CN105303833B - Overpass accident method of discrimination based on microwave vehicle detector - Google Patents

Abstract

The invention belongs to urban viaduct Information Collecting ＆ Processing technical field, and in particular to a kind of overpass accident method of discrimination based on microwave vehicle detector.Step is as follows：Microwave vehicle detector is installed and is debugged；Obtain microwave vehicle detector data；Calculate the equivalent volume of traffic Q in single track_Lj；Calculate the averag density K in single track_Lj；Calculate the averag density K in single track_Lj；Calculate overpass road-section average travel speedPredict t-th road-section average travel speed V in sampling period_tp；Calculate the road-section average travel speed standard deviation S in past 4 sampling periods；Obtain t-th road-section average travel speed in sampling period predicted value and actual value difference and standard deviation ratio Q；Traffic incident differentiates.Faster, measuring and calculating process more succinctly facilitates the response of data acquisition of the present invention, and the precise effect of online results of measuring is higher, can in time, effectively process overpass accident, and the generation of traffic jam is greatly reduced.

Description

Viaduct emergency discrimination method based on microwave vehicle detector

Technical Field

The invention belongs to the technical field of urban viaduct information acquisition and processing, and particularly relates to a viaduct emergency discrimination method based on a microwave vehicle detector.

Background

The viaduct occupies an important position in large and medium-sized urban traffic systems and is a main artery of urban traffic. If an emergency happens to the viaduct, traffic jam in a large range can be caused, and traveling of urban residents is affected, so that judgment of the emergency of the viaduct is very necessary.

The traffic information collection of urban roads is the basis for judging the emergency of the viaduct. At present, common detection devices include video detection, coil detection and geomagnetic detection, but in practical application, the detection methods all have various disadvantages. For example, the video detection is greatly interfered by light, the coil detection can damage the road surface, and the geomagnetic detection is influenced by wireless communication to cause frequent data loss. In addition, for the current developing direction of urban traffic which is advancing day by day, the requirement of traffic management cannot be met even if the road is in a congestion state by simply judging as above, and the calculation is faster and more efficient, has shorter response time and higher accuracy, and gradually becomes the main melody for calculating the elevated road condition. How to seek a traffic measurement and calculation mode aiming at the viaduct emergency meeting the requirements, so as to synchronously ensure the high efficiency of the measurement and calculation process and the high accuracy of the measurement and calculation result while having faster data responsiveness, thereby ensuring that a traffic manager can carry out reasonable and scientific traffic organization in a very short time when an incident occurs, so as to achieve the purposes of avoiding secondary accidents and congestion, reducing the influence of accidents and driving delay, and finally improving the decision level and the intelligent level of event handling of the traffic manager, thereby solving the technical problem to be solved urgently in the field of traffic management for nearly ten years.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a more efficient and rapid viaduct emergency discrimination method based on a microwave vehicle detector; the data acquisition responsiveness is faster, the measurement and calculation process is simpler and more convenient, the high-accuracy effect of the online measurement and calculation result can be synchronously realized, and the rapid and efficient management requirement of the existing viaduct traffic can be effectively met.

In order to achieve the purpose, the invention adopts the following technical scheme:

a viaduct emergency distinguishing method based on a microwave vehicle detector is characterized by comprising the following steps:

1) installing a microwave vehicle detector on the section of the elevated bridge to be detected and debugging the microwave vehicle detector;

2) acquiring data measured by the microwave vehicle detector, wherein the data comprises corresponding serial numbers of all lanes, vehicle types of vehicles running on the lanes, the number of each vehicle type and time occupancy;

3) converting the traffic volume of each motor vehicle and non-motor vehicle on the lane into the equivalent traffic volume of the standard vehicle type by the conversion coefficient to obtain the equivalent traffic volume Q of a single lane_LjThe formula is as follows:

Q_Lj＝∑Q_iE_i

wherein,

Q_Ljis the equivalent traffic volume for the jth lane;

Q_ithe absolute number of the vehicles of the ith vehicle type in the jth lane;

E_iis the conversion coefficient of the ith vehicle type in the jth lane;

4) calculating the average density K of the single lane_Lj：

Wherein:

