Bus speed and signal timing collaborative optimization method based on time window

Abstract

The invention discloses a bus speed and signal timing collaborative optimization method based on a time window, and the method comprises the steps: firstly collecting the position of an intelligent network connection bus, the current speed, the position of a station, the distance between the station and a stop line of an intersection, and a signal timing scheme for an urban road signal control intersection; and then calculating a time window when the bus arrives at the stop line of the intersection and a time window when the bus is allowed to pass at the intersection, judging whether the bus must be stopped or not according to the arrival time window, the passing time window and the green light time of the signal lamp obtained by calculation, and optimizing the running speed and signal timing of the bus. According to the method, the concept of a time window is introduced, and the limitation that speed and signal timing optimization is carried out only on the basis of the time point when a common vehicle arrives at an intersection in an existing method is overcome. The method can effectively reduce the bus delay and stop times, and improves the efficiency of the intelligent network connection bus passing through the intersection.

Description

Technical Field

[0001] The present invention belongs to the field of traffic engineering and traffic information and control systems, and relates to the technical field of intelligent traffic systems, and more specifically, to a method for coordinated optimization of bus speed and signal timing based on a time window. Background Art

[0002] In recent years, the rapid development of intelligent and connected vehicles (ICVs) technology has provided a new idea for the optimization and control of traffic systems, especially in the coordinated optimization of vehicle trajectory and signal timing, which has become one of the hot spots in the research of intelligent transportation systems. ICVs obtain dynamic information of vehicles through real-time communication technology, and combined with traffic signal control strategies, can significantly improve road traffic efficiency, reduce traffic delays, and optimize energy consumption. Professor Yang Xiaoguang and others conducted a comprehensive review of trajectory-level traffic control in a vehicle-road collaborative environment, demonstrating the cutting-edge research progress in this field (Yang Xiaoguang et al. A review of trajectory-level traffic control in a vehicle-road collaborative environment [J]. China Journal of Highway and Transport, 2023, 36(09): 225-243.). Currently, research on vehicle speed guidance for intelligent connected vehicles mainly focuses on optimizing signal timing by adjusting the vehicle's speed so that the vehicle can pass through the intersection smoothly between traffic lights. This method relies on the accurate arrival time of the vehicle and improves the traffic efficiency of the intersection through precise spatiotemporal synchronization. However, this type of method faces certain challenges when dealing with driving guidance for buses. Because buses serve the needs of passengers, they not only have to pass through intersections like ordinary vehicles, but also need to stop at designated stations to pick up and drop off passengers, which increases the volatility and uncertainty of travel time. The stop time of buses is closely related to factors such as the number of passengers and the speed of getting on and off, making it difficult to accurately predict the time when buses stop at stations, resulting in the existing speed guidance and signal timing optimization methods based on ordinary vehicles being difficult to effectively apply to buses. The frequent stops of buses disrupt the coordination of signal timing and vehicle driving trajectories, reducing the overall efficiency of the transportation system. In response to the above problems, the present invention proposes a coordinated optimization method for bus speed and signal timing based on time windows. By considering the arrival time window and passing time window of the bus, combined with the dynamic characteristics of the bus stop, a new optimization method is proposed to improve the punctuality and traffic efficiency of the bus. A control strategy based on dynamic time windows is used to cope with the uncertainty factors in bus operation and realize the intelligent networked bus priority passage mechanism under vehicle-road collaborative control. When the stop time of the bus stop is uncontrollable, it can achieve coordinated optimization of intersection signal timing and vehicle speed, thereby improving the operational efficiency of the public transportation system. Summary of the invention

[0003] Technical problem: In view of the deficiency that the existing research on coordinated optimization of vehicle speed and signal timing cannot be directly applied to buses, the purpose of the present invention is to provide a coordinated optimization method of bus speed and signal timing based on time windows. By introducing arrival time windows and passing time windows, it is determined whether the vehicle can pass through the intersection without stopping, and it is decided whether to implement speed optimization and the specific method of optimization, so as to improve the operating efficiency of buses on urban roads.

