JP2003240866A - Road condition judgment method - Google Patents

Abstract

(57) [Summary] [Problem] To improve a method of estimating a road surface state based on a road surface temperature measurement value and a ground meteorological measurement value proposed in the past, and to enable a determination of a snow condition to be possible. Providing a way. SOLUTION: A snow density on a road is estimated from a road surface temperature measurement value, a ground meteorological amount measurement value, and medicine spraying information, and a snow condition on the road surface is determined based on a temporal change of the estimation value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface condition judging method capable of judging a snow cover condition and a pressure snow plate (freezing) on a road surface over a long distance at low cost.

[0002]

2. Description of the Related Art In road traffic, slip conditions are likely to occur when road surface conditions such as wetness, snowfall, and freezing occur.
For this reason, it is necessary to promptly detect a dangerous road surface condition such as wet road surface or freezing of the road surface and call attention to the driver of the vehicle. However, it is difficult to constantly patrol a long-distance road in terms of manpower and cost. Therefore, the road surface state detection sensor is used as a means for grasping the state of the road surface.

The conventional road surface condition detecting sensor is mainly divided into two. The first group is to irradiate the road surface with infrared rays or electromagnetic waves and measure the reflectance from the road surface. A typical configuration of this sensor is shown in FIG. An ultrasonic distance meter 23, an infrared device 26 including an infrared irradiation device 24 and an infrared light receiving device 25, and a signal processing device 27 are installed in the vicinity of the road 22, and incident light 28 and reflected light 29 on the road are provided.
The road surface state is estimated by using the fact that the intensity ratio of the reflected light 30 differs depending on the road surface state. 21 is a support pole,
21a is a sensor mounting portion.

The second group includes sensors for measuring the amount of weather and road surface temperature near the road. For road surface temperature measurement, in addition to sensors for single-point measurement such as thermocouples and infrared radiation thermometers, a method using an optical fiber temperature radar that is capable of multipoint measurement and suitable for long-distance temperature measurement is available. Proposed. This sensor information is used as a material for estimating the road surface condition based on past knowledge by a road management person, and a method for estimating the road surface condition in combination with the observed amount of meteorological data near the road has been proposed.

By the way, in order to continuously grasp the road surface condition along the longitudinal direction of the road by using a sensor of the type that emits infrared rays or electromagnetic waves, it is necessary to install a large number of sensors, which is costly. . On the other hand, in the case of measuring the road surface temperature and the amount of weather, the optical fiber temperature radar can be installed over a long distance and the amount of weather can be used as a representative value in a wide range, so that the cost is low. However, in order for the road manager to judge the road surface condition from these information, there are problems that experience is required and it is difficult to limit the area judged to be dangerous. Further, in the method of estimating the road surface condition from the meteorological amount and the road surface temperature that has been proposed in the past, it is difficult to judge the snow cover condition such as pressure snow, sorbet, etc., and the freeze condition that the upper surface of the snow cover is frozen. . In particular, freezing is dangerous because friction is small even in a normal snowy state, and correct determination is required.

[0006]

In view of the above problems, the present invention provides a method for estimating the road surface condition based on the road surface temperature measurement value and the ground meteorological measurement value that have been proposed in the past. An object of the present invention is to provide an improved road surface condition determination method that enables determination of the snow cover condition.

[0007]

In order to achieve the above-mentioned object, the invention of claim 1 estimates the snow density on the road from the road surface temperature measurement value, the ground meteorological amount measurement value and the chemical spray information, and the estimated value thereof. It is characterized in that the state of snow on the road surface is determined based on the change with time of. The invention of claim 2 is characterized in that, in claim 1, after determining the snow-covered state, the snow-compacted ice plate is subsequently determined. A third aspect of the present invention is characterized in that, in the first or second aspect, a value obtained from a measurement value of an optical fiber temperature radar embedded inside the road is used as the road surface temperature measurement value. According to the invention of claim 4, in any one of claims 1 to 3, the snow accumulation state is fresh snow,
It is characterized in that the judgment is made based on three states of pressure snow and sherbet snow. A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, the heat balance amount of the road surface is used when determining the snow cover state.

According to the first to fifth aspects of the present invention, the road surface condition and the road surface condition are determined from the relationship between the road surface temperature obtained from the change amount of the road internal temperature measurement value within a certain time and the road surface temperature obtained from the meteorological observation value. It is possible to estimate the snow cover thickness in the snow cover state and further estimate the snow cover density from the snow cover thickness. From the estimated snow cover density, determine the snow cover state (snow cover 3 states: fresh snow, compressed snow, sorbet),
Furthermore, freezing can be determined based on the change over time.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram. Various meteorological sensors 1, such as a thermometer, anemometer, and rain / snow meter, which are installed near the target road 4, an optical fiber 2 embedded in the road, and a meteorological sensor 1. The signal transmission device 3 for transmitting the data measured by the signal line 6, the signal transmission device 5 for transmitting the data measured by the optical fiber 2 through the signal line 6, and the information for receiving the measurement data. It is composed of a collection device 7, a road surface state estimation device 8 that performs road surface state determination calculation based on the received data, and a display unit 9 that outputs the result.

