KR102017385B1 - Adaptive traffic light control method in road intersection - Google Patents

Abstract

In the adaptive intersection traffic signal control method, a signal control device obtains traffic information related to a traffic situation of a target intersection, and the signal controller controls the traffic signal of the target intersection at a predetermined time interval using the traffic information. Determining a mode; when the signal controller determines the mode as the first mode, controlling traffic at the target intersection based on a combination of traffic signals at the target intersection in the time interval; And controlling the traffic at the target intersection based on the flow of the vehicle entering the specific direction at the target intersection and advancing in the specific direction when the mode is determined as the second mode, at the target intersection during the time interval. At least once in each possible direction of the signal, Group is a traffic signal combination contains the green light to the direction in at least one process.

Description

Adaptive intersection traffic signal control method {ADAPTIVE TRAFFIC LIGHT CONTROL METHOD IN ROAD INTERSECTION}

The technology described below relates to a method of controlling a traffic signal at an intersection.

Dense cars in urban areas cause traffic jams, accidents, energy consumption and environmental problems. Therefore, research into a technology for controlling vehicle traffic (traffic) is in progress. The ITS (intelligent transportation system) typically monitors road conditions using camera images and sensing data, and delivers certain information to individual vehicles.

Vehicle traffic control technology has been studied in two directions. One study is to collect traffic data using vehicle communication (VANET, etc.) and to analyze the data to control the moving path of the vehicle. The other study is to identify road conditions and adaptively control traffic signals in real time.

C. Hu and Y. Wang, "A novel intelligent traffic light control scheme," in Grid and Cooperative Computing (GCC), 9th International Conference on, pp. 372-376, 2010.

Most adaptive traffic light control (ATLC) has limitations in optimizing traffic signals without considering the information of surrounding intersections. The technique described below is intended to provide the maximum traffic flow in consideration of the traffic conditions of the intersection and the surrounding intersection at one intersection.

In the adaptive intersection traffic signal control method, a signal control device obtains traffic information related to a traffic situation of a target intersection, and the signal controller controls the traffic signal of the target intersection at a predetermined time interval using the traffic information. Determining a mode; when the signal controller determines the mode as the first mode, controlling traffic at the target intersection based on a combination of traffic signals at the target intersection in the time interval; Controlling the traffic at the target intersection based on the flow of the vehicle entering the specific direction at the target intersection and advancing in the specific direction when the mode is determined as the second mode. At least one signal in each direction that can travel at the target intersection occurs during the time interval, and the traffic signal combination includes a green signal for at least one travel direction.

The technology described below adaptively controls the order of traffic signals and the length of a specific signal section at one intersection to have an optimal traffic flow at that intersection.

1 is an example of a signal control system at an intersection.
2 is an example of a road network.
3 illustrates an example of possible signals at an intersection.
4 is an example of a traffic signal at an intersection.
5 is an example of a traffic signal cycle.
6 illustrates an example of a process of monitoring road conditions of intersections in consideration of neighboring intersections.
7 is an example for explaining a mode conversion for traffic signal control.
8 is an example of four cases for controlling a traffic signal in the CAP mode.

The following description may be made in various ways and have a variety of embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the technology described below to specific embodiments, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the technology described below.

The terms first, second, A, B, etc. may be used to describe various components, but the components are not limited by the terms, but merely for distinguishing one component from other components. Only used as For example, the first component may be referred to as the second component, and similarly, the second component may be referred to as the first component without departing from the scope of the technology described below. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is to be understood that the present invention means that there is a part or a combination thereof, and does not exclude the presence or addition possibility of one or more other features or numbers, step operation components, parts or combinations thereof.

Prior to the detailed description of the drawings, it is to be clear that the division of the components in the present specification is only divided by the main function of each component. That is, two or more components to be described below may be combined into one component, or one component may be provided divided into two or more for each function. Each of the components to be described below may additionally perform some or all of the functions of other components in addition to the main functions of the components, and some of the main functions of each of the components are different. Of course, it may be carried out exclusively by.

In addition, in carrying out the method or operation method, each process constituting the method may occur differently from the stated order unless the context clearly indicates a specific order. That is, each process may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

The technique described below maximizes vehicle traffic by taking into account the traffic conditions of an intersection at one intersection. Generally, graph data structures are used to analyze traffic flows on roads. In G = (V, E), V is an intersection, and E is a road connecting the intersections.

The technique described below adaptively controls the order of traffic signals and the length of the signal sections in order to reduce the green signal section of the vehicle density and idle state at one intersection. Basically, the techniques described below increase traffic throughput and reduce latency at intersections. Furthermore, the techniques described below dynamically adjust traffic throughput and latency in consideration of the degree of road congestion at particular intersections and surrounding intersections.

In the following description, a device for controlling the order or the section length of the traffic signal is called a signal control device. Assume that the signal control device controls the traffic signal control at a particular intersection i _c . The signal controller may be a signal controller disposed at an intersection. Alternatively, the control device may be a controller in a control center that controls the flow of the entire road.

