A simulation-based method for emergency rescue vehicle layout in expressway systems

Abstract

The present invention discloses a method for arranging emergency rescue vehicles for an expressway system based on simulation, comprising: S1, establishing a road model of an expressway system in traffic simulation software; S2, inputting traffic flow and path; S3, inputting simulation parameters, wherein the simulation parameters include road capacity, following parameters and lane-changing parameters; S4, determining key sections affected by traffic events; S5, establishing a traffic event scenario library through key sections; S6, establishing a traffic event impact index system to evaluate traffic operation conditions under different traffic event scenarios; S7, determining emergency rescue time thresholds for key sections; S8, determining an emergency rescue vehicle layout plan in combination with the distribution of different key sections and key thresholds. According to the present invention, under limited resources, the rationality of the emergency rescue vehicle layout is ensured, the time required for emergency rescue is reduced, the impact of traffic events on the expressway is reduced, and the efficient operation of the entire expressway system is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of traffic management and control, and in particular to a simulation-based expressway system emergency rescue vehicle layout method. Background Art

[0002] The expressway system plays an extremely important role in the entire urban road network. According to statistics, the expressway network, which accounts for 8% of the total mileage of Beijing's road network, has taken on more than 70% of Beijing's traffic. The expressway, with its limited access and relatively closed characteristics, ensures the rapid passage of vehicles. However, while this design improves the efficiency of vehicle traffic, it is also more fragile. Unlike ground roads, once a traffic accident occurs, vehicles on the expressway will have to continue to queue upstream of the incident because there is no other path to choose, which will lead to comprehensive congestion in the region or even the entire expressway system, which has a serious impact on the role of the entire expressway system. Studies have shown that after a traffic accident occurs, the road capacity gradually decreases as the duration of the accident increases. When the duration of a traffic accident exceeds 30 minutes, the expressway capacity will be reduced to 53%.

[0003] Therefore, timely and effective emergency rescue of expressway systems is particularly critical, which depends to a large extent on the rationality of the layout of emergency rescue vehicles. At present, the common methods we use to deal with traffic incidents are local rescue and nearby rescue. While the responsibilities are clearly defined, the rescue time is often unsatisfactory. Related research is more from the perspective of emergency rescue vehicle scheduling or path optimization, and lacks emergency rescue vehicle layout methods based on the design and operation characteristics of the expressway system itself. Reasonable layout is undoubtedly the basis for reasonable scheduling, which can fundamentally reduce emergency rescue time. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for the layout of emergency rescue vehicles in an expressway system based on simulation, which ensures the rationality of the layout of emergency rescue vehicles under limited resources, reduces the time required for emergency rescue, reduces the impact of traffic incidents on the expressway, and ensures the efficient operation of the entire expressway system. In order to achieve the above-mentioned purpose and other advantages of the present invention, a method for the layout of emergency rescue vehicles in an expressway system based on simulation is provided, comprising:

[0005] S1. Establish a road model of the expressway system in the traffic simulation software;

[0006] S2, input traffic flow and path;

[0007] S3. Calibrate and input simulation parameters, including road capacity, following parameters and lane-changing parameters. Although there are many default parameters in the simulation software, the behavioral characteristics of drivers in different regions are different, which are specifically reflected in following and lane-changing behaviors. This is related to the composition of local drivers, driving habits, etc., which in turn affects the road capacity. The road capacity is not only related to driving behavior, but also to road design parameters such as lane width, longitudinal slope, and traffic composition such as the proportion of different vehicle models. Therefore, these simulation parameters need to be calibrated.

[0008] S4. Determine the key road sections affected by the traffic incident;

[0009] S5. Establish a traffic event scenario library;

[0010] S6. Establish a traffic incident impact index system to evaluate traffic operation under different traffic incident scenarios;

[0011] S7, determining the emergency rescue time threshold of key sections, and determining the emergency rescue time threshold of different key sections according to the impact indicators of different key sections in different traffic event scenarios;

[0012] S8. Determine the layout plan for emergency rescue vehicles based on the distribution of different key road sections and key thresholds.

[0013] Preferably, step S4 specifically includes the following steps:

[0014] S41. Under the current or predicted traffic flow, according to the operation results of the traffic simulation software, determine the bottleneck section of the expressway system;

[0015] S42, potential bottleneck sections under extreme traffic or abnormal weather conditions based on reliability;

[0016] S43, bottleneck sections, potential bottleneck sections, and diverging areas, merging areas, and weaving areas in the superimposed road system together constitute key sections.