[0004] Technical solution: To solve the above technical problems, a bus speed and signal timing coordinated optimization method based on a time window of the present invention comprises the following steps: Step 1: Collect information, including the location of the intelligent network bus, current speed, station location, distance between the station and the intersection stop line, and signal timing plan; Step 2: Calculate the bus arrival time window and travel time window; Step 3: Determine whether the vehicle must stop based on the arrival time window, travel time window, and green light time of the smart connected bus. Based on the judgment result, implement speed guidance and coordinated optimization of traffic lights without stopping.

[0005] In the present invention, the method for calculating the bus arrival time window and the travel time window in step 2 comprises the following steps: Step 21: The bus arrival time window refers to the time range in which the bus arrives at the intersection stop line during the bus operation. The start time of the arrival time window is and end time Together they determine the range of the arrival time window The starting time of the bus arrival time window is the time when the bus leaves the station plus the time when the bus accelerates to the maximum speed V max The time taken, and the position of the intersection stop line at the maximum speed, is calculated by formula (1): in, is the starting time of the bus arrival time window; T0 is the departure time of the bus from the bus station; L2 is the distance from the bus station to the intersection stop line in the speed guidance area, in meters; V max is the maximum speed allowed on the road section, in m / s; a is the acceleration of the smart connected bus, in m / s 2 ; The end time of the bus arrival time window is determined by the distance between the vehicle and the intersection stop line, the minimum speed V allowed by the road section, and the min , acceleration, and the time when the vehicle departs from the bus station are calculated, as shown in formula (2): in, is the end time of the bus arrival time window; V min Indicates the minimum speed allowed for the road section, in m / s. Step 22: The public transportation travel time window refers to the time range in which a bus can pass through the intersection without stopping when it reaches the stop line. Indicates the start time of the public transportation time window The signal light turns green and the start time is G s The difference between the maximum time Δ1 allowed for early off of the red light is calculated as shown in formula (3): in, is the starting time of the bus travel time window; G s is the time when the green light of the current phase signal light starts turning on; Δ1 is the maximum time allowed for the red light to be turned off early. End time of the public transportation travel time window It can be calculated by the sum of the green light end time of the signal light and the maximum time Δ2 allowed to extend the green light, as shown in formula (4): in, G is the end time of the bus travel time window; e is the time when the green light of the current phase signal light ends; Δ2 is the maximum time that the green light is allowed to be extended.

