Emergency vehicle speed release method and device in tunnel environment

Abstract

The application provides an emergency vehicle speed publishing method and device in a tunnel environment. The method comprises the following steps: determining an accident position in the tunnel, obtaining traffic flow parameters in the tunnel according to the accident position, calculating a vehicle queue length, a queue dissipation time and an accident coefficient according to the traffic flow parameters, wherein the accident coefficient is a relationship coefficient between a vehicle driving speed upstream of the accident and an accident handling time, calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time and the accident coefficient, and finally publishing the tunnel speed limit value on an indicator upstream of the accident position. The application dynamically adjusts a publishing position of speed limit information upstream according to an actual accident handling time, so as to timely prompt an emergency vehicle speed in a tunnel environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of traffic safety, and in particular to an emergency vehicle speed publishing method and device in a tunnel environment. BACKGROUND

[0002] Highway tunnels have the particularity of being closed, low-speed, and non-variable lane relative to the main line driving section. Traffic accidents in tunnels make it difficult to evacuate and rescue. At the same time, the light in tunnels is significantly different from that in ordinary road sections. Vehicles on highways travel at high speed, which can easily lead to secondary accidents. Due to the closed nature, when a traffic accident occurs in a tunnel, the road section is often blocked for accident handling, which greatly affects the normal operation of upstream traffic.

[0003] Publishing vehicle speed on the upstream section can effectively evacuate and disperse queued vehicles, reduce queuing delay, and reduce the risk of secondary accidents. As the accident handling time continues, the bottleneck influence area expands, so it is necessary to dynamically adjust the upstream speed limit value and the speed limit information publishing position.

[0004] Research on variable speed limits is based on various traffic models from a macro and micro perspective. When a reasonable speed limit value is proposed, the specific scene results are simulated by simulation software, and the reasonableness of each speed limit value is compared. However, variable speed limits dynamically adjust the speed limit strategy by changing the speed limit value, and few dynamically adjust the speed limit information publishing position, which greatly affects traffic efficiency. SUMMARY

[0005] To solve the problem of low traffic efficiency caused by untimely vehicle speed updating and publishing, in a first aspect, some embodiments of the present application provide an emergency vehicle speed publishing method in a tunnel environment, the method comprising:

[0006] Determining the accident occurrence position in the tunnel according to the monitoring video data;

[0007] Obtaining traffic flow parameters in the tunnel according to the accident occurrence position;

[0008] Calculating the vehicle queue length, queue dissipation time, and accident coefficient according to the traffic flow parameters, the accident coefficient being a relationship coefficient between the vehicle speed upstream of the accident and the accident handling time;

[0009] Calculating the tunnel speed limit value according to the vehicle queue length, the queue dissipation time, and the accident coefficient;

[0010] Publishing the tunnel speed limit value in the signboard upstream of the accident occurrence position.

[0011] In some embodiments, obtaining traffic flow parameters in the tunnel according to the accident occurrence position further comprises:

[0012] The tunnel is divided into a first state section, a second state section and a third state section according to the location of the accident;

[0013] The first traffic flow parameter of the first state section is acquired, the second traffic flow parameter of the second state section is acquired, and the third traffic flow parameter of the third state section is acquired.

[0014] In some embodiments, the vehicle queue length, the queue dissipation time and the accident coefficient are calculated according to the traffic flow parameters, and the method further comprises:

[0015] The slope of a first shock path is calculated according to the first traffic flow parameter and the third traffic flow parameter, and the slope of a second shock path is calculated according to the second traffic flow parameter and the third traffic flow parameter.

[0016] The vehicle queue length and the queue dissipation time are calculated according to the slope of the first shock path and the slope of the second shock path.

[0017] In some embodiments, the first traffic flow parameter comprises a first flow and a first density, the second traffic flow parameter comprises a second flow and a second density, and the third traffic flow parameter comprises a third flow and a third density, the slope of the first shock path is calculated according to the first traffic flow parameter and the third traffic flow parameter, and the method further comprises:

[0018] The slope of the first shock path is calculated according to the first flow, the first density, the third flow and the third density, according to the following formula:

[0019]

[0020] wherein U AC is the slope of the first shock path, q A is the first flow, k A is the first density, q C is the third flow, k C is the third density;

[0021] The slope of the second shock path is calculated according to the second traffic flow parameter and the third traffic flow parameter, and the method further comprises:

[0022] The slope of the second shock path is calculated according to the second flow, the second density, the third flow and the third density, according to the following formula:

[0023]

[0024] wherein U CB is the slope of the second shock path, q B is the second flow, k B is the second density.

