An intersection control method based on the combination of variable turning lanes and lane changing

Abstract

The present invention discloses an intersection control method based on the combination of variable turning lanes and lane changing, which specifically includes the following steps: S1. Start the variable turning lane and lane changing control algorithm at the intersection, and the roadside unit receives vehicle information and transmits it to the central server; S2. Control the vehicles that need to change lanes in the lane changing control area to change to the target lane; S3. Calculate the passing priority of the vehicles that have not been allocated the right of way in the speed control area; S4. Adjust the speed of the vehicles in the speed control area to ensure that they can pass through the intersection safely and efficiently. When the traffic flow at the intersection is unbalanced, especially when the traffic flow on the same road section is unbalanced, the present invention enables vehicles to change from congested lanes to smooth lanes through a method that combines flexible variable turning lanes with lane changing and speed adjustment, so as to achieve the purpose of sharing the traffic flow, allowing turning vehicles with a large traffic flow to pass through the intersection simultaneously from multiple lanes, reducing the average waiting time of vehicles, and improving the passing efficiency of the intersection.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent transportation information technology, and particularly relates to an intersection control method based on the combination of variable turning lanes and lane changing. Background Art

[0002] In the context of increasingly complex national road designs, more intersections, and a growing number of people choosing to travel by private cars, large-scale traffic congestion has ensued. Especially at intersections, due to the fixed cycle duration of traffic lights and the limited number of turning lanes, it is easy to cause congestion at the intersection. Particularly during the peak commuting hours, there will be a serious imbalance in traffic flow. For the imbalance in traffic flow on lanes, the number of traffic lights and turning lanes will severely limit the traffic efficiency at intersections. For the imbalance in traffic flow on road sections, the fixed cycle duration of traffic lights will cause congestion at intersections.

[0003] Currently, most scholars adopt adaptive traffic lights or intelligent traffic light control algorithms to solve the problem of reduced traffic efficiency in the case of unbalanced traffic flow at intersections. Most traffic light control algorithms transmit real-time data of traffic parameters within kilometers around the intersection to the central server through detection devices such as in-vehicle networks and wireless communications, and train the traffic lights through algorithms such as adaptive, fuzzy control, or reinforcement learning, enabling them to determine the duration of each color signal light in the next cycle according to the real-time traffic conditions. However, this control method that only targets traffic lights has many drawbacks. The control algorithm can only control the duration of one cycle of the traffic lights and cannot respond in a timely manner to sudden increases and decreases in traffic flow. Vehicles will also stop and go due to waiting for the green light, constantly starting and stopping, resulting in higher fuel consumption and exhaust emissions, increasing the risk of rear-end collisions, and serious driving discomfort.

[0004] With the development of vehicle networking and autonomous driving technologies, emerging connected and autonomous vehicles can not only transmit real-time information but also drive strictly according to given instructions. They can not only overcome the disadvantages of traffic light control but also respond in a timely manner according to the real-time traffic conditions, reduce the frequency of vehicle starts and stops, and can also control vehicles or vehicle fleets to reach the center of the intersection at a specified speed. Therefore, the emerging connected and autonomous vehicle technology can more efficiently utilize the advantages of variable turning lanes and lane change control.

[0005] Patent document CN104240522A discloses an adaptive crossroads control technology based on vehicle - to - everything (V2X) network and fuzzy neural network. This method is based on the vehicle network, and the road conditions are transmitted to the central controller in real - time through wireless communication. The central controller gives a scheduling plan in real - time. At the same time, the central controller combines fuzzy neural network technology to control vehicle groups to pass through the crossroads and enables the controller to have the ability of continuous learning through reinforcement learning algorithm. However, this method still follows the immutable turning lanes. In the case where the traffic flow in a certain turning direction is large while the traffic flow in other turning directions is small, it will severely limit the traffic fairness and traffic efficiency of vehicles at the crossroads. Summary of the Invention

[0006] The purpose of the present invention is to provide a crossroads control method based on the combination of variable turning lanes and lane - changing. Under the traffic conditions of connected and autonomous vehicles, at the crossroads, through the control method combining variable turning lanes and lane - changing, lane - changing, grouping, and speed - adjustment control are carried out on the vehicles on the road section, so as to reduce the average waiting time of vehicles and ensure the fairness of vehicle traffic and improve the crossroads traffic efficiency even in the case of severely unbalanced traffic flow.