The weather sensor 1 is not particularly limited as long as it can obtain an electrical output. Signal transmission devices 3 and 5
As the above, a wireless transmitter may be used, and the configuration in that case is shown in FIG. Receiving antenna 10 instead of signal line 6
Is used. The information collecting device 7 receives information from the weather sensor 1 and the optical fiber 2, and gives necessary data to the road surface state estimating device 8 in consideration of the type of data, delay time, and the like. The road surface state estimation device 8 determines the road surface state based on these input data.

FIG. 3 shows the flow of road surface condition determination calculation. The individual contents are as follows. (A) Basic road surface condition judgment The basic road surface condition (dry / wet / snow / snow cover) Freeze).
The basic road surface condition is determined by two different methods based on the road surface temperature measurement value and the ground meteorological amount measurement value. Regarding these two different methods, Japanese Patent Application No. 20 related to the applicant's proposal
The details are described in No. 01-111367 and used in the above determination as well, and therefore the description thereof is omitted.

(B) Judgment of 3 snowfall states When the road surface condition is classified as snowfall by the basic judgment of the road surface condition, the snowfall 3 condition (fresh snow, pressure snow, sherbet) is further judged. When the basic road surface condition is other than snow (dry / wet / freeze), the process returns to item (a) without executing this determination process. (C) Judgment of a snow-packed ice plate When the basic road surface condition is determined to be snow and three snow-packed conditions are judged, the snow-ice plate (frozen) is continuously judged. This determination processing is executed regardless of the determination result of the snow 3 state. Then, the process returns to item (a). Here, the inflow heat amount Wa and the inflow heat amount W estimated from the weather information
The road surface temperature Ta estimated based on a, the inflow heat amount We estimated from the underground temperature change amount, and the road surface temperature Te estimated based on the inflow heat amount We will be described in detail below.

(1) Detection of snow depth The heat balance relationship when the snow road surface is regarded as a three-layer structure of atmosphere-snow-soil is shown in FIG. As the snow cover thickness increases, the heat input Wa to the snow surface and the heat input W to the soil
The snow thickness can be estimated from the measured phase difference by utilizing the fact that the phase difference of e increases. First, the changes with time of Wa and We are respectively subjected to Fourier series expansion, and the phase difference between them is obtained by focusing on their superior components. The relationship between the snow thickness and the phase difference is the same as the relationship between the underground depth and the underground phase difference,
Since the phase difference is proportional to the snow cover thickness and to the square root of the period, the snow cover thickness can be estimated from these relationships.

(2) Detecting physical quantity of snow cover When the snow thickness ds is known, the temperature Ts in the snow cover, the heat flow Ws to the surface of the snow, and the physical properties of the snow (density, specific heat) are determined using Te, We, and Wa. I understand. The calculation method is the same as the method of calculating Te and We from the optical fiber temperature Tf. As a calculation formula, first, a method of incorporating a snow cover part as a heat equivalent circuit can be considered. If the snow surface is treated in the same way as the ground surface that has been conventionally implemented, the temperature T of the snow surface will be
s, inflow heat Ws is obtained. At this time, since the thermal constant in the snow cover state can be approximated by the ice occupancy rate η, ρs = η · ρi Cs = Ci λs = η · λi. Note that ρi, Ci, λi are the density, specific heat and thermal conductivity of ice, respectively. Calculation is performed by changing this η to obtain η corresponding to Ws-Wa. By doing so, ρs, Cs, and λs can be known as physical quantities in the snowy state.

As another calculation method, it is possible to independently calculate the heat inside the soil and the heat in the snow cover. First, Te and We are calculated by the same equivalent circuit as the conventional method. Next, regarding the snow cover, the distance from the snow surface is x,
The temperature Ts (x) inside the snow cover and the inflow heat Ws (x) are obtained. An equivalent temperature source: Tes and an equivalent thermal resistance: Res are required as an equivalent circuit on the ground side, and the values obtained when calculating Te can be used for these. That is, as the change amount of the temperature Te after the lapse of the calculation time Δt, the change amount of Te when ΔTe: We = 0 is set, and the change amount of Te when a certain value δWe is changed as δTe: We is obtained. Using the values, Tes = Te0 + ΔTe · (t / ΔT) Res = δTe / δWe Te0: Te before the start of calculation At this time, the thermal constant in the snow cover state can be approximated by the ice occupancy ratio η, so ρs = η · ρi Cs = Ci λs = η · λi. Calculate by changing this η and satisfy the boundary condition η
You should ask. When X = 0, Ws (0) = We Ts (0) = Te When X = ds, Ws (ds) = Wa By doing in this way, the physical quantity in the snowy state is ρs, C
It is possible to obtain s and λs. Ρs of this is snowfall 3
It will be the criterion for the condition.