[0025] In some embodiments, according to the slope of the first shock wave path and the slope of the second shock wave path, a vehicle queue length and a queue dissipation time are calculated according to the following formula:

[0026] x = t d · |U AC = (t d -t m ) · |U CB |;

[0027] wherein x is the vehicle queue length, t d is the queue dissipation time, and t m is the accident handling time.

[0028] In some embodiments, a tunnel speed limit value is calculated according to the vehicle queue length, the queue dissipation time, and the accident coefficient, further comprising:

[0029] calculating a speed limit queue length according to the vehicle queue length and the queue dissipation time, the speed limit queue length being a queue length upstream of the accident occurrence position under a speed limit state;

[0030] calculating the tunnel speed limit value according to the speed limit queue length.

[0031] In some embodiments, calculating the speed limit queue length according to the vehicle queue length and the queue dissipation time further comprises:

[0032] obtaining a first speed limit traffic flow parameter, the first speed limit traffic flow parameter comprising a first speed limit density and a first speed limit flow;

[0033] calculating the speed limit queue length according to the first speed limit density according to the following formula:

[0034]

[0035] wherein x' is the speed limit queue length, d is a safe braking distance located on the first shock wave path, and k A' is the first speed limit density.

[0036] In some embodiments, the method further comprises:

[0037] obtaining a proportional relationship between the first speed limit flow and a second flow according to an accident coefficient;

[0038] calculating a first speed limit speed expression according to the proportional relationship;

[0039] calculating a tunnel speed limit value by simultaneously solving the first speed limit speed expression and the speed limit queue length.

[0040] In some embodiments, the tunnel speed limit value is published in a signboard upstream of the accident occurrence location, and the method further comprises:

[0041] calculating a safe braking distance on the first shock wave path;

[0042] publishing the tunnel speed limit value in a signboard of a safe braking distance upstream of the accident occurrence location.

[0043] In a second aspect, some embodiments of the present application also provide an emergency vehicle speed publishing device in a tunnel environment, comprising a vehicle speed publishing module, which is configured to execute the following method:

[0044] determining an accident occurrence location in the tunnel;

[0045] obtaining traffic flow parameters in the tunnel according to the accident occurrence location;

[0046] calculating a vehicle queue length, a queue dissipation time, and an accident coefficient according to the traffic flow parameters, the accident coefficient being a relationship coefficient between a vehicle driving speed upstream of the accident and an accident handling time;

[0047] calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time, and the accident coefficient;

[0048] publishing the tunnel speed limit value in a signboard upstream of the accident occurrence location.

[0049] As can be seen from the above solutions, the present application provides an emergency vehicle speed publishing method and device in a tunnel environment, which determines an accident occurrence location in the tunnel, obtains traffic flow parameters in the tunnel according to the accident occurrence location, then calculates a vehicle queue length, a queue dissipation time, and an accident coefficient according to the traffic flow parameters, the accident coefficient being a relationship coefficient between a vehicle driving speed upstream of the accident and an accident handling time. A tunnel speed limit value is calculated according to the vehicle queue length, the queue dissipation time, and the accident coefficient, and finally the tunnel speed limit value is published in a signboard upstream of the accident occurrence location. The present application dynamically adjusts the publishing position of the speed limit information upstream according to the actual accident handling time, so as to timely prompt the emergency vehicle speed in the tunnel environment. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0051] Figure 1 a flowchart of an emergency vehicle speed publishing method in a tunnel environment provided in the embodiments of the present application;

[0052] Figure 2 Flow chart for calculating the slope of the first shock wave path in the embodiments of the present application;

[0053] Figure 3 Flow chart for calculating the slope of the second shock wave path in the embodiments of the present application;

[0054] Figure 4 State diagram of each road section under the relationship between flow and density in the embodiments of the present application;

[0055] Figure 5 State diagram of each road section under the relationship between vehicle queuing distance and time in the embodiments of the present application. DETAILED DESCRIPTION

[0056] Hereinafter, the present application will be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0057] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence.

