Method for controlling multi-intersection emergency vehicle priority passage based on maximum pressure signal

Abstract

The application discloses a multi-intersection emergency vehicle priority passing method based on maximum pressure signal control and belongs to the technical field of intelligent traffic signal control. The method forms an intersection sequence according to the expected passing sequence of multiple signal intersections on the emergency vehicle driving path, and takes an NEMA ring grid structure as the phase organization framework of each intersection. According to the emergency vehicle position, expected arrival time, driving direction, speed and emergency degree, the intersections are divided into priority execution, preparation coordination and conventional control intersections. Based on the number of import and export vehicles, the phase group basic pressure difference is calculated, and the strong priority pressure correction and weak preparation pressure correction are respectively applied to the target phase group of the priority execution intersection and the preparation coordination intersection. Then, the release grid direction phase group and the dynamic release time length are determined according to the grid direction comprehensive pressure difference after the correction. After the emergency vehicle passes through the corresponding intersection, the intersection pressure difference and the release time length gradually recover, and the downstream intersection continues to roll over the priority control.

Description

Technical Field

[0001] This invention belongs to the field of intelligent traffic control technology, specifically relating to a method for prioritizing emergency vehicles at multi-intersection intersections based on maximum pressure signal control. Background Technology

[0002] With the continuous growth of urban traffic demand, multi-intersection signal control systems play a crucial role in ensuring the efficiency and safety of road network operations. In recent years, adaptive signal control methods based on real-time traffic condition feedback have gradually become a research hotspot. Among them, the max-pressure signal control method constructs a pressure difference index between approach and exit lanes to select the phase or phase group with the highest pressure for release. It can maximize the network throughput and pressure balance without relying on traffic demand forecasting, and has good theoretical properties and engineering application prospects. For example, the max-pressure control method proposed by Varaiya P (2013) has been widely regarded as a class of efficient distributed signal control strategies (The max-pressure controller for arbitrary networks of signalized intersections, 2013: 27-66).

[0003] Building upon this foundation, related research has further expanded the application of the maximum pressure method in complex road networks. For example, Hua Wei et al. (2019) optimized maximum pressure control by introducing reinforcement learning methods, making it more adaptable in multi-intersection environments. However, these methods are still mainly geared towards optimizing regular traffic flow, with control objectives focusing on overall efficiency and pressure balance, without specifically addressing the needs of emergency vehicles (Presslight: Learningmax pressure control to coordinate traffic signals in arterial network. 2019:1290-1298.).

[0004] To address the priority passage problem, existing research has attempted to introduce priority control mechanisms within the maximum pressure framework. For example, Xu et al. (2022) integrated a bus priority strategy within the maximum pressure signal control framework, achieving bus priority passage by adjusting phase selection constraints or extending the green light time for specific phases. However, these methods are primarily geared towards bus scenarios, relying mainly on rule constraints or phase extensions for priority passage. They lack characterization of the dynamic operating characteristics of emergency vehicles and do not consider continuous weight construction based on vehicle position and operating state, phase selection constraints under the NEMA ring grid structure, or smooth recovery mechanisms after priority passage ends. Therefore, they are ill-suited to the high timeliness and high uncertainty of emergency vehicle passage requirements (Transportation Research Part C: Emerging Technologies, 2022, 138: 103614.).

[0005] On the other hand, for the problem of priority passage for emergency vehicles, existing research has proposed a variety of priority control methods for intersections and road networks. For example, Su et al. (2023) jointly modeled emergency vehicle route selection and traffic signal control, and achieved network-level cooperative optimization through multi-agent reinforcement learning (Transportation Research Part C: Emerging Technologies, 2023, 146: 103955); Lin et al. (2023) constructed a multi-emergency vehicle cooperative priority model based on the connected vehicle environment, and incorporated the operating behavior of emergency vehicles and surrounding vehicles into unified decision-making (IEEE Transactions on Intelligent Transportation Systems, 2023, 25(1): 173-188.). The above methods have improved the efficiency of emergency vehicle passage to a certain extent, but they mainly rely on reinforcement learning or cooperative optimization frameworks, focusing on path-signal joint decision-making or vehicle behavior coordination. They have not yet formed a unified method that takes into account priority passage, vehicle dynamics constraints and smooth recovery under the maximum pressure signal control framework, especially lacking a pressure reconstruction priority mechanism for NEMA ring grid structures and a gradual recovery design after priority ends.

[0006] Furthermore, existing emergency vehicle priority methods rely heavily on signal scheme switching or simple transitions during the recovery phase, lacking a continuous adjustment mechanism coupled with real-time traffic conditions. This makes it difficult to achieve a smooth recovery after priority ends and easily triggers secondary traffic disturbances. While some improved methods based on the maximum pressure concept attempt to support priority passage, they mostly achieve this by adjusting the phase selection strategy as a whole, lacking differentiated processing for target and non-target phases, and failing to establish a clear mathematical quantitative expression for the recovery process.

