelization data to determine a range region of a physical region, and generating a phase based on a lane flow direction; the abnormal state is judged according to the vehicle operation indexes in the physical area; selecting phases from a phase set formed by taking straight movement and left turning as main control phases to carry out non-conflict phase analysis, and establishing a compatible phase set; on the basis of an NEMA double-loop phase structure, an improved NEMA double-loop phase structure based on the passing state of a physical area is constructed, and green light phase control logics under different passing states are designed in a control system. According to the method, traffic flow passing at the intersection can be flexibly regulated and controlled, the green light phase is switched while an abnormal state occurs in a physical area, phase idle and deadlock states are avoided, and therefore the green light utilization rate and passing efficiency of the intersection are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent transportation, and in particular relates to an improved NEMA phase control method based on the traffic status of a physical area of ​​an intersection. Background Art

[0002] The signal phase design of urban intersections is the basic guarantee for achieving reasonable signal control. There is a complete set of processes and methods from intersection sensing to output signal phase design. The existing traffic signal phase design is aimed at fixed vehicle flow, and signal control is achieved through inherent phase schemes and signal timing methods. It cannot meet the reasonable control under unbalanced and changing traffic, which will cause phase idleness, and cannot be reasonably regulated in the face of abnormal conditions in the physical area, which leads to "deadlock".

[0003] For an intelligent system that can intelligently detect intersection traffic and vehicle operating status within the intersection, what is needed is an adjustable phase solution that can adjust signals in real time based on the acquired traffic status. The existing fixed phase solution and timing method cannot meet the dynamic release requirements of the adjustable phase. Summary of the invention

[0004] The object of the present invention is to provide an improved NEMA phase control method based on the traffic status of the physical area of ​​the intersection, which has solved the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An improved NEMA phase control method based on the traffic status of a physical area of ​​an intersection, the method comprising:

[0007] The physical area of ​​the intersection is the area surrounded by the stop line of the entrance road of the intersection. The intersection channelization data and historical traffic flow data are obtained to determine the scope of the physical area. The lanes and signal light groups of each direction of the four entrance roads of the intersection are analyzed. The control channel is determined based on the analysis results, and the control channel generates a phase based on the lane flow direction.

[0008] The abnormal state is determined based on the running speed of vehicles in the physical area and the interval time of vehicles passing the stop line of the entrance lane.

[0009] Taking straight ahead and left turn as the main control phases, phases are selected from the phase set consisting of all main control phases for non-conflicting phase analysis and a compatible phase set is established.

[0010] Phase sorting is performed based on the NEMA double-ring phase structure, with the north-south direction as the primary ring and the east-west direction as the secondary ring, and the corresponding phases of each flow direction are numbered respectively.

[0011] The first loop phase starts with the north-south left turn phase and ends with the straight phase; the second loop starts with the east-west left turn phase and ends with the straight phase. In order to ensure that the main road and the secondary road do not have the same green light on the signal light group, a partition (grid) is set between the two loops; determine the non-conflicting phases in the phase structure, and use this to perform phase combination.

[0012] When an abnormal state occurs in the one-way release flow, the next phase is switched, and the switched phase needs to be in a non-conflicting state with the phase of the release flow.

[0013] A further improvement scheme is to combine the positive sequence NEMA phase and the reverse sequence NEMA phase into one phase structure in order to ensure that the release is always in a non-conflicting phase and is not limited to the combination between the four phases; in this way, after a NEMA phase ends, the last phase will be combined with the next phase in a non-conflicting phase.

[0014] To further improve the solution, the east-west straight phase is used as the first phase for phase switching, which can ensure that the released traffic is in a non-conflicting state when the phase is released in one direction.

[0015] Determine the phase switching rule, release the east-west straight phase, and if one flow direction is abnormal, switch the abnormal flow direction phase to the south or north left turn phase; if both are abnormal, switch to the north-south left turn phase at the same time.

[0016] A further improvement plan is to set the gates between the two rings as invisible barriers, and the gates between the phases as adjustable areas. The green light duration of each phase can be extended or shortened, but the green light time shall not be less than the minimum green light time and shall not exceed the maximum green light time.

[0017] When the released flow direction is detained or in other abnormal conditions, the green light time of the flow direction is extended to the maximum green light time. The green light time can be extended in the first ring. If the released flow direction has not reached the maximum green light time, but its non-conflicting flow phase switching is completed, and the next switching phase is its conflicting phase, the release of the flow direction is stopped.