(3) Judgment of three snowfall states The snowfall densities in the three snowfall states (fresh snow, compressed snow, sorbet) are greatly different. Fresh snow is about 0.1, compressed snow is about 0.5, and sorbet is about 1.0. Is. Therefore, by setting an appropriate threshold, the calculated ρs
It becomes possible to separately measure the three snow conditions. FIG. 5 shows an example of determination of the snow cover 3 state. Here, the threshold value is determined with reference to the above-mentioned “structure and physical properties of snow and ice”, but the determination accuracy can be improved by adjusting the threshold value based on the data collected on the actual road.

(4) Judgment of compressed snow ice plate By judging the snow cover 3 state, the following information can be obtained at all times. Ts: Snow surface temperature Ws: Inflow heat to snow surface ds: Snow thickness (uses snowfall measurement values and snow removal work information) ρs: Density of snow cover Snow ice plate (freezing) is determined from these trend information To do. This point is focused on because the compressed snow plate does not generate from fresh snow or sherbet, but only from the compressed snow state. There are sensible heat process, melting process, and solidification process in the snow-blown state. Is the process when there is no latent heat. on the other hand,,
Is a process when there is latent heat, and is generated by the effects of solar radiation, chemical spraying, and traffic vehicles. In particular, the solidification process is likely to occur when the effect of radiative cooling is great. In order to produce a compressed snow plate, the process of and is required. On the other hand, since the determination of the snow cover 3 state is performed under the condition of,
How the calculation result of changes in the process of is described below.

(A) Melting Process As described above, the melting process occurs due to the effects of solar radiation, spraying of chemicals, and traffic vehicles. If the heat of melting when the snow on the snow surface is thawed is ΔWm, then Equation 1 is obtained.

[0019]

[Formula 1] ΔWm = Wa-Ws (ds) Since ΔWm is sufficiently larger than Ws (ds) during melting, if the snow cover 3 state is judged under the condition of ΔWm = 0, the result is far from the actual value. . That is, since Ws (ds) is set to be larger than the actual value in the melting process, the thermal conductivity λ (theoretical maximum value is 1) becomes significantly larger than 1. In other words, this melting process occurs just before λ ≧ 1. In the melting process, λ
By assuming that λ = 1 as a constant,
Since Ws (ds) can be approximately calculated, ΔWm can be calculated from Equation 1.

(B) Solidification Process The solidification process is a reverse phenomenon to the melting process, and occurs when the heat of radiation cooling is larger than the heat of solar radiation or traffic, or when the concentration of the drug is reduced. Letting ΔWr be the heat of solidification when the water on the surface of the snow is solidified, Equation 2 is obtained.

[0021]

## EQU2 ## ΔWf = Wa-Ws (ds) Both are negative values. Seen by absolute value, Δ
Since Wf has a value sufficiently larger than Ws (ds), Δ
If the determination of three snow conditions is made under the condition of Wf = 0, the thermal conductivity will be a value far from the actual state. There is a melting process before the solidification process, and at this point, is fixed,
ΔWf is obtained from the equation (2). Summarizing the above, the conditions for determining the compressed snow ice plate are as follows. The road surface is covered with snow due to the detection of snowfall with a rain gauge or the determination of snowfall due to calorific value calculation (continuation of the snowfall condition). In the road surface condition determination calculation from the start of snow accumulation to the present, the melting process of item (a) has passed (water that can solidify exists). In the calculation of the solidification process of item (b), ΔWf has a negative value.

[0022]

According to the first to fifth aspects of the invention, when applied to an actual road (long distance, wide range), the road surface condition can be determined at a lower cost than the method of irradiating infrared rays or electromagnetic waves. . In addition, it becomes possible to determine the state of snow cover 3 and the determination of pressure snow plates, which was not possible with the conventional method of estimating the road surface condition from the amount of meteorology and road surface temperature, and it is possible to provide more appropriate road information. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is an overall configuration diagram showing another embodiment in which a receiving antenna is used instead of a signal line.

FIG. 3 is a road surface state determination calculation flow in the above.

FIG. 4 is a conceptual diagram of heat conduction in snow.

FIG. 5 is a diagram showing an example of a method for determining the state of three snowfalls.

FIG. 6 is a diagram showing a configuration example of a conventional radio wave type road surface state detection sensor.

[Explanation of symbols]

1 weather sensor 2 optical fiber 3 signal transmission equipment 4 roads 5 Signal transmission equipment 6 signal lines 7 Information collection device 8 Road surface condition estimation device 9 Display

Claims (5)

[Claims] 1. A snowfall density on a road is estimated from a road surface temperature measurement value, a surface meteorological amount measurement value, and chemical spraying information, and a snowfall state on the road surface is determined based on a temporal change of the estimated value. Road condition determination method. 2. The road surface condition determining method according to claim 1, wherein after determining the snow cover condition, the pressure snow ice plate is subsequently determined. 3. The road surface condition determining method according to claim 1, wherein a value obtained from a measurement value of an optical fiber temperature radar embedded inside the road is used as the road surface temperature measurement value. 4. The road surface condition determination method according to claim 1, wherein the snow accumulation condition is determined based on three snow accumulation conditions of fresh snow, compressed snow, and sorbet. 5. The road surface condition determining method according to claim 1, wherein the heat balance amount of the road surface is used when determining the snow cover condition.