[0007] In practical engineering applications, NEMA ring grid structures are commonly used for signal control at urban intersections to meet phase conflict constraints and release logic requirements. However, most existing studies have not fully considered phase group division, grid synchronization relationships, and cross-grid constraints under the ring grid structure. Therefore, in multi-phase, multi-ring, and multi-intersection coordinated control scenarios, it is difficult to guarantee the feasibility and stability of the control strategy. In summary, existing technologies still have the following shortcomings in prioritizing emergency vehicle passage:

[0008] (1) The principle of prioritizing emergency vehicles and balancing road network pressure were not achieved under the maximum pressure signal control framework;

[0009] (2) Priority control methods are mostly rigid pre-occupancy or overall strategy adjustment, which can easily lead to traffic flow interruption and reduced operational efficiency;

[0010] (3) The lack of a smooth recovery mechanism coupled with traffic conditions makes it difficult to avoid secondary disturbances after the priority ends;

[0011] (4) The constraints of the NEMA ring grid structure and the coordination requirements of multiple intersections were not fully considered.

[0012] Therefore, it is necessary to propose a signal control method that balances the rapid passage of emergency vehicles with the overall stability of the road network under the maximum pressure signal control framework, and achieves coordination between priority control and traffic status restoration while satisfying the constraints of the ring grid structure. Summary of the Invention

[0013] To address the challenges of existing emergency vehicle priority control methods in balancing rapid emergency vehicle passage, road network pressure balance, NEMA ring grid structure constraints, and smooth recovery after priority release within the maximum pressure signal control framework, this invention provides a multi-intersection emergency vehicle priority passage method based on maximum pressure signal control. This method uses multiple signalized intersections along the emergency vehicle's path as the control object, arranging each intersection into an intersection sequence according to the expected passage order of the emergency vehicles. Under the constraints of the NEMA ring grid structure, based on the emergency vehicle's operating status and intersection traffic pressure, it performs graded pressure correction, grid-direction phase selection, dynamic release duration calculation, and gradual recovery control after priority release for the target phase group, thereby achieving continuous priority passage for emergency vehicles in multi-intersection scenarios.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] The multi-intersection emergency vehicle priority passage method based on maximum pressure signal control takes multiple signalized intersections along the emergency vehicle's travel path as the control object. These intersections are arranged into an intersection sequence according to the expected passage order of the emergency vehicles. A NEMA ring grid structure is used as the phase organization framework for each intersection. Based on basic maximum pressure signal control, rolling priority control is applied to the intersections in the intersection sequence. Specifically, this includes the following:

[0016] 1. Determining the control objects and priority states at multiple intersections

[0017] Based on the current location, direction of travel, or planned route of the emergency vehicle, determine the sequence of signalized intersections the emergency vehicle will pass through:

[0018] (1)

[0019] in, The sequence of intersections along the emergency vehicle's route. The emergency vehicle is expected to pass through the [number]th An intersection, Number of intersections, subscript Indicates an emergency vehicle.

[0020] The system obtains the number of vehicles entering the intersection lanes, the number of vehicles exiting the intersection lanes, the current release phase group, the duration of the phase release, the location of emergency vehicles, the direction of travel of emergency vehicles, the speed of emergency vehicles, and the urgency of the emergency task for each intersection in the intersection sequence.

[0021] For any intersection in the intersection sequence Emergency vehicles and intersections The distance between them is calculated using the following formula:

[0022] (2)

[0023] Emergency vehicles arrive at the intersection The estimated arrival time is calculated using the following formula:

[0024] (3)

[0025] in, For emergency vehicles at all times Intersection distance, For emergency vehicles at all times Arriving at the intersection The estimated arrival time, For emergency vehicles at all times Location, Intersection The center position or stop line position, For emergency vehicles at all times driving speed, This is the minimum speed threshold. (Set by...) This can prevent errors in the estimated arrival time calculation when emergency vehicles are traveling at low speeds or temporarily stopped.

[0026] According to emergency vehicles and intersections Based on the distance and estimated arrival time, determine the intersection. Priority state variables:

[0027] (4)

[0028] in, Indicates an intersection To prioritize the execution of intersections, Indicates an intersection In preparation for coordinating the intersection, Indicates an intersection This is a conventionally controlled intersection; Intersection Emergency vehicles should prioritize operating within the detection range. Intersection The preparatory coordination perception range, and ; Prioritize execution time thresholds, To prepare for the coordination time threshold, and .

[0029] When an emergency vehicle is approaching or is expected to arrive at an intersection, that intersection enters a priority execution state; when an emergency vehicle has not yet entered the immediate priority execution range but has entered the pre-coordination range or the expected arrival time meets the pre-coordination conditions, that intersection enters a pre-coordination state; the remaining intersections remain in a normal control state.

[0030] 2. Calculation of maximum foundation pressure under NEMA ring grid structure

[0031] intersection The inlet and outlet pressures are calculated using the following formulas:

[0032] (5)

[0033] (6)

[0034] in, For the import lane number, Number the exit lane; Intersection import channel At any moment Import pressure, Intersection exit At any moment The pressure on the exit channel; For import channels At any moment The number of vehicles or the number of vehicles in the queue. For the exit channel At any moment The number of vehicles or the number of vehicles in queue; For import channels Maximum number of vehicles that can be accommodated For the exit channel The maximum number of vehicles that can be accommodated.

[0035] intersection The NEMA ring gate structure includes two circumferential phase groups. and two grid-directed phase groups ,in , Phase group The basic pressure difference is calculated according to the following formula:

[0036] (7)

[0037] in, Intersection Mid-phase group At any moment The basic pressure difference, Phase group The collection of inbound lanes covered For import channels Exit lanes in the corresponding release direction; Intersection exit At any moment The pressure on the export channel.