1 is an example of a signal control system 100 at an intersection. The signal control system 100 includes signal control devices 120A and 120B, RSUs 150A and 150B, and a control center 180. 1 illustrates a case where the signal controllers are the signal controllers 120A and 120B disposed at the intersection. The RSUs 150A and 150B correspond to roadside APs that communicate with the vehicles 110A, 110B and 110C. The RSUs 150A and 150B may also communicate with the signal control devices 120A and 120B. The RSUs 150A and 150B and the vehicles 110A, 110B and 110C may exchange information using various vehicle wireless communication techniques. The RSUs 150A and 150B and the signal controllers 120A and 120B may exchange information by wire or wireless communication. The RSUs 150A and 150B may exchange information with the control center 180 through wireless communication such as wired or mobile communication. In the following description, the communication technique used in the signal control system 100 is not limited to a specific communication technique.

The vehicle 110A transmits driving information such as a location, a destination, a moving direction, a moving speed, and the like to the RSU 150A (V2I communication). Furthermore, the vehicle 110A may transmit the surrounding information, traffic conditions, and the like acquired by the camera to the RSU 150A. The vehicle 110B may transmit driving information, traffic conditions, and the like to the vehicle 110C (V2V communication). The vehicle 110C may transmit its information and the information transmitted by the vehicle 110B to the RSU 150A. The signal control device 120A may obtain information about a vehicle located at an intersection through the RSUs 150A and 150B. The signal control apparatus 120A may acquire information such as the number of vehicles located on a specific road at an intersection, the speed of the vehicle, the entry path of each vehicle, the entry route of each vehicle, and the like. Although the signal control device 120A is shown as receiving information through the RSU in FIG. 1, in some cases, the signal control device 120A may directly receive information from the vehicle or the control center 180.

Furthermore, the signal control device 120A may receive information from another signal control device 120B located at a peripheral intersection. The signal controller 120A may obtain information (a number of vehicles, a vehicle speed, a target route of the vehicle, etc.) of the vehicle entering the intersection of the signal controller 120A at the peripheral intersection.

Meanwhile, the signal controller 120A may receive information collected by the control center 180 from the control center 180. The control center 180 may transmit information such as vehicle information of the entire road traffic network, traffic conditions of neighboring intersections, and the like to the signal controller 120A. In the following description, it is assumed that the signal control apparatus 120A can obtain information about the traffic situation of the surrounding intersection and the traffic condition of the intersection in charge thereof through at least one of various paths. Through this, the signal control apparatus 120A can grasp the congestion degree of the road, the number of vehicles on a specific road, the waiting time of the vehicle, and the like. In addition, since the signal control device 120A is a device for controlling intersection traffic signals, it is assumed that information about the traffic signals (such as the order of traffic signals and the length of a specific signal) of the intersection is known in advance.

It is assumed that the signal controller controls the intersection i _c signal. The signal control device needs information indicating the traffic conditions at the intersection. For example, the information is required, such as latency, traffic density of the road to reach the intersection i _c for all directions each possible expansion in the number of vehicles passing the intersection, i _c, the number of vehicles arriving at the intersection i _c, the intersection i _c Do. It is assumed that the signal controller collects traffic conditions at the intersection through V2V, V2I and / or I2I communication.

Briefly signal control apparatus to increase the number of vehicles passing the intersection, i _c, and controls the signal in the direction of reducing the wait time for the vehicle at the intersection i _c. The signal controller controls the signal in a direction that balances the number of vehicles passing through the intersection i _c with the average waiting time of the vehicle. The signal controller controls signals in two directions. (i) If a road near (intersection) i _c (connected) has a low traffic level (vehicle density), the signal control focuses on reducing the invalid green signal interval to reduce the waiting time of the vehicle passing through intersection i _c . (ii) On the contrary, if the road near the intersection i _c (connected) has a high degree of traffic, the signal controller focuses on mitigating the high traffic.

The signal controller basically adjusts the length of the signal section. For example, the signal controller may reduce the length of the left turn signal section in a specific direction and increase the length of the straight signal section in a specific direction. Furthermore, the signal control device can control the order of signals for each traveling direction that can proceed at the corresponding intersection. For example, the signal control apparatus changes the sequence of signals "go straight in the first direction → left turn in the first direction → go straight in the second direction → left turn in the second direction" to "go straight in the first direction → go straight in the second direction → Left turn in the direction → left turn in the first direction ". The signal controller may control the section length of the specific signal together with the order of the signals.

The signal controller dynamically adjusts traffic throughput and waiting time in consideration of road congestion at the current intersection i _c and surrounding intersections.

The signal control device controls the signal at the intersection i _c to maximize traffic flow. Signal control device, taking into account traffic conditions in and around the intersection i _c intersection in real time, and controls the signal of the intersection i _c.

2 is an example of a road network. For convenience of description, FIG. 2 illustrates a grid network.

The signal control device controls the signal at the intersection i _c . Intersection i _c has another intersection nearby. Peripheral intersections that the signal controller should consider are those that affect the traffic flow at intersection i _c . In FIG. 2, the peripheral intersections of the intersections i _c are four intersections directly connected by roads. The four peripheral intersections are i _c ^N , i _c ^S , i _c ^W and i _c ^E. Four peripheral intersections are intersections located at north (N), south (S), west (W) and east (E), respectively, based on the intersection i _c in FIG. 2. There may also be different types of intersections than FIG. 2. However, for convenience of description, the following description will be made based on a crossroad intersection as shown in FIG. 2.

