Emergency vehicle travel road impedance measuring and calculating method in network connection traffic environment

Abstract

The invention relates to an emergency vehicle travel road impedance measuring and calculating method in a network connection traffic environment. The method comprises the following steps: step 1, establishing a vehicle state information matrix of an emergency vehicle travel path space; 2, constructing an emergency vehicle travel road section impedance model; 3, constructing an emergency vehicle travel intersection delay model; and step 4, generating a lane-level emergency vehicle travel road impedance model. According to the method, the road impedance borne by the emergency vehicle in the travel process in the network connection traffic environment can be accurately measured and calculated, a theoretical foundation is laid for travel path planning of the emergency vehicle, and the method is suitable for global optimization control of the emergency vehicle in the network connection traffic environment and has a wide application prospect. The method is subsidized by the natural science fund project (PL2024E012) of Heilongjiang Province.

Description

Technical Field

[0001] The present invention belongs to the field of traffic engineering, and constructs a lane-level emergency vehicle travel road impedance calculation method based on a networked traffic environment. Background Art

[0002] With the rapid development of V2X technology and the large-scale application of intelligent network technology, it has become more convenient to obtain vehicle information in a networked traffic environment. Most of the current research on emergency vehicle travel path planning is based on the traditional road impedance function, which plans the travel path by predicting the shortest travel time. However, these studies do not consider the impact of the controllable trajectory of connected autonomous vehicles (CAVs) and the speed induction of connected manually driven vehicles (CHVs) on the travel impedance of emergency vehicles. There are: (1) The accuracy of emergency vehicle travel time prediction is reduced, and the reliability of path planning cannot be guaranteed. (2) Existing control methods face the risk of failure in a networked traffic environment.

[0003] Based on this, a lane-level road impedance calculation method for emergency vehicle travel in a connected traffic environment is established by making full use of the controllable and inducible advantages of CAV and CHV trajectories, so as to improve the reliability of emergency vehicle travel path planning and achieve the purpose of improving road traffic travel efficiency and safety. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a method for calculating the impedance of emergency vehicle travel roads in a networked traffic environment.

[0005] The present invention relates to a method for calculating impedance of a road for emergency vehicles under a networked traffic environment, comprising the following steps:

[0006] Step 1: Establish the vehicle status information matrix of the emergency vehicle travel path space;

[0007] Step 2: Construct an impedance model for emergency vehicle travel sections;

[0008] Step 3: Construct an intersection delay model for emergency vehicle travel;

[0009] Step 4: Generate a lane-level emergency vehicle travel road impedance model.

[0010] Furthermore, in step 1, an intersection in the emergency vehicle travel path is taken as point A, and the adjacent intersection is taken as point B. All lanes that the emergency vehicle may pass through are included in the information collection scope, and are divided into a road section control area and an intersection control area, with lengths L and L respectively. lin and L int ,like Figure 2As shown. Based on V2X technology, the roadside unit and intersection controller detect the operation information of all vehicles in the area in real time, including position, speed, acceleration, etc., and establish the vehicle state information matrix L in the emergency vehicle travel path space. AB .

[0011] Assume that there are n vehicles in the road section control area and m vehicles in the intersection control area, X is the position matrix, V is the velocity matrix, and A is the acceleration matrix.

[0012]

[0013]

[0014]

[0015] Where, L lin Represents the vehicle status information matrix of the road section control area; L int represents the vehicle status information matrix of the intersection control area; x lin,ibl 、v lin,ibl 、a lin,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the road section control area. 2 ); x int,ibl 、v int,ibl 、a int,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the intersection control area. 2 ). The dynamic behavior of each vehicle on the path needs to be considered:

[0016] x ibl (t+Δt)=x ibl (t)-v ibl (t)Δt-0.5a ibl (t)(Δt) 2

[0017] v ibl (t+Δt)=v ibl (t)+a ibl (t)Δt

[0018] Where Δt is a time unit (s).

[0019] Furthermore, in step 2, in the road section control area, in order to calculate the road impedance of the emergency vehicle, it is necessary to identify the vehicles that conflict with the emergency vehicle on a certain lane. The road impedance mainly depends on the time required for these conflicting vehicles to clear and the time required for the emergency vehicle to freely travel through the road section. At the same time, the impact of CAV penetration on the driving speed of the emergency vehicle should also be considered.

[0020] (1) Calculate the free travel time of emergency vehicles and define conflicting vehicles

[0021] Free travel time for emergency vehicles It refers to the time required for the emergency vehicle to travel through the road section without any obstacles. Assume that the speed of the emergency vehicle in the road section control area is v lin,e , considering the impact of CAV penetration on the speed of emergency vehicles, then:

[0022]

[0023]

[0024]

[0025]

[0026] In the formula, p CAV is the penetration rate of CAV; is the critical value. This indicates that the vehicle will not affect the passage of emergency vehicles; otherwise, vehicle i on lane b in lane group l is a conflicting vehicle.

[0027] (2) Calculate impedance vehicle clearing time

[0028] The following formula can be used to determine whether the conflicting vehicle can accelerate and change lanes: if it cannot accelerate, the vehicle needs to change lanes; if there is not enough space in the adjacent lane, the vehicle cannot change lanes. These vehicles that cannot accelerate or change lanes will create impedance for the emergency vehicle.