[0007] To achieve the above - mentioned purpose, the present invention provides the following technical solutions: A crossroads traffic flow optimization control method based on the combination of variable turning lanes and lane - changing. Specifically, it includes the following steps:

[0008] S1. Divide the crossroads into a central conflict area and four arm - expansion road sections (e). The arm - expansion road sections are divided into a lane - change (LC) control area, a constant - speed area, and a speed - adjustment (SA) control area along the direction of the vehicle driving towards the central conflict area;

[0009] The four arm - expansion road sections are numbered as e = 0, 1, 2, 3 in the northwest - southeast direction respectively; along the lane width direction, the lanes are numbered as k, k ∈ {0, 1, …, N} from right to left; Since the lane turning is variable and each lane has three possible passing trajectories, all possible paths for vehicles to pass through the central conflict area are represented by a triple {arm - expansion road section number e, lane number k, turning direction}. In the traffic environment of a three - lane crossroads, there are 36 such combinations in total. According to the northwest - southeast turning, with the lane from right to left as the reference, they are numbered as p in the order of right - turn, straight - ahead, and left - turn, p = 0, 1, …, 35;

[0010] Road - side units (RSUs) are respectively deployed on the four road sections of the crossroads. The position, speed, and path information of each vehicle in the control area are collected through the RSUs; the information collected by the RSUs is transmitted to the central server for operation;

[0011] S2. Calculate the lane grades of the LC control area for each arm-span section, and then determine whether it is necessary to balance the lane traffic loads; perform lane-changing control on the vehicles in the lane-changing control area according to the lane grades of the LC control area and the load balancing urgency of each lane;

[0012] S3. Calculate the passing priority of each lane according to the driving time and platoon length of the leading vehicles in the SA control area and the constant-speed area;

[0013] Allocate passing rights to the leading vehicles with the highest priority and non-conflicting paths;

[0014] S4. Perform speed control on the vehicles in the constant-speed area and the SA control area;

[0015] Calculate the speed adjustment period of the vehicle according to the time when the leading vehicle of the platoon receives the passing right, the time to reach the central conflict area without speed adjustment, and the time required for the leading vehicle to reach the central conflict area calculated by the control algorithm;

[0016] Control the speed of the leading vehicle according to the speed adjustment period of the leading vehicle;

[0017] Control the following vehicles in the platoon to maintain the minimum safe distance from the vehicle in front according to the platoon length.

[0018] Furthermore, in S1, the RSU and the vehicle use wireless connection to transmit information, and use wired connection to transmit information with the central server; the vehicles are all equipped with a positioning system and a wireless communication device.

[0019] Furthermore, the S2 includes the following steps:

[0020] S21: Calculate the lane grades in units of arm-span sections according to the number of vehicles in each lane in the LC control area, the number of platoons that have obtained passing rights in each lane, and the platoon length;

[0021] S22: Introduce a parameter r ∈ [0,1] to describe the relationship between the load balancing urgencies of the lanes in the LC control area. The value of the parameter r is related to the ratio of the unit traffic flow between lanes. The larger the ratio of the unit traffic flow between the high-flow lane and the low-flow lane, the larger the value of r. The larger r is, the more unbalanced the traffic flow is;

[0022] S23: Perform lane-changing control on the vehicles in the LC control area. If the first-class lane is adjacent to the third-class lane, control m vehicles in the first-class lane to change to the third-class lane; if the first-class lane is not adjacent to the third-class lane, first control the vehicles in the second-class lane to change to the third-class lane, and then control m vehicles in the first-class lane to change to the second-class lane;

[0023] Furthermore, the S3 includes the following steps:

[0024] S31: Obtain the information of the first vehicle without allocated right of way on each lane in the speed regulation control area, and these vehicles are called priority leading vehicles;

[0025] Obtain the information of the first vehicle on each lane in the constant speed area, and these vehicles are called secondary priority leading vehicles;

[0026] S32: Calculate the priority of the lane according to the driving time of the first vehicle without allocated right of way on each lane in the speed regulation control area, that is, the leading vehicle of the lane;