[0006] In the present invention, in step 3, determining whether the vehicle must stop, non-stop speed guidance and signal timing optimization include the following steps: Step 31: When the smart connected bus accelerates to the maximum speed after leaving the station and drives to the stop line of the intersection at this speed, it is just within the maximum extension time of the green light, that is, the time when the smart connected bus arrives at the stop line of the intersection Equivalent to and In this case, consider accelerating the intelligent networked bus to the maximum speed V max Driving, so we only need to find a reasonable acceleration; where: G e The green light end time of the current phase signal light. is the start time of the public transportation time window, is the end time of the bus travel time window, is the starting time of the bus arrival time window, is the end time of the bus arrival time window, T1 is the time when the smart connected bus arrives at the intersection stop line; In the above case, the objective function for accelerating to the maximum speed is set as the shortest time for the smart connected bus to travel from the bus stop to the intersection stop line, including the time for the smart connected bus to accelerate to the maximum speed from the stop, and the time for the smart connected bus to travel to the intersection stop line at the maximum speed, as shown in the formula: Among them, T j represents the time when the intelligent network-connected bus arrives at the stop line of the intersection; T0 represents the time when the bus leaves the bus station; V max It indicates the maximum speed allowed on the road section, in m / s; a indicates the acceleration of the smart connected bus, in m / s 2 ; L2 represents the distance between the vehicle exiting the bus stop and the stop line at the intersection, in meters. The time constraints are shown in formulas (6)-(7). Formula (6) ensures that the intelligent networked bus can reach the intersection stop line within the travel time window; Formula (7) ensures that the research vehicle maintains a safe headway between the vehicle and the preceding vehicle; T j ≥T j-1 +t a (7) Among them, T j-1 Indicates the time when the last vehicle passed the stop line of the intersection; t a The headway time required to ensure the safe operation of smart connected buses, unit: m. Since the operation of intelligent networked buses is also strictly in accordance with traffic regulations, their operation in the speed guidance area should also meet the speed limit of the road section. The full-time driving speed shall not be greater than the maximum driving speed allowed by the road section. The speed constraint is shown in formula (8): V j ≤V max (8) Among them, V j It represents the formal velocity of the research target j in the velocity guidance area, in m / s. In order to ensure the comfort of passengers on the intelligent connected bus, the acceleration and deceleration of the vehicle needs to be set within a reasonable range. The acceleration and deceleration constraints are shown in formula (9): a min ≤a≤a max (9) Among them, a min Indicates the minimum acceleration of the bus; a max Indicates the maximum acceleration. When guiding the speed of an intelligent network-connected bus, a certain safe distance should be maintained from the vehicle in front to ensure driving safety. The distance constraint of adjacent vehicles is shown in formula (10): Where S represents the safe distance between the front and rear vehicles, in meters; V j-1 It indicates the speed of the previous vehicle in the speed guidance area, in m / s; Δt is the sum of the loss time due to communication delay, mechanical delay, etc., in s; L j-1 represents the length of the j-1th vehicle, in meters; j represents the vehicle number, which can be 1, 2,…, n. When a vehicle travels at the maximum speed to the stop line of the intersection, it does not always occupy the entire maximum green light delay time. If the green light delay time is maximized at this time, it will inevitably cause a waste of resources and affect the passage of vehicles in other phases. Therefore, taking the intelligent networked bus passing the intersection stop line as a benchmark, after the vehicle passes the intersection, the green light of the current phase ends and the next phase of vehicles passes; the green light extension time can be calculated by formula (11): Among them, Δ′1 is the green light extension time, unit is s; T j represents the time when the jth vehicle reaches the stop line of the intersection; L j represents the body length of the j-th vehicle, in meters; Step 32: When the smart connected bus accelerates to the minimum speed after leaving the station and drives to the stop line of the intersection at this speed, it is just within the maximum early off time range of the red light, that is, the time when the smart connected bus arrives at the stop line of the intersection Equivalent to and In this case, consider accelerating the smart connected bus to the minimum speed V min Driving, G s The green light start time of the current phase signal light; In this case, the objective function for accelerating to the minimum speed is set as the longest time for the smart connected bus to travel from the bus stop to the intersection stop line, including the time for the smart connected bus to accelerate to the minimum speed from the stop, and the time for the smart connected bus to travel to the intersection stop line at the minimum speed. That is: Among them, V min The minimum speed allowed for the road section, in m / s. The time constraints in this case are shown in formulas (13)-(14). Formula (13) can ensure that the intelligent networked bus arrives within the travel time window, and formula (14) constrains the two vehicles in front and behind to maintain a safe headway. T j ≥T j-1 +t a (14) The speed of the intelligent networked bus in the speed guidance area shall not be less than the minimum speed allowed by the road section. The speed constraint and acceleration constraint are shown in formula (15) and formula (9) respectively. In this case, the vehicle should also maintain a certain safe distance from the vehicle in front to ensure driving safety and meet the constraint of formula (10); V j ≥V min (15) When a vehicle travels to the intersection stop line at the minimum speed, it does not always occupy the entire maximum early red light off time. If the early red light off time is maximized at this time, it will also cause a waste of resources and affect the traffic efficiency of the signalized intersection. Therefore, based on the intelligent network bus reaching the intersection stop line, when the vehicle reaches the intersection, the current phase red light ends and switches to green light for the intelligent network bus to pass. The red light time can be calculated by formula (16). Δ′2=G s -T j (16) Wherein, Δ′2 is the early off time of the red light, in seconds. Step 33: After the smart connected bus leaves the station, it accelerates to any speed between the maximum speed and the minimum speed, and maintains this speed until it reaches the stop line of the intersection. At this time, the traffic light turns green, that is, the smart connected bus arrives at the stop line of the intersection at time T1∈[G s ,G e ], which is equivalent to and In this case, consider accelerating the smart connected bus to an intermediate speed V between the maximum speed and the minimum speed mid Therefore, a random value between the two is taken as the driving speed of the intelligent connected bus. Step 34: When there is no intersection between the arrival time window and the travel time window, the vehicle must stop without optimizing the vehicle speed and signal timing.

