Active traffic safety control method and system under rainfall conditions

Abstract

The present invention provides an active traffic safety control method and system under rainfall conditions, which can formulate accurate and refined speed limit schemes in real time according to different road characteristics and rainfall intensity, can effectively reduce traffic accidents, and is easy to promote and apply. The technical solution adopted by the present invention is: first, the basic linear parameters of the road are obtained according to the road completion drawing file, and the rainfall meteorological data are obtained by using the traffic meteorological monitoring station; then the composite slope of the road surface is calculated, and the length of the rainwater runoff on the road surface under rainfall weather is calculated using the gradient descent algorithm according to the three-dimensional model of the road surface; finally, the water film thickness and its corresponding hydroplaning speed are calculated, and then the dynamic speed limit scheme of the road under rainfall conditions is obtained, and a highway traffic safety control system under rainfall conditions is established.

Description

Technical Field

[0001] The present invention belongs to the technical field of active traffic safety control, and relates to an active traffic safety control method and system under rainfall conditions. Background Art

[0002] Rainfall affects the friction of the road surface. Different rainfall intensities form different water film thicknesses on the road surface. When the water film thickness reaches a certain level, hydroplaning will occur, which will lead to traffic accidents. In addition, the water mist splashed by vehicles during driving will also reduce the visibility level during driving, thus seriously affecting driving safety. According to statistics, the traffic accident rate on rainy days is about 2 to 3 times that of normal weather. Especially in the case of continuous rainfall, the thickness of the water film on the road surface increases. At this time, the friction coefficient between the tire and the road surface is close to zero. If the vehicle still maintains a high speed, it is very easy to cause traffic accidents such as skidding and rear-end collisions.

[0003] The driving environment of highways in rainy weather is a complex system. Different rainfall types, pavement materials and drainage systems on real roads will lead to different pavement water film thicknesses. Existing research lacks quantitative research on rainfall intensity and water film thickness, and it is impossible to intuitively understand the relationship between the two, making it impossible to truly apply the changes in rainfall intensity to the transportation industry.

[0004] Traditional dynamic speed limit control measures for rainy days are specified based on meteorological indicators such as rainfall and visibility, and do not consider the impact of changes in water film thickness caused by the combination of multiple variables such as rainfall intensity, road geometry, and road surface structure depth, resulting in the speed control measures adopted by existing highway management departments in rainy weather being inaccurate and refined. At the same time, the traditional determination of water film thickness values ​​is mostly based on empirical values, and does not analyze the deep-seated reasons for the changes in water film thickness. If the water film thickness corresponding to different rainfall intensities is clarified, it will be more convenient to provide a theoretical basis for speed limits on rainy days for road operation management departments and traffic police departments, thereby improving the safety of car driving on rainy days. Therefore, studying the law of water film changes on rainy days plays an important role in reducing the occurrence of traffic accidents, and is also a key basis for establishing active safety prevention and control strategies on rainy days.

[0005] As the concept of active safety control becomes more mature, research on dynamic speed limit under rainfall conditions is gradually increasing.

[0006] Invention patent 202110846794.3 comprehensively considers traffic meteorological data as well as factors such as sight distance, hydroplaning speed and vehicle driving stability to determine the maximum allowable speed of highways in bad weather;

[0007] Invention patent 202011263224.3 proposes a speed collaborative control method for highway speed limit selection based on the influence of traffic meteorological elements, traffic flow and speed limit areas on variable speed limits;

[0008] Invention patent 202110099504.3 establishes a sample library for rainy day control of highways based on cellular automaton models and cellular transmission models. By continuously improving the knowledge base through controller optimization algorithms, the integrated coordination of ramp and main line speed limits can be achieved.

[0009] The dynamic speed limit scheme formulated in the above invention does not take into account the impact of changes in road water film thickness caused by rainfall. Since changes in water film thickness will lead to a decrease in the road friction coefficient, the safe driving speeds corresponding to different water film thicknesses also have certain differences.