[0017] Preferably, in step S42, the potential bottleneck road section refers to a road section that performs well under normal operating conditions, but traffic operation will deteriorate rapidly under extreme traffic or abnormal weather conditions, thereby potentially becoming a bottleneck.

[0018] The potential bottleneck sections under extreme traffic are determined by the following steps: by combining extreme traffic prediction, the sections prone to congestion except conventional bottleneck points under extreme traffic are tested in the simulation as potential bottleneck sections under extreme traffic;

[0019] The potential bottleneck sections under abnormal weather are determined through the following steps: by analyzing the historical data of abnormal weather in the region, the main abnormal weather types are determined, and the abnormal weather types are converted into impacts on traffic parameters. In the simulation, by changing parameters, the sections that are prone to congestion except for conventional bottleneck points under different abnormal weather types are determined as potential bottleneck sections.

[0020] Preferably, in step S5, the severity and duration of different traffic events are reproduced through the traffic event scenario library to test the resilience of the expressway system, especially the upstream vehicle queue situation when the traffic event continues, and the time required for the upstream traffic situation to recover after the traffic event ends. The severity is represented by the number of lane closures and the duration of the event.

[0021] Preferably, the traffic incident impact index system in step S6 includes average queue length, maximum queue length, average vehicle delay and queue dissipation time, wherein:

[0022] Average queue length refers to the average queue length of vehicles upstream of the traffic incident after the incident continues and is resolved;

[0023] The maximum queue length refers to the maximum queue length of vehicles upstream of the traffic incident after the incident continues and is resolved;

[0024] The average vehicle delay refers to the average delay of the maximum queue length of each vehicle upstream of the traffic incident after the incident continues and is resolved;

[0025] Dissipation time refers to the time required for upstream traffic flow to return to normal after the traffic event is resolved.

[0026] Preferably, the emergency rescue time threshold in step S7 represents the critical time required for emergency rescue once a traffic incident occurs. If this emergency rescue time threshold is exceeded, the recovery time of the traffic congestion caused by the incident will increase rapidly.

[0027] Compared with the prior art, the present invention has the following beneficial effects: the present invention proposes a method and system for the layout of emergency rescue vehicles in the expressway system, comprehensively considers conventional bottleneck points and segments, identifies potential bottleneck points and segments based on reliability, superimposes merging areas, diverging areas and interweaving areas, and finally obtains more representative key points and segments affected by traffic events. On the basis of establishing a traffic event scenario library and an event impact index system, the rescue critical time thresholds of different key points and segments are identified based on resilience evaluation, and on this basis, the layout plan of emergency rescue vehicles can be obtained by applying methods such as linear programming, thereby ensuring the rationality of the layout of emergency rescue vehicles under limited resources, reducing the time required for emergency rescue, reducing the impact of traffic events on the expressway, and ensuring the efficient operation of the entire expressway system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flowchart of a method for arranging emergency rescue vehicles for an expressway system based on simulation according to the present invention;

[0029] Figure 2 A flow chart for determining key sections of the method for arranging emergency rescue vehicles for an expressway system based on simulation according to the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Reference Figure 1-2 , a simulation-based method for layout of emergency rescue vehicles for an expressway system, comprising the following steps:

[0032] S1. Establish a road model of the expressway system in the traffic simulation software, so that the entire expressway system can be accurately reproduced;

[0033] S2. Input traffic flow and path. For expressways that are already in operation, the traffic flow input data in the simulation can be determined based on historical traffic flow data, and the vehicle path can be determined based on high-definition checkpoint data. For expressways under construction or planning, it is based on traffic flow forecast data; traffic flow forecast data mainly includes traffic arriving from different directions, vehicle composition and destination. Most of the time, OD allocation is required and the specific traffic path is determined based on this.

[0034] S3. Calibrate and input simulation parameters, including road capacity, following parameters and lane-changing parameters, to more accurately reproduce traffic flow. Usually simulation software has default parameters, but it is recommended to determine them according to local actual survey data; because a considerable number of simulation software parameters cannot represent the driving behavior of local vehicles, and these parameters are very important for the reasonable operation of simulation software. Taking lane-changing parameters as an example, the distance to start lane changing is a very important parameter. Given that the lane-changing behavior in a considerable number of simulation software is far less than the actual one, if this distance is too small, it will cause more vehicles to queue up a certain distance before changing lanes, which will lead to congestion.