[0029]

[0030]

[0031] In the formula, v max is the maximum speed limit of the road section (m / s); t ibl is the reaction time (s) of the conflicting vehicle i on lane b in lane group l; d front,ibl ,d rear,ibl is the distance (m) between the conflicting vehicle i in lane b of lane group l and the preceding and following vehicles in the adjacent lane; d s is the safety distance (m); l ibl is the length (m) of vehicle i on lane b in lane group l. A value of 0 means the vehicle cannot accelerate or change lanes.

[0032] The clearance time t of the impedance vehicle is calculated by the time required for each vehicle that generates impedance to the emergency vehicle to leave the road section control area from its current position. clear,ibl .

[0033] t clear,ibl =x lin,ibl / v lin,ibl

[0034] Then, the time t required to simultaneously clear all conflicting vehicles that generate impedance is clear for:

[0035] t clear =max(t clear ,1bl,...,t clear,ibl )

[0036] (3) Calculate road delays for emergency vehicles

[0037] The calculation formula for the delay of emergency vehicles in the road section control area is:

[0038]

[0039] Through the above steps, the road impedance encountered by emergency vehicles on the road section can be calculated.

[0040] Furthermore, in step 3, in the road impedance model of emergency vehicles, not only the impedance on the road section needs to be considered, but also the delay of emergency vehicles within the intersection range. The intersection is divided into three types: unsignalized intersection, signalized intersection without dedicated lane, and signalized intersection with dedicated lane. In the networked traffic environment, different types of intersections have different control methods, so the calculation of emergency vehicle delay is also different.

[0041] (1) Unsignalized intersection

[0042] At an unsignalized intersection, the emergency vehicle requests other vehicles to give way via V2X. The delay time mainly depends on the avoidance time of the conflicting vehicles and the congestion of the intersection. Since vehicles cannot change lanes within the intersection, the avoidance time of each vehicle depends on its current position, speed, and the length of its avoidance path. The rest of the calculation method is similar to the road section. Assume that the speed of the emergency vehicle in the intersection control area is v int,e , considering the impact of V / C on the speed of the emergency vehicle, then:

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] In the formula, v cross is the maximum speed limit at the intersection (m / s). Each vehicle passing through creates impedance to the emergency vehicle The time required to leave the intersection control area from the current position is used to calculate the avoidance time t of the impedance vehicle aviod,ibl .

[0049] t avoid,ibl =x int,ibl / v int,ibl

[0050] Then, the avoidance time t required for all conflicting vehicles that generate impedance is avoid for:

[0051] t avoid =max(t avoid,1bl ,...,t avoid,ibl )

[0052] The formula for calculating the delay of emergency vehicles at unsignalized intersections is:

[0053]

[0054] (2) Intersection with signal but no dedicated lane

[0055] At intersections with signals but no dedicated lanes, emergency vehicles need to communicate with the signal control system to request a priority green light. If the current state of the emergency vehicle is green (w = 0), its delay time depends on the time it takes for the vehicle ahead to clear, which is the same as the calculation method for intersections without signals; if the current state of the emergency vehicle is red (w = 1), its delay time depends on the signal switching time and the time it takes to clear the vehicle ahead.

[0056] Signal switching time t switch It refers to the time from when the emergency vehicle requests a priority green light to when the signal actually switches to green, including the yellow light time Y and the red light clearing time t rc The time required to clear the vehicles in front of the emergency vehicle is calculated using whether the vehicle can reach the end of the queue as the criterion.

[0057]

[0058]

[0059]

[0060]

[0061] In the formula, is the maximum time (s) required for the conflicting vehicle i in lane b of lane group l to reach the tail of the front team; ibl (t) is the shortest time (s) required for conflicting vehicle i in lane b of lane group l to reach the stop line without being affected; t front is the time (s) required to clear the last vehicle in front of the emergency vehicle; q is the serial number of the last vehicle in front of the emergency vehicle; τ ibl is the starting loss time (s) of conflicting vehicle i on lane b in lane group l; h ibl is the saturated headway time (s) of conflicting vehicle i on lane b in lane group l; a max is the maximum acceleration (m / s 2 );a acc is the expected acceleration (m / s 2 );a dec is the expected deceleration (m / s 2 );v min is the minimum speed limit (m / s); t l,k The time (s) when the green light is turned on for emergency vehicles.

[0062] (3) Intersections with signals and dedicated lanes

[0063] At intersections with signals and dedicated lanes, emergency vehicles should 0 Enter the dedicated lane at any time for priority passage, and the delay time It mainly depends on the traffic conditions of the dedicated lane. If there are no other vehicles blocking the dedicated lane, the emergency vehicle can move at a maximum speed of v cross otherwise, the speed of the emergency vehicle will be affected by the vehicle ahead.

[0064] There is no car in front of the emergency vehicle.

[0065]

[0066] There is a car ahead of the emergency vehicle.