K_Ljis the jth lane average density;

occ_jis the time occupancy of the jth lane;

a is a constant;

5) calculating the average driving speed V of the single lane_Lj：

Wherein:

V_Ljis the j-th lane average travel speed;

6) and obtaining the average running speed of the viaduct road sectionThe calculation formula is as follows:

wherein:

n is the total number of lanes contained in the road segment;

7) predicting the average running speed V of the road section in the t sampling period_tp；

Wherein:

is the road section average traveling speed of the t-1 th sampling period; by the way of analogy, the method can be used,

8) and calculating the standard deviation S of the average running speed of the road section in the past 4 sampling periods:

9) establishing a calculation formula of a ratio Q of the difference between a predicted value and an actual value of the average running speed of the road section in the t-th sampling period to the standard deviation, wherein the calculation formula comprises the following steps:

wherein:is the actual value of the average running speed of the road section in the t-th sampling period;

V_tpthe predicted value is the average running speed of the road section in the t-th sampling period;

s is the standard deviation of the average running speed of the road section in the past 4 sampling periods;

10) and judging the traffic emergency:

and (3) judging traffic emergencies:

comparing Q with a set threshold value M, wherein M is 2;

when Q is larger than M, judging that an emergency occurs;

and when Q is less than or equal to M, judging that no emergency occurs.

In the step 1), the angle and the height of the detector are adjusted according to the range of the lane to be detected, so that the beam projection of the detector can cover all lanes to be detected, and the length directions of the projection and the detected road are orthogonal to each other.

In the step 3), the standard vehicle type is a passenger car, and the conversion coefficient is 1.

The invention has the beneficial effects that:

1) according to the scheme, on one hand, the microwave vehicle detector utilizes the advantages of reliable and efficient performance and multi-target detection function of the microwave vehicle detector. Compared with the traditional fixed-point measurement video, geomagnetic and coil detectors, the fixed-point acquisition precision of the microwave vehicle detector is higher, accurate identification and information acquisition can be realized from a motorcycle to a multi-axle and high-body vehicle, the microwave vehicle detector can also perform high-precision detection on the trailer, the defect that the trailer is mistakenly reported as multiple vehicle types in similar products is avoided, the parameters of traffic flow, vehicle speed, lane occupancy, vehicle type classification and the like of each lane on the road can be detected, and the acquisition accuracy can also be effectively guaranteed. And because the construction cost of the viaduct is high, the maintenance is difficult, the bridge body can not be damaged, and the microwave detector with the advantages of simple and convenient installation and maintenance and no damage to the road surface is more suitable. On the other hand, through an objective formula calculation process specially aiming at the viaduct, the section to be detected of the viaduct is taken as a research object, data obtained by the microwave vehicle detector is processed and analyzed, and whether the ratio of the difference value between the average driving speed predicted value and the actual value of the section of the viaduct and the normal standard deviation is larger than a preset threshold value or not is judged so as to judge whether an emergency occurs or not. If an accident happens, an alarm is given in time, measures are taken to reduce loss, and the traffic management level of the viaduct under the emergency is improved. The method has the advantages of simple calculation process, high accuracy and strong objectivity, the accuracy of judging the traffic state of the viaduct section to be detected on line is extremely high, and the requirement of rapid and efficient management of the existing viaduct traffic can be effectively met.

Drawings

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a time-axis profile for each sampling period;

FIG. 3 is a diagram showing the effect of the installation and layout of microwave vehicle detectors.

Detailed Description

For the sake of understanding, the following description of the present invention is made with reference to the accompanying drawings 1-3:

as shown in fig. 1, the method for determining an emergency of a viaduct based on a microwave vehicle detector disclosed by the invention comprises the following steps:

1) installing a microwave vehicle detector on the section of the elevated bridge to be detected and debugging the microwave vehicle detector;

2) acquiring microwave vehicle detector data;

3) calculating the equivalent traffic Q of a single lane_Lj；

4) Calculating the average density K of the single lane_Lj；

5) Calculating the average density K of the single lane_Lj；

6) And calculating the average running speed of the viaduct road section

7) Predicting the average running speed V of the road section in the t sampling period_tp；

8) Calculating the standard deviation S of the average driving speed of the road section in the past 4 sampling periods;

9) obtaining the ratio Q of the difference between the predicted value and the actual value of the average running speed of the road section in the t-th sampling period to the standard deviation;

10) and judging the traffic emergency.