[0035] S4. Determine the key road sections affected by the traffic incident; specifically, the following steps are included:

[0036] S41. Under the existing or predicted traffic flow, according to the operation results of the traffic simulation software, determine the bottleneck sections of the expressway system, which are sections that are more likely to be congested under the existing traffic flow;

[0037] S42. Potential bottleneck sections under extreme traffic or abnormal weather conditions based on reliability judgment; the potential bottleneck sections refer to sections that perform well under normal operating conditions, but traffic operation will deteriorate rapidly under extreme traffic or abnormal weather conditions, thus potentially becoming bottlenecks.

[0038] The judgment of potential bottleneck sections is based on their reliability, which is divided into two aspects: reliability under extreme traffic and reliability under abnormal weather. The method for judging potential bottleneck sections under extreme traffic is to modify the input traffic flow accordingly based on the traffic growth caused by local important holidays and important exhibition days, so as to determine the reliability of the expressway system under extreme traffic and identify potential bottleneck sections according to the operation of the expressway system under this traffic. The method for judging potential bottleneck sections under abnormal weather is to determine the main abnormal weather types in the local area based on historical weather statistics, and convert the impact of the main abnormal weather types on traffic operation into changes in traffic parameters. For example, in heavy rain, the vehicle speed will decrease, while maintaining a greater safety distance. Change the corresponding simulation parameters in the simulation software, and then determine the reliability of the expressway system under this situation through multiple simulation runs, and identify sections prone to congestion as potential bottleneck sections.

[0039] S43, bottleneck sections, potential bottleneck sections, and diversion areas, merging areas, and interweaving areas in the superimposed road system together constitute the key sections affected by traffic incidents; usually, merging areas, diversion areas, and interweaving areas are key sections that need to be considered during emergency rescue, because these areas are more prone to traffic accidents due to the need for merging, diversion, or interweaving, and once a traffic accident occurs in these areas, it will have a serious impact on the operation of the entire road system. But in fact, key sections include not only these sections, but some conventional sections may also be bottlenecks of the entire road system due to insufficient traffic capacity, high traffic volume, or other reasons. Therefore, it is necessary to determine the bottleneck sections and potential bottleneck sections other than these areas through simulation tests.

[0040] S5. Establish a traffic event scenario library through key sections. It is necessary to simulate different traffic event scenarios in the traffic simulation software to reproduce the severity and duration of different traffic events and test the resilience of the expressway system; specifically, the severity of the event is reflected by the number of lane closures. Assuming that there are N lanes in the key section, there are N-1 lane closure schemes, from closing 1 lane to closing all N lanes. The event duration is divided into M levels, and in each level, the time duration increases at a certain interval.

[0041] S6. Evaluate traffic operation under different traffic incident scenarios and establish a traffic incident impact index system; Traffic incident impact index system To evaluate traffic operation under different traffic incident scenarios, establish a traffic incident impact index system, including average queue length, maximum queue length, average vehicle delay, and queue dissipation time. The average queue length refers to the average queue length of vehicles upstream of the incident after the traffic incident continues and is resolved; the maximum queue length refers to the maximum queue length of vehicles upstream of the incident after the traffic incident continues and is resolved; the average vehicle delay refers to the average delay of the maximum queue length of each vehicle upstream of the incident after the traffic incident continues and is resolved; the dissipation time refers to the time it takes for the upstream traffic flow to return to normal after the traffic incident ends. For each key section, by deploying queue detectors, travel time detectors, and vehicle speed detectors, etc., the corresponding impact indicators under different traffic incident scenarios are measured.

[0042] S7. Determine the emergency rescue time threshold of key sections. According to the impact indicators of different key sections in different traffic event scenarios, determine the emergency rescue time threshold of different key sections. This threshold represents the critical time required for emergency rescue once a traffic event occurs. If this emergency rescue time threshold is exceeded, the recovery time of traffic congestion caused by the event will increase rapidly. Specifically, assuming that the lane of key section I is completely closed and the event lasts for 10 minutes, severe congestion will occur upstream, and even after the traffic event is resolved, it will take a long time to recover in the rear. When half of the lanes are closed, they will fall into severe congestion when the traffic event lasts for about 20 minutes. The emergency rescue time threshold for a serious traffic event that causes all lanes to be closed on key section I can be selected as 10 minutes, that is, it is recommended that emergency rescue vehicles must arrive within 10 minutes, and at least half of the lanes must be unobstructed within 20 minutes after the traffic event begins.