[0067] t b,s =t 0 +x b (t 0 ) / v b (t 0 )

[0068] t e,min =t b,s +t sa

[0069]

[0070] Where, t e,min ,te,max The earliest and latest time (s) for the emergency vehicle to pass the stop line; l e is the length of the emergency vehicle (m); t b,s is the time (s) when the vehicle in front of the emergency vehicle reaches the stop line; t sa The reserved safety time (s); v b (t 0 ) is the vehicle in front of the emergency vehicle at t 0 Speed ​​at the moment (m / s); x b (t 0 ) is the vehicle in front of the emergency vehicle at t 0 Position at the moment (m); l b is the length of the vehicle in front of the emergency vehicle (m); x e,m is the distance (m) between the entrance parking line where the emergency vehicle is located and the lower boundary of the mth conflict area; x m is the length of the mth conflict region (m); is the phase green light on time (s) when lane group u conflicts with the emergency vehicle in the kth cycle; is the phase green light end time (s) when lane group u conflicts with the emergency vehicle in the kth cycle.

[0071] According to the optimal time t of the emergency vehicle arriving at the intersection stop line es (Borrowing the green light at the head of conflicting traffic: +g EMV , Use the green light at the tail end of the conflicting traffic flow: Or interspersed passage: t es =t e,min -g EMV ), the delay time of emergency vehicles on the dedicated lane can be expressed as:

[0072]

[0073] By considering the delays of emergency vehicles at different types of intersections and combining real-time data and control strategies in a connected traffic environment, the path planning of emergency vehicles can be optimized to ensure that they arrive at their destination with minimal delay, which not only improves the efficiency of emergency response but also enhances the reliability of path planning.

[0074] Furthermore, in step 4, in order to calculate the total delay of the emergency vehicle on the entire path, the delays of the road sections and intersections need to be summed up so that the overall delay is closer to the actual situation.

[0075]

[0076] Beneficial Effects

[0077] By utilizing the controllable and inducible advantages of CAV and CHV trajectories, including real-time traffic information, inter-vehicle communication, and the active avoidance strategy of connected vehicles to emergency vehicles, the accuracy of emergency vehicle travel time prediction is improved, and the basic theory is provided for emergency vehicle travel path planning. Based on this, a lane-level emergency vehicle travel road impedance calculation method in a connected traffic environment is established, which can improve the travel time prediction accuracy of emergency vehicles by more than 15%, thereby improving the speed and reliability of emergency response, and ultimately improving the efficiency and safety of the overall traffic management system. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 Flow chart for implementing the present invention

[0079] Figure 2 Schematic diagram of road impedance zoning calculation in the present invention DETAILED DESCRIPTION

[0080] The following combination Figure 1-2 The embodiments of the present invention will be described in detail.

[0081] The purpose of the present invention is to establish a method for calculating the road impedance of emergency vehicles at the lane level in a networked traffic environment. The process is summarized as follows:

[0082] First, the roadside units and intersection controllers on the emergency vehicle travel path collect all vehicle operation information in the space, including position, speed, acceleration, etc., and establish a state information matrix. Then, based on the vehicle operation status and the penetration rate of CAVs, the road impedance of the emergency vehicle on the road section is analyzed and calculated. Secondly, the delay of the emergency vehicle is calculated based on the control method of the emergency vehicle in the intersection range (whether there is signal control or dedicated lane). Finally, a complete road impedance model for the emergency vehicle is generated to ensure the accuracy of the emergency vehicle travel time prediction.

[0083] The above-mentioned method for calculating the road impedance of emergency vehicles at the lane level in a networked traffic environment is implemented as follows: Figure 1 , the specific implementation steps are as follows:

[0084] Step 1: Establish the vehicle status information matrix of the emergency vehicle travel path space

[0085] Take an intersection in the travel path of the emergency vehicle as point A and the adjacent intersection as point B. Include all lanes that the emergency vehicle may pass through in the information collection scope and divide them into a road section control area and an intersection control area with lengths L and L respectively. lin and L int ,like Figure 2As shown. Based on V2X technology, the roadside unit and intersection controller detect the operation information of all vehicles in the area in real time, including position, speed, acceleration, etc., and establish the vehicle state information matrix L in the emergency vehicle travel path space. AB .

[0086] Assume that there are n vehicles in the road section control area and m vehicles in the intersection control area, X is the position matrix, V is the velocity matrix, and A is the acceleration matrix.

[0087]

[0088]

[0089]

[0090] Where, L lin Represents the vehicle status information matrix of the road section control area; L int represents the vehicle status information matrix of the intersection control area; x lin,ibl 、v lin,ibl 、a lin,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the road section control area. 2 ); x int,ibl 、v int,ibl 、a int,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the intersection control area. 2 ). The dynamic behavior of each vehicle on the path needs to be considered:

[0091] x ibl (t+Δt)=x ibl (t)-v ibl (t)Δt-0.5a ibl (t)(Δt) 2

[0092] v ibl (t+Δt)=v ibl (t)+a ibl (t)Δt

[0093] Where Δt is a time unit (s).

[0094] Assume that a path has 4 lanes and there are 11 vehicles in the road section control area. The vehicle status information matrix is ​​as follows:

[0095]

[0096]

[0097] Update the positions and velocities of all vehicles with a time step of Δt=1s:

[0098]

[0099]

[0100] Step 2: Construct an impedance model for emergency vehicle travel sections

[0101] In the road section control area, in order to calculate the road impedance of the emergency vehicle, it is necessary to identify the vehicles that conflict with the emergency vehicle on a certain lane. The road impedance mainly depends on the time required for these conflicting vehicles to clear and the time required for the emergency vehicle to travel freely through the road section. At the same time, the impact of CAV penetration on the travel speed of emergency vehicles must also be considered.