The microwave vehicle detector is arranged and debugged on the section of the viaduct to be detected, the angle and the height of the detector are adjusted according to the range of the lane to be detected, the beam projection of the detector can cover all lanes to be detected, and meanwhile, the projection is orthogonal to the detected road. And the acquired microthin detector data comprises lane numbers, vehicle types, the number of each vehicle type and time occupancy.

Calculating equivalent traffic Q of a single lane_LjThe method is to convert the actual traffic volume of various motor vehicles and non-motor vehicles into the equivalent traffic volume of a certain standard vehicle type according to a certain conversion coefficient. Because different vehicle types occupy different road spaces, in the traffic profession, vehicles of different vehicle types must be converted into standard vehicles to calculate the flow for scientific traffic statistics. The calculation formula is as follows:

Q_Lj＝∑Q_iE_i

wherein,

Q_Ljis the equivalent traffic volume for the jth lane;

Q_iis the vehicle of the ith vehicle type in the jth laneThe absolute number of vehicles;

E_iis the conversion coefficient of the ith vehicle type in the jth lane.

Conversion factor E_iThe value of (A) is specified in the technical standards of highway engineering and the design specifications of urban roads in China. The conversion coefficient in the urban road and the conversion coefficient in the highway are slightly different, and the intersection and the road section are also different. In China, passenger cars are used as standard cars, and the technical standards of highway engineering and the design specifications of urban roads can be specifically referred to. For the viaduct, the following is stipulated according to CJJ37-2012 "urban road engineering design specification" 4.1.2: the conversion of the traffic volume should adopt a passenger car as a standard car type, and the conversion system of various vehicles should meet the regulations of the table 1.

TABLE 1 vehicle conversion factor

Type of vehicle	Small passenger car	Large-scale passenger car	Large truck	Articulated vehicle
					Conversion factor	1.0	2.0	2.5	3.0

Calculating the average density K of the individual lanes_LjThe calculation formula is as follows:

wherein:

K_Ljis the jth lane average density;

occ_jis the time occupancy of the jth lane;

a is a constant, and the specific value needs to be calibrated according to actual data. The currently and conventionally adopted method is to record actual traffic flow parameters of the viaduct through a simulation platform, obtain a group of average density and time occupancy, and obtain the value of A through linear fitting of the data.

The average running speed V of the single lane is calculated_Lj：

Wherein:

V_Ljis the average driving speed of the jth lane

Calculating the average driving speed of the section of the viaductThe calculation formula is as follows:

wherein:

n is the total number of lanes contained in the road segment.

Is the average driving speed of the viaduct section.

The average running speed V of the road section in the t sampling period is predicted_tp. Calculating the road section average running speed V of the next sampling period according to the road section average running speed weighted average of the past 4 sampling periods_tp. The specific symbol designations are shown in figure 2 below.

V_tpThe calculation formula is as follows:

is the road section average traveling speed of the t-1 th sampling period; by the way of analogy, the method can be used,

the standard deviation S of the average driving speed of the road section in the past 4 sampling periods is calculated by the following formula:

the ratio K formula of the difference between the predicted value and the actual value of the average running speed of the road section in the t-th sampling period and the standard deviation is obtained as follows:

wherein:is the actual value of the average running speed of the road section in the t-th sampling period;

V_tpthe predicted value is the average running speed of the road section in the t-th sampling period;

s is the link average travel speed standard deviation over the past 4 sampling periods.

And (3) comparing Q with a set threshold value M to judge whether an emergency occurs:

when Q is larger than M, an emergency occurs; otherwise, judging that no emergency occurs.

M takes a value of 2, i.e. not more than 2 times the standard deviation (more than 2 times the standard deviation means the sample offset). In other words, the number 2 is a common general knowledge problem of mathematical statistics, which is an alpha value when the confidence is 95%, and 95% is a set value of the confidence (confidence level) in the normal case.