[0007] Beneficial effects: Compared with the prior art, the present invention has the following advantages

[0008] The method of the present invention implements coordinated optimization of speed and signal timing for buses based on arrival and passing time windows, overcoming the limitation of existing methods that only optimize speed and signal timing based on the time point when ordinary vehicles arrive at the intersection. It can effectively reduce vehicle delays and the number of stops, and improve the efficiency of intelligent networked buses passing through intersections. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a flow chart of the method of the present invention;

[0010] Figure 2 A schematic diagram of the research object of the method of the present invention;

[0011] Figure 3 This is the spatiotemporal trajectory diagram of 12 buses under the coordinated control of speed and signal. DETAILED DESCRIPTION

[0012] In conjunction with the accompanying drawings and embodiments, the technical solution of the present invention is described in detail as follows:

[0013] Step 1: Collect information, including the location of the smart connected bus, current speed, station location, distance between the station and the intersection stop line, and signal timing plan; select Figure 2 The urban road intersection and connecting road sections shown are the research objects. The maximum speed allowed on the road section is 40km / h; the minimum speed is 20km / h; the guidance length of the vehicle from the bus station to the intersection stop line is 200 meters, the initial speed of the bus is set to 8m / s, and an average of one bus arrives every 5 minutes. The intersection signal control scheme adopts the most basic two-phase sequence control specific signal timing information, the signal cycle is 80s, including two phases, that is, all north-south entrances are released and all east-west entrances are released. Step 2: Calculate the bus arrival time window and travel time window; Step 3: Determine whether the vehicle must stop based on the arrival time window, travel time window, and green light time of the smart connected bus. Based on the judgment result, implement speed guidance and coordinated optimization of traffic lights without stopping.

[0014] Taking the parameters of step 1 as input, optimize the 12 buses that arrive within 3600s and get the space-time trajectory diagram of the vehicles as follows: Figure 3 As shown in the figure, the trajectory curve changes many times, and the dwell time varies, but none of the 12 vehicles stops at the intersection. Compared with no control measures and speed control alone, the coordinated control of signal timing can significantly improve the operation of buses. Compared with no control measures: the average bus delay of the scheme of the present invention is reduced from 11.96 seconds to 0 seconds, the average number of stops is reduced from 0.47 times to 0 times, and the queue length is reduced from 3.58 meters to 0 meters. Compared with speed control only: the average bus delay is reduced from 2.18 seconds to 0 seconds, the average number of stops is reduced from 0.17 times to 0 times, and the queue length is reduced from 0.75 meters to 0 meters. Therefore, the coordinated control of bus speed and signal timing not only further optimizes the operating efficiency of the bus, but is also more effective than simple speed control.