[0038] To avoid negative pressure differentials directly participating in phase selection and release time allocation, the non-negative pressure differential function is defined as follows:

[0039] (8)

[0040] in, Phase group Non-negative base pressure difference, This represents a non-negative truncation function.

[0041] 3. Target phase group determination and emergency priority pressure correction

[0042] For intersections in a priority execution or pre-coordination state, the candidate phase group set corresponding to the emergency vehicle is determined based on the approach lane and direction of travel of the emergency vehicle:

[0043] (9)

[0044] in, For emergency vehicles at intersections The set of candidate phase groups, For emergency vehicles at all times The entrance lane is located at. Phase group The collection of import lanes served For emergency vehicles at all times The direction of travel, Phase group The set of allowed directions.

[0045] The target phase group corresponding to the emergency vehicle is determined according to the following formula:

[0046] (10)

[0047] in, Intersection The target phase group corresponding to the emergency vehicle. Intersection Mid-phase group The corresponding stop line position of the approach lane, the center position of the approach lane, or the phase service area position. The independent variable is the value of the function when it reaches its minimum value.

[0048] To ensure that the emergency vehicle priority pressure correction factor is aligned with the current traffic pressure at the intersection, the intersection... The average non-negative pressure difference is calculated using the following formula:

[0049] (11)

[0050] The priority pressure base value for emergency vehicles is defined as:

[0051] (12)

[0052] in, Intersection At any moment The average non-negative pressure difference, Intersection Emergency vehicle priority pressure base value, The minimum pressure correction baseline required for priority passage of emergency vehicles. When traffic pressure at the intersection is low, passage is still permitted. Ensure that the target phase group of the emergency vehicle receives the necessary pressure correction.

[0053] The weighted coefficient for emergency vehicle status under priority execution is calculated using the following formula:

[0054] (13)

[0055] The emergency vehicle status weighting factor under the pre-coordination state is calculated according to the following formula:

[0056] (14)

[0057] in, This is the weighting coefficient for the emergency vehicle status under priority execution conditions. This refers to the weighting coefficient for the emergency vehicle status under the pre-coordination state. This is the upper limit of the weighted coefficient for emergency vehicle status. These are the non-negative weight coefficients for each item. The maximum speed allowed for emergency vehicles or the road speed limit. The urgency level of the emergency task after normalization. This represents a non-negative truncation function.

[0058] The emergency priority pressure correction term is calculated according to the following formula:

[0059] (15)

[0060] in, Intersection At any moment Emergency priority pressure correction item; To prioritize the strong priority correction factor for intersections, To prepare a weak preparatory correction factor for the coordinated intersection, and When the intersection is in priority execution state, a strong priority pressure correction is applied to the target phase group; when the intersection is in pre-coordination state, a weak pre-coordination pressure correction is applied to the target phase group; when the intersection is in normal control state, no emergency priority pressure correction is applied.

[0061] Based on the above emergency priority pressure correction term, the corrected phase group pressure difference is calculated according to the following formula:

[0062] (16)

[0063] The indicator variables of the target phase group of the emergency vehicle satisfy:

[0064] (17)

[0065] in, Intersection Mid-phase group At any moment The corrected pressure difference This is an indicator variable for the target phase group of emergency vehicles. When the phase group... When the target phase group is an emergency vehicle, the pressure difference of that phase group is increased by an emergency priority pressure correction term; when the phase group When it is not the target phase group for emergency vehicles, the pressure difference of that phase group remains unchanged under the control of the base maximum pressure.

[0066] 4. Calculation of integrated pressure difference along the grid and selection of release phase.

[0067] intersection The corrected grid-direction combined pressure difference is calculated according to the following formula:

[0068] (18)

[0069] in, Intersection Central grating phase group At any moment The corrected overall pressure difference This represents the non-negative value of the pressure difference in the phase group after correction.

[0070] The phase group for the release of emergency vehicles under priority passage conditions is determined according to the following formula:

[0071] (19)

[0072] in, Intersection At any moment Select the gate phase group for release. The independent variable is the one that corresponds to the maximum value of the function.

[0073] When the current release gate phase group is At the same time, after satisfying the minimum clearance duration, yellow light time, and all-red light time constraints of the current phase group, switch to .

[0074] When the intersection When preparing for intersection coordination, if the current open phase group is the same as the target phase group for emergency vehicles, the serviceability of that phase group is maintained based on the expected arrival time of the emergency vehicles. If the current open phase group is different from the target phase group for emergency vehicles, the priority of the target phase group in the next phase selection is increased through weak preparation pressure correction, provided that the minimum open time, yellow light time and all-red light time constraints of the current phase group are met.

[0075] When the intersection When prioritizing intersections, under the condition of satisfying the NEMA ring grid structure constraints, the release grid direction phase group is determined and switched according to the modified grid direction comprehensive pressure difference.

[0076] 5. Dynamic release time calculation and gate synchronization constraints

[0077] The dynamic passage duration for emergency vehicles under priority passage conditions is calculated using the following formula:

[0078] (20)

[0079] in, Intersection At any moment Release gate phase group The allocated emergency priority dynamic release time, To the maximum permitted clearance time, To ensure emergency vehicles can pass through intersections Minimum clearance time required Intersection The basic signal period, Intersection Phase loss time, To prevent extremely small positive numbers with a denominator of zero, Intersection Select the gate phase group for release At any moment The corrected overall pressure difference.