Example 1:

1) installing a microwave vehicle detector on a road section selected from the south and north elevated roads of the Hefei city and debugging the microwave vehicle detector;

2) and acquiring data measured by the microwave vehicle detector in a certain period of time:

lane 1: the number of vehicles of model 1 98; the number of vehicles 2 of the vehicle type 2; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 31%.

Lane 2: number of vehicles 63 of model 1; the number of vehicles of type 2 is 0; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 19%.

Lane 3: vehicle number of model 1 76; the number of vehicles of type 2 is 0; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 23%.

3) Calculating the equivalent traffic volume of a single lane:

lane 1: equivalent traffic volume Q_L1＝∑Q_iE_i＝98*1+2*2+0+0＝102，

Lane 2: equivalent traffic volume Q_L2＝∑Q_iE_i＝63*1+0+0+0＝63，

Lane 3: equivalent traffic volume Q_L3＝∑Q_iE_i＝76*1+0+0+0＝76。

4) Calculating the average density K of the single lane_Lj：

A is obtained by fitting a group of densities and time occupancy obtained by a simulation platform, and A takes a value of 0.15.

Lane 1: k_L1＝0.31÷0.15＝2.067；

Lane 2: k_L2＝0.19÷0.15＝1.267；

Lane 3: k_L3＝0.23÷0.15＝1.533。

5) Calculating the average driving speed V of the single lane_Lj：

Lane 1: v_L1＝102÷2.067＝49.35；

Lane 2: v_L2＝63÷1.267＝49.72；

Lane 3: v_L1＝76÷1.533＝49.57。

6) And calculating the average running speed of the viaduct road section

7)、Predicting the average speed V of the road section in the t sampling period_tp：

Repeating the previous 6 steps to respectively obtain

V_tp＝(48.55*4+50.01*3+49.33*2+49.60*1)/10＝49.28。

8) And calculating the standard deviation S of the average running speed of the road section in the past 4 sampling periods:

9) obtaining the ratio Q of the difference between the predicted value and the actual value of the average running speed of the road section in the t-th sampling period to the standard deviation:

Q＝|49.55-49.28|/0.53＝0.51。

10) judging the traffic emergency:

since Q < 2, no traffic events occurred.

Example 2:

1) installing a microwave vehicle detector on a road section selected from the south and north elevated roads of the Hefei city and debugging the microwave vehicle detector;

2) and acquiring data measured by the microwave vehicle detector in a certain period of time:

lane 1: number of vehicles 150 for model 1; the number of vehicles 4 of the vehicle type 2; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 71%.

Lane 2: number of vehicles 122 for model 1; the number of vehicles of the vehicle type 2 is 1; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 58%.

Lane 3: vehicle number of model 1 90; the number of vehicles of type 2 is 0; the number of vehicles of type 3 is 0; the number of vehicles of vehicle type 4 is 0; the time occupancy was 33%.

3) Calculating the equivalent traffic volume of a single lane:

lane 1: equivalent traffic volume Q_L1＝∑Q_iE_i＝150*1+4*2+0+0＝158；

Lane 2: equivalent traffic volume Q_L2＝∑Q_iE_i＝122*1+1*2+0+0＝124；

Lane 3: equivalent traffic volume Q_L3＝∑Q_iE_i＝90+0+0+0＝90。

4) Calculating the average density K of the single lane_Lj：

A is obtained by fitting a group of densities and time occupancy obtained by a simulation platform, and A takes a value of 0.15.

Lane 1: k_L1＝0.71÷0.15＝4.71；

Lane 2: k_L2＝0.58÷0.15＝3.87；

Lane 3: k_L3＝0.33÷0.15＝2.2。

5) Calculating the average driving speed V of the single lane_Lj：

Lane 1: v_L1＝158÷4.71＝33.54；

Lane 2: v_L2＝124÷3.87＝32.04；

Lane 3: v_L1＝90÷2.2＝40.91。

6) And calculating the average running speed of the viaduct road section

7) Predicting the average running speed V of the road section in the t sampling period_tp：

Repeating the previous 6 steps to respectively obtain

V_tp＝(48.55*4+50.01*3+49.33*2+49.60*1)/10＝49.28。

8) And calculating the standard deviation S of the average running speed of the road section in the past 4 sampling periods:

9) obtaining the ratio Q of the difference between the predicted value and the actual value of the average running speed of the road section in the t-th sampling period to the standard deviation:

Q＝|35.49-49.28|/0.53＝26.01。

10) judging the traffic emergency:

judging that a traffic emergency occurs because Q is more than 2; the viaduct traffic control center receives the system alarm and takes measures to reduce loss.