[0015] The present invention is not limited to this single example; any other changes, modifications, substitutions, combinations, simplifications that deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for coordinated optimization of bus speed and signal timing based on time windows, characterized in that: The method comprises the following steps: Step 1: Collect information, including the location of the intelligent network bus, current speed, station location, distance between the station and the intersection stop line, and signal timing plan; Step 2: Calculate the bus arrival time window and travel time window; Step 3: Determine whether the vehicle must stop based on the arrival time window, travel time window, and green light time of the smart connected bus. Based on the judgment result, implement speed guidance and coordinated optimization of traffic lights without stopping; Step 21: The bus arrival time window refers to the time range in which the bus arrives at the intersection stop line during the operation of the bus. The start time of the arrival time window is and end time Together they determine the range of the arrival time window The starting time of the bus arrival time window is the time when the bus leaves the station plus the time when the bus accelerates to the maximum speed V max The time taken, and the position of the intersection stop line at the maximum speed, is calculated by formula (1): in, is the starting time of the bus arrival time window; T0 is the departure time of the bus from the bus station; L2 is the distance from the bus station to the intersection stop line in the speed guidance area, in meters; V max is the maximum speed allowed on the road section, in m / s; a is the acceleration of the smart connected bus, in m / s 2 ; The end time of the bus arrival time window is determined by the distance between the vehicle and the stop line of the intersection, the minimum speed V allowed by the road section, and the min , acceleration, and the time when the vehicle departs from the bus station are calculated, as shown in formula (2): in, is the end time of the bus arrival time window; V min Indicates the minimum speed allowed for the road section, in m / s; Step 22: The public transportation travel time window refers to the time range in which a bus can pass through the intersection without stopping when it reaches the stop line. Indicates the start time of the public transportation time window The signal light turns green and the start time is G s The difference between the maximum time Δ1 allowed for early off of the red light is calculated as shown in formula (3): in, is the starting time of the bus travel time window; G s The green light start time of the current phase signal light; Δ1 is the maximum time allowed for the red light to be turned off early; End time of the public transportation travel time window It can be calculated by the sum of the green light end time of the signal light and the maximum time Δ2 allowed to extend the green light, as shown in formula (4): in, G is the end time of the bus travel time window; e is the time when the green light of the current phase signal light ends; Δ2 is the maximum time that the green light is allowed to be extended.