[0018] Design the green light phase control logic under different traffic conditions in the control system, re-detect the traffic status of the physical area after a cycle ends, and repeat the above steps.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] According to the traffic status of the physical area, the present invention proposes a more flexible and non-conflicting theory-compliant improved NEMA strategy, and analyzes traffic flow from the perspective of the interrupted state and the abnormal state that causes "deadlock". For the first time, the phase design is carried out for the traffic status of the physical area, and the phase switching method and non-conflicting flow combination under different abnormal states are considered, which avoids the "deadlock" caused by the lack of traffic police control after the traffic accident occurs and solves the problem of uneven traffic flow during peak and flat hours. The phase control method is adapted to the intelligent sensing system of the intersection, which can improve the traffic efficiency of the intersection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the overall flow chart of the present invention;

[0022] Figure 2 is the intersection channelization diagram of the present invention;

[0023] Figure 3 It is the NEMA double ring phase numbering diagram of the present invention;

[0024] Figure 4 is a non-conflicting phase diagram of the present invention;

[0025] Figure 5 It is the improved NEMA phase structure diagram of the present invention;

[0026] Figure 6 It is a phase switching law diagram of the present invention;

[0027] Figure 7 It is a time length control phase structure diagram of the present invention;

[0028] Figure 8 is a phase control logic diagram of the present invention; DETAILED DESCRIPTION

[0029] S101: The intersection physical area is the area surrounded by the entrance road stop line of the intersection, and the intersection channelization data and historical traffic flow data are obtained, such as Figure 2 Determine the range of the physical area, analyze the lanes and signal light groups of each direction of the four entrances of the intersection, determine the control channel based on the analysis results, and generate the phase of the control channel based on the lane flow direction.

[0030] S102: Determine the abnormal state according to the running speed of the vehicles in the physical area and the interval time of the vehicles passing the stop line of the entrance lane. The criteria for judging the interrupted flow state: if no vehicle passes within 5 seconds after the vehicle passes the stop line, the flow is considered to be interrupted; the criteria for judging the detained state: if the vehicle speed in the physical area is close to 0 and the duration exceeds 5 seconds when the vehicle flow is released on the green light, the flow is considered to be detained; the criteria for judging the conflict or collision: if two or more vehicles in the released flow slow down or stop at the intersection of the trajectories, the flow is considered to have a conflict or collision.

[0031] S103: Taking straight ahead and left turn as main control phases, selecting phases from a phase set consisting of all main control phases to perform non-conflicting phase analysis and establish a compatible phase set.

[0032] In order to effectively obtain the non-conflicting phases of the intersection, each phase of the intersection is represented by the letter p, and the set P of each phase p in the intersection is:

[0033] P={pp=1,2,3,...,v,...,n}

[0034] Among them, P is the set of phases p in the intersection;

[0035] p,v——specific signal phases in the intersection;

[0036] n——The number of signal phases.

[0037] If the driving trajectories of any two phases in the intersection do not intersect, the two phases are considered to be non-conflicting phases, otherwise, the two phases are considered to be in a conflicting relationship.

[0038] The intersection phase conflict matrix P is an n-order square matrix:

[0039]

[0040] Where: pv ——Phase conflict elements

[0041] In order to clearly represent the conflict state of each phase, the phase conflict element u pv Defined as 0 or 1, if u pv =1, the phases p and v are considered to be conflicting phases, otherwise, the phases p and v are considered to be compatible.

[0042]

[0043] Since the phase conflict relationship at the intersection is symmetrical, when phase p conflicts with phase v, phase v also conflicts with phase p, that is, u pv =u vp At the same time, the phase relationship at the intersection is also reflexive, and the phase itself is compatible, not conflicting, that is, u pp =u vv =0.

[0044] by Figure 3 For example, the phase set P of the intersection is {1, 2, ..., 8}, so the phase conflict matrix U can be obtained as:

[0045]

[0046] S104: Phase sorting is performed based on the NEMA double-ring phase structure, with the north-south direction as the primary ring and the east-west direction as the secondary ring, and the corresponding phases of each flow direction are numbered respectively.

[0047] The first loop phase starts with the north-south left turn phase and ends with the straight phase; the second loop phase starts with the east-west left turn phase and ends with the straight phase. In order to ensure that the main road and the secondary road do not have the same green light on the signal light group, a partition (grid) is set between the two loops. Determine the non-conflicting phases in the phase structure to perform phase combination.

