JP2000009855A - Road surface freezing prediction method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability by predicting that a road surface has frozen when water exists on the road surface and a change in road surface temperature in a specific temperature range near 0 deg.C indicates falling characteristics due to the radiation cooling of the road surface. SOLUTION: The device consists of a water detection means 1, a road surface temperature detection means 2, a road surface temperature change calculation means 3, and a road surface freezing prediction means 4. The measurement timing for every specific time is judged by the road surface freezing prediction means 4, and it is judged whether output from the water detection means 1 indicates water leakage or not when it is judged to be the measurement timing. When water leakage output is inputted, it is judged whether a road surface temperature being measured by the road surface temperature change calculation means 3 is within a set temperature range or not. Then, it is judged whether the temperature gradient in reference to a stored temperature at specific time before is equal to or more than a set value or not. When output is transmitted indicating that output obtained by the road surface temperature change calculation means 3 indicates a radiation cooling state, output is available from the water detection means 1 and road surface freezing prediction output is outputted from the road surface freezing prediction means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface freezing prediction method and apparatus for predicting freezing of a road surface based on the presence of water on the road surface and the characteristic of the temperature drop of the road surface due to radiant cooling in fine weather.

[0002]

2. Description of the Related Art As a conventional road surface freezing prediction apparatus, there are, for example, JP-A-57-7629 and JP-A-62-21038. The former device performs freezing prediction by inputting only actual measurement data of the road surface temperature for a predetermined time every day, and the latter device uses a regression equation to calculate the time change of the difference between the road surface temperature and the atmospheric dew point temperature. Freezing prediction is performed by formulating.

[0003]

However, in any of the above-mentioned conventional examples, the road surface temperature is used as a main criterion for predicting road surface freezing, and the road surface temperature of 0 ° C. is not checked without confirming the presence of water on the road surface. There is a problem in that the temperature is used as a criterion for freezing prediction.

That is, in order for road surface freezing to occur, it is necessary for the road surface to be sufficiently wet. Even if freezing is predicted from a road surface temperature or humidity of 0 ° C. or less in an environment where the road surface is not wet, the freezing will not occur. Will only occur if the road is accidentally wet.

[0005] In most cases related to the prediction of freezing including the above-mentioned conventional example, the determination criteria for the freezing prediction is 0 ° C or lower. However, on a road surface on which a car is running, freezing occurs from 0 ° C. In the natural environment, the road surface freezes for the first time at around −3 ° C. after passing through a sherbet state in which water and ice are mixed.

On the other hand, in some of the currently marketed products, there is moisture on the road surface, and the detection of the road surface temperature of 0 ° C. is used as a criterion for determining whether the road surface is frozen. It has been found from experiments conducted by the present applicant that even if is present, freezing does not occur at −3 ° C. unless radiative cooling of the road surface occurs during fine weather. In such a conventional example and a commercially available product, there is a problem that the reliability of the prediction is reduced due to excessive output of the freezing prediction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to output a freezing prediction only when the road surface is sufficiently wet and radiant cooling occurs in fine weather. Accordingly, it is an object of the present invention to provide a road surface freezing prediction method and a device therefor which can improve the reliability of the freezing prediction.

[0008]

SUMMARY OF THE INVENTION A road surface freezing prediction method according to the present invention achieves the above-mentioned object. The method includes the steps of: presenting a road surface temperature in a specific temperature range near 0 ° C. when water exists on the road surface; The method is characterized in that road surface freezing is predicted when the change of the road surface indicates a descending characteristic due to radiation cooling of the road surface.

Further, the means of the road surface freezing prediction device of the present invention comprises: a water detecting means for detecting whether or not water exists on the road surface; a road surface temperature measuring means for measuring the road surface temperature; Road surface temperature change calculating means for detecting whether or not the change in the road surface temperature in the temperature range is a descending characteristic due to radiant cooling of the road surface; an output in which the road surface temperature change calculating means detects the descending characteristic due to radiant cooling; Road surface freezing prediction means for outputting a road surface freezing prediction signal when the output of the means detecting water is input.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a road surface freezing prediction apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram, and 1 indicates whether there is water on the road surface due to a change in electric resistance between electrodes arranged on the road surface, or irradiates the road surface with light, and changes in the amount of reflected light from the road surface. Any of a variety of moisture sensors, such as detecting whether there is water on the road surface, or detecting whether there is water on the road surface due to the change in light and dark density between the horizontal and vertical polarization images obtained by the video camera. Is a water detecting means constituted by the above-mentioned sensor.