[0102] (1) Calculate the free travel time of emergency vehicles and define conflicting vehicles

[0103] Free travel time for emergency vehicles It refers to the time required for the emergency vehicle to travel through the road section without any obstacles. Assume that the speed of the emergency vehicle in the road section control area is v lin,e , considering the impact of CAV penetration on the speed of emergency vehicles, then:

[0104]

[0105]

[0106]

[0107]

[0108] In the formula, p CAV is the penetration rate of CAV; is the critical value. This indicates that the vehicle will not affect the passage of emergency vehicles; otherwise, vehicle i on lane b in lane group l is a conflicting vehicle.

[0109] Assume that the length of the road section control area is L lin =200m, maximum speed limit of the road section v max =15m / s. CAV permeability p CAV = 0.3, the speed of the emergency vehicle v lin,e =10m / s, and the rest of the vehicle attributes and initial states are the same as the matrix in step 1.

[0110] According to formula (6), the critical CAV permeability is calculated = 0.3, considering the impact of CAV penetration on the speed of emergency vehicles, from equations (7) and (8), we can know that the speed and free travel time of emergency vehicles are 13 m / s and 15.38 s. Assuming the safety distance d s =5m, vehicle length l ibl =4m, calculate the free travel time of vehicles on each lane:

[0111] Lane 1: Car 1 is 5.9s, Car 2 is 16.125s;

[0112] Lane 2: Car 1 takes 9.86s, Car 2 takes 24.83s, and Car 3 takes 23.22s;

[0113] Lane 3: Car 1 takes 3.9s, Car 2 takes 10.82s, and Car 3 takes 16.58s;

[0114] Lane 4: Car 1 is 5.27s, car 2 is 23.625s, and car 3 is 17.42s.

[0115] like This means that the vehicle will not affect the passage of emergency vehicles; otherwise, vehicle i on lane b in lane group l is a conflicting vehicle. Therefore, vehicle 2 on lane 1, vehicle 2 and vehicle 3 on lane 2, vehicle 3 on lane 3, and vehicle 2 and vehicle 3 on lane 4 are conflicting vehicles.

[0116] (2) Calculate impedance vehicle clearing time

[0117] The following formula can be used to determine whether the conflicting vehicle can accelerate and change lanes: if it cannot accelerate, the vehicle needs to change lanes; if there is not enough space in the adjacent lane, the vehicle cannot change lanes. These vehicles that cannot accelerate or change lanes will create impedance for the emergency vehicle.

[0118]

[0119]

[0120] In the formula, v max is the maximum speed limit of the road section (m / s); t ibl is the reaction time (s) of the conflicting vehicle i on lane b in lane group l; d front,ibl ,d rear,ibl is the distance (m) between the conflicting vehicle i in lane b of lane group l and the preceding and following vehicles in the adjacent lane; d s is the safety distance (m); l ibl is the length (m) of vehicle i on lane b in lane group l. A value of 0 means the vehicle cannot accelerate or change lanes.

[0121] The clearance time t of the impedance vehicle is calculated by the time required for each vehicle that generates impedance to the emergency vehicle to leave the road section control area from its current position. clear,ibl .

[0122] t clear,ibl =x lin,ibl / v lin,ibl

[0123] Then, the time t required to simultaneously clear all conflicting vehicles that generate impedance is clear for:

[0124] t clear =max(t clear ,1bl,...,t clear,ibl )

[0125] Based on formulas (10) and (11), it is determined whether the conflicting vehicles in step (1) can accelerate and change lanes: if they cannot accelerate, the vehicle needs to change lanes; if there is not enough space in the adjacent lane, the vehicle cannot change lanes. These vehicles that cannot accelerate or change lanes will create impedance for the emergency vehicle. Assume a acc =3m / s 2 ,t ibl =3s,

[0126] Lane 1:

[0127] Lane 2:

[0128] Lane 3:

[0129] Lane 4:

[0130] This indicates that the vehicle 3 on the lane 4 will generate impedance to the emergency vehicle.

[0131] (3) Calculate road delays for emergency vehicles

[0132] The calculation formula for the delay of emergency vehicles in the road section control area is:

[0133]

[0134] Through the above steps, the road impedance encountered by emergency vehicles on the road section can be calculated.

[0135] From equations (12) to (14), it can be obtained that the time required to clear the impedance vehicles is 16.67 s, and the road impedance experienced by the emergency vehicle on lane 4 in the section control area is calculated to be 1.29 s.

[0136] Step 3: Construct an intersection delay model for emergency vehicle travel

[0137] In the road impedance model for emergency vehicles, not only the impedance on the road section needs to be considered, but also the delay of emergency vehicles within the intersection range. Intersections are divided into three types: unsignalized intersections, signalized intersections without dedicated lanes, and signalized intersections with dedicated lanes. In a connected traffic environment, different types of intersections have different control methods, so the calculation of emergency vehicle delays is also different.