[0048] Figure 4 In (a), the second and third phases (2,7) and (3,6) are non-conflicting merging phases. When the straight-moving traffic 6 is interrupted, the next phase can be switched to the left-turn phase to release the left-turning traffic 7. Similarly, when the straight-moving traffic 2 is interrupted, the next phase can be switched to the left-turn phase to release the left-turning traffic 3. Figure 4 The third and fourth phases (3,8)(4,7) in (b) are non-conflicting phases. When traffic flow 3 or 7 is interrupted, traffic flow 8 or 4 can be released to meet the non-conflicting traffic release requirement after the interruption.

[0049] To further improve the solution, in order to ensure that the release is always in a non-conflicting phase, it is not limited to the combination between the four phases. The positive sequence NEMA phase and the reverse sequence NEMA phase are combined into a phase structure. In this way, after a NEMA phase ends, the last phase can also be combined with the next phase in a non-conflicting phase. The east-west straight phase is used as the first phase for phase switching, which can ensure that the released traffic is in a non-conflicting state when the phase is released in one direction. Figure 5 shown.

[0050] Determine the phase switching rule, release the east-west straight phase, and if one flow direction is abnormal, switch the abnormal flow direction phase to the south or north left turn phase; if both are abnormal, switch to the north-south left turn phase at the same time. The overall switching rule is as follows Figure 6 In order to describe the process more clearly, the determination process of the interruption state and the phase switching conditions are defined. The specific steps are as follows:

[0051] Step 1: Define the traffic flow direction as S n ,{n|1,2,3,···,8}.

[0052] Step 2: If another vehicle passes the stop line within 5 seconds after the front vehicle passes the physical zone entrance stop line, T n ≤5s, it is considered that the flow direction has not been interrupted, and S n =0 means: No other vehicle passes the stop line T within 5 seconds after the front vehicle passes the physical zone entrance stop line n≥5s, that is, the front vehicle leaves, it is considered that the flow direction is interrupted, and S n =1 indicates.

[0053] Step 3: Taking the east-west straight flow as an example, when T4∨T8≥5s, S4∨S8=1, and the merging non-conflicting S1 or S5 of the interrupted traffic flow is switched; when T4∧T8≥5s, S4∧S8=1, the two-way traffic flow is prohibited and switched to the next phase, that is, the traffic flow S1&S5 is released.

[0054] Step 4: Repeat Step 3 until the phase switching completes a cycle.

[0055] A further improvement is to set the gates between the two rings as invisible barriers and the gates between the phases as adjustable areas, so that the green light duration of each phase can be extended or shortened, but the green light duration is not less than the minimum green light duration and does not exceed the maximum green light duration. Figure 7 shown.

[0056] When a released flow direction is detained or in other abnormal conditions, the green light time of the flow direction is extended to the maximum green light time. The green light time can be extended in the first ring. If the released flow direction has not reached the maximum green light time, but its non-conflicting flow direction phase switching is completed, and the next switching phase is its conflicting phase, the release of the flow direction is stopped.

[0057] The phase control steps after obtaining the sensing results are as follows:

[0058] Step 1: Define the traffic flow direction as S n ,{n1,2,3,···,8}, when it is detected that there is a vehicle staying in this flow direction for a duration of T' n ≥5s, it is determined that the flow direction is trapped, S n =1, otherwise S n =0.

[0059] Step 2: Determine S n =1, if n≤3, then extend the green light duration g n =g max , in the opposite direction, the green light duration is g n+4 After reaching the normal value, S is prohibited n+4 , allowing its non-conflicting flow to S n+5 ; If n = 4, extend the green light duration g4 = g max , prohibit S8, release non-conflicting flow S1; if n>4, extend the green light duration g n =g max , the green light duration in the opposite direction g n-4 After reaching the normal value, S is prohibited n-4 , allowing its non-conflicting flow to S n-3 .

[0060] Step 3: Determine S n =0, the phase is switched normally according to the signal timing.

[0061] S105: The green light phase control logic of the induction control system is as follows Figure 8 As shown, the phase switching system can obtain the traffic status of the physical area according to the induction control, and select the corresponding phase for switching after determining the current traffic status, thereby realizing dynamic and humanized regulation.