[0010] To sum up, it is an urgent problem to clarify the water film thickness corresponding to different rainfall intensities and road environment characteristics, and to propose more scientific, reasonable and refined speed control measures in rainy weather. Summary of the invention

[0011] In view of this, the present invention provides an active traffic safety control method and system under rainfall conditions to solve the problem that the speed control measures adopted by existing highway management departments under rainfall conditions are not accurate and refined enough.

[0012] The technical solution adopted by the present invention is: an active traffic safety control method and system under rainfall conditions, firstly obtaining the basic linear parameters of the road according to the road completion drawing file, and obtaining rainfall meteorological data using the traffic meteorological monitoring station; then calculating the composite slope of the road surface, and calculating the length of rainwater runoff on the road surface under rainfall weather using the gradient descent algorithm according to the three-dimensional model of the road surface; finally calculating the water film thickness and its corresponding hydroplaning speed, and then obtaining a dynamic speed limit scheme for the road under rainfall conditions.

[0013] The specific steps are:

[0014] 1) Obtaining road basic data: Obtain road linear index parameters according to the completion drawing file, including the design speed V d 、The current speed limit value of the road is V 限 、Road crown cross slope i G , road longitudinal slope i, circular curve superelevation i h , the length of the transition curve is L c and carriageway width B;

[0015] 2) Determine the factors affecting the thickness of the water film:

[0016] The factors that affect the thickness of the water film are rainfall intensity q, composite road slope I, and rainy day road runoff length L. f and the pavement structure depth TD;

[0017] 3) Method for determining the index affecting water film thickness:

[0018] 3-1) Rainfall intensity q: Rainfall intensity is obtained through the traffic meteorological monitoring station on the road section, and the unit is mm / h;

[0019] 3-2) Composite road surface slope I: The composite road surface slope is the slope formed by the combination of the longitudinal slope of the road and the transverse slope of the superelevation or road crown. The calculation formulas for general road sections and superelevation transition sections are:

[0020] a: General road section refers to the road section with stable cross slope, including straight road section and circular curve road section. The superelevation and longitudinal slope on this road section are fixed values ​​after the road construction is completed;

[0021] The general formula for calculating the composite slope of a road section is:

[0022]

[0023] in:

[0024] I——composite slope of road surface;

[0025] i G ——Road crown cross slope;

[0026] i——road longitudinal slope;

[0027] b: Superelevation transition section refers to the section with continuously changing curvature between a straight line and a circular curve or between two circular curves with the same turning direction and a large difference in radius;

[0028] The calculation formula for the composite slope of the superelevation transition section is:

[0029]

[0030] in:

[0031] i x ——The cross slope of the lane at the distance x from the starting point of the superelevation transition section, m,

[0032] L c ——length of transition curve, m;

[0033] i h ——Circular curve superelevation;

[0034] 3-3) Road runoff length L f : The road runoff length is calculated through mathematical analysis, and the specific steps are as follows:

[0035] a: General road section: In general road sections, water flows along the synthetic slope of the road surface, and the flow trajectory is a straight line. The formula for calculating the runoff length is:

[0036]

[0037] in:

[0038] L f ——Length of road runoff on rainy days, m;

[0039] i G ——Road crown and transverse slope;

[0040] i——road longitudinal slope;

[0041] I——composite slope of road surface;

[0042] B——lane width, m;

[0043] b: Superelevation transition section: A three-dimensional function model of the superelevation transition section pavement is constructed by mathematical modeling, and the runoff path length is obtained by theoretical calculation;

[0044] 3-4) Construction depth TD: The construction depth is measured by manual sanding method or based on experience, and is recommended to be 0.3-0.5 mm;

[0045] 4) Pavement water film thickness regression model:

[0046] The model parameters were calibrated using artificial rainfall tests, and the final regression formula for water film thickness was obtained as follows:

[0047]

[0048] in:

[0049] h——water film depth, mm;

[0050] L f ——Length of road runoff on rainy days, m;