Explaining the graph G = (V, E), the intersection where the signal controller should consider traffic conditions for signal control is V = {i _c , i _c ^N , i _c ^S , i _c ^W , i _c ^E } . E is the road connecting the intersection. Road which the vehicle inlet, based on the intersection _c i is a four road leading to the intersection i _c of any of the four surrounding intersections. Also, the road from which the vehicle flows out based on the intersection i _c is four roads leading to four neighboring intersections.

The flow of the vehicle is called F _i . F _i = {src _i , dst _i , n _i } src _i is the intersection at which the vehicle arriving at intersection i _c departed. dst _i is the intersection at which the vehicle reaches through intersection i _c . n _i is the number of vehicles along the path from src _i to dst _i .

Specific vehicle flows can be defined as F (i _c ^b , i _c ^a ). a, b ∈ {N, S, W, E}. F (i _c ^b , i _c ^a ) can be simplified and written as F _ba . That is the vehicle flow is a flow through the i _c i _c ^b at the intersection reaches the intersection i _c ^a. For example, if the vehicle is an intersection i _c ^S direction and enters the intersection i _c i _c ^N intersection toward the stay on, the vehicle flow may be denoted as F ^(S i _c, i _c ^N) or simply F _SN.

It also defines road segments that connect intersections. Mark the road segment S. There are two types of road segments based on intersection i _c . One is a road segment entering another intersection i _c at another intersection. The other is a road segment that proceeds from intersection i _c to another intersection. The entering road segment may be represented as S (i _c ^x , i _c ). The advancing road segment may be expressed as S (i _c , i _c ^x ). Where x ∈ {N, S, W, E}.

3 shows an example of possible vehicle flows at an intersection. 3 shows the type of vehicle flow passing (entering) at the intersection i _c . At an intersection where four roads meet, the vehicle can proceed to turn left (GL), go straight (GS) and turn right (GR). In FIG. 3, the vertical axis represents the starting direction (starting point) at which the vehicle starts at the intersection i _c . There are three basic traffic flows for each vehicle flow. Therefore, there are 12 vehicle flows in the intersection of the road network as shown in FIG. All vehicle flows entering the intersection i _c are named S _{in_flow} . N _{in_flow} is | S _{in_flow} | N _{in_flow} is the number of vehicle flows, which is 12 in FIG. 3.

4 is an example of a traffic signal at an intersection. FIG. 4 (a) illustrates an example of the types of traffic signals possible at an intersection, and FIG. 4 (b) illustrates an example of a traffic signal according to a traveling direction at an intersection. Here, the traffic signal means a green signal that the vehicle can proceed in the corresponding direction. In FIG. 4A, the vertical axis represents the starting direction in which the vehicle starts at the intersection i _c . For example, in FIG. 4B, if the vehicle has entered from i _c ^S , the starting direction of the vehicle is S. FIG. In FIG. 4A, the horizontal axis is an example of a traffic signal according to a vehicle traveling direction. Referring to FIG. 4 (a), 20 different types of traffic signals are shown at an intersection. Of course, there may be logically different types of traffic signals, but in general the straight (GS), left turn (GL), right turn (GR), left turn and straight (GL & GS), right turn and just before (GS & GR) are common. Corresponds to the signal FIG. 4 (b) exemplarily shows 15 different traffic signals according to the traveling direction at the actual intersection. Hereinafter, signals that may occur at a specific intersection are called candidate traffic signals.

Analyzed Parameters

First, the parameters analyzed by the signal controller for traffic signal control will be described. The signal controller monitors the traffic conditions around the intersection and determines the traffic congestion. The criteria for determining the traffic congestion will be described later. The signal controller controls the section length of the traffic signal based on the traffic congestion degree. Furthermore, the signal control apparatus may control the order of traffic signals to be used among the candidate traffic signals and the section length of each signal. First, signals or sections controlled by the signal control apparatus will be described.

CYC _t means the traffic signal cycle at which the green signal occurs at least once for all possible vehicle flows F _ba at the intersection. Logically, there may be more than one green signal interval for the same vehicle flow in one CYC _t .

ph: Refers to a combination of traffic signals that can occur at an intersection at a particular point in time. The traffic signal combination includes at least one traffic signal. The traffic signal combination includes at least one traffic signal capable of proceeding without collision by vehicles entering the same or different directions at the same time.

dur _t (ph): The length of the interval where the green signal occurs for any one ph in a specific CYC _t .

dur (CYC _t ): means the length of the entire interval of CYC _t . This is equal to the sum of dur _t (ph) for all phs present in the period. On the other hand, dur (CYC _t ) is the longest time a vehicle arrives at intersection i _c to wait for a green signal. The signal controller can adjust dur (CYC _t ) to solve traffic congestion. This means adjusting the length of at least one of the plurality of phs appearing in CYC _t .

PH (CYC _t ): This is the order (list) of phs that the signal control device changes according to traffic conditions at CYC _t .

5 is an example of a traffic signal cycle. 5 shows CYC ₀ and CYC ₁ . CYC ₀ and CYC ₁ each consist of four phs. CYC ₀ consists of traffic signals for (F _NS , F _SN ), (F _NE , F _SW ), (F _EW , F _WE ) and (F _WN , F _ES ) traffic flows in sequence. CYC ₁ consists of traffic signals for (F _NE , F _SW ), (F _EW , F _WE ), (F _WN , F _ES ) and (F _NS , F _SN ) traffic flows in _sequence . 5 illustrates a waiting time for (F _NE , F _SW ) progression and a waiting time for (F _NS , F _SN ) progression as an example.