[0138] (1) Unsignalized intersection

[0139] At an unsignalized intersection, the emergency vehicle requests other vehicles to give way via V2X. The delay time mainly depends on the avoidance time of the conflicting vehicles and the congestion of the intersection. Since vehicles cannot change lanes within the intersection, the avoidance time of each vehicle depends on its current position, speed, and the length of its avoidance path. The rest of the calculation method is similar to the road section. Assume that the speed of the emergency vehicle in the intersection control area is v int,e , considering the impact of V / C on the speed of the emergency vehicle, then:

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] In the formula, v cross is the maximum speed limit at the intersection (m / s). Each vehicle passing through creates impedance to the emergency vehicle The time required to leave the intersection control area from the current position is used to calculate the avoidance time t of the impedance vehicle aviod,ibl .

[0146] t avoid,ibl =x int,ibl / v int,ibl

[0147] Then, the avoidance time t required for all conflicting vehicles that generate impedance is avoid for:

[0148] t avoid =max(t avoid,1bl ,...,t avoid,ibl )

[0149] The formula for calculating the delay of emergency vehicles at unsignalized intersections is:

[0150]

[0151] Assume that there are 12 vehicles in the intersection control area, and the vehicle status information matrix is ​​as follows:

[0152]

[0153]

[0154] Update the positions and velocities of all vehicles with a time step of Δt=1s:

[0155]

[0156]

[0157] At an unsignalized intersection, the emergency vehicle requests other vehicles to actively give way through V2X. The delay time mainly depends on the avoidance time of the conflicting vehicles and the congestion of the intersection. Since vehicles cannot change lanes within the intersection, the avoidance time of each vehicle depends on its current position, speed, and the length of its avoidance path. Assume that the speed v of the emergency vehicle in the intersection control area is int,e =10m / s, V / C=0.6, v cross =12m / s. Considering the influence of V / C on the speed of emergency vehicles, according to formula (15) is 0.2. From equations (16) and (17), we can know that the speed and free travel time of the emergency vehicle are 12 m / s and 8.33 s. Assuming d s =3m,l ibl =4m,t ibl =1s, τ ibl =1s,h ibl =2s Calculate the free travel time of vehicles on each lane:

[0158] Lane 1: Car 1 is 4s, Car 2 is 8s, Car 3 is 9.4s, Car 4 is 8.2s;

[0159] Lane 2: Car 1 takes 4 seconds, car 2 takes 8 seconds, car 3 takes 4.625 seconds, and car 4 takes 6.83 seconds;

[0160] Lane 3: Car 1 takes 3s, Car 2 takes 9.5s, and Car 3 takes 7.9s;

[0161] Lane 4: Car 1 is 2.33s, car 2 is 8.86s, and car 3 is 12.83s.

[0162] like This means that the vehicle will not affect the passage of emergency vehicles; otherwise, vehicle i on lane b in lane group l is a conflicting vehicle. Therefore, vehicle 3 on lane 1, vehicle 2 on lane 3, and vehicles 2 and 3 on lane 4 are conflicting vehicles.

[0163] Each vehicle that creates impedance to the emergency vehicle The time required to leave the intersection control area from the current position is used to calculate the avoidance time t of the impedance vehicle aviod,ibl Based on formula (19), it is determined whether the conflicting vehicles can accelerate. These vehicles that cannot accelerate will generate impedance to the emergency vehicle. Assume a acc =3m / s 2 ,

[0164] Lane 1:

[0165] Lane 3:

[0166] Lane 4:

[0167] This shows that vehicle 3 on lane 4 will generate impedance to the emergency vehicle. From equations (20) to (22), it can be obtained that the time required to clear the impedance vehicle is 11.67s, and the road impedance experienced by the emergency vehicle on lane 4 in the intersection control area is calculated to be 3.34s.

[0168] (2) Intersection with signal but no dedicated lane

[0169] At intersections with signals but no dedicated lanes, emergency vehicles need to communicate with the signal control system to request a priority green light. If the current state of the emergency vehicle is green (w = 0), its delay time depends on the time it takes for the vehicle ahead to clear, which is the same as the calculation method for intersections without signals; if the current state of the emergency vehicle is red (w = 1), its delay time depends on the signal switching time and the time it takes to clear the vehicle ahead.

[0170] Signal switching time t switch It refers to the time from when the emergency vehicle requests a priority green light to when the signal actually switches to green, including the yellow light time Y and the red light clearing time t rc The time required to clear the vehicles in front of the emergency vehicle is calculated using whether the vehicle can reach the end of the queue as the criterion.

[0171] t switch =Y+t rc

[0172]

[0173]

[0174]

[0175]

[0176] In the formula, is the maximum time (s) required for the conflicting vehicle i in lane b of lane group l to reach the tail of the front team; ibl (t) is the shortest time (s) required for conflicting vehicle i in lane b of lane group l to reach the stop line without being affected; t front is the time (s) required to clear the last vehicle in front of the emergency vehicle; q is the serial number of the last vehicle in front of the emergency vehicle; τ ibl is the starting loss time (s) of conflicting vehicle i on lane b in lane group l; h ibl is the saturated headway time (s) of conflicting vehicle i on lane b in lane group l; a max is the maximum acceleration (m / s 2 );a acc is the expected acceleration (m / s 2 );a dec is the expected deceleration (m / s 2 );v min is the minimum speed limit (m / s); t l,k The time (s) when the green light is turned on for emergency vehicles.