[0051] I——composite slope of road surface;

[0052] q——rainfall intensity, mm / h;

[0053] TD——pavement structure depth, mm;

[0054] 5) Water slide speed corresponding to different water film thickness:

[0055] When the water film thickness exceeds 1 mm, the vehicle begins to hydroplaning. The relationship between the hydroplaning speed v and the water film thickness h is calculated according to the hydroplaning speed model as follows:

[0056]

[0057] Where:

[0058] a——rotational deceleration;

[0059] P——tire pressure, Kpa;

[0060] TD——pavement structure depth, mm;

[0061] A is the larger value of the following two formulas:

[0062]

[0063] Where:

[0064] TD——pavement structure depth, mm;

[0065] h——water film thickness, mm;

[0066] 6) Establish a highway traffic safety control system under rainfall conditions

[0067] When the weather conditions are good and the rainfall intensity is low, the road surface water film thickness is less than 1mm, and the speed limit of the expressway remains the same. 限 ; As the rainfall intensity increases, the thickness of the water film on the road surface increases. When the thickness of the water film exceeds 1 mm, the speed limit on the highway is the hydroplaning speed v and the current speed limit V 限 The smaller value of ;

[0068] According to the water slide speed formula determined in step 5), calculate the corresponding water slide speed v under different water film thicknesses, and take v and V 限 The minimum value is used as the basis for determining the dynamic speed limit value. Referring to the general provisions of the basic data of the geometric line shape of highways in the Highway Route Design Specifications (JTG D20-2017), the dynamic speed limit values ​​of highways under different rainfall levels under normal circumstances are determined as follows:

[0069] Dynamic speed limit for highway incident management under rainy weather conditions

[0070]

[0071] The specific method for calculating the runoff path length of the superelevation transition section in step 3-3) above is:

[0072] a: Construct the function model of the superelevation transition section pavement: take the superelevation rotation axis as the x-axis, the increasing direction of the pile number as the positive direction, and the starting point of the superelevation transition section as the x-axis origin; the x-axis parallel to the ground and perpendicular to the x-axis and toward the outside of the lane is the positive direction of the y-axis; the z-axis is perpendicular to the xy plane, and the vertical upward is the positive direction to construct a coordinate system, then the superelevation transition section pavement is a three-dimensional surface, and its function model is:

[0073]

[0074] Among them, i G ——Road crown and transverse slope;

[0075] ih ——circular curve superelevation value;

[0076] L c ——length of transition curve, m;

[0077] x, y, and z are the distances from each point on the road surface to the origin of the coordinate axis, m;

[0078] b: Calculate the gradient vector: Use the surface function to calculate the gradient vector of the surface at a certain point:

[0079]

[0080] c: Define the runoff length function:

[0081]

[0082] d: Initialize the starting point coordinates (x 1 ,y 1 ,z 1 ) and learning rate α;

[0083] e: Update the starting point coordinates according to the gradient descent method:

[0084]

[0085] f: After each move, calculate the length of the path traveled:

[0086]

[0087] g: Determine whether the constraint condition y=0 or y=B / 2 is satisfied. If so, update the maximum runoff length and output the corresponding end point coordinates. Otherwise, continue iterating.

[0088] Repeat the above steps eg until the constraints are met, and the runoff path length of the superelevation transition section can be obtained.

[0089] An active traffic safety control system under rainfall conditions, characterized by comprising an input end, a decision end and an early warning end;

[0090] Input end: The input end uses a traffic road weather monitoring system, which is set up on the roadside in a single column to obtain weather data in real time;

[0091] Decision-making end: The decision-making end uses an edge computing unit to automatically calculate the variable speed limit value under rainfall conditions based on the internally stored road completion map data and real-time transmitted meteorological data, and independently decides to issue warning information instructions;

[0092] Early warning end: The early warning end is divided into two safety control measures: variable speed limit signs and intelligent guidance facilities;

[0093] The variable speed limit sign is a single-column variable information board installed on the roadside, 100m ahead of the road section where the speed limit is required;

[0094] The intelligent guidance device adopts information plate type or box type intelligent guidance light. The device displays red warning light and yellow linear guidance arrow to warn and guide the driver. The setting interval is 15-20m.