The parameters measured by the signal controller for traffic signal control will also be described.

TH _t (F _ba ): The number of vehicles departing (crossing the intersection) from intersection i _c in the green signal section for traffic flow F _ba in section CYC _t . TH _t (F _ba ) is the throughput of intersection i _c for traffic flow F _ba .

NDV _t (F _ba ): Number of vehicles waiting at the intersection i _c in the intended direction F _ba . That is, NDV _t (F _ba ) is the number of vehicles that do not cross the intersection at CYC _t-1 and wait to enter the intersection at CYC _t .

Delay _t (F _ba ): Average time for the vehicle to go to F _ba with CYC _t in the green signal in the direction of travel. Delay _t (F _ba ) corresponds to the average latency of the vehicles in NDV _t (F _ba ).

Speed _t (F _ba ): The average travel speed of the vehicles in traffic flow F _ba . The signal controller may know Speed _t (F _ba ) as the speed information transmitted by the vehicle.

NAV _t (F _ba ): The number of vehicles entering the intersection i _c at the surrounding intersection between the green signal of CYC _t-1 and the green signal of CYC _t for traffic flow F _ba .

NEV _{t + 1} (F _ba ): The number of vehicles expected to enter the intersection i _c for the traffic flow F _ba in the next cycle, CYC _{t + 1} .

It has been described that the signal control device determines the traffic congestion level at the intersection and controls the traffic signal accordingly. The signal control apparatus analyzes the traffic congestion degree at each cycle to control at least one of the traffic signal section length and the traffic signal sequence of the next cycle. The traffic congestion is described below.

FOR _t (F _ba ): The road occupancy rate measured in section CYC _t for traffic flow F _ba . The road occupancy is inversely proportional to the vehicle capacity of the road used in the traffic flow and is a relative value proportional to the number of vehicles occupying the road and the road occupancy time. FOR _t (F _ba ) may be expressed as Equation 1 below.

Here, S (i _c ^b , i _c ) is the road segment occupied by the vehicle passing the intersection i _c for the traffic flow F _ba . CP () refers to the vehicle capacity of a particular road segment.

CL _t (F _ba ): This means the traffic congestion relative to the traffic flow F _ba compared to other traffic flows passing through the intersection i _c at CYC _t . CL _t (F _ba ) may be expressed as Equation 2 below.

In Equation 2, TH _t-1 (i _c ) is the number of all vehicles passing through the intersection i _c at CYC _t-1 , and TH _t-1 (F _ba ) is the intersection in the direction of traffic flow F _ba at CYC _t-1 . The number of all cars passing by i _c . In Equation 2, NEV _{t + 1} (F _ba ) is the number of vehicles expected to enter the intersection i _c for the traffic flow F _ba in the CYC _{t + 1} interval. NEV _{t + 1} (i _c ) is the number of vehicles expected to enter the intersection i _c during the CYC _{t + 1} interval. NEV _{t + 1} () may be predicted according to the number of vehicles traveling toward the intersection i _c at the peripheral intersection in the CYC _t interval. That is, NEV _{t + 1} () may be determined according to the number of vehicles in the traffic flow from the peripheral intersection toward the intersection i _c and the throughput of the peripheral intersection.

The signal controller can calculate CL _t (F _ba ) to know the change in traffic requested for the traffic flow F _ba in real time.

로 연산될 수 있다.CL _t (ph): The traffic congestion relative to a specific ph in the CYC _t interval. CL _t (ph) is the traffic congestion relative to all traffic F _ba handled by ph. CL _t (ph) is

Can be calculated as

이다. 예컨대, 주변 교차로 i_C ^E에서 교차로 i_C를 연결하는 도로 세그먼트 S(i_C ^E,i_C)에 대한 상대적인 트래픽 혼잡도는

이다.CL _t (S): Mean traffic congestion relative to a specific road segment S in the CYC _t interval.

to be. For example, the relative traffic congestion for the road segment S (i _C ^E , i _C ) connecting the intersection i _C at the surrounding intersection i _C ^E is

to be.

Traffic signal control of signal controller

Now, the process of controlling the traffic signal according to the traffic condition of the intersection will be described. As described above, it is assumed that the signal control apparatus can obtain information on traffic conditions. The signal control apparatus may know the number of vehicles existing at the intersection and the number of vehicles located in a specific road segment through a camera or a sensor device installed at the intersection. Alternatively, the signal control apparatus may acquire the position of the vehicle, the direction of travel of the vehicle, the speed of the vehicle, and the like through communication (I2I) with an infrastructure such as a control center. Alternatively, the signal control apparatus may determine a moving direction desired by the vehicle through communication with the vehicle (V2I). In addition, the signal control device may know the number of vehicles to enter the corresponding intersection from the peripheral intersection through communication between control devices installed at the intersection. Various techniques that have been studied in the past can be utilized for a system or a technique for the traffic controller to obtain traffic information.

을 최대화하고,

및

를 최소화하는 목표를 갖는다. The signal control device aims to minimize the travel time of the vehicle while maximizing the traffic throughput in a certain area (whole city or unit area). That is, the signal control device is for every period t at the intersection i _C.

To maximize

And

Has the goal of minimizing.