Claims (3)

1. A viaduct emergency distinguishing method based on a microwave vehicle detector is characterized by comprising the following steps:

1) installing a microwave vehicle detector on the section of the elevated bridge to be detected and debugging the microwave vehicle detector;

2) acquiring data measured by the microwave vehicle detector, wherein the data comprises corresponding serial numbers of all lanes, vehicle types of vehicles running on the lanes, the number of each vehicle type and time occupancy;

3) converting the traffic volume of each motor vehicle and non-motor vehicle on the lane into the standard vehicle type by the conversion coefficientObtaining the equivalent traffic volume Q of a single lane_LjThe formula is as follows:

Q_Lj＝∑Q_iE_i

wherein,

Q_Ljis the equivalent traffic volume for the jth lane;

Q_ithe absolute number of the vehicles of the ith vehicle type in the jth lane;

E_iis the conversion coefficient of the ith vehicle type in the jth lane;

4) calculating the average density K of the single lane_Lj：

$K_{Lj}=\frac{{\mathrm{occ}}_j}{A}$

Wherein:

K_Ljis the jth lane average density;

occ_jis the time occupancy of the jth lane;

a is a constant;

5) calculating the average driving speed V of the single lane_Lj：

$V_{Lj}=\frac{Q_{Lj}}{K_{Lj}}$

Wherein:

V_Ljis the j-th lane average travel speed;

6) and obtaining the average running speed of the viaduct road sectionThe calculation formula is as follows:

$\stackrel{\&OverBar;}{V}=\frac{\underset{j=1}{\overset{n}{\&Sigma;}}{V}_{Lj}}{n}$

wherein:

n is the total number of lanes contained in the road segment;

7) predicting the average running speed V of the road section in the t sampling period_tp：

$V_{tp}=\frac{{\stackrel{\&OverBar;}{V}}_{t-1}*4+{\stackrel{\&OverBar;}{V}}_{t-2}*3+{\stackrel{\&OverBar;}{V}}_{t-3}*2+{\stackrel{\&OverBar;}{V}}_{t-4}*1}{10}$

Wherein:

is the road section average traveling speed of the t-1 th sampling period; by the way of analogy, the method can be used,

8) and calculating the standard deviation S of the average running speed of the road section in the past 4 sampling periods:

$S={\left\{\frac{1}{4}\underset{i=1}{\overset{4}{\&Sigma;}}{\&lsqb;{\stackrel{\&OverBar;}{V}}_{t-i}-{\stackrel{\&OverBar;}{V}}_t\&rsqb;}^2\right\}}^{1/2}$

9) establishing a calculation formula of a ratio Q of the difference between a predicted value and an actual value of the average running speed of the road section in the t-th sampling period to the standard deviation, wherein the calculation formula comprises the following steps:

$Q=\frac{|\stackrel{\&OverBar;}{V_t}-V_{tp}|}{S}$

wherein:is the actual value of the average running speed of the road section in the t-th sampling period;

V_tpthe predicted value is the average running speed of the road section in the t-th sampling period;

s is the standard deviation of the average running speed of the road section in the past 4 sampling periods;

10) and judging the traffic emergency:

comparing Q with a set threshold value M, wherein M is 2;

when Q is larger than M, judging that an emergency occurs;

and when Q is less than or equal to M, judging that no emergency occurs.

2. The viaduct emergency discrimination method based on the microwave vehicle detector as claimed in claim 1, wherein: in the step 1), the angle and the height of the detector are adjusted according to the range of the lane to be detected, so that the beam projection of the detector can cover all lanes to be detected, and the length directions of the projection and the detected road are orthogonal to each other.

3. The viaduct emergency discrimination method based on the microwave vehicle detector according to claim 1 or 2, characterized in that: in the step 3), the standard vehicle type is a passenger car, and the conversion coefficient is 1.