[0058] A tunnel is a traffic passage. When laying a highway, due to topographical factors, the highway needs to pass through a mountain or a large bridge. In order to shorten the distance of the highway, a tunnel can be opened in the middle of the mountain for vehicle traffic. However, for a long distance tunnel, only under the sunlight at the entrance and exit of the tunnel, the road can be seen. When the vehicle enters the tunnel, the large brightness difference will affect the driver's vision, so that the driver cannot make a judgment on the road condition in the first time, and therefore, the driving safety inside the tunnel is low, which is a potential accident-prone section.

[0059] When a traffic accident occurs in a tunnel, due to the long length of the tunnel, the emergency response and rescue work after the accident is difficult, thus causing great personnel casualties and property losses due to the missed best rescue time. In addition to causing personnel casualties and property losses, the occurrence of a traffic accident will also greatly reduce the traffic capacity of the tunnel, causing serious traffic congestion and even traffic paralysis.

[0060] After a traffic accident occurs, in order to prevent the occurrence of secondary accidents, it is necessary to adjust the speed limit value located upstream of the accident site and the release position of the speed limit information. There are various traffic models based on macro and micro in the research on variable speed limits. When a reasonable speed limit value is proposed, the specific scene results are simulated by simulation software, and the rationality of each speed limit value is compared. However, the variable speed limit dynamically adjusts the speed limit strategy by changing the speed limit value, and few dynamically adjusts the release position of the speed limit information, which has a great impact on traffic efficiency.

[0061] To improve the traffic efficiency when an accident occurs, some embodiments of the present application provide an emergency vehicle speed publishing method in a tunnel environment, as shown in the following formula (1). Figure 1

[0062] S100: determining an accident occurrence position in the tunnel according to the monitoring video data.

[0063] In this embodiment, the monitoring video data can be obtained by an intelligent inspection robot in the tunnel. The intelligent inspection robot can analyze the accident occurrence position based on the obtained monitoring video data, and can obtain the GPS positioning information of the accident vehicle by requesting the GPS system, so as to determine the accident occurrence position.

[0064] In some embodiments, the intelligent inspection robot can also obtain accident vehicle information, which can include the model of the accident vehicle, such as small car, medium car, small truck, medium truck, large truck, trailer, etc., and the type of the accident vehicle, such as family car, police car, oil tank truck, water truck, ambulance, etc., so as to facilitate the risk analysis of the accident site. The accident vehicle information can also include the running direction of the vehicle, the driving speed when the accident occurs, etc.

[0065] S200: obtaining traffic flow parameters in the tunnel according to the accident occurrence position.

[0066] In this embodiment, the traffic flow parameters can include the flow, density, speed of the normal road section and the bottleneck road section where the accident occurs, the tunnel traffic capacity, the critical density, etc.

[0067] In some embodiments, in order to accurately obtain the traffic flow parameters of each road section after the accident, the tunnel can be divided into a first state road section, a second state road section and a third state road section according to the accident occurrence position. For convenience of description, in this embodiment, the road section approaching the accident occurrence position is defined as the upstream road section, and the road section leaving the accident occurrence position is defined as the downstream road section. Among them, the first state road section is the road section approaching the accident occurrence position upstream of the tunnel, denoted as A, the second state road section is the road section with reduced traffic capacity due to the accident, denoted as B, and the third state road section is the road section that can normally drive downstream of the accident occurrence position, denoted as C.

[0068] After dividing each road section, the first traffic flow parameters of the first state road section, the second traffic flow parameters of the second state road section and the third traffic flow parameters of the third state road section can be obtained, so as to calculate the vehicle queue length, the queue dissipation time and the accident coefficient subsequently.

[0069] ​S300: calculating a vehicle queue length, a queue dissipation time and an accident coefficient according to the traffic flow parameter.

[0070] The accident coefficient is a relationship coefficient of a vehicle driving speed upstream of the accident and an accident handling time. The vehicle queue length is a queue length from the accident position as a starting point, and the queue dissipation time is a time for the queue vehicles to enter a normal driving speed.

