Research On Expressway Variable Speed Limit System Based On Traffic Meteorological Environment Monitoring

Severe meteorological conditions such as heavy fog,rain and snow,and road area water,icing,snow,etc.often have a very serious negative impact on traffic safety.Expressway speed is fast,drivers are prone to fatigue,and under severe weather conditions,high-speed vehicles often cause serious traffic accidents.In China,the expressway speed limit has been basically static for a long time,and the speed management method is single,which cannot effectively adapt to the demand of dynamic speed management under severe weather conditions.In order to reasonably determine the safe speed limit of highways under severe meteorological conditions such as fog.rain and snow,road water,ice,snow,etc.,and provide drivers with the maximum acceptable safety speed,this paper proposes a freeway variable speed limit system based on traffic meteorological environment monitoring.In the collection of meteorological parameters,this paper uses the principle of visibility measurement and the principle of road surface measurement.The principle of visibility measurement is based on Koschmieder’s law.According to the law,the essence of measuring meteorological visibility is to measure the extinction coefficient of the atmospheric level,and the attenuation of light in the atmosphere is mainly caused by scattering and absorption.Therefore,in engineering,it can be approximated that the extinction coefficient and the scattering coefficient are equal.By measuring the scattering coefficient,the atmospheric visibility values are reversed by Koschmieder’s law.Based on the change of the incident angle and the single-wavelength principle of the 1064nm and 1550nm bands,the spatial distribution of the post-emitter energy of these two bands has a certain relationship with several pavement states such as drying,icing and water accumulation.Based on this,the road surface state detection uses a dual-wavelength detection method,which has a simple principle and high feasibility,and can efficiently and conveniently detect and distinguish the highway road surface state.With reference to domestic and foreign research,a variable speed limit model based on visibility and a variable speed limit model based on road friction coefficient are established.The speed limit values of the two models are integrated,and the speed limit is used to correct the time limit values by day and right and low illumination conditions.Take the three minimum values as the final variable speed limit value.This paper proposes the STM32f103 chip as the core controller.The road condition monitoring equipment,the visibility measuring instru,ment and the illuminance measuring instrument are used to collect meteorologyical information in real time,and the LED information board is used to pronpt the maximum safe speed and weather information in real time.Based on Qt5 development of the host computer client,the development sofrtware has the advantages of high modularity and good reusability,and can expand other functions as needed.