[0177] Assume that the current emergency vehicle is in the red light state (w = 1) and Y = 3s, t rc =3s, then the signal switching time t switch = 6s. Using whether the vehicle can reach the end of the queue as the judgment condition, calculate the time required to clear the vehicles in front of the emergency vehicle. Let v min =4m / s, a max =4m / s 2 、a dec =-3m / s 2 ,but

[0178] Lane 1: Lane 2:

[0179] Lane 3:

[0180] Lane 4:

[0181] From formula (27), it can be obtained that if the current state of the emergency vehicle is green light (w = 0), the delay time is 3.34s; if the current state of the emergency vehicle is red light (w = 1), the delay time of lanes 1 and 2 is 13.67s, the delay time of lane 3 is 6.61s, and the delay time of lane 4 is 6.67s. The lane with the smallest delay time should be selected, so the delay time of the emergency vehicle in the control area of ​​the signal intersection is 6.61s.

[0182] (3) Intersections with signals and dedicated lanes

[0183] At intersections with signals and dedicated lanes, emergency vehicles should 0 Enter the dedicated lane at any time for priority passage, and the delay time It mainly depends on the traffic conditions of the dedicated lane. If there are no other vehicles blocking the dedicated lane, the emergency vehicle can move at a maximum speed of v cross otherwise, the speed of the emergency vehicle will be affected by the vehicle ahead.

[0184] There is no car in front of the emergency vehicle.

[0185]

[0186] There is a car ahead of the emergency vehicle.

[0187] t b,s =t 0 +x b (t 0 ) / v b (t 0 )

[0188] t e,min =t b,s +t sa

[0189]

[0190] In the formula, t e,min ,t e,max The earliest and latest time (s) for the emergency vehicle to pass the stop line; l e is the length of the emergency vehicle (m); t b,s is the time (s) when the vehicle in front of the emergency vehicle reaches the stop line; t sa The reserved safety time (s); v b (t 0 ) is the vehicle in front of the emergency vehicle at t 0 Speed ​​at the moment (m / s); x b (t 0 ) is the vehicle in front of the emergency vehicle at t 0 Position at the moment (m); lb is the length of the vehicle in front of the emergency vehicle (m); x e,m is the distance (m) between the entrance parking line where the emergency vehicle is located and the lower boundary of the mth conflict area; x m is the length of the mth conflict region (m); is the phase green light on time (s) when lane group u conflicts with the emergency vehicle in the kth cycle; is the phase green light end time (s) when lane group u conflicts with the emergency vehicle in the kth cycle.

[0191] According to the optimal time t of the emergency vehicle arriving at the intersection stop line es (Borrowing the green light at the head of conflicting traffic: +g EMV , Use the green light at the tail end of the conflicting traffic flow: Or interspersed passage: t es =t e,min -g EMV ), the delay time of emergency vehicles on the dedicated lane can be expressed as:

[0192]

[0193] By considering the delays of emergency vehicles at different types of intersections and combining real-time data and control strategies in a connected traffic environment, the path planning of emergency vehicles can be optimized to ensure that they arrive at their destination with minimal delay, which not only improves the efficiency of emergency response but also enhances the reliability of path planning.

[0194] Assume that the emergency vehicle is traveling straight from south to north: at time t 0 0s, length l e is 10m, entry speed v int,e is 10m / s, maximum acceleration a max 4m / s 2 , minimum acceleration a min -4m / s 2 , maximum speed v max is 15m / s, minimum speed v min is 4m / s, the maximum speed limit at the intersection is v cross 12m / s; front vehicle: initial position x b (t 0 ) is 50m, initial speed v b (t 0 ) is 9m / s, length l b In addition, the reserved safety time t sa 3s.

[0195] If the signal phase scheme of the intersection is: (1) 20 seconds for left turn green light and 3 seconds for yellow light in the north-south direction; (2) 30 seconds for straight green light and 3 seconds for north-south direction; (3) 20 seconds for left turn green light and 3 seconds for yellow light in the east-west direction; (4) 30 seconds for straight green light and 3 seconds for east-west direction. When the emergency vehicle enters, the east-west straight green light is on, and the north-south left turn green light is on at 13 seconds. There is a car in front of the emergency vehicle. The earliest time t at which it passes the stop line can be obtained from equations (28) to (30). e,min is 8.56s, the latest time is t e,max It is 24.375s.

[0196] According to the overlap between the time interval of the emergency vehicle passing the stop line and the signal phase scheme, vehicles turning left from the north will hinder the passage of the emergency vehicle in the second conflict zone, and the length of the conflict zone x m The distance between the lower boundary of the second conflict zone and the entrance stop line where the emergency vehicle is located is 16m. At this time, the emergency vehicle is released at the head of the green light for turning left in the north-south direction, which is the best time for the emergency vehicle to arrive at the stop line. According to formula (31), g EMV =3.75s, so t es =9.25s. From formula (32), the delay time of the emergency vehicle is 0s, indicating that the emergency vehicle can pass smoothly on the dedicated lane without being hindered.