[0043] S8. Combine the distribution of different key sections and key thresholds to determine the layout of emergency rescue vehicles, so as to ensure that the expressway system will not be seriously congested due to traffic incidents and to ensure the normal operation of the expressway network. Specifically, a linear programming model can be established based on the rescue time required for each point, the distance between points, and the speed of vehicles on the rescue path, and the total number of rescue vehicles is used as a constraint, and finally solved using an optimization algorithm.

[0044] The number of devices and processing scales described here are used to simplify the description of the present invention, and the application, modification and variation of the present invention will be obvious to those skilled in the art.

[0045] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A simulation-based method for the layout of emergency rescue vehicles on an expressway system, characterized in that: The following steps are involved: S1. Establish a road model of the expressway system in the traffic simulation software; S2, input traffic flow and path; S3, calibrating and inputting simulation parameters, wherein the simulation parameters include road capacity, car-following parameters, and lane-changing parameters; S4, determining the key road sections affected by the traffic incident; Step S4 specifically includes the following steps: S41. Under the current or predicted traffic flow, according to the operation results of the traffic simulation software, determine the bottleneck section of the expressway system; S42. Reliability-based judgment of potential bottleneck sections under extreme traffic or abnormal weather conditions; S43, bottleneck sections, potential bottleneck sections, and the diverging areas, merging areas, and interweaving areas in the road system together constitute the key sections affected by traffic incidents; The potential bottleneck sections under abnormal weather conditions are determined through the following steps: by analyzing the historical data of abnormal weather in the region, the main abnormal weather types are determined, and the abnormal weather types are converted into the impact on traffic parameters. In the simulation, by changing the parameters, the sections prone to congestion other than the conventional bottleneck points under different abnormal weather types are determined as potential bottleneck sections; S5. Establish a traffic event scenario library; S6. Establish a traffic incident impact indicator system to evaluate traffic operation under different traffic incident scenarios; S7. Determination of emergency rescue time thresholds for key sections. Determine emergency rescue time thresholds for different key sections based on the impact indicators of different key sections in different traffic event scenarios. The emergency rescue time threshold represents the critical time required for emergency rescue once a traffic event occurs. If this emergency rescue time threshold is exceeded, the recovery time for traffic congestion caused by the event will increase rapidly. S8. Determine the emergency rescue vehicle layout plan based on the distribution of different key road sections and the emergency rescue time threshold.

2. The method for arranging emergency rescue vehicles for an expressway system based on simulation according to claim 1, characterized in that: In step S5, the severity and duration of different traffic events are reproduced through the traffic event scenario library to test the resilience of the expressway system, the duration of the traffic event, the upstream vehicle queue situation, and the time required for the upstream traffic conditions to recover after the traffic event ends; The severity is represented by the number of lane closures.

3. The method for arranging emergency rescue vehicles for an expressway system based on simulation according to claim 1, characterized in that: The traffic incident impact index system in step S6 includes the average queue length, the maximum queue length, the average vehicle delay and the queue dissipation time, among which: Average queue length refers to the average queue length of vehicles upstream of the traffic incident after the incident continues and is resolved; The maximum queue length refers to the maximum queue length of vehicles upstream of the traffic incident after the incident continues and is resolved; The average vehicle delay refers to the average delay of each vehicle upstream of the traffic incident after the incident continues and is resolved; Dissipation time refers to the time required for upstream traffic flow to return to normal after the traffic event is resolved.

4. The method for arranging emergency rescue vehicles for an expressway system based on simulation according to claim 1, characterized in that: The potential bottleneck road section in step S43 refers to a road section that performs well under normal operating conditions, but the traffic operation will deteriorate rapidly under extreme traffic or abnormal weather, and thus may become a bottleneck; The potential bottleneck sections under extreme traffic are determined by the following steps: by combining extreme traffic prediction, the sections prone to congestion except conventional bottleneck points under extreme traffic are tested in the simulation as potential bottleneck sections.

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