[0071] In some embodiments, the vehicle queue length and the queue dissipation time can be calculated according to the slope of the first shock wave path and the slope of the second shock wave path. For this purpose, the slope of the first shock wave path and the slope of the second shock wave path need to be calculated first.

[0072] In some embodiments, the relationship of the queue length, the upstream speed and the accident handling time can also be obtained according to the LWR model.

[0073] In some embodiments, the slope of the first shock wave path can be calculated according to the first traffic flow parameter and the third traffic flow parameter. The first traffic flow parameter can include a first flow and a first density, and the third traffic flow parameter can include a third flow and a third density.

[0074] As shown in FIG. 3, P is the position of the accident, where congestion occurs, and the speed and the traffic capacity decrease to 0. For calculating the slope of the first shock wave path, the slope of the first shock wave path can be calculated according to the first flow, the first density, the third flow and the third density, according to the following formula: Figure 2

[0075]

[0076] wherein U1 is the slope of the first shock wave path, q1 is the first flow, k1 is the first density, q3 is the third flow, and k3 is the third density. AC A A C C

[0077] As shown in FIG. 4, for calculating the slope of the second shock wave path, the slope of the second shock wave path can be calculated according to the second flow, the second density, the third flow and the third density, according to the following formula: Figure 3

[0078]

[0079] wherein U2 is the slope of the second shock wave path, q2 is the second flow, and k2 is the second density. CB B B

[0080] ​​​​​​​​​​After obtaining the slopes of the first and second shock wave paths, the vehicle queue length and queue dissipation time can be calculated using the following formula:

[0081] x = t d ·|U AC |=(t d -t m )·|U CB |;

[0082] Where x is the length of the vehicle queue, t d For the time it takes for the queue to dissipate, t m This refers to the time allotted for handling the accident.

[0083] The queue dissipation time can be obtained as follows:

[0084]

[0085] The length of the vehicle queue is:

[0086]

[0087] In some embodiments, the accident factor is a proportional relationship coefficient of the three parameters in the traffic flow, and the proportional relationship coefficient is:

[0088] q = k·u;

[0089] Where q is the flow rate, k is the density, and u is the upstream velocity. For example... Figure 4 As shown, controlling the upstream speed u to decrease, assuming the vehicle arrival rate remains constant, the density of the speed limit zone at the time the speed limit is issued is the same as the original k. A Similarly, due to speed restrictions, the traffic flow is compressed, and at the next moment, k increases, causing the traffic flow state upstream of the bottleneck to change from point A to A',k. A' >k A ,|U A'C |<|U AC | A' represents a road segment under speed limit conditions.

[0090] From the above formula, we can see that the queue dissipation time t d Queue length x and incident handling time t m It is proportional to |UAC|. Therefore, |U| can be reduced by limiting the upstream velocity. AC This reduces queue length, shortens queue dissipation time, and reduces vehicle queue delays.

[0091] S400: Calculate the tunnel speed limit based on the vehicle queue length, the queue dissipation time, and the accident coefficient.

[0092] To remind vehicles located upstream of the accident occurrence position, a tunnel speed limit value needs to be calculated to remind upstream vehicles to adjust the driving speed according to the tunnel speed limit value. In the present embodiment, a speed limit queue length can be calculated according to the vehicle queue length and the queue dissipation time, wherein the speed limit queue length is the queue length upstream of the accident occurrence position in a speed limit state.

[0093] To this end, the signboard of the tunnel after the accident occurrence can be marked as a speed limit state, and a first speed limit traffic flow parameter in the tunnel can be obtained according to the speed limit state, wherein the first speed limit traffic flow parameter includes a first speed limit density and a first speed limit flow. Then, the speed limit queue length can be calculated according to the first speed limit density, as follows:

[0094]

[0095] wherein x' is the speed limit queue length, d is a safe braking distance located on the first shock wave path, k A' is the first speed limit density.

[0096] After the speed limit queue length is calculated, the tunnel speed limit value can be calculated according to the speed limit queue length. In some embodiments, the proportional relationship between the first speed limit flow and the second flow can be obtained according to the accident coefficient, so as to calculate a first speed limit speed expression according to the proportional relationship, so as to maximize the traffic efficiency, and control q A' to be 0.8q B , that is:

[0097] q A' = 0.8q B = k A' · u A' ;

[0098] q A' is the first speed limit flow, u A' is the first speed limit speed.