[0027] S33: Calculate all priority leading vehicles with non-conflicting paths as the first-level passing leading vehicles on the premise of preferentially satisfying the right of way of the high-priority lanes according to the priority calculated in S31;

[0028] S34: According to the leading vehicle information in the constant speed area, first traverse the leading vehicles in the constant speed area, calculate the leading vehicles with non-conflicting paths with the first-level passing leading vehicles to obtain the candidate secondary passing leading vehicles, then calculate the priority of the secondary passing leading vehicles, and calculate the non-conflicting secondary passing leading vehicles on the premise of preferentially satisfying the right of way of the high-priority leading vehicles. These secondary passing leading vehicles and the first-level passing leading vehicles together form the passing leading vehicles for this time;

[0029] Further, the path calculation method of the vehicles in S33 and S34 includes the following steps (only considering the path trajectory of the vehicle passing through the central conflict area):

[0030] 1) Straight-line trajectory equation:

[0031]

[0032] The time required for a straight-going vehicle to pass through the central conflict area

[0033]

[0034] 2) Left-turn trajectory equation:

[0035]

[0036] The time required for a left-turning vehicle to pass through the central conflict area

[0037]

[0038] 3) Right-turn trajectory equation:

[0039]

[0040] The time for a right-turning vehicle to pass through the central conflict area

[0041]

[0042] where {x ek (t), y ek (t)} ξ represents the central coordinates of the vehicle at time t, ξ = (s, l, r) represents going straight, turning left, and turning right respectively, e represents the number of the arm section where the vehicle enters the central conflict area, k represents the vehicle entering the central conflict area from lane number k, and R ek represents the path radius of the vehicle passing through the central conflict area from arm section e and lane k, and θ ek (t) represents the angle formed by the line connecting the center point of the vehicle at time t and the origin and the horizontal axis, and ω represents the angular velocity of the vehicle L represents the vehicle length, W represents the lane width, and K represents the number of lanes;

[0043] Since the above trajectory equation uses the arm section where the vehicle enters the central conflict area as the relative coordinate system, it is necessary to convert the path trajectory to a coordinate system through formula (1.7):

[0044]

[0045] Among them, formula (1.7) uses the westward arm section as the standard coordinate system, and sequentially converts the relative coordinates of the north, east, and south directions into standard coordinates;

[0046] Furthermore, the trajectory equation obtains the central coordinates of the vehicle at time t. Combining the vehicle length L, the vehicle width B, and the angle θ(τ) of the vehicle at time t, calculate the rectangular area occupied by the vehicle at time t; according to the time when the vehicle enters the central conflict area and the time when the vehicle passes through the central conflict area a series of discrete rectangular areas occupied by the vehicle can be obtained; based on this, it is judged whether the vehicle paths conflict;

[0047]

[0048] Furthermore, the S4 includes the following steps:

[0049] S41: According to the speed v0 specified by the central server for the vehicle to pass through the central conflict area, calculate the time T for the vehicle to enter the central conflict area while maintaining the speed v0 n ;

[0050] S42: According to the resource occupancy situation in the central conflict area, calculate the safe time T s for the vehicle to enter the central conflict area, that is, the vehicle entering the central conflict area at time T s and passing through the central conflict area at speed v0 will not conflict;

[0051] S43: Calculate the speed adjustment period of the vehicle through formulas (1.9) to (1.11);

[0052] Furthermore, in Formulas (1.9) to (1.11), it is default that the speed v = v0 when the vehicle starts to perform the speed regulation task. Considering that the vehicle speed v≠v0 may occur due to the safety following mechanism restriction of the car-following model, T in the formula should be replaced;

[0053]

[0054]

[0055]

[0056] where T represents the time when the vehicle starts to perform the speed regulation task,

[0057] 1) T s -T n >0: The vehicle starts to decelerate at time T. c represents the time when the vehicle finishes decelerating, d represents the time when the vehicle starts to accelerate, and e represents the time when the vehicle finishes accelerating (i.e., the vehicle completes the speed regulation cycle and the speed returns to v again);

[0058] 2) T s -T n <0: The vehicle starts to accelerate at time T. c represents the time when the vehicle finishes accelerating, d represents the time when the vehicle starts to decelerate, and e represents the time when the vehicle finishes decelerating (i.e., the vehicle completes the speed regulation cycle and the speed returns to v again);

[0059] Adjust the vehicle speed according to the relationship among the three parameters c, d, e, T s and T n ;

[0060] S44: According to the safe following distance D and the current distance between the following vehicle and the preceding vehicle, use Formula (1.12) to calculate whether the (i + 1)-th vehicle can join the vehicle fleet:

[0061]

[0062] where S i represents the distance of the i-th vehicle in the vehicle fleet from the central conflict area (the leading vehicle is the 0-th vehicle), D represents the minimum safe following distance, represents the average chasing speed of the vehicle (generally select ), and v m represents the maximum driving speed of the vehicle.

