HIGHWAY/EXPRESSWAY WEATHER MONITORING
Weather sensors are used within the automatic traffic control to warn the driver of adverse weather situations. Highway road weather station is specially designed for traffic, drivers get information about adequate speed limits during adverse weather situations. Therefore road weather data are necessary. To detect the danger of aquaplaning measurements of precipitation intensity and water film thickness as well as the status of the road surface are needed. To detect these atmospheric data different weather sensors are located near the
The highway is a typical and comprehensive road detection station. It focuses on detecting visibility, weather phenomena, and road condition, measuring related basic meteorology parameters, mainly used for timely detecting abnormal traffic environmental factors & meteorological conditions, providing the scientific real-time basis for meteorological services and traffic management department.
For detecting road temperature, water film thickness, and condition of the road surface the sensors plays a vital role.
To ensure an adequate display there are requirements the sensors have to meet. Among the location which has to be homogeneous, the sensors have to transmit a measured value every minute. Depending on the parameter there are specific requirements which are explained in the next section.
Sensors for road weather data should be located every 2-5 km. Variable message signs however are located closer. That is why the data needs to be very accurate as it is the input for more than one sign.
Application and uses
Condition of the Road Surface: The status of the road defines the qualitative coverage of the road surface. The sensors need to be able to distinguish the status “dry” and “not dry” which includes moist and wet. Additionally the status
“Frozen” has to be detected as well. The status of the road is mainly used to detect the danger of sleekness. The model uses the status of the road, the road temperature, dewing temperature, and air temperature.
Water film Thickness: Water film thickness is defined as the moistening of the road with water or dilution (salt). It is based on a plain surface. Its range is from 0.01 to 3 mm. The value per minute has to be determined by six measurements within the last minute.
Road Temperature: The road temperature defines the temperature of the layer between the road surface and the air mass or the water film above the road. The range needs to be from -30 to +80 °C and the resolution needs to 0.1 °C.
Components of Weather Station for the road weather:
Anemometer– Measures wind direction and speed.
Thermometer – Measures atmospheric temperature.
Pyranometer – Measures solar radiation levels from the sun in watts per square meter (used to calculate ‘Evapotranspiration’, the rate at which water evaporates from the soil).
Hygrometer – Measures relative humidity using a percentage measure of water vapor in the air.
Barometer – Measures atmospheric pressure to predict precipitation
Rain Gauge – Measures liquid precipitation using an open container. They usually empty automatically and measure the amount of rainfall over a given time interval.