The operation of the signal controller can be classified into two types. The signal control device operates independently of the two configurations. Two agents are the Traffic Flow Watcher and Evaluator (TFW) and the Traffic Flow Manager (TFM). The TFW is a component that collects and updates information about traffic conditions. The TFM determines an operation mode for control based on the traffic congestion information generated by the TFW, and controls the traffic signal according to the operation mode.

TFW estimates the change in each traffic flow F _ba towards intersection i _C. The TFW collects and analyzes traffic flow changes for neighboring intersections at intersection i _C. The TFW consists of three sub-tasks: update, exchange and estimation. The update is a process of updating parameters based on the obtained traffic information, and the exchange is a process of exchanging the updated information with a signal control device (TFW) at a nearby intersection, and the estimation is a signal control device at an intersection different from the generated parameter. It is the process of inferring information such as traffic flows based on the information obtained from the system.

The TFW monitors the state of the inflow flows to intersection i _C. The TFW updates the parameters related to the traffic flow. TFW can update NDV _t (F _ba ), Delay _t (F _ba ), Speed _t (F _ba ), and NAV _t (F _ba ) at the end of one cycle CYC _t . The TFW may obtain relevant traffic situation information and update the parameter based on the obtained information.

The TFW may receive the parameter updated over time from the signal control device (TFW) at the peripheral intersection. The TFW can also send its updated parameters to nearby intersections. Since multiple intersections may have different CYC _t , information exchange between intersections may occur in the middle of a control period. The TFW receives the information collected by the surrounding intersection (TFW), analyzes the traffic conditions on the road entering the intersection i _C , and estimates the flow NEV _{t + 1} (F _ba ) to be introduced in the next cycle.

6 illustrates an example of a process of monitoring road conditions of intersections in consideration of neighboring intersections.

For example, when explained on the basis of traffic flow entering from the east side of the i _c, i _c of TFW updates the traffic situation of the first _(c i ^E, i _c) of the road segment S shown in dark shading in FIG. And using the acquired information from the i ^E _c a i _c in the east to estimate the amount of vehicle to be introduced from the _c i ^E _{t + 1} in the next cycle CYC. The flow of the vehicle into i _c is F _NW , F _EW and F _SW in i _c ^E. The flow of the vehicle flowing into i _c from i _c ^E is indicated by {F _NW , F _EW , F _SW | i _c ^E }. A vehicle entering i _c from i _c ^E at CYC _{t + 1} will join F _EW , F _EN and F _ES at i _c . Information on the traveling direction of the vehicle introduced into i _c can be obtained from the individual vehicle. As such, the TFW may update NEV _{t + 1} (F _Ea ) and a ∈ {N, S, W}.

Furthermore, the TFW observes traffic flows (S (i _c , i _c ^a ), a∈ {N, S, W, E}) that can enter from i _c to maximize the number of vehicles passing through the intersection i _c . Share this with TFM. For example, in the next period, the F _EW throughput at S (i _c ^E , i _c ) is affected by the congestion of S (i _c , i _c ^W ). The TFW assesses the flow of exit in i _c ^W based on the congestion of S (i _c , i _c ^W ). The value of CL _t (S (i _c , i _c ^W )) is three road segments {S (i _c ^W , (i _c ^W ) ^N ), S (i _c ^W , (i _c ^W ) ^W ), S (i _c ^W , (i _c ^W ) ^S ))

In summary, the TFW of i _c optimizes the traffic considering the real-time traffic conditions of the surrounding intersection.

The TFM (signal control device) determines the congestion mode and controls the traffic signal in accordance with the determined congestion mode. Each process is explained.

The TFM first determines the congestion mode based on the collected information. The congestion mode refers to a mode of control operation for controlling traffic conditions at intersections. TFM determines congestion based on the number of vehicles at an intersection, the vehicle's waiting time, and the number of vehicles passing through the actual intersection. The TFM considers the road occupancy, the degree of delay and the number of vehicles passing through the intersection to determine the congestion level for the intersection i _C at CYC _t . Described with the above parameters, TFM determines FOR _t (i _C ), Delay _t (i _C ) and TH _t (i _C ). This calculates an average value for all traffic flowing through the intersection i _C , and each parameter can be expressed as Equation 3 below.

TFM determines the congestion mode using the three parameters represented in Equation 3. The congestion mode for the period CYC _t at intersection i _C is named Mode _t (i _C ).

The congestion mode is one of two things. The congestion mode is divided into a free flow period (FFP) mode and a continuously adjusted period (CAP). In the FFP mode, the TFM focuses on adjusting the length of the CYC _{t to} the length of the signal interval with low traffic congestion. In the FFP mode, it may be desirable to have a short period to reduce the average waiting time. CAP is a high traffic congestion situation. In the CAP mode, the TFM adjusts the length of the signal interval and the combination of signals constituting CYC _t . That is, the TFM adjusts the type and order of phs constituting the cycle according to the congestion degree by traffic flow, and also adjusts the length of each signal.

7 is an example for explaining a mode conversion for traffic signal control. The TFM tries to maintain the proper mode according to traffic conditions and prevent unnecessary mode switching.