[0063] Beneficial effects:

[0064] In view of the problem that the traffic capacity of intersections decreases under the condition of unbalanced traffic flow in the prior art, the present invention provides an intersection control method combining variable turning lanes and lane changing, and the beneficial effects are as follows:

[0065] 1. Compared with traditional traffic lights, the intersection control method combining variable turning lanes and lane changing is based on a real-time microscopic traffic model, takes the information of each vehicle as a reference, and combines macroscopic traffic information such as the average waiting time of lanes and lane occupancy rate to determine the lane-changing behavior and passing priority of each vehicle; it can not only determine the passing behavior of vehicles in real time, but also avoid the frequent starting and stopping of vehicles due to waiting for green lights, making the vehicles safer and more comfortable during driving.

[0066] 2. Compared with the intersection control method of fixed turning lanes, the steering direction of the lane is flexibly changed according to the currently passing vehicles, overcoming the objective influence brought by the limitation of the number of turning lanes under the condition of unbalanced traffic flow of vehicles with different expected turning directions.

[0067] 3. The present invention combines variable turning lanes and lane changing. On the one hand, lane-changing control is used to balance the traffic flow load of lanes. On the other hand, vehicles with the same expected turning direction can pass through the central conflict area from different lanes at the same time, greatly improving the traffic efficiency of intersections, especially in the case of unbalanced traffic flow, which helps to improve the fairness of intersection traffic. Description of the Drawings

[0068] Figure 1 is a flow chart of an intersection control method combining variable turning lanes and lane changing;

[0069] Figure 2 is the road network structure of an intersection control method combining variable turning lanes and lane changing. Detailed Embodiments

[0070] The present invention will be further described below in conjunction with the detailed embodiments. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end.

[0071] Embodiment 1

[0072] As Figures 1 to 2 shown, this embodiment provides an intersection control method combining variable turning lanes and lane changing, which specifically includes the following steps:

[0073] Step A: Start the crossroads control method combining variable turning lanes and lane changes. Divide the crossroads into two major areas: the extended arm sections and the central conflict area. Deploy one RSU in each extended arm section. Vehicles transmit information to the RSU via wireless communication, and the RSU transmits information to the central server via a wired connection. The optimized control method for crossroads combining variable turning lanes and lane changes runs on the server.

[0074] Step B: Calculate the lane grades for each extended arm section separately, and then determine whether it is necessary to balance the lane traffic load. If not, execute Step C; otherwise, execute lane change control.

[0075] Step C: Determine the leading vehicle entering the SA control area and the leading vehicle entering the constant speed area, and calculate the conflict-free leading vehicle with the highest priority path according to the passing priority.

[0076] Step D: Adjust the speed of the leading vehicle that has obtained the right of way in the SA control area so that it can reach the central conflict area within T s ±0.1 s, determine the vehicle fleet length, and control the passing groups to pass through the central conflict area in the form of vehicle fleets.

[0077] Furthermore, in Step A, the entire road network is divided into two major parts, namely the extended arm sections and the central conflict area. The extended arm sections are further divided into three parts, namely the LC control area, the constant speed area, and the SA control area, which are numbered k from right to left along the lane width direction, where k = 0, 1, 2. According to the northwest-southeast turning direction, the extended arm roads are numbered e, where e = 0, 1, 2, 3. Based on the lanes from right to left, the paths for vehicles to cross the crossroads are numbered p in the order of right turn, straight, and left turn, where p = 0, 1,..., 35. The crossroads control method combining variable turning lanes and lane changes runs on the central server, and the central server is connected to the Road Side Unit (RSU) via a wired connection. One RSU is deployed in each extended arm section, and the RSU transmits information to the vehicle via wireless connection. Assuming that devices such as the Global Positioning System and wireless communication devices are already embedded in the vehicle, when the vehicle is driving on the road, the RSU can collect real-time traffic information (such as the vehicle speed and position information) through communication with the vehicle; the RSU transmits information to the central server via a wired connection and uploads the real-time traffic information to the central server.