Reference numeral 2 denotes a road surface temperature measuring means which is installed at a height of 5 to 6 m above the road surface and comprises a radiation thermometer or the like for measuring the temperature of the road surface. This is a road surface temperature change calculation means for detecting whether or not a radiant cooling state occurs at times. This road surface temperature change calculating means 3
Is determined from the characteristic diagram when radiant cooling occurs in FIG. 3A and the characteristic diagram in FIG. 3B when radiant cooling does not occur.

In FIG. 3, the vertical axis indicates temperature and the horizontal axis indicates time, and indicates the maximum road surface temperature (about 1 ° C.) at around 13:00, regardless of whether radiant cooling occurs or not. However, when radiant cooling occurs from this maximum road surface temperature, the temperature drops to −5 ° C. in a sharp curve. On the other hand, when no radiative cooling occurred, the applicant's experiments revealed that the temperature decreased only from 0 ° C. to −2 ° C. with a gentle curve.

Therefore, for example, a temperature gradient is calculated by the road surface temperature change calculating means 3 every fixed time (for example, 30 minutes) between 1 ° C. and −2 ° C. An output is sent out when it is determined whether the temperature is low or a gradual temperature decrease, and when it is determined that radiant cooling has occurred.

Reference numeral 4 denotes a road surface freezing prediction unit which receives the outputs from the water detection unit 1 and the road surface temperature change calculation unit 3 as inputs. The outputs from both the water detection unit 1 and the road surface temperature change calculation unit 3 are input. Then, a freezing prediction signal indicating that road surface freezing will occur is output. The road surface temperature change calculating means 3 and the road surface freezing predicting means 4 in FIG. 1 may of course be processed by one processing device (CPU).

Next, the operation will be described with reference to the flowchart of FIG. First, the road surface freezing prediction means 4 determines whether or not the measurement timing is every 5 minutes (step S1).
When it is determined that the timing is the measurement timing, it is determined whether or not the output from the water detecting means 2 is wet (step S2). It is determined whether the road surface temperature is within the set temperature range (step S3).

Next, it is determined whether or not the stored temperature gradient with the temperature 30 minutes ago is equal to or greater than a set value (step S).
4). As a result, when the road surface temperature is higher than 1 ° C., the program returns to the start. When the road surface temperature is lower than −2 ° C., a program for judging freezing is executed.

The output obtained by the road surface temperature change calculating means 3 is in a radiant cooling state (for example, 0.5 ° C. in 30 minutes).
When the output is sent, the output is sent from the water detecting means 1 and the road surface freeze prediction means 4 outputs the road surface freeze prediction output (step S).
5) For example, the display of "caution of danger of freezing ahead" is displayed on the road information board.

Then, it is determined whether or not the measurement is completed (step S6). If not, the measurement is not completed (step S1).
Return to On the other hand, when it is determined in step S4 that the temperature gradient is equal to or smaller than the set value, it is determined whether the number of times is counted a plurality of times (step S7). Release the freeze prediction signal output once. Note that the set temperature in step S3 is a value set according to the topography, traffic volume, and the like of the point where freezing is predicted.

[0019]

As described above, according to the present invention, the presence of water at the freezing observation point and the detection of a decrease in the road surface temperature indicating radiant cooling in a specific temperature range (around 0 ° C.) are detected. Since the freeze prediction output is transmitted, the road surface freezing state can be accurately and quickly predicted, and the reliability of the road surface freezing prediction can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a road surface freezing prediction device according to the present invention.

FIG. 2 is a flowchart showing an operation.

FIG. 3A is a characteristic diagram of a road surface temperature during radiant cooling,
(b) is a characteristic diagram of a normal road surface temperature.

[Explanation of symbols]

 1 water detection means 2 road surface temperature measurement means 3 road surface temperature change calculation means 4 road surface freezing prediction means

Claims (2)

[Claims] 1. A road surface freezing is predicted when water is present on the road surface and a change in the road surface temperature in a specific temperature range near 0 ° C. indicates a descending characteristic due to radiation cooling of the road surface. Freezing prediction method. 2. A water detecting means for detecting whether or not water exists on a road surface, a road surface temperature measuring means for measuring a road surface temperature, and a change in the road surface temperature in a specific temperature range near 0 ° C. Road surface temperature change calculating means for detecting whether or not the cooling characteristic has a descending characteristic, an output of the road surface temperature change calculating means detecting a descending characteristic by radiant cooling, and an output of the water detecting means detecting water are input. And a road surface freezing prediction means for outputting a road surface freezing prediction signal.