[0099] In some embodiments, the tunnel speed limit value can also be calculated by simultaneously solving u A' and x', wherein the tunnel speed limit value is calculated as follows:

[0100]

[0101] wherein the obtained speed limit value is a dynamic value about the accident handling time t m .

[0102] S500: publishing the tunnel speed limit value in the signboard upstream of the accident occurrence position.

[0103] In the present embodiment, as Figure 5As shown, at time t, the bottleneck propagates to a distance tU AC upstream from the accident location, at which time the vehicle should be alerted at a safe braking distance upstream. To this end, a safe braking distance on the first shock wave path can be calculated to alert the vehicle in front of the vehicle and to alert the vehicle to slow down. The safe braking distance can be calculated as follows:

[0104]

[0105] where V max is the maximum speed of the upstream vehicle, which is taken as the speed limit value, t r is the reaction time, which can be taken as 2.5 s, is the adhesion coefficient between the tire and the road surface, and i is the road surface slope (%), which is positive for uphill and negative for downhill.

[0106] After the safe braking distance is obtained, a sign at the safe braking distance upstream from the accident location is posted with the tunnel speed limit value.

[0107] In some embodiments, the location at which the tunnel speed limit value is posted can also be calculated in advance, and the location at which the tunnel speed limit value is posted can be calculated as follows:

[0108]

[0109] where D is the location at which the tunnel speed limit value is posted.

[0110] In some embodiments, the location at which the tunnel speed limit value is posted can also be calculated in advance, and the location at which the tunnel speed limit value is posted can be calculated as follows:

[0111] A traffic accident in a certain highway tunnel is taken as an example to illustrate the method. First, the relevant state parameters are obtained. State A represents the first state road section, the traffic flow is q A = 1400 veh / h, the traffic flow density is k A = 20 veh / km, and the traffic flow speed is u A = 70 km / h. State B represents the second state road section, the traffic flow is q B = 1800 veh / h, the traffic flow density is k B = 45 veh / km, and the traffic flow speed is u B = 40 km / h. State C represents the third state road section, the traffic flow is 0, the traffic flow density is k C = 150 veh / km, and the traffic flow speed is 0. The time at which the accident occurs is taken as time 0, t m is the accident handling time, and t dThe queue dissipation time is t

[0112] Table 1

[0113] State Description q (veh / h) k (veh / km) u (km / h) A First state road section 1400 20 70 B Second state road section 1800 45 40 C Third state road section 0 150 0

[0114] The relationship between the queue length and the upstream speed and the accident handling time can be obtained according to the LWR model. If P is the position where the accident occurs, the speed and the traffic capacity decrease to 0 due to the congestion, the upstream first-state road section reaches the accident position, and according to the shock wave theory, the first-state road section propagates upstream to the third-state road section at the following speed:

[0115]

[0116] After the accident is handled for t m , the queue vehicles dissipate at the traffic capacity, and the third-state road section propagates downstream to the second-state road section at the following speed:

[0117]

[0118] x is the queue length, t d is the queue dissipation time, the queue length and the queue dissipation time have the following relationship:

[0119] x = t d · |U AC | = (t d -t m ) · |U CB |;

[0120] The queue dissipation time is obtained as follows:

[0121]

[0122] The queue length is obtained as follows:

[0123]

[0124] At the time t, the position of the safe braking distance d is:

[0125]

[0126] where V max is the maximum speed of the upstream vehicle, which is taken as the tunnel speed limit value 80 km / h, t r is the reaction time, taken as 2.5 s, is the adhesion coefficient between the tire and the road surface, taken as 0.8, i is the road surface slope (%), positive for uphill and negative for downhill, and the slope is 0 here.