[0078] In Step B, to make full use of the property of variable turning lanes, some vehicles in the lanes with larger traffic flow are changed to the lanes with lower traffic flow. The specific method is described in the following steps

[0079] Step B1: Calculate the lane grades in the LC control area. Taking the arm span section as the unit and the lane vehicle occupancy rate as the benchmark, sort the lanes on each arm span section from large to small as the first-level lane, the second-level lane, and the third-level lane;

[0080] Step B2: If the occupancy rate of the first-level lane is greater than the sum of the occupancy rates of the second-level lane and the third-level lane, then the vehicles in the first-level lane need to change direction to the second-level and third-level lanes; if it is determined that no load balancing operation is required, directly execute Step C;

[0081] Step B3: If the first-level lane is adjacent to the third-level lane, half of the vehicles in the first-level lane in the LC control area change direction to the third-level lane. If there are vehicles blocking in the third-level lane, decelerate the vehicles in the third-level lane behind the vehicles in the first-level lane; if the first-level lane is not adjacent to the third-level lane, change m vehicles in the first-level lane in the LC control area to the second-level lane. If there are vehicles blocking in the second-level lane, change the blocking vehicles to the third-level lane. If there are vehicles blocking in the third-level lane, decelerate the blocking vehicles in the third-level lane behind the vehicles in the second-level lane.

[0082] In Step C, sort the leading vehicles entering the SA control area and the leading vehicles entering the uniform speed area according to the vehicle driving time, and allocate the passing priorities in descending order; traverse the sorted leading vehicle information in the SA control area, and then add the leading vehicles with non-conflicting paths to the group in turn according to the priority order as the passing group allowed this time; traverse the sorted leading vehicle information in the uniform speed area, and then add the leading vehicles with non-conflicting paths to the group in turn according to the priority order, and finally obtain all the leading vehicles with passing rights this time; the calculation method of the vehicle paths in the central conflict area is described in the following steps:

[0083] Step C1: According to the expected turning direction of the vehicle, the lane number where it is located, and the arm span section number where it is located, use formula (1.13) to calculate the central coordinate point of the vehicle at time t after entering the central conflict area;

[0084]

[0085] Step C2: According to the expected turning direction of the vehicle and the lane number where it is located, use formula (1.14) to calculate the time consumed by the vehicle to pass through the central conflict area;

[0086]

[0087] Step C3: Convert the path coordinates to a coordinate system through formula (1.15). Taking the west-direction arm span section as the standard coordinate system, convert the relative coordinates in the north, east, and south directions to the standard coordinates in turn;

[0088]

[0089] Step C4: Calculate the rectangular area occupied by the vehicle at time t using formula (1.16) based on the length, width of the vehicle, and the angle between the center point and the horizontal axis at time t;

[0090]

[0091] Step C5: According to the calculation results of C1, C2, and C3, is split into multiple time nodes, and the central coordinates of the vehicle at these time nodes are calculated respectively. The rectangular area occupied by the vehicle is calculated based on the central coordinates, and finally a seemingly discrete but actually continuous trajectory area that occupies most of the space is obtained; the calculated trajectory contains time and space information, and based on this, it is judged whether there will be a collision between vehicles in the central conflict area;

[0092] In step D, according to the time when the leading vehicle of the convoy receives the right of way, the time to reach the central conflict area without speed adjustment, and the safe time for the leading vehicle to reach the central conflict area calculated by the control algorithm, calculate the speed adjustment period of the vehicle; according to the speed adjustment period of the leading vehicle, control the speed of the leading vehicle; according to the length of the convoy, control the following vehicles in the convoy to maintain a minimum safe distance from the vehicle in front. The specific steps of speed adjustment and convoy selection can be described by the following steps:

[0093] Step D1: Calculate the time T when the vehicle enters the central conflict area while maintaining the speed v according to the speed v at which the vehicle specified by the central server passes through the central conflict area; n ; Calculate the safe time T for the vehicle to enter the central conflict area according to the resource occupancy situation in the central conflict area; s ; Considering the situation where the speed of the vehicle is not v when it receives the speed adjustment task, should be used to replace T in the formula;

[0094] Step D2: Calculate the deceleration period of the vehicle through formula (1.17);

[0095]

[0096] Step D3: Calculate the acceleration period of the vehicle through formula (1.18) and formula (1.19);

[0097]

[0098]

[0099] After the vehicle receives the command to allow passage, it will also receive a speed adjustment command at the same time; the vehicle immediately executes the speed adjustment task. First, it starts to decelerate at time T until time c or the speed reduces to 0, then it starts to accelerate at time d until time e or the speed returns to v0 again, and finally the vehicle will maintain the speed v0 until it passes through the central conflict area;

[0100] Further, if T s -T n < 0, it indicates that the time for the vehicle to travel to the central conflict area at the desired speed is later than the safety time, and it is necessary to control the vehicle to accelerate to ensure that the vehicle can enter the central conflict area around time T s ; Similarly, use formulas (1.17), (1.18) and (1.19) to calculate the speed adjustment period, but the meanings represented by the parameters and the speed adjustment steps will change as follows: The vehicle starts to accelerate at time T and keeps accelerating until time c or the speed reaches v m , and then keeps driving at the speed after the acceleration period ends until d, starts to decelerate at d until time e or the speed returns to v0 again, and finally the vehicle will keep the speed v0 until it passes through the central conflict area;

[0101] Step D4: After calculating the speed adjustment period of the leading vehicle, it is necessary to determine the actual length of the vehicle fleet. The following vehicles will follow the leading vehicle and pass through the central conflict area together in the form of a fleet; According to the safe following distance D and the current distance between the following vehicle and the vehicle in front, use formula (1.20) to calculate whether the (i + 1)-th vehicle can join the fleet:

[0102]

[0103] where S i represents the distance of the i-th vehicle in the fleet from the central conflict area (the leading vehicle is the 0-th vehicle), D represents the minimum safe following distance, represents the average chasing speed of the vehicle (generally select ), v m represents the maximum driving speed of the vehicle.

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A crossroads control method based on the combination of variable turning lanes and lane changing, characterized in that, It includes the following steps: S1. Divide the intersection into a central conflict area and four arm sections e. The arm sections are divided into a lane-changing control area, a constant-speed area, and a speed-regulating control area along the direction of vehicles driving towards the central conflict area; The four arm sections are numbered e = 0, 1, 2, 3 in the northwest, southeast direction respectively; Along the lane width direction, the lanes are numbered k, k ∈ {0, 1, …, N} from right to left; Since the lane turns are variable and each lane has three possible passing trajectories, all possible paths for vehicles to pass through the central conflict area are represented by a triple {arm section number e, lane number k, turning direction}. In the traffic environment of a three-lane intersection, there are 36 such combinations in total. According to the northwest-southeast turn, with the lanes from right to left as the reference, they are numbered p in the order of right turn, straight, and left turn, p = 0, 1, …, 35; Deploy roadside units RSU on the four arm sections respectively. Collect the position, speed, and path information of each vehicle in the four arm sections through the RSU; Transmit the information collected by the RSU to the central server for calculation; S2. Calculate the lane grades of the lane-changing control area for each arm section respectively; Perform lane-changing control on the vehicles in the lane-changing control area according to the lane grades of the lane-changing control area; Specifically, it includes the following steps: S21: Take each arm section as a unit, and calculate the lane grades according to the number of vehicles in each lane in the lane-changing control area, the number of vehicle fleets that have obtained the right of way in each lane, and the fleet lengths; S22: According to the lane grades of the lane-changing control area, calculate the load balancing urgency value of the first-level lanes and the load balancing urgency values of the second-level and third-level lanes. Introduce a parameter r ∈ [0, 1] to describe the relationship between the two. The larger the value of r, the more unbalanced the traffic flow. If the condition is met, control the vehicles in the high-level lanes to change to the low-level lanes; S3. Calculate the passing priority of each fleet according to the driving time and fleet length of the leading vehicle in the speed-regulating control area; Allocate the passing resources of the central conflict area to each fleet according to the passing priority of the fleets in the speed-regulating control area; Specifically, it includes the following steps: S31: Obtain the information of the first vehicle in each lane in the speed-regulating control area that has not been allocated the right of way. These vehicles are called priority leading vehicles; Obtain the information of the first vehicle in each lane in the constant-speed area. These vehicles are called sub-priority leading vehicles; S32: Calculate the priority of the lane according to the driving time of the first vehicle in each lane in the speed-regulating control area that has not been allocated the right of way, that is, the leading vehicle of the lane; S33: According to the priority calculated in S31, calculate all non-conflicting priority leading vehicles as the first-level passing leading vehicles on the premise of giving priority to the right of way of the high-priority lanes; S34: According to the information of the leading vehicle in the constant-speed area, first traverse the leading vehicles in the constant-speed area, calculate the leading vehicles whose paths do not conflict with the path of the first-level passing leading vehicle to obtain the candidate secondary passing leading vehicles, then calculate the priorities of the secondary passing leading vehicles, and on the premise of giving priority to the passing rights of the leading vehicles with high priorities, calculate the non-conflicting secondary passing leading vehicles. These secondary passing leading vehicles and the first-level passing leading vehicles together form the passing leading vehicles for this time. S4: Control the speeds of the vehicle fleets that have obtained the passing rights. Calculate the speed adjustment period of the vehicle according to the time when the leading vehicle of the fleet receives the passing right, the time to reach the central conflict area without speed adjustment, and the time required for the leading vehicle to reach the central conflict area calculated by the control algorithm. Control the speed of the leading vehicle according to the speed adjustment period of the leading vehicle. Control the following vehicles in the fleet to keep the minimum safe distance from the vehicle in front according to the length of the fleet.