[0095] The beneficial effects of the present invention are:

[0096] 1) The present invention determines the factors affecting the water film thickness, constructs a three-dimensional road surface function, establishes a quantitative model of water film thickness on rainy roads, and proposes a functional relationship between hydroplaning speed based on different water film thicknesses. It also gives dynamic speed limit values ​​for highways under different rainfall levels, and finally establishes a highway traffic safety management and control system under rainfall conditions.

[0097] 2) The present invention quantifies the relationship between rainfall intensity and road environment characteristics and water film thickness, determines the hydroplaning speed corresponding to different water film thicknesses, and scientifically and reasonably proposes rainy day speed control measures to improve road driving safety in rainy days.

[0098] 3) The present invention directly obtains the runoff length through mathematical calculation, and the result is accurate and reliable, and can truly reflect the thickness of the road surface water film under different rainfall levels.

[0099] 4) The dynamic speed limit value proposed in the present invention can provide a reference for the scientific, reasonable and refined management and control of expressways, and has important practical significance for the safe operation of expressways. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 This is a flow chart of the method for determining the dynamic speed limit value on rainy days based on water film thickness.

[0101] Figure 2 It is the system algorithm decision logic diagram.

[0102] Figure 3 This is a three-dimensional modeling diagram of the superelevation transition section.

[0103] Figure 4 It is an active safety control system for highways under rainfall conditions.

[0104] Figure 5 It is a road contour and drainage path map. DETAILED DESCRIPTION

[0105] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0106] The present invention provides an active traffic safety control method and system under rainfall conditions, which constructs a water film thickness regression formula through theoretical modeling, and determines the hydroplaning speed under different rainfall levels based on the water film thickness, and then establishes a reasonable speed limit value and control strategy for rainy days, such as Figure 1 and Figure 2 shown.

[0107] The specific steps include:

[0108] 1. Obtaining road basic data: Obtain road linear index parameters according to the completion drawing file, including design speed V d 、Current speed limit value V 限 、Road crown cross slope i G , road longitudinal slope i, circular curve superelevation i h , the length of the transition curve is L c and lane width B.

[0109] 2. Determine the factors affecting the thickness of the water film:

[0110] The factors that affect the thickness of the water film are mainly the rainfall intensity q, the composite slope of the road surface I, and the length of the road runoff on rainy days L. f And the road surface structure depth TD. The rainfall intensity q is an environmental factor, assuming that it does not change with time within a certain period of time; the road surface composite slope I and the road surface runoff length L f It takes into account the characteristic variables of the road environment. Different drainage system designs have a significant impact on the thickness of the pavement water film. The pavement structural depth TD mainly considers the differences in pavement structure. Different pavement materials have different permeability to accumulated water.

[0111] 3. Determination of indicators affecting water film thickness:

[0112] 1) Rainfall intensity (q): Rainfall intensity is obtained by obtaining rainfall meteorological data from the traffic meteorological monitoring station within the road section, and the unit is mm / h;

[0113] 2) Composite road surface slope (I): The composite road surface slope is the slope formed by the longitudinal slope of the road and the transverse slope of the superelevation or road crown. The calculation formulas for the general road section and the superelevation transition section are as follows:

[0114] a: General road sections refer to road sections with stable cross slopes, including straight sections and circular curve sections. The superelevation and longitudinal slope on these sections are fixed values ​​after the road is built. The formula for calculating the composite slope of general road sections is:

[0115]

[0116] in:

[0117] I——composite slope of road surface;

[0118] i G ——Road crown cross slope;

[0119] i——road longitudinal slope;

[0120] b: A superelevation transition section refers to a section of road with a continuously changing curvature between a straight line and a circular curve or between two circular curves with the same turning direction and a large radius difference. The formula for calculating the composite slope of a superelevation transition section is:

[0121]

[0122] in:

[0123] i h ——Circular curve superelevation.