[0197] Step 4: Generate lane-level emergency vehicle travel road impedance model

[0198] In order to calculate the total delay of the emergency vehicle on the entire path, the delays of the road sections and intersections need to be summed up to make the overall delay closer to the actual situation.

[0199]

[0200] Similarly, if the combination is "road section + intersection without signalization", the road impedance of the emergency vehicle is 4.63s; if the combination is "road section + intersection with signalization but no dedicated lane", the road impedance of the emergency vehicle is 7.9s; if the combination is "road section + intersection with signalization and dedicated lane", the road impedance of the emergency vehicle is 1.29s.

[0201] The above contents of the present invention are only preferred implementation cases of the present invention and are not intended to limit the implementation scheme of the present invention. Ordinary technicians in the field can easily make corresponding changes or modifications based on the main concept and spirit of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope required by the claims.

Claims

1. A method for calculating the road impedance of emergency vehicles under a networked traffic environment, characterized in that: The steps include: Step 1: Establish the vehicle status information matrix of the emergency vehicle travel path space; Step 2: Construct an impedance model for emergency vehicle travel sections; Step 3: Construct an intersection delay model for emergency vehicle travel; Step 4: Generate a lane-level emergency vehicle travel road impedance model.

2. The method for calculating the road impedance of emergency vehicles under a networked traffic environment according to claim 1 is characterized in that: In step 1, an intersection in the emergency vehicle's travel path is taken as point A, and the adjacent intersection is taken as point B. All lanes that the emergency vehicle may pass through are included in the information collection scope and divided into a road section control area and an intersection control area, with lengths L and L respectively. lin and L int , as shown in Figure 2. The roadside unit and intersection controller detect the operation information of all vehicles in the area in real time based on V2X technology, including position, speed, acceleration, etc., and establish the vehicle state information matrix L in the emergency vehicle travel path space. AB . Assume that there are n vehicles in the road section control area and m vehicles in the intersection control area, X is the position matrix, V is the velocity matrix, and A is the acceleration matrix. Where, L lin Represents the vehicle status information matrix of the road section control area; L int represents the vehicle status information matrix of the intersection control area; x lin,ibl 、v lin,ibl 、a lin,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the road section control area. 2 ); x int,ibl 、v int,ibl 、a int,ibl represents the current position (m), speed (m / s) and acceleration (m / s) of the i-th vehicle in lane b of lane group l in the intersection control area. 2 ). The dynamic behavior of each vehicle on the path needs to be considered: x ibl (t+Δt)=x ibl (t)-v ibl (t)Δt-0.5a ibl (t)(Δt) 2 v ibl (t+Δt)=v ibl (t)+a ibl (t)Δt Where Δt is a time unit (s).

3. The method for calculating the road impedance of emergency vehicles under a networked traffic environment according to claim 1, characterized in that: In step 2, in the road section control area, in order to calculate the road impedance to the emergency vehicle, it is necessary to identify the vehicles that conflict with the emergency vehicle on a certain lane. The road impedance mainly depends on the time required for these conflicting vehicles to clear and the time required for the emergency vehicle to travel freely through the road section. At the same time, the impact of CAV penetration on the travel speed of the emergency vehicle must also be considered. (1) Calculate the free travel time of emergency vehicles and define conflicting vehicles Free travel time for emergency vehicles It refers to the time required for the emergency vehicle to travel through the road section without any obstacles. Assume that the speed of the emergency vehicle in the road section control area is v lin,e , considering the impact of CAV penetration on the speed of emergency vehicles, then: In the formula, p CAV is the penetration rate of CAV; is the critical value. It indicates that the vehicle will not affect the passage of emergency vehicles; Otherwise, vehicle i in lane b in lane group l is a conflicting vehicle. (2) Calculate impedance vehicle clearing time The following formula can be used to determine whether the conflicting vehicle can accelerate and change lanes: if it cannot accelerate, the vehicle needs to change lanes; if there is not enough space in the adjacent lane, the vehicle cannot change lanes. These vehicles that cannot accelerate or change lanes will create impedance for the emergency vehicle. In the formula, v max is the maximum speed limit of the road section (m / s); t ibl is the reaction time (s) of the conflicting vehicle i on lane b in lane group l; d front,ibl ,d rear,ibl is the distance (m) between the conflicting vehicle i in lane b of lane group l and the preceding and following vehicles in the adjacent lane; d s is the safety distance (m); l ibl is the length (m) of vehicle i on lane b in lane group l. A value of 0 means the vehicle cannot accelerate or change lanes. The clearance time t of the impedance vehicle is calculated by the time required for each vehicle that generates impedance to the emergency vehicle to leave the road section control area from its current position. clear,ibl . t clear,ibl =x lin,ibl / v lin,ibl Then, the time t required to simultaneously clear all conflicting vehicles that generate impedance is clear for: t clear =max(t clear,1bl ,...,t clear,ibl ) (3) Calculation of road delays for emergency vehicles The calculation formula for the delay of emergency vehicles in the road section control area is: Through the above steps, the road impedance encountered by emergency vehicles on the road section can be calculated.