[0127] The speed control information is released at a distance d upstream of the accident location, so that the traffic flow is converted from state A to A'. Suppose that the traffic flow arriving at state A and the vehicles in congestion state C can be completely evacuated to state A', i.e.:

[0128]

[0129] where the queue length under speed limit is:

[0130]

[0131] To maximize the traffic efficiency, q A' is controlled at 0.8C, i.e. 0.8qB ， Thus, we have:

[0132] q A' = 0.8q B = k A' ·u A' ;

[0133] According to the queue length under speed limit, U A'C needs to be calculated, and U A'C is calculated as follows:

[0134]

[0135] Thus, we have:

[0136]

[0137] By combining the above equations, we can obtain an expression for u A' :

[0138]

[0139] Thus, the tunnel speed limit value can be calculated according to the expression for u A' , which is a dynamic value related to the accident handling time t m . The corresponding tunnel speed limit value can be obtained according to the fixed value t m .

[0140] The position for releasing the prompt information is D, which is in the upstream direction of the accident location and is at a position that is a safe braking distance away from the accident location:

[0141]

[0142] The upstream dynamic speed limit control scheme is shown in Table 2 below:

[0143] Table 2

[0144]

[0145]

[0146] To facilitate the implementation of the tunnel emergency vehicle speed release method described above, some embodiments of the present application also provide a tunnel emergency vehicle speed release device, which comprises a vehicle speed release module, which can be electrically connected with a server for traffic management or a traffic sign, for sending the tunnel speed limit value to the server or the sign in the form of a signal. The vehicle speed release module is configured to execute the tunnel emergency vehicle speed release method, comprising:

[0147] S100: determining the accident location in the tunnel.

[0148] S200: obtaining the traffic flow parameters in the tunnel according to the accident location.

[0149] S300: calculating the vehicle queue length, queue dissipation time and accident coefficient according to the traffic flow parameters.

[0150] The accident coefficient is the relationship coefficient between the vehicle speed upstream of the accident and the accident handling time.

[0151] S400: calculating the tunnel speed limit value according to the vehicle queue length, the queue dissipation time and the accident coefficient.

[0152] S500: releasing the tunnel speed limit value in the sign upstream of the accident location.

[0153] From the above scheme, the present application provides a tunnel emergency vehicle speed release method and device, which determines the accident location in the tunnel, obtains the traffic flow parameters in the tunnel according to the accident location, then calculates the vehicle queue length, queue dissipation time and accident coefficient according to the traffic flow parameters, the accident coefficient is the relationship coefficient between the vehicle speed upstream of the accident and the accident handling time. And according to the vehicle queue length, the queue dissipation time and the accident coefficient, the tunnel speed limit value is calculated, and finally the tunnel speed limit value is released in the sign upstream of the accident location. The present application dynamically adjusts the release position of the speed limit information upstream according to the actual accident handling time, to real-time prompt the emergency vehicle speed in the tunnel environment.

[0154] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0155] For the sake of convenience, the foregoing description has been presented in terms of specific implementations. However, the foregoing examples are not intended to exhaust or limit the implementations to the particular forms disclosed. Modifications and variations are possible in light of the above teachings. The implementation was chosen and described in order to provide the best illustration of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to use the disclosure in practical implementations and applications.

Claims

1. A method for issuing an emergency vehicle speed in a tunnel environment, characterized by, The method comprises: determining an accident occurrence position in a tunnel according to monitored video data; acquiring traffic flow parameters in the tunnel according to the accident occurrence position; calculating a vehicle queue length, a queue dissipation time and an accident coefficient according to the traffic flow parameters, the accident coefficient being a relationship coefficient of a vehicle driving speed upstream of the accident and an accident handling time; calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time and the accident coefficient; publishing the tunnel speed limit value in a signboard upstream of the accident occurrence position; acquiring traffic flow parameters in the tunnel according to the accident occurrence position further comprises: dividing the tunnel into a first state road section, a second state road section and a third state road section according to the accident occurrence position; acquiring a first traffic flow parameter of the first state road section, a second traffic flow parameter of the second state road section and a third traffic flow parameter of the third state road section, the first traffic flow parameter comprising a first flow and a first density, the second traffic flow parameter comprising a second flow and a second density, and the third traffic flow parameter comprising a third flow and a third density; calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time and the accident coefficient further comprises: calculating a speed limit queue length according to the vehicle queue length and the queue dissipation time, the speed limit queue length being a queue length upstream of the accident occurrence position under a speed limit state; calculating the tunnel speed limit value according to the speed limit queue length; calculating a speed limit queue length according to the vehicle queue length and the queue dissipation time further comprises: acquiring a first speed limit traffic flow parameter, the first speed limit traffic flow parameter comprising a first speed limit density and a first speed limit flow; calculating the speed limit queue length according to the first speed limit density according to the following formula: where x is the vehicle queue length, t d is the queue dissipation time, t m is the incident handling time, x' is the speed limit queue length, d is the safe braking distance on the first shockwave path, k A′ is the first speed limit density, k A is the first density, k C is the third density.