Assume that the total amount of traffic on the surrounding road at the initial intersection i _C is small. In this case, Mode _t (i _C ) is the FFP mode. That is, the TFM operates in the FFP mode when FOR _t (i _C ) ≤ P _FFP . After that, if the traffic on the road gradually increases and exceeds the predefined threshold (P _FFP ), the TFM enters a ready-to-leave before switching to CAP mode. During the temporary state, the TFM controls the traffic signal in the same way as the FFP mode. However, the TFM additionally monitors traffic state changes on individual traffic flows F _ba .

In the temporary state, if TH _t (i _C ) or Delay _t (i _C ) improves (ie increases TH _t (i _C ) or Delay _t (i _C ) decreases), TFM does not switch modes. If TH _t (i _C ) and Delay _t (i _C ) deteriorate in a temporary state, the TFM switches to CAP mode. In the transient state, the TFM switches to CAP mode if TH _t (i _C ) decreases and Delay _t (i _C ) increases or if FOR _t (F _ba )> P _FFP for any traffic flow F _ba .

In CAP mode, TFM optimizes traffic on a flow basis. The CAP mode is FOR _t (i _C )> P _FFP and is maintained if FOR _t (F _ba )> P _FFP for at least one traffic flow F _ba . Conversely, for all traffic flows F _ba , if FOR _t (F _ba ) ≤ P _FFP , the TFM enters a ready-to-leave in CAP mode.

When entering the temporary state in CAP mode, TFM switches to FFP mode when TH _t (i _C ) or Delay _t (i _C ) is improved in the temporary state so that FOR _t (i _C ) ≤ P _FFP .

Hereinafter, the operation of controlling the traffic signal in each mode by the TFM will be described.

In FFP mode, TFM can progressively utilize three strategies. TFM adjusts one cycle length dur (CYC _t ). ② Reconstruct the order PH (CYC _t ) of the combination of traffic signals in one cycle. ③ Adjust the length dur _t (ph) of the green signal section at each ph.

Specifically, three strategies are described. First, the TFM adjusts the length of the cycle to reduce the waiting time of the vehicle by using Equation 4 below when the traffic on the road around the intersection is lower than the threshold.

TFM determines the period length in the next period CYC _{t + 1} according to the average delay time Delay _t (i _C ) and the number of ph in the current period CYC _t .

If the number of waiting vehicles NDV _t (i _C ) does not decrease even after adjusting the cycle length dur (CYC _t ) and the number of vehicles entering the intersection i _C increases, the second TFM determines the PH according to the congestion of each ph. Reconstruct (CYC _t ). The reconstructed PH (CYC _t) is arranged in order to be gradually lowered from the high ph value CL _t (ph).

If the second approach also fails to reduce the average latency Delay _t (i _C ), then TFM optimizes the interval length of each individual ph in the last (third) next cycle. The interval length adjustment of ph may be determined by Equation 5 below.

TFM is the length of the ph adjusted according to each traffic flow F _ba based on the number and the vehicle speed of the traffic flow of vehicles entering the intersection is expected, or _C i for a particular traffic flow F _ba. The TFM uses the vehicle NDV _t (F _ba ), the newly introduced vehicle NAV _t (F _ba ), and the vehicle NEV expected to flow in the next cycle for the ph associated with the specific traffic flow F _ba at the intersection i _C at the current cycle. Adjust the length of ph based on the number of _{t + 1} (F _ba ).

이다.According to the third approach, adjusting the length of the ph also adjusts the length of the entire cycle. The next cycle length dur (CYC _{t + 1} ) is

to be.

In CAP mode, TFM seeks to reduce the number of vehicles present in the traffic flow to reduce road congestion. In other words, in CAP mode, TFM tries to maximize traffic throughput. Even in CAP mode, the TFM predicts the amount of vehicles entering the intersection i _C at neighboring intersections. However, unlike the FFP mode, the TFM analyzes traffic based on traffic flow, not as a combination of traffic signals, ph. In CAP mode, the TFM considers three parameters Delay _t (F _ba ), NDV _t (F _ba ), and TH _t (F _ba ) related to traffic flow.

In CAP mode, the TFM is also responsible for traffic on each road segment S (i _c , i _c ^a ) where vehicles in traffic flow F _ba , b, a∈ {N, S, W, E} are directed at the next period CYC _{t + 1} . Consider congestion. In other words, the TFM controls the traffic signal based on CL _t (S (i _c , i _c ^a )). For example, if the next road segment is very crowded at intersection i _C , simply increasing the green signal section in that direction does not improve traffic throughput. Therefore, TFM considers the traffic congestion of S (i _c , i _c ^a ).

In CAP mode, TFM first estimates dur _{t + 1} (F _ba ) by considering CL _t (S (i _c , i _c ^a )). TFM also checks for changes in Delay _t (F _ba ), NDV _t (F _ba ), TH _t (F _ba ), and NEV _{t + 1} (F _ba ) over the previous period. 8 is an example of four cases for controlling a traffic signal in the CAP mode. Based on the checked parameters, the TFM is divided into four cases as shown in FIG. 8 to control traffic signals. The TFM adjusts the period dur _{t + 1} (F _ba ) for the traffic flow of the next period and optimizes the traffic signal combination PH (CYC _{t + 1} ). Each case is demonstrated.