2. The bus speed and signal timing coordinated optimization method based on time window according to claim 1 is characterized in that: In step 3, determining whether the vehicle must stop, non-stop speed guidance and signal timing optimization include the following steps: Step 31: When the smart connected bus accelerates to the maximum speed after leaving the station and drives to the stop line of the intersection at this speed, it is just within the maximum extension time of the green light, that is, the time when the smart connected bus arrives at the stop line of the intersection Equivalent to and represents an empty set; in this case, consider accelerating the intelligent connected bus to the maximum speed V max Driving, so we only need to find a reasonable acceleration; where: G e The green light end time of the current phase signal light. is the start time of the public transportation time window, is the end time of the bus travel time window, is the starting time of the bus arrival time window, is the end time of the bus arrival time window, T1 is the time when the smart connected bus arrives at the intersection stop line; In the above case, the objective function of accelerating to the maximum speed is set as the shortest time for the smart connected bus to travel from the bus stop to the intersection stop line, including the time for the smart connected bus to accelerate from the stop to the maximum speed and the time for the smart connected bus to travel to the intersection stop line at the maximum speed, as shown in formula (5): Among them, T j represents the time when the intelligent network-connected bus arrives at the stop line of the intersection; T0 represents the time when the bus leaves the bus station; V max It indicates the maximum speed allowed on the road section, in m / s; a indicates the acceleration of the smart connected bus, in m / s 2 ; L2 represents the distance between the vehicle exiting the bus stop and the stop line at the intersection, in meters; The time constraints are shown in formulas (6)-(7). Formula (6) ensures that the intelligent networked bus can reach the intersection stop line within the travel time window; Formula (7) ensures that the research vehicle maintains a safe headway between the vehicle and the preceding vehicle; T j ≥T j-1 +t a (7) Among them, T j-1 Indicates the time when the last vehicle passed the stop line of the intersection; t a The headway time required to ensure safe operation of the intelligent networked bus, in meters; Since the operation of intelligent networked buses is also strictly in accordance with traffic regulations, their operation in the speed guidance area should also meet the speed limit of the road section. The full-time driving speed shall not be greater than the maximum driving speed allowed by the road section. The speed constraint is shown in formula (8): In j ≤V max (8) Among them, V j It represents the formal speed of the research target j in the speed guidance area, in m / s; In order to ensure the comfort of passengers on the intelligent connected bus, the acceleration and deceleration of the vehicle needs to be set within a reasonable range. The acceleration and deceleration constraints are shown in formula (9): a min ≤a≤a max (9) Among them, a min Indicates the minimum acceleration of the bus; a max Indicates the maximum acceleration; When guiding the speed of an intelligent network-connected bus, a certain safe distance should be maintained from the vehicle in front to ensure driving safety. The distance constraint of adjacent vehicles is shown in formula (10): Where S represents the safe distance between the front and rear vehicles, in meters; V j-1 It indicates the speed of the previous vehicle in the speed guidance area, in m / s; Δt is the sum of the loss time due to communication delay, mechanical delay, etc., in s; L j-1 represents the length of the j-1th vehicle, in meters; j represents the vehicle number, which can be 1, 2, ..., n; When a vehicle travels at the maximum speed to the stop line of the intersection, it does not always occupy the entire maximum green light delay time. If the green light delay time is maximized at this time, it will inevitably cause a waste of resources and affect the passage of vehicles in other phases. Therefore, taking the intelligent networked bus passing the intersection stop line as a benchmark, after the vehicle passes the intersection, the green light of the current phase ends and the next phase of vehicles passes. The green light extension time can be calculated by formula (11): Among them, Δ′1 is the green light extension time, unit is s; T j represents the time when the jth vehicle reaches the stop line of the intersection; L j represents the body length of the jth vehicle, in meters; Step 32: When the smart connected bus accelerates to the minimum speed after leaving the station and drives to the stop line of the intersection at this speed, it is just within the maximum early off time range of the red light, that is, the time when the smart connected bus arrives at the stop line of the intersection Equivalent to and In this case, consider accelerating the smart connected bus to the minimum speed V min Driving, G s The green light start time of the current phase signal light; In this case, the objective function for accelerating to the minimum speed is set as the longest time for the smart connected bus to travel from the bus stop to the intersection stop line, including the time for the smart connected bus to accelerate from the stop to the minimum speed, and the time for the smart connected bus to travel to the intersection stop line at the minimum speed; that is: Among them, V min The minimum speed allowed for the road section, in m / s. The time constraints in this case are shown in formulas (13)-(14). Formula (13) can ensure that the intelligent networked bus arrives within the travel time window, and formula (14) constrains the two vehicles in front and behind to maintain a safe headway. T j ≥T j-1 +t a (14) The speed of the intelligent networked bus in the speed guidance area shall not be less than the minimum speed allowed by the road section. The speed constraint and acceleration constraint are shown in formula (15) and formula (9) respectively. In this case, the vehicle should also maintain a certain safe distance from the vehicle in front to ensure driving safety and meet the constraint of formula (10); In j ≥V min (15) When a vehicle travels to the stop line of an intersection at the minimum speed, it does not always occupy the entire maximum early red light off time. If the early red light off time is maximized at this time, it will also cause a waste of resources and affect the traffic efficiency of the signalized intersection. Therefore, based on the intelligent networked bus reaching the stop line of the intersection, when the vehicle arrives at the intersection, the current phase red light ends and switches to green light for the intelligent networked bus to pass. The red light time can be calculated by formula (16); Δ′2=G s -T j (16) Where Δ′2 is the early off time of the red light, unit is s; Step 33: After the smart connected bus leaves the station, it accelerates to any speed between the maximum speed and the minimum speed, and maintains this speed until it reaches the stop line of the intersection. At this time, the traffic light turns green, that is, the smart connected bus arrives at the stop line of the intersection at time T1∈[G s , G e ], which is equivalent to and In this case, consider accelerating the smart connected bus to an intermediate speed V between the maximum speed and the minimum speed mid Therefore, the random value between the two is taken as the driving speed of the intelligent connected bus; Step 34: When the arrival time window and the travel time window do not intersect, the vehicle must stop without optimizing the vehicle speed and signal timing.

Images