[0080] The emergency vehicles were passing through the intersection. The minimum clearance time required is calculated using the following formula:

[0081] (twenty one)

[0082] in, For emergency vehicles at all times Distance from the intersection The distance from the stop line or the entrance to the conflict zone. Intersection The length of the conflict zone, This refers to the length of the emergency vehicle.

[0083] When the intersection In preparation for coordinating intersections, the dynamic release duration is used to maintain the switchable state of the target gate phase group; when the intersection When switching to priority execution mode, the dynamic release time shall not be less than the minimum release time required for emergency vehicles to pass through the intersection.

[0084] The release duration of two circumferential phase groups under the same grid phase group satisfies the grid synchronization constraint:

[0085] (twenty two)

[0086] in, and Intersections Release duration of Ring1 and Ring2 under the same release gate phase group.

[0087] 6. Prioritize the removal and gradual restoration of controls.

[0088] When emergency vehicles pass through the intersection and enter the downstream exit area of ​​the intersection, or pass through the intersection. When the vehicle exits the detection range of the intersection, the intersection is triggered. The priority release mechanism.

[0089] After priority release, the intersection The recovery progress coefficient is calculated according to the following formula:

[0090] (twenty three)

[0091] in, Intersection At any moment Recovery progress coefficient, Allowing emergency vehicles to pass through intersections Or the moment when the vehicle leaves the perception range of the intersection. Intersection Recovery time.

[0092] intersection The pressure difference of the phase group recovers gradually according to the following formula:

[0093] (twenty four)

[0094] in, The phase group pressure difference during the recovery process; when hour, This indicates that the situation remains in a state of emergency priority; when hour, This indicates a return to the baseline maximum pressure control state.

[0095] intersection The release time will be gradually restored according to the following formula:

[0096] (25)

[0097] in, The phase group release duration during the recovery process. This refers to the release duration of the phase group under emergency priority status. This refers to the release time of the phase group under the base maximum pressure control state.

[0098] When the intersection When entering recovery mode, the intersection The pressure differential and release time are gradually restored to the basic maximum pressure control state according to the recovery progress coefficient; at the same time, the intersection sequence located at the intersection downstream intersection Continue to perform pre-coordinated control, priority execution control, or basic maximum pressure control according to their respective priority state variables.

[0099] Compared with the prior art, the present invention has the following beneficial effects:

[0100] 1. This invention constructs a sequence of multiple signalized intersections along the emergency vehicle's path and categorizes each intersection into priority execution, preparatory coordination, and routine control states based on the emergency vehicle's location and estimated arrival time. Compared to isolated priority control of a single intersection, this invention enables rolling priority control of multiple intersections along the route, making it more suitable for scenarios where emergency vehicles continuously pass through multiple signalized intersections.

[0101] 2. Under the basic maximum pressure signal control framework, this invention applies enhanced priority pressure correction or weak preparatory pressure correction only to the target phase group of emergency vehicles, while non-target phase groups maintain the basic maximum pressure control logic. Compared to methods such as directly extending green lights, rigidly preempting, or completely covering the original signal scheme, this invention can improve the priority of emergency vehicles while taking into account the traffic pressure balance at intersections and the stability of ordinary traffic flow.

[0102] 3. This invention incorporates a gradual recovery mechanism after priority control is lifted. After an emergency vehicle passes through an intersection or leaves the sensing range, the phase group pressure difference and release time gradually return to the baseline maximum pressure control state. Compared to direct switching or simple transitions after priority control ends, this invention reduces the impact of sudden changes in control parameters on traffic operation and improves operational stability after priority control is lifted. Attached Figure Description

[0103] Figure 1 This is a flowchart of the method of the present invention.

[0104] Figure 2 This is a schematic diagram of the NEMA ring grid structure of the present invention, used to illustrate the circumferential phase group, grid phase group and phase conflict constraint relationship under the 8-phase signal control conditions of the intersection.

[0105] Figure 3This is a bar chart showing the queue lengths at each entrance of intersection 1, illustrating the changes in the number of vehicles queuing in each phase direction during the simulation. The vertical lines of different colors represent the trigger detection, entry priority control, and completion time of different emergency vehicles, respectively.

[0106] Figure 4 This is a bar chart showing the queue lengths at each entrance of intersection 2, used to represent the changes in the number of vehicles queuing at downstream intersection 2 in each phase direction during the simulation. The vertical lines in the chart represent the detection, priority control, and passage process of emergency vehicles at the downstream intersection.

[0107] Figure 5 This diagram illustrates the signal timing schemes for intersections 1 and 2, representing the traffic light sequence at these two consecutive intersections during simulation. The upper part of the diagram shows the signal timing for intersection 1, and the lower part shows the signal timing for intersection 2. Green periods indicate that the corresponding phase is in a permitted state, while red periods indicate that the corresponding phase is in a prohibited state. Vertical lines indicate the times when emergency vehicles have priority control.

[0108] Figure 6 This diagram illustrates the pressure changes at intersections 1 and 2, showing the pressure correction and recovery during the approach, entry into priority control, passage through the intersection, and priority release processes of emergency vehicles. The upper part of the diagram shows the pressure changes at intersection 1, and the lower part shows the pressure changes at intersection 2. Detailed Implementation

[0109] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or conventional modifications made by those skilled in the art based on the content of this specification without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0110] This embodiment uses a city road segment consisting of two consecutive signalized intersections as an example to illustrate the proposed method for priority passage of emergency vehicles at multiple intersections based on maximum pressure signal control. This method takes multiple intersections along the emergency vehicle's travel path as the control objects. Under the basic maximum pressure signal control framework, it determines the priority status of intersections based on the positional relationship between the emergency vehicle and each intersection and the estimated arrival time. Through target phase group pressure correction, grid phase selection, dynamic release duration calculation, and gradual recovery after priority is released, it achieves rolling priority passage of emergency vehicles among multiple consecutive intersections.