[0124] i x is the cross slope of the lane at the distance x from the starting point of the superelevation transition section. The meanings of other symbols are as shown above.

[0125] 3) Road runoff length (L) f ): The road runoff length is calculated by mathematical analysis, and the specific steps are as follows:

[0126] ① General road sections: In general road sections, water flows along the synthetic slope runoff of the road surface, and the flow trajectory is a straight line. The formula for calculating the runoff length is:

[0127]

[0128] in:

[0129] i G ——Road crown cross slope;

[0130] i——road longitudinal slope;

[0131] I——composite slope of road surface;

[0132] B——lane width, m;

[0133] L f ——Length of road runoff on rainy days, m.

[0134] ②Superelevation transition section: In the superelevation transition section, the road surface cross slope will change from positive to negative. At this time, the water flow will be affected by the combined effect of the longitudinal slope and the changing cross slope. Its flow trajectory will flow along the direction of the fastest road surface gradient descent, and the longest runoff path will pass through the zero cross slope point of the road surface. The present invention uses a mathematical modeling method to construct a three-dimensional function model of the superelevation transition section road surface, and obtains the runoff path length through theoretical calculation. The specific steps are as follows:

[0135] a: Construct the pavement function model of the superelevation transition section: take the superelevation rotation axis as the x-axis, the increasing direction of the pile number as the positive direction, and the starting point of the superelevation transition section as the x-axis origin; the positive direction of the y-axis is parallel to the ground and perpendicular to the x-axis and toward the outside of the lane; the z-axis is perpendicular to the xy plane, and the vertical upward direction is the positive direction to construct a coordinate system. Figure 3 As shown in the figure: the curve with arrows on the road surface is the rainwater runoff path of the superelevation transition section;

[0136] i J ——road shoulder cross slope;

[0137] i h ——Circular curve superelevation;

[0138] L c ——length of transition curve, m;

[0139] h c ——Maximum elevation of the outer edge of the roadbed, m

[0140] h cx ——The height of the outer edge of the roadbed at the distance x, m

[0141] h' cx ——The height of the road centerline at the x distance, m

[0142] B——lane width, m;

[0143] The superelevation transition section pavement is a three-dimensional surface, and its function model is:

[0144]

[0145] in:

[0146] i G ——Road crown and transverse slope;

[0147] i h ——Circular curve superelevation;

[0148] L c ——length of transition curve, m;

[0149] x, y, and z are the distances from each point on the road surface to the origin of the coordinate axis, in meters.

[0150] b: Calculate the gradient vector: Use the surface function to calculate the gradient vector of the surface at a certain point:

[0151]

[0152] c: Define the runoff length function:

[0153]

[0154] d: Initialize the starting point coordinates (x 1 ,y 1 ,z 1 ) and learning rate α.

[0155] e: Update the starting point coordinates according to the gradient descent method:

[0156]

[0157] f: After each move, calculate the length of the path traveled:

[0158]

[0159] g: Determine whether the constraint condition y=0 or y=B / 2 is satisfied. If so, update the maximum runoff length and output the corresponding end point coordinates. Otherwise, continue iterating.

[0160] Repeat the above steps eg until the constraints are met, and the runoff path length of the superelevation transition section can be obtained.

[0161] 4) Construction depth (TD): The construction depth can be measured by manual sanding method, or it can be recommended to use 0.3-0.5mm based on empirical values;

[0162] 4. Pavement water film thickness regression model:

[0163] Considering the factors affecting the water film thickness determined in step 2 and calibrating the model parameters using artificial rainfall tests, the final regression formula for the water film thickness is:

[0164]

[0165] in:

[0166] h——water film thickness, mm;

[0167] L f ——Length of road runoff on rainy days, m;

[0168] I——composite slope of road surface;

[0169] q——rainfall intensity, mm / h;

[0170] TD——pavement structure depth, mm.