Case 1

에 따라 dur_t+1(F_ba)를 줄인다. 이하

를 γ_NDV라고 표기한다. 결과적으로 대기하는 트래픽 양은 줄어든다. 즉, γ_NDV < 1이면 dur_t+1(F_ba)는 γ_NDV 만큼 줄어든다. γ_NDV ≥ 1이면, 주기의 길이는 동일하게 유지된다.Case 1 has increased traffic but relatively low road congestion. In this case, the traffic throughput of traffic flow F _ba at intersection i _C is increased to the current period CYC _t compared to the previous period CYC _t-1 . The associated Delay _t (F _ba ) decreases and the waiting vehicle NDV _t (F _ba ) increases. In other words, the inflow and outflow roads are not congested in this case, and the amount of incoming traffic is within the road capacity range. Therefore, the signal control device TFM determines that the current period length is sufficiently long. As a result, the signal controller maintains the length of the current period, or the amount of traffic remaining between two consecutive periods.

Reduce dur _{t + 1} (F _ba ). Below

_Denotes γ _NDV . As a result, the amount of traffic waiting is reduced. That is, if γ _NDV <1, dur _{t + 1} (F _ba ) is reduced by γ _NDV . If γ _NDV ≥ 1, the length of the period remains the same.

Case 2

Case 2 is a case where the amount of traffic on the load segment S (i _c ^b , i _c ) is increased and both TH _t (F _ba ) and Delay _t (F _ba ) are increased. The throughput for traffic flow F _ba is high because congestion is not high at S (i _c , i _c ^a ) yet. In this case, the signal controller determines that the moving speed on the road segment decreases more than expected when the waiting time (delay) of the vehicle increases. Therefore, the signal controller increases or maintains dur _{t + 1} (F _ba ) according to NDV _t (F _ba ). In other words, if the amount of waiting traffic increases, γ _NDV > 1, the signal controller increases dur _{t + 1} (F _ba ) by “dur _t (F _ba ) × γ _NDV ”.

Case 3

로 판단한다. 이하

를 γ_DELAY 라고 명명한다. 신호제어장치는 γ_DELAY < 1이면, 다음 주기 dur_t+1(F_ba) = dur_t(F_ba) ×γ_DELAY로 줄인다. 반대로 신호제어장치는 γ_DELAY ≥ 1이면, 다음 주기 dur_t+1(F_ba)를 dur_t(F_ba)와 동일하게 유지한다.Case 3 is a case where the amount of traffic entering the road decreases and TH _t (F _ba ) decreases in two successive cycles. In this case, the signal control device determines that du _t (F _ba ) is unnecessarily long. Therefore, if the number NEV _{t + 1} (F _ba ) of vehicles entering F _ba during the next period CYC _{t + 1} does not increase compared to CYC _t , then the signal controller reduces the length of the next period dur _{t + 1} (F _ba ). . To reduce the frequency

Judging by. Below

Is called γ _DELAY . If γ _DELAY <1, the signal controller reduces to the next period dur _{t + 1} (F _ba ) = dur _t (F _ba ) × γ _DELAY . On the contrary, the signal controller maintains the next period dur _{t + 1} (F _ba ) equal to dur _t (F _ba ) if γ _DELAY ≥ 1.

Case 4

Case 4 is in a state in which congestion increases in the outflow segment S (i _c , i _c ^a ), resulting in a decrease in TH _t (F _ba ). The signal controller determines that traffic congestion is one of two possibilities.

First, observe whether the number of vehicles for CYC _t decreases compared to CYC _t-1 . That is, it is determined whether γ _NDV <1 or not. If so, the traffic throughput decreases due to the congestion of the outflow segment S (i _c , i _c ^a ). Thus, the signal control device keeps dur _{t + 1} (F _ba ) similar to dur _t (F _ba ).

에 비례하게 줄인다. 이하

를 γ_TH 라고 명명한다. 결국 신호 제어 장치는 다음 주기 dur_t+1(F_ba) = dur_t(F_ba) ×γ_TH"로 줄인다. 이때 γ_TH < 1 && γ_NDV > 1이다.If not, the signal controller determines that NDV _t (F _ba ) is greater than NDV _t-1 (F _ba ). That is, γ _NDV > 1, which means that the inflow road segment S (i _c ^b , i _c ) is also congested. Since both the outflow and inflow roads are congested, the efficiency of the green signal cycle is reduced. The signal controller therefore reduces the green signal time, making dur _{t + 1} (F _ba ) less than dur _t (F _ba ). Where dur _{t + 1} (F _ba ) is the change in traffic throughput.

Reduce in proportion to Below

Is called γ _TH . Eventually the signal control unit reduces to the next period dur _{t + 1} (F _ba ) = dur _t (F _ba ) × γ _TH ", where γ _TH <1 && γ _NDV > 1.

The signal controller calculates dur _{t + 1} (F _ba ) for all traffic flows and reconfigures PH (CYC _t ) so that the traffic flow F _ba with the largest value of CL _t (F _ba ) is preferentially placed. That is, the traffic flow F _ba with the largest value of {CL _t (F _ba ) is selected first, and PH (CYC _t) is bundled with other F _ba that can receive green signal simultaneously without colliding with the selected F _ba. ) At the beginning of the line). The {} part is repeated until all F _ba are included in PH (CYC _t ), so that the deviation of the dur _{t + 1} (Fba) values bound to the same ph is minimized. As a result, in the next cycle, the traffic signal for the more congested flows will precede the traffic signal for the less congested flows. Traffic signal sequence reconstruction stops when one cycle contains signals for all traffic flows.