[0111] This embodiment sets up two consecutive signalized intersections, denoted as Intersection 1 and Intersection 2. Intersection 1 is located upstream, and Intersection 2 is located downstream, with a distance of 500m between them. The average propagation time for vehicles traveling from Intersection 1 to Intersection 2 is set to 50s, corresponding to an average travel speed of 10m / s.

[0112] Both intersections employ an 8-phase NEMA ring grid structure, such as Figure 2 As shown. Phase 1 is left turn at the east entrance, Phase 2 is left turn at the west entrance, Phase 3 is straight at the east entrance, Phase 4 is straight at the west entrance, Phase 5 is left turn at the north entrance, Phase 6 is left turn at the south entrance, Phase 7 is straight at the north entrance, and Phase 8 is straight at the south entrance.

[0113] Phases 1, 2, 5, and 6 are each configured as one lane; phases 3, 4, 7, and 8 are each configured as two lanes. During signal control, the left-turn and straight-ahead phases are organized according to the NEMA ring grid structure, and the grid direction is switched under the conditions of meeting phase conflict constraints, minimum clearance duration, yellow light time, and full red light time requirements.

[0114] In this embodiment, social vehicles enter the intersection in a random manner.

[0115] For intersection 1, vehicles arrive independently and randomly in each phase, with one vehicle arriving in each lane every 6 to 10 seconds. Therefore, the average arrival rate for phase 1 lane is approximately 0.125 vehicles per second, and the average arrival rate for phase 2 lane is approximately 0.25 vehicles per second.

[0116] For intersection 2, in addition to receiving vehicles from intersection 1, a separate background traffic flow is also set up. Background vehicles arrive at one vehicle per lane every 5 to 9 seconds, with an average arrival rate of approximately 0.143 vehicles per second per lane.

[0117] To reflect the traffic flow relationship between upstream and downstream intersections, this embodiment sets up a system where vehicles released from intersection 1, specifically those in phase 7 corresponding to the northbound straight-through direction, continue towards intersection 2 and join phase 4 of intersection 2 (the westbound straight-through direction) after a 50-second delay. This setup reflects the impact of upstream intersection release results on queuing and pressure changes at downstream intersections.

[0118] The release capacity of each phase is determined based on the number of lanes. The maximum release capacity per lane is set at 0.5 vehicles per second. Therefore, the maximum release capacity of a 1-lane phase is 0.5 vehicles per second, and the maximum release capacity of a 2-lane phase is 1.0 vehicle per second.

[0119] When there is no priority demand for emergency vehicles, both intersection 1 and intersection 2 implement basic maximum pressure signal control. The control system calculates the pressure difference between phase groups based on the number of vehicles in the approach lanes and exit lanes corresponding to each phase, and further compares the combined pressure of the left-turn gate group and the straight-ahead gate group, prioritizing the gate group with the higher pressure for passage.

[0120] Under basic control conditions, the maximum green light duration is set to 30 seconds, and the minimum green light duration is set to 7 seconds. No gate switching occurs when the current gate group has not yet reached the minimum green light duration; once the current gate group has reached the minimum green light duration, the system determines whether to switch to another gate group based on the overall gate pressure.

[0121] The aforementioned basic maximum pressure control serves as the foundational state for the priority control of emergency vehicles in this invention. When no emergency vehicle enters the sensing range, the intersection maintains the basic maximum pressure control; when an emergency vehicle enters the sensing range, the system performs pressure correction on the target phase group of the emergency vehicle based on this basic control logic, rather than directly overriding the original signal control scheme.

[0122] This embodiment uses three emergency vehicles to illustrate the implementation process of the invention under different departure times, different traffic directions, and different intersection conditions. The emergency vehicle configuration is shown in Table 1.

[0123] Table 1 Emergency Vehicle Setup

[0124]

[0125] Phase 1 and Phase 3 correspond to the east-to-west direction and are not considered as candidate phases for random emergency vehicles in this embodiment.

[0126] East-west emergency vehicles are described using road coordinates; north-south emergency vehicles are described using virtual distances as they approach intersections. North-south emergency vehicles only affect the single intersection they approach and do not participate in the upstream and downstream propagation process between intersection 1 and intersection 2.

[0127] In this embodiment, the emergency vehicle's speed is set to 10 m / s, consistent with the average speed of ordinary vehicles. The emergency vehicle is constrained by both the traffic light status and the queue status ahead. The emergency vehicle can only proceed through the intersection if the current traffic light group matches the target traffic light group to which it belongs, and if there is no queue obstructing the emergency vehicle's path. Otherwise, the emergency vehicle must wait before the intersection.

[0128] Regarding priority control parameters, the pre-coordination sensing range is set to 400m, and the priority execution sensing range is set to 200m; the pre-coordination time threshold is set to 40s, and the priority execution time threshold is set to 20s. When an emergency vehicle enters the pre-coordination range, or when its expected arrival time meets the pre-coordination threshold, the relevant intersection enters the pre-coordination state; when an emergency vehicle enters the priority execution range, or when its expected arrival time meets the priority execution threshold, the relevant intersection enters the priority execution state.