2. The crossroads control method based on the combination of variable turning lanes and lane changing according to claim 1, characterized in that, In S1, the RSU and the vehicle use wireless connection to transmit information, and the RSU and the central server use wired connection to transmit information. All the vehicles are equipped with a global positioning system and a wireless communication device.

3. The crossroads control method based on the combination of variable turning lanes and lane changing according to claim 1, characterized in that The lane-changing control steps of the vehicle in S2 are as follows: Control the vehicles in the lane-changing control area. If the first-level lane is adjacent to the third-level lane, control m vehicles in the first-level lane to change lanes to the third-level lane; if the first-level lane is not adjacent to the third-level lane, first control the vehicles in the second-level lane to change lanes to the third-level lane, and then control m vehicles in the first-level lane to change lanes to the second-level lane.

4. The crossroads control method based on the combination of variable turning lanes and lane changing according to claim 1, characterized in that: S4 includes the following steps: S41: Adjust the speed of the leading vehicle according to the latest idle time of the intersection, i.e., the time T when all the passing vehicle convoys in the previous level have left the intersection l , the time T when the vehicle normally travels to the intersection n , the expected driving speed v0 of the vehicle and the expected acceleration a0 of the vehicle S42: Select the safe time T for the vehicle to enter the central conflict area s , let T s = T l ; If then the leading vehicle will decelerate, but the speed will not be reduced to 0, and then go through the speed adjustment process of accelerating, and finally pass through the intersection at a constant speed of v0; If the leading vehicle will first decelerate to 0, wait for a period of time, and then accelerate. Finally, it will pass through the intersection at a constant speed v0 during the speed adjustment process. If T s -T n ≤0, it means that the time for the leading vehicle to normally reach the intersection is later than the time when all the vehicles in the previous passing fleet have left the intersection. Then, the speed of the leading vehicle needs to be adjusted so that it can reach the intersection at time T s ±0.1 S43: Determine the number of following vehicles of the leading vehicle that obtains the right of way, that is, determine the length of the vehicle platoon, and according to the time T when the leading vehicle reaches the intersection after adjusting the speed s , calculate whether the following vehicle can keep up with the vehicle platoon led by the leading vehicle before the leading vehicle enters the intersection under the limit of the maximum speed limit v m of the road section. If it can, grant the vehicle the right of way and allow it to pass through the intersection together with the vehicle platoon passing this time; If it cannot or the desired steering direction of the vehicle is different from that of the fleet, the vehicle in front of this vehicle is used as the tail vehicle of the current passing fleet, and the selection of the passing vehicles in the current lane ends.

Images