[0171] 5. Water slide speed corresponding to different water film thickness:

[0172] When the water film thickness exceeds 1 mm, the vehicle begins to hydroplaning. The relationship between the hydroplaning speed v and the water film thickness h is calculated according to the hydroplaning speed model as follows:

[0173]

[0174] Where:

[0175] a – rotational deceleration (10% at the initial stage of hydroplaning);

[0176] P——tire pressure, Kpa (the recommended design value is 165Kpa);

[0177] TD——Pavement structure depth, mm (the recommended setting value is 0.5 mm);

[0178] A is the larger value of the following two formulas:

[0179]

[0180] Where:

[0181] TD——pavement structure depth, mm (0.5 mm is recommended);

[0182] h——water film thickness, mm.

[0183] 6. Establish a highway traffic safety control system under rainfall conditions

[0184] When the weather conditions are good and the rainfall intensity is low, the road surface water film thickness is less than 1mm, and the speed limit of the expressway remains the same. 限 ; As the rainfall intensity increases, the thickness of the water film on the road increases. At this time, vehicles are prone to hydroplaning accidents when driving on the road. Therefore, when the thickness of the water film exceeds 1mm, the speed limit of the highway should take into account the hydroplaning speed v and the existing speed limit value V 限 The smaller value in .

[0185] According to the water sliding speed formula determined in step 5, calculate the corresponding water sliding speed v under different water film thicknesses, and take v and V 限 The minimum value is used as the basis for determining the dynamic speed limit. Referring to the general provisions of the basic data of the geometric line shape of highways in the "Highway Route Design Specifications" (JTG D20-2017), the dynamic speed limit values ​​of highways under different rainfall levels under normal circumstances are determined as follows:

[0186] Table 1 Dynamic speed limit values ​​for highway incident management under rainfall conditions

[0187]

[0188] The framework and deployment scheme of the highway active safety control system under rainfall conditions Figure 4 As shown:

[0189] The active safety control system of highways under rainfall conditions consists of an input end, a decision end, and a warning end:

[0190] Input end: The input end can adopt the traffic road weather monitoring system, which is set up on the roadside in a single column to obtain meteorological data in real time.

[0191] Decision-making end: The decision-making end usually adopts an edge computing unit to automatically calculate the variable speed limit value under rainfall conditions based on the internally stored road completion map data and real-time transmitted meteorological data, and make independent decisions to issue warning information instructions.

[0192] Early warning end: The early warning end is divided into two safety control measures: variable speed limit signs and intelligent guidance facilities. The variable speed limit signs can be set up on the roadside in the form of a single-column variable information board, 100m ahead of the section where speed limit is required; the intelligent guidance device can use an information board or box-type intelligent guidance light. The device displays a red warning light and a yellow linear guidance arrow to warn and guide the driver, and the setting interval is 15-20m.

[0193] Example:

[0194] This embodiment uses a superelevation transition section of a bidirectional 6-lane highway for example verification and analysis, and the pavement type is a dense asphalt concrete pavement, including the following steps:

[0195] 1. Obtain road geometry data as follows:

[0196] serial number <![CDATA[V d (km / h)]]> <![CDATA[V 限 (km / h)]]> <![CDATA[i G (%)]]> i(％) <![CDATA[i h (%)]]> B(m) Lc(m) A 100 100 2 6 6 34.5 350

[0197] The road elevations are as follows Figure 5 As shown;

[0198] 2. Determination of indicators affecting water film thickness

[0199] like Figure 5 As shown in the figure, 4 drainage paths are marked. For drainage path DP1, the path length is about 26m, and the water flows from the outermost hard shoulder into the central dividing strip; drainage paths DP2, 3, and 4 all converge from the hard shoulder to the innermost lane and then converge to the outer hard shoulder from the opposite direction; among the several drainage paths, the path with the longest drainage length is the most unfavorable critical drainage path, that is, path DP2 as shown in the figure, so path DP2 is analyzed.