[0129] The strong priority correction factor is set to 30 under the priority execution state, and the weak preparatory correction factor is set to 18 under the preparatory coordination state. Under the emergency vehicle priority control state, the maximum green light duration is extended from 30s under the basic control to 60s to ensure that emergency vehicles have the necessary clearance time to approach the stop line, enter the conflict zone, and complete the passage.

[0130] During the simulation, the control system first determines the sequence of intersections that the emergency vehicles will pass through based on their current location, direction of travel, and planned route. For the first emergency vehicle traveling straight from west to east, the sequence of intersections is intersection 1 and intersection 2.

[0131] Subsequently, at each control moment, the system determines the positional relationship and estimated arrival time of the emergency vehicle relative to intersection 1 and intersection 2, and determines the priority status of each intersection accordingly. If the emergency vehicle has not yet entered the pre-coordination range of the intersection, the intersection remains in the normal control state; if the emergency vehicle enters the pre-coordination range or the estimated arrival time meets the pre-coordination conditions, the intersection enters the pre-coordination state; if the emergency vehicle approaches the intersection further or the estimated arrival time meets the priority execution conditions, the intersection enters the priority execution state.

[0132] Under normal control conditions, the intersection operates according to the base maximum pressure control. The system calculates the phase group pressure difference based on the number of vehicles in the approach and exit lanes, and selects the release gate group based on the overall gate pressure.

[0133] In the pre-coordination state, the system determines the target phase group based on the approach lane and direction of travel of the emergency vehicle. If the current release gate group matches the target gate group for the emergency vehicle, the system maintains the serviceability of that gate group, enabling it to continue providing release conditions for the emergency vehicle's direction as it approaches. If the current release gate group does not match the target gate group for the emergency vehicle, the system, while satisfying the minimum green light, yellow light, and all-red light constraints, improves the priority of the target gate group in the next phase selection through weak pre-coordination pressure correction.

[0134] In priority execution mode, the system applies a stronger priority pressure correction to the target phase group, giving the direction of the emergency vehicle a higher release priority in the grid-direction comprehensive pressure comparison. This correction only applies to the target phase group for emergency vehicles; non-target phase groups are still calculated and compared according to the basic maximum pressure control logic. Therefore, the system can improve the release chances for the direction of the emergency vehicle without completely overriding the original maximum pressure control structure.

[0135] After determining the release grid group, the system further determines the dynamic release duration based on the revised grid direction integrated pressure and emergency vehicle passage requirements. When emergency vehicles are in the pre-coordination phase, the dynamic release duration is mainly used to maintain the switchable state of the target grid group; when emergency vehicles enter the priority execution phase, the dynamic release duration should meet the minimum release time required for emergency vehicles to pass through the intersection. For two circumferential phase groups under the same release grid group, the system maintains grid synchronization, ensuring that the two circumferential phase groups have consistent release durations under the same grid direction conditions.

[0136] When an emergency vehicle passes through an intersection or leaves its sensing range, the system triggers the priority release mechanism for that intersection. After priority release, the phase group pressure difference and release duration at the intersection do not immediately jump to the basic maximum pressure control state, but gradually return to the basic control values ​​according to the recovery progress. At the same time, for downstream intersections where the emergency vehicle has not yet passed, the system continues to perform preparatory coordination control or priority execution control based on the emergency vehicle's location and expected arrival time, thus forming a rolling priority control process along the intersection sequence.

[0137] The total simulation duration in this embodiment is set to 1800 seconds. To highlight the priority control process for emergency vehicles, the simulation plotting begins at 300 seconds.

[0138] like Figure 3 As shown, queuing fluctuations of varying degrees occur in each direction of intersection 1 during the simulation. When an emergency vehicle enters the detection range, enters the priority state, and passes through the intersection, the queue length and release status of the corresponding direction change with the control strategy. The different colored vertical lines in the figure correspond to the detection, priority, and passage times of different emergency vehicles. It can be seen that the present invention can trigger pre-coordination, priority execution, and recovery control for intersection 1 based on the approach process of multiple emergency vehicles.

[0139] like Figure 4 As shown, the queuing changes at intersection 2 are affected by both the background traffic flow and the upstream traffic flow from intersection 1. Because some of the vehicles released at intersection 1 enter the corresponding phase queue at intersection 2 after a delay, the pressure changes at the downstream intersection have a certain lag. Figure 4 The relevant road markings for emergency vehicles indicate that the system can continue to perform rolling priority control on intersection 2 when the emergency vehicle approaches the downstream intersection.

[0140] like Figure 5 As shown, the traffic light timings at intersections 1 and 2 are dynamically adjusted based on maximum pressure comparison and the priority needs of emergency vehicles. During normal hours, signal passage is mainly determined by the basic maximum pressure control; when an emergency vehicle enters the pre-coordination or priority execution state, the chance of its target phase group passing increases; after the emergency vehicle passes, the signal timing gradually returns to the basic maximum pressure control state. Figure 5 This invention demonstrates the process of dynamically selecting release gate groups under the constraint of NEMA ring gate structure.

[0141] like Figure 6 As shown, when an emergency vehicle approaches an intersection, the pressure corresponding to the target phase group undergoes a correction change; during the priority execution phase, the pressure correction amplitude further increases, enabling the target grid group to obtain higher priority in phase selection; after the emergency vehicle passes, the pressure gradually decreases and returns to the basic maximum pressure control state. This result demonstrates that the present invention can achieve emergency vehicle priority through pressure correction and reduce control abrupt changes after priority deactivation through gradual recovery.