4. The method for calculating road impedance of emergency vehicles under a networked traffic environment according to claim 1, characterized in that: In step 3, in the road impedance model for emergency vehicles, not only the impedance on the road section needs to be considered, but also the delay of emergency vehicles within the intersection range. The intersections are divided into three types: unsignalized intersections, signalized intersections without dedicated lanes, and signalized intersections with dedicated lanes. In a connected traffic environment, different types of intersections have different control methods, so the calculation of emergency vehicle delays is also different. (1) Unsignalized intersection At an unsignalized intersection, the emergency vehicle requests other vehicles to give way via V2X. The delay time mainly depends on the avoidance time of the conflicting vehicles and the congestion of the intersection. Since vehicles cannot change lanes within the intersection, the avoidance time of each vehicle depends on its current position, speed, and the length of its avoidance path. The rest of the calculation method is similar to the road section. Assume that the speed of the emergency vehicle in the intersection control area is v int,e , considering the impact of V / C on the speed of the emergency vehicle, then: In the formula, v cross is the maximum speed limit at the intersection (m / s). Each vehicle passing through creates impedance to the emergency vehicle The time required to leave the intersection control area from the current position is used to calculate the avoidance time t of the impedance vehicle aviod,ibl . t avoid,ibl =x int,ibl / v int,ibl Then, the avoidance time t required for all conflicting vehicles that generate impedance is avoid for: t avoid =max(t avoid,1bl ,...,t avoid,ibl ) The formula for calculating the delay of emergency vehicles at unsignalized intersections is: (2) Intersection with signal but no dedicated lane At intersections with signals but no dedicated lanes, emergency vehicles need to communicate with the signal control system to request a priority green light. If the current state of the emergency vehicle is green (w = 0), its delay time depends on the time it takes for the vehicle ahead to clear, which is the same as the calculation method for intersections without signals; if the current state of the emergency vehicle is red (w = 1), its delay time depends on the signal switching time and the time it takes to clear the vehicle ahead. Signal switching time t switch It refers to the time from when the emergency vehicle requests a priority green light to when the signal actually switches to green, including the yellow light time Y and the red light clearing time t rc The time required to clear the vehicles in front of the emergency vehicle is calculated using whether the vehicle can reach the end of the queue as the criterion. t switch =Y+t rc In the formula, is the maximum time (s) required for the conflicting vehicle i in lane b of lane group l to reach the tail of the front team; ibl (t) is the shortest time (s) required for conflicting vehicle i in lane b of lane group l to reach the stop line without being affected; t front is the time (s) required to clear the last vehicle in front of the emergency vehicle; q is the serial number of the last vehicle in front of the emergency vehicle; τ ibl is the starting loss time (s) of conflicting vehicle i on lane b in lane group l; h ibl is the saturated headway time (s) of conflicting vehicle i on lane b in lane group l; a max is the maximum acceleration (m / s 2 );a acc is the expected acceleration (m / s 2 );a dec is the expected deceleration (m / s 2 );v min is the minimum speed limit (m / s); t l,k The time (s) when the green light is turned on for emergency vehicles. (3) Intersections with signals and dedicated lanes At an intersection with a signal and a dedicated lane, the emergency vehicle enters the dedicated lane at time t0 and has priority. The delay time is It mainly depends on the traffic conditions of the dedicated lane. If there are no other vehicles blocking the dedicated lane, the emergency vehicle can move at a maximum speed of v cross otherwise, the speed of the emergency vehicle will be affected by the vehicle ahead. There is no car in front of the emergency vehicle. There is a car ahead of the emergency vehicle. t b,s =t0+x b (t0) / v b (t0) t e,min =t b,s +t sa Where, t e,min ,t e,max The earliest and latest time (s) for the emergency vehicle to pass the stop line; l e is the length of the emergency vehicle (m); t b,s is the time (s) when the vehicle in front of the emergency vehicle reaches the stop line; t sa The reserved safety time (s); v b (t0) is the speed of the vehicle in front of the emergency vehicle at time t0 (m / s); x b (t0) is the position of the vehicle in front of the emergency vehicle at time t0 (m); l b is the length of the vehicle in front of the emergency vehicle (m); x e,m is the distance (m) between the entrance parking line where the emergency vehicle is located and the lower boundary of the mth conflict area; x m is the length of the mth conflict region (m); is the phase green light on time (s) when lane group u conflicts with the emergency vehicle in the kth cycle; is the phase green light end time (s) when lane group u conflicts with the emergency vehicle in the kth cycle. According to the optimal time t of the emergency vehicle arriving at the intersection stop line es (Borrowing the green light at the head of conflicting traffic: +g EMV , Use the green light at the tail end of the conflicting traffic flow: Or interspersed passage: t es =t e,min -g EMV ), the delay time of emergency vehicles on the dedicated lane can be expressed as: By considering the delays of emergency vehicles at different types of intersections and combining real-time data and control strategies in a connected traffic environment, the path planning of emergency vehicles can be optimized to ensure that they arrive at their destination with minimal delay, which not only improves the efficiency of emergency response but also enhances the reliability of path planning.

5. The method for calculating road impedance of emergency vehicles under a networked traffic environment according to claim 1, characterized in that: In step 4, in order to calculate the total delay of the emergency vehicle on the entire path, the delays of the road sections and intersections need to be summed up to make the overall delay closer to the actual situation.

Images