[0200] The indicators that affect the water film thickness are as follows:

[0201]

[0202] 3. Determination of pavement water film thickness

[0203] Substitute the data in the table into the water film thickness calculation formula, and obtain the water film thickness values ​​for each analysis point as listed in the following table.

[0204] Analysis point location Distance(m) Water film thickness (mm) Drainage path starting point 0.0 Flat location start 24.2 2.03 Flat position end 17.7 3.08 Inside lane wheel track 10.5 3.47 Center lane wheel track 6.4 3.60 Outside lane wheel track 7.2 3.68

[0205] 4. Determination of water slide speed

[0206] Substitute the data in the table into the water sliding speed calculation formula and calculate according to the most unfavorable position, that is, the point with the maximum water film thickness.

[0207] Rainfall intensity (mm / h) Water film thickness (mm) Construction depth (mm) Water slide speed (km / h) 50 3.68 0.5 59.51

[0208] 5. Based on a comprehensive comparison of the existing speed limit and hydroplaning speed, it is finally determined that when the rainfall intensity is 50mm / h, the recommended speed limit for this section of road is 60km / h.

[0209] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for active traffic safety control under rainfall conditions, characterized in that: Firstly, the basic linear parameters of the road are obtained according to the road completion drawing file, and the rainfall meteorological data are obtained by using the traffic meteorological monitoring station; then the composite slope of the road surface is calculated, and the length of the rainwater runoff on the road surface under rainy weather is calculated using the gradient descent algorithm according to the three-dimensional road surface model; finally, the water film thickness and its corresponding hydroplaning speed are calculated, and then the dynamic speed limit scheme of the road under rainy conditions is obtained; The specific steps are: 1) Obtaining road basic data: Obtain road linear index parameters according to the completion drawing file, including the design speed V d 、The current speed limit value of the road is V 限 、Road crown cross slope i G , road longitudinal slope i, circular curve superelevation i h , the length of the transition curve is L c and carriageway width B; 2) Determine the factors affecting the thickness of the water film: The factors that affect the thickness of the water film are rainfall intensity q, composite road slope I, and rainy day road runoff length L. f and the pavement structure depth TD; 3) Method for determining the index affecting water film thickness: 3-1) Rainfall intensity q: Rainfall intensity is obtained through the traffic meteorological monitoring station on the road section, and the unit is mm / h; 3-2) Composite road surface slope I: The composite road surface slope is the slope formed by the combination of the longitudinal slope of the road and the transverse slope of the superelevation or road crown. The calculation formulas for general road sections and superelevation transition sections are: a: General road section refers to the road section with stable cross slope, including straight road section and circular curve road section. The superelevation and longitudinal slope on this road section are fixed values ​​after the road construction is completed; The general formula for calculating the composite slope of a road section is: in: I——composite slope of road surface; i G ——Road crown cross slope; i——road longitudinal slope; b: Superelevation transition section refers to the section with continuously changing curvature between a straight line and a circular curve or between two circular curves with the same turning direction and a large difference in radius; The calculation formula for the composite slope of the superelevation transition section is: in: i x ——The cross slope of the lane at the distance x from the starting point of the superelevation transition section, m, L c ——length of transition curve, m; i h ——Circular curve superelevation; 3-3) Road runoff length L f : The road runoff length is calculated through mathematical analysis, and the specific steps are as follows: a: General road section: In general road sections, water flows along the synthetic slope of the road surface, and the flow trajectory is a straight line. The formula for calculating the runoff length is: in: L f ——Length of road runoff on rainy days, m; i G ——Road crown cross slope; i——road longitudinal slope; I——composite slope of road surface; B——lane width, m; b: Superelevation transition section: A three-dimensional function model of the superelevation transition section pavement is constructed by mathematical modeling, and the runoff path length is obtained by theoretical calculation; 3-4) Pavement construction depth TD: The construction depth is measured by manual sand laying method or based on experience, and it is recommended to use 0.3-0.5mm; 4) Pavement water film thickness regression