[0142] As can be seen from the above embodiments, the present invention can divide the intersection into priority states based on the location of emergency vehicles, their expected arrival time, the approach lane, and the direction of travel in two consecutive intersection scenarios, and perform pressure correction on the target phase group within the basic maximum pressure signal control framework.

Claims

1. A method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control, characterized in that: Taking multiple signalized intersections along the emergency vehicle's travel path as the control object, the multiple signalized intersections are arranged into an intersection sequence according to the expected passing order of the emergency vehicles. A NEMA ring grid structure is used as the phase organization framework for each intersection. Based on basic maximum pressure signal control, rolling priority control is applied to the intersections in the intersection sequence. The method includes: Based on the position and estimated arrival time of the emergency vehicle relative to each intersection in the intersection sequence, the priority status of each intersection is determined, including priority execution status, preparatory coordination status, and routine control status. Based on the number of vehicles entering and exiting each intersection, calculate the base pressure difference of each phase group under the NEMA ring grid structure at each intersection. For intersections in a priority execution state or a pre-coordination state, a target phase group is determined based on the approach lane and direction of travel of the emergency vehicle, and an emergency priority pressure correction is applied to the target phase group. The emergency priority pressure correction term is calculated according to the following formula: (1) in, Intersection At any moment Emergency priority pressure correction items, For any intersection in the intersection sequence, To control the timing, subscripts Indicates an emergency vehicle; Indicates an intersection Priority state variables, Indicates an intersection It is in a priority execution state. Indicates an intersection In a state of pre-coordination, Indicates an intersection Under normal control status; Intersection Emergency vehicle priority pressure base value; This is a weighted coefficient for the emergency vehicle status under priority execution conditions; This is the weighting coefficient for the emergency vehicle status under the pre-coordination state; To prioritize the strong priority correction factor for intersections, To prepare a weak preparatory correction factor for the coordinated intersection, and ; The basic pressure difference of the target phase group is corrected according to the emergency priority pressure correction item, and the grid-direction comprehensive pressure difference of each intersection is calculated according to the corrected phase group pressure difference. Under the condition of satisfying the NEMA ring grid structure constraint, the release grid-direction phase group and dynamic release time are determined. When an emergency vehicle passes through the corresponding intersection or leaves the intersection's sensing range, the intersection's priority release mechanism is triggered, causing the phase group pressure difference and release time of the intersection to gradually return from the emergency priority state to the basic maximum pressure control state, and rolling priority control continues to be implemented for downstream intersections.

2. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 1, characterized in that: Based on the current location, direction of travel, or planned route of the emergency vehicle, determine the sequence of signalized intersections the emergency vehicle will pass through: (2) in, The sequence of intersections along the emergency vehicle's route. The emergency vehicle is expected to pass through the [number]th An intersection, Number of intersections; The number of vehicles entering the intersection, the number of vehicles exiting the intersection, the current release phase group, the duration of the phase release, the location of emergency vehicles, the direction of travel of emergency vehicles, the speed of emergency vehicles, and the urgency of the emergency task are obtained for each intersection in the intersection sequence. Emergency vehicles and intersections The distance between them is calculated using the following formula: (3) Emergency vehicles arrive at the intersection The estimated arrival time is calculated using the following formula: (4) in, For emergency vehicles at all times Intersection distance, For emergency vehicles at all times Arriving at the intersection The estimated arrival time, For emergency vehicles at all times Location, Intersection The center position or stop line position, For emergency vehicles at all times driving speed, Minimum speed threshold; intersection Priority state variables Determined according to the following formula: (5) in, Intersection Emergency vehicles should prioritize operating within the detection range. Intersection The preparatory coordination perception range, and ; Prioritize execution time thresholds, To prepare for the coordination time threshold, and .

3. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 2, characterized in that: intersection The inlet and outlet pressures are calculated using the following formulas: (6) (7) in, For the import lane number, Number the exit lane; Intersection import channel At any moment Import pressure, Intersection exit At any moment The pressure on the exit channel; For import channels At any moment The number of vehicles or the number of vehicles in the queue. For the exit channel At any moment The number of vehicles or the number of vehicles in queue; For import channels Maximum number of vehicles that can be accommodated For the exit channel Maximum number of vehicles that can be accommodated; intersection The NEMA ring gate structure includes two circumferential phase groups. and two grid-directed phase groups ,in , Phase group The basic pressure difference is calculated according to the following formula: (8) in, Intersection Mid-phase group At any moment The basic pressure difference, Phase group The collection of inbound lanes covered For import channels Exit lanes in the corresponding release direction Intersection exit At any moment The pressure on the exit channel; Define the non-negative pressure difference function as: (9) in, Phase group Non-negative base pressure difference, This represents a non-negative truncation function.

4. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 3, characterized in that: Emergency vehicles at intersections The corresponding set of candidate phase groups is determined according to the following formula: (10) in, For emergency vehicles at intersections The set of candidate phase groups, For emergency vehicles at all times The entrance lane is located at. Phase group The collection of import lanes served For emergency vehicles at all times The direction of travel, Phase group The set of permitted directions; The target phase group corresponding to the emergency vehicle is determined according to the following formula: (11) in, Intersection The target phase group corresponding to the emergency vehicle. Intersection Mid-phase group The corresponding stop line position of the approach lane, the center position of the approach lane, or the phase service area position. The independent variable corresponding to the minimum value of the function; intersection The average non-negative pressure difference is calculated using the following formula: (12) The priority pressure base value for emergency vehicles is defined as: (13) in, Intersection At any moment The average non-negative pressure difference, Intersection Emergency vehicle priority pressure base value, Minimum pressure correction base value required to give priority to emergency vehicles; The weighted coefficient for emergency vehicle status under priority execution is calculated using the following formula: (14) The emergency vehicle status weighting factor under the pre-coordination state is calculated according to the following formula: (15) in, This is the weighting coefficient for the emergency vehicle status under priority execution conditions. This refers to the weighting coefficient for the emergency vehicle status under the pre-coordination state. This is the upper limit of the weighted coefficient for emergency vehicle status. These are the non-negative weight coefficients for each item. The maximum speed allowed for emergency vehicles or the road speed limit. The urgency level of the emergency task after normalization. Represents a non-negative truncation function; Based on the aforementioned emergency priority pressure correction term, the corrected phase group pressure difference is calculated according to the following formula: (16) The indicator variables of the emergency vehicle target phase group satisfy: (17) in, Intersection Mid-phase group At any moment The corrected pressure difference For emergency vehicle target phase group indicator variables; when phase group When the target phase group is an emergency vehicle, the pressure difference of that phase group is increased by an emergency priority pressure correction term; when the phase group When it is not the target phase group for emergency vehicles, the pressure difference of that phase group remains unchanged under the control of the base maximum pressure.

5. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 4, characterized in that: intersection The corrected grid-direction combined pressure difference is calculated according to the following formula: (18) in, Intersection Central grating phase group At any moment The corrected overall pressure difference This represents the non-negative value of the pressure difference in the phase group after correction. The phase group for the release of emergency vehicles under priority passage conditions is determined according to the following formula: (19) in, Intersection At any moment Select the gate phase group for release. The independent variable corresponding to the maximum value of the function; When the current release gate phase group is At the same time, after satisfying the minimum clearance duration, yellow light time, and all-red light time constraints of the current phase group, switch to ; When the intersection When preparing to coordinate at an intersection, if the current open gate direction phase group is the same as the target gate direction phase group for emergency vehicles, then the serviceable status of that gate direction phase group shall be maintained according to the expected arrival time of the emergency vehicles. When the intersection To prepare for the coordination of the intersection, and when the current green light phase group is different from the target green light phase group of the emergency vehicle, under the condition of meeting the minimum green light duration, yellow light time and all-red light time constraints of the current phase group, the priority of the target green light phase group in the next phase selection is increased through weak preparation pressure correction. When the intersection When prioritizing intersections, under the condition of satisfying the NEMA ring grid structure constraints, the release grid direction phase group is determined and switched according to the modified grid direction comprehensive pressure difference.

6. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 5, characterized in that: The dynamic passage duration for emergency vehicles under priority passage conditions is calculated using the following formula: (20) in, Intersection At any moment Release gate phase group The allocated emergency priority dynamic release time, To the maximum permitted clearance time, To ensure emergency vehicles can pass through intersections Minimum clearance time required Intersection The basic signal period, Intersection Phase loss time, To prevent extremely small positive numbers with a denominator of zero; The emergency vehicles were passing through the intersection. The minimum clearance time required is calculated using the following formula: (21) in, For emergency vehicles at all times Distance from the intersection The distance from the stop line or the entrance to the conflict zone. Intersection The length of the conflict zone, The length of the emergency vehicle body; When the intersection In preparation for coordinating intersections, the dynamic release duration is used to maintain the switchable state of the target gate phase group; when the intersection When switching to priority execution mode, the dynamic release time shall not be less than the minimum release time required for emergency vehicles to pass through the intersection; The release duration of two circumferential phase groups under the same grid phase group satisfies the grid synchronization constraint: (22) in, and Intersections Release duration of Ring1 and Ring2 under the same release gate phase group.

7. The method for prioritizing emergency vehicle passage at multiple intersections based on maximum pressure signal control according to claim 6, characterized in that: When emergency vehicles pass through the intersection And enter the downstream exit area of ​​the intersection, or pass through the intersection. When the vehicle exits the detection range of the intersection, the intersection is triggered. Priority release mechanism; After priority release, the intersection The recovery progress coefficient is calculated according to the following formula: (23) in, Intersection At any moment Recovery progress coefficient, Allowing emergency vehicles to pass through intersections Or the moment when the vehicle leaves the perception range of the intersection. Intersection Recovery time; intersection The pressure difference of the phase group recovers gradually according to the following formula: (24) in, The pressure difference of the phase group during the recovery process; when hour, This indicates that the situation remains in a state of emergency priority; when hour, This indicates a return to the baseline maximum pressure control state; intersection The release time will be gradually restored according to the following formula: (25) in, The phase group release duration during the recovery process. This refers to the release duration of the phase group under emergency priority status. The phase group release time under the basic maximum pressure control state; When the intersection When entering recovery mode, the intersection The pressure differential and release time are gradually restored to the basic maximum pressure control state according to the recovery progress coefficient; at the same time, the intersection sequence located at the intersection downstream intersection Continue to perform pre-coordinated control, priority execution control, or basic maximum pressure control according to their respective priority state variables.

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