Claims

1. An improved NEMA phase control method based on the traffic status of the physical area of ​​the intersection, characterized in that: The method comprises the following steps: S1: Obtain intersection channelization data to determine the range area of ​​the physical zone and generate phases based on lane flow directions; S2: judging the abnormal state of vehicles according to the running speed of vehicles in the physical area and the interval time of vehicles passing through the stop line of the entrance lane; S3: Selecting phases from a phase set consisting of going straight and turning left as main control phases to perform non-conflicting phase analysis and establish a compatible phase set; S4: Based on the NEMA double-ring phase structure, the phase structure is improved based on the traffic status in the physical zone; S5: Design green light phase control logic under different traffic conditions in the control system, re-detect the traffic status of the physical area after a cycle, and release it according to the green light phase control logic.

2. The method according to claim 1, characterized in that The obtaining of intersection channelization data to determine the range of the physical area includes: Obtain intersection channelization data, including: the number of lanes at the intersection and the number of lanes in each flow direction; Determine the scope of the physical zone, where the physical zone is the area surrounded by the entrance lane stop line of the intersection.

3. The method according to claim 1, characterized in that The generating phase based on lane flow direction includes: According to the lane flow direction of the intersection, the corresponding left turn, straight and right turn phases are matched, and the phases are generated according to the lane flow direction.

4. The method according to claim 1, characterized in that The method of judging the abnormal state of a vehicle according to the running speed of the vehicle in the physical area and the interval time of the vehicle passing through the stop line of the entrance lane includes: Physical zone interruption state judgment standard: define the traffic flow direction as S n ,{n|1,2,3,···,8}, if another vehicle passes the stop line within 5 seconds after the front vehicle passes the physical zone entrance stop line, T n ≤5s, it is considered that the flow direction has not been interrupted, and S n =0 means: No other vehicle passes the stop line T within 5 seconds after the front vehicle passes the physical zone entrance stop line n ≥5s, if the front vehicle leaves, it is considered that the flow is interrupted, and S n =1 means; Physical zone retention status judgment standard: define the traffic flow direction as S n ,{n|1,2,3,···,8}, when it is detected that there is a vehicle staying in this flow direction for a duration of T' n ≥5s, it is determined that the flow direction is trapped, S n =1, otherwise S n =0; Physical zone conflict or collision judgment criteria: When the physical zone release flow shows that vehicles continue to decelerate or two or more vehicles stop within the conflict range, the vehicles are deemed to have conflicted or collided.

5. The method according to claim 1, characterized in that The step of selecting a phase from a phase set consisting of going straight and turning left as main control phases to perform non-conflicting phase analysis and establish a compatible phase set includes: Each phase of the intersection is represented by the letter p, then the phase set is P, and the phase non-conflict matrix U is constructed.

6. The method according to claim 1, characterized in that The phase structure is improved based on the NEMA double-ring phase structure and the traffic status in the physical area, including: Improvements based on the interruption state include: in order to ensure that the release is always in a non-conflicting phase, not limited to the combination between four phases, the positive sequence NEMA phase and the reverse sequence NEMA phase are combined into a phase structure; so that after a NEMA phase ends, the last phase will also be combined with the next phase in a non-conflicting phase; the east-west straight phase is used as the first phase for phase switching, which will ensure that the released traffic is in a non-conflicting state when the phase is released in one direction; Improvements are made based on the abnormal state that causes 'deadlock': the gates between the two rings are set as adjustable areas, and the green light duration of each phase can be extended or shortened, but the green light time is not less than the minimum green light time and does not exceed the maximum green light time.

7. The method according to claim 1, characterized in that The green light phase control logic under different traffic conditions is designed in the control system, including: For the interrupted flow state, it includes: taking the east-west straight flow as an example, when T4∨T8≥5s, S4∨S8=1, and the interrupted flow of vehicles is switched to the non-conflicting merge S1 or S5; when T4∧T8≥5s, S4∧S8=1, the interrupted two-way traffic is prohibited, and the next phase is switched, that is, the traffic S1&S5 is released; For abnormal conditions such as detention, including: Determine S n =1, if n≤3, then extend the green light duration g n =g max , in the opposite direction, the green light duration is g n+4 After reaching the normal value, S is prohibited n+4 , allowing its non-conflicting flow to S n+5 ; If n = 4, extend the green light duration g4 = g max , prohibit S8, release non-conflicting flow S1; if n>4, extend the green light duration g n =g max , the green light duration in the opposite direction g n-4 After reaching the normal value, S is prohibited n-4 , allowing its non-conflicting flow to S n-3 .

Images