The embodiments and the drawings attached to this specification are merely to clearly show a part of the technical idea included in the above-described technology, and those skilled in the art can easily make it within the scope of the technical idea included in the description and the drawings of the above-described technology. It will be apparent that both the inferred modifications and the specific embodiments are included in the scope of the above-described technology.

100: signal control system of intersection
Vehicle: 110A, 110B, 110C
120A, 120B: Signal control device
150A, 150B: RSU
180: control center

Claims (12)

Obtaining, by the signal control device, traffic information related to traffic conditions at a target intersection;
Determining, by the signal control apparatus, a mode for controlling a traffic signal of the target intersection at a predetermined time interval using the traffic information;
Controlling the traffic at the target intersection based on a combination of traffic signals at the target intersection in the time interval when the signal controller determines the mode as the first mode; And
And controlling the traffic at the target intersection based on the flow of the vehicle entering the specific direction at the target intersection and advancing in the specific direction when the signal controller determines the mode as the second mode.
At least one signal in each direction that can proceed at the target intersection is generated during the time interval, and the traffic signal combination includes a green signal for at least one travel direction,
The signal control apparatus determines the mode as the first mode when the road occupancy of the target intersection is less than or equal to a threshold value, and transfers the throughput of the target intersection in the time interval while the road occupancy exceeds the threshold. The mode is determined as the second mode when the throughput is equal to or less than a throughput of the section and the number of vehicles waiting at the target intersection in the time section is equal to or greater than the number of vehicles waiting in the previous section.
The signal control device performs at least one of adjusting the length of the time interval, reconstructing the order of traffic signal combinations occurring in the time interval, and adjusting the green signal length for the traffic signal combination in the first mode,
The signal control device may be configured to: when the number of vehicles waiting at the target intersection in the time section, the number of vehicles entering the target intersection in the time section, and the next section of the time section are the first mode, the next section. Adjust the length of each traffic signal constituting the traffic signal combination based on the number of vehicles expected to enter the target intersection from the surrounding intersection of the target intersection;
The signal control apparatus may be configured to determine the number of vehicles passing through the target intersection in the green signal in the time interval for the vehicle entering and exiting in the specific direction in the second mode, and the target intersection in the time interval. If the next section of the time interval is the second mode, based on the number of vehicles that cannot pass by and the green signal in the time section based on the average waiting time of the vehicle passing the target intersection, the target intersection in the next section The adaptive intersection traffic signal control method for adjusting the length of the target section to enter from the specific direction in the specific direction. The method of claim 1,
The signal control apparatus may be configured based on at least one of a road occupancy rate of the target intersection in the time section, a number of vehicles passing the target intersection in the time section, and a number of vehicles that do not proceed in the traveling direction in the time section. Adaptive intersection traffic signal control method for determining the mode. delete delete delete The method of claim 1,
And the signal control apparatus reconstructs the sequence of traffic signal combinations occurring in the next section when the next section of the time section is the first mode in the first mode. The method of claim 6,
The traffic signal combination is composed of a plurality of traffic signals,
The signal controller is a traffic signal having a relatively high traffic congestion degree based on a relative traffic congestion degree of the traffic flow processed by each traffic signal among the plurality of traffic signals and the remaining traffic flows among all traffic flows that can proceed at the target intersection. Adaptive traffic signal control method for reconstructing the traffic signal combination of the next section in the first mode so that first occurs. delete The method of claim 1,
When the signal control device increases the traffic throughput of the time interval in the second mode than the previous interval of the time interval,
When the next section of the time section is the second mode, the length of the target section is equal to the length of the time section, or the number of vehicles waiting at the target intersection in the previous section and vehicles waiting in the time section Adaptive intersection traffic signal control method for reducing the length of the next section based on the difference in the number of. The method of claim 1,
In the second mode, when the signal control device increases both the traffic throughput of the target intersection and the number of vehicles waiting at the target intersection in the time interval, compared to the previous interval of the time interval,
Adaptive to increase the length of the target section when the next section of the time interval is the second mode, based on the difference between the number of vehicles waiting at the target intersection in the previous section and the number of vehicles waiting in the time section Intersection traffic signal control method. The method of claim 1,
When the signal control device reduces the traffic flowing into the target intersection in the second mode, the traffic throughput of the target intersection decreases continuously in the previous section and the time section,
When the next section of the time interval is the second mode based on a difference between the average time that the vehicle passing the target intersection waits in the previous section and the average time that the vehicle passing the target intersection waits in the time section, Adaptive intersection traffic signal control method for adjusting the length of the target section. The method of claim 1,
In the second mode, when the traffic congestion of the target intersection decreases due to an increase in congestion of the road entering the specific direction at the target intersection in the second direction, the signal control device decreases.
If the number of vehicles waiting in the time section is smaller than the number of vehicles waiting at the target intersection in the previous section of the time section, the length of the target section is determined when the next section of the time section is the second mode. Equal to the length of the time interval,
If the number of vehicles waiting in the time section is equal to or greater than the number of vehicles waiting in the target intersection in the previous section of the time section, the target intersection in the previous section with respect to the direction entering the specific direction and advancing in the specific direction Adaptive traffic signal control method for reducing the green signal length to enter in the specific direction in the next section based on the difference between the traffic throughput of the traffic intersection and the traffic throughput of the target intersection in the time interval.

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