model: The model parameters were calibrated using artificial rainfall tests, and the final regression formula for water film thickness was obtained as follows: in: h——water film thickness, mm; L f ——Length of road runoff on rainy days, m; I——composite slope of road surface; q——rainfall intensity, mm / h; TD——pavement structure depth, mm; 5) Water slide speed corresponding to different water film thickness: When the water film thickness exceeds 1 mm, the vehicle begins to hydroplaning. The relationship between the hydroplaning speed v and the water film thickness h is calculated according to the hydroplaning speed model as follows: Where: a——rotational deceleration; P——tire pressure, Kpa; TD——pavement structure depth, mm; A is the larger value of the following two formulas: Where: TD——pavement structure depth, mm; h——water film thickness, mm; 6) Establish a highway traffic safety control system under rainfall conditions When the weather conditions are good and the rainfall intensity is low, the road surface water film thickness is less than 1mm, and the speed limit of the expressway remains the same. 限 ; As the rainfall intensity increases, the thickness of the water film on the road surface increases. When the thickness of the water film exceeds 1 mm, the speed limit on the highway is the hydroplaning speed v and the current speed limit V 限 The smaller value of ; According to the water slide speed formula determined in step 5), calculate the corresponding water slide speed v under different water film thicknesses, and take v and V 限 The minimum value is used as the basis for determining the dynamic speed limit value. Referring to the general provisions of the basic data of the geometric line shape of highways in the Highway Route Design Specifications (JTG D20-2017), the dynamic speed limit values ​​of highways under different rainfall levels under normal circumstances are determined as follows: Dynamic speed limit value for highway incident management under rainy weather conditions The specific method for calculating the runoff path length of the superelevation transition section in step 3-3) is as follows: a: Construct the function model of the superelevation transition section pavement: take the superelevation rotation axis as the x-axis, the increasing direction of the pile number as the positive direction, and the starting point of the superelevation transition section as the x-axis origin; the x-axis parallel to the ground and perpendicular to the x-axis and toward the outside of the lane is the positive direction of the y-axis; the z-axis is perpendicular to the xy plane, and the vertical upward is the positive direction to construct a coordinate system, then the superelevation transition section pavement is a three-dimensional surface, and its function model is: in, i G ——Road crown cross slope; i h ——Circular curve superelevation; L c ——length of transition curve, m; x, y, and z are the distances from each point on the road surface to the origin of the coordinate axis, m; b: Calculate the gradient vector: Use the surface function to calculate the gradient vector of the surface at a certain point: c: Define the runoff length function: d: Initialize the starting point coordinates (x1, y1, z1) and the learning rate α; e: Update the starting point coordinates according to the gradient descent method: f: After each move, calculate the length of the path traveled: g: Determine whether the constraint condition y=0 or y=B / 2 is satisfied. If so, update the maximum runoff length and output the corresponding end point coordinates. Otherwise, continue iterating. Repeat the above steps eg until the constraints are met, and the runoff path length of the superelevation transition section can be obtained.

2. A system using the method for active traffic safety control under rainfall conditions as claimed in claim 1, characterized in that: Including input end, decision end and early warning end; Input end: The input end uses a traffic road weather monitoring system, which is set up on the roadside in a single column to obtain weather data in real time; Decision-making end: The decision-making end uses an edge computing unit to automatically calculate the variable speed limit value under rainfall conditions based on the internally stored road completion map data and real-time transmitted meteorological data, and independently decides to issue warning information instructions; Early warning end: The early warning end is divided into two safety control measures: variable speed limit signs and intelligent guidance facilities; The variable speed limit sign is a single-column variable information board installed on the roadside, 100m ahead of the road section where the speed limit is required; The intelligent guidance device adopts information plate type or box type intelligent guidance light. The device displays red warning light and yellow linear guidance arrow to warn and guide the driver. The setting interval is 15-20m.

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