2. The method of claim 1, wherein, calculating a vehicle queue length and a queue dissipation time according to the first traffic flow parameter and the third traffic flow parameter further comprises: calculating a slope of a first shock wave path according to the first traffic flow parameter and the third traffic flow parameter, and calculating a slope of a second shock wave path according to the second traffic flow parameter and the third traffic flow parameter; calculating the vehicle queue length and the queue dissipation time according to the slope of the first shock wave path and the slope of the second shock wave path.

3. The method of claim 2, wherein, calculating a slope of a first shock wave path according to the first traffic flow parameter and the third traffic flow parameter further comprises: calculating the slope of the first shock wave path according to the first flow, the first density, the third flow and the third density according to the following formula: wherein U AC is the slope of the first shock path, q A is the first flow rate, k A is the first density, q C is the third flow rate, k C is the third density; calculating a slope of a second shock wave path according to the second traffic flow parameter and the third traffic flow parameter further comprises: calculating the slope of the second shock wave path according to the second flow, the second density, the third flow and the third density according to the following formula: where U CB is the slope of the second shock path, q B is the second flow rate, k B is the second density.

4. The method of claim 3, wherein, calculating a vehicle queue length and a queue dissipation time according to the slope of the first shock wave path and the slope of the second shock wave path according to the following formula: x = t d • |u AC = (t d - t m ) • |u CB |; where x is the vehicle queue length, t d is the queue dissipation time, t m is the incident handling time.

5. The method of claim 1, wherein, The method further comprises: acquiring a proportional relationship between the first speed limit flow and the second flow according to the accident coefficient; calculating a first speed limit speed expression according to the proportional relationship; The tunnel speed limit value is calculated by combining the first speed limit expression and the speed limit queue length.

6. The method of claim 1, wherein, The tunnel speed limit value is posted on a sign upstream of the accident location, and the method further comprises: calculating a safe braking distance on a first shock wave path; The tunnel speed limit value is posted on a sign upstream of the safe braking distance at the accident location.

7. An emergency vehicle speed announcement device in a tunnel environment, characterized by, The device comprises a vehicle speed posting module configured to perform the following method: determining an accident location within a tunnel; obtaining traffic flow parameters in the tunnel according to the accident location; calculating a vehicle queue length, a queue dissipation time, and an accident coefficient according to the traffic flow parameters, the accident coefficient being a relationship coefficient between a vehicle speed upstream of the accident and an accident handling time; calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time, and the accident coefficient; posting the tunnel speed limit value on a sign upstream of the accident location; obtaining traffic flow parameters in the tunnel according to the accident location, the method further comprising: dividing the tunnel into a first state section, a second state section, and a third state section according to the accident location; obtaining first traffic flow parameters of the first state section, second traffic flow parameters of the second state section, and third traffic flow parameters of the third state section, the first traffic flow parameters comprising a first flow and a first density, the second traffic flow parameters comprising a second flow and a second density, and the third traffic flow parameters comprising a third flow and a third density; calculating a tunnel speed limit value according to the vehicle queue length, the queue dissipation time, and the accident coefficient, the method further comprising: calculating a speed limit queue length according to the vehicle queue length and the queue dissipation time, the speed limit queue length being a queue length upstream of the accident location in a speed limit state; calculating the tunnel speed limit value according to the speed limit queue length; calculating a speed limit queue length according to the vehicle queue length and the queue dissipation time, the method further comprising: obtaining first speed limit traffic flow parameters, the first speed limit traffic flow parameters comprising a first speed limit density and a first speed limit flow; calculating the speed limit queue length according to the first speed limit density according to the following formula: where x is the vehicle queue length, t d is the queue dissipation time, t m is the incident handling time, x' is the speed limit queue length, d is the safe braking distance on the first shockwave path, k A′ is the first speed limit density, k A is the first density, k C is the third density.

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