Research On Traffic Flow Characteristic Parameters Of City Intersection In Adverse Weather Conditions

In recent years, the increasingly extreme adverse weather has a seriously impacton the socio-economic life of the city as well as the traffic operations. Rain, snow, fogand other adverse weather bring the changes of the external traffic environment androad conditions. Besides, driver behaviors, traffic flow characteristics, as well as themacro situation of the road network running are very different from normal weatherconditions. However, due to the lack of scientific theoretical guidance and support ofthe traffic flow theory, the formulation of the traffic management measures, thedevelopment and adjustment of the traffic plans and signal control programs in adverseweather conditions are usually based on experience, so that the transport system caneasily cause paralysis in adverse weather conditions. Therefore, in order to reduce theimpact of extreme weather on the urban transport system and develop reasonabletraffic management and control strategies, the traffic flow characteristic parameters inadverse weather conditions should be obtained.In the study, signalized intersection traffic flow characteristics in adverse weatherconditions such as rain, snow are the objects. The goal for this paper is to analyze thechanges of traffic flow characteristics of urban signalized intersections in varyingdegrees of adverse weather conditions.6signalized intersections of different sizes andtypes in Beijing urban and suburban areas were selected as the observed object. Basedon the intersection video data, continuous observation and analysis of the intersectionstraffic flow in different levels of rain, snow were conducted. The headway, start-up losttime and saturation flow rate were selected as the characteristic indexes, and the trafficcharacteristic parameter reductions at signalized intersections were obtained bysignificant difference analysis and the relationship fitting in different levels of rainfalland snowfall conditions. In addition, according to the degree of parameters reductionin different types of adverse weather conditions, the unified grading standards ofadverse weather based on the traffic impact was proposed, and traffic flowcharacteristic parameter reduction models in different adverse weather conditions werebuilt. The test results by using on-site survey data proved that the reduction modelshave good applicability and accuracy. This paper presents a unified classificationmethod of adverse weather, and builds reduction models of traffic flow characteristicsin different weather conditions. It provides important basic parameters for thedevelopment of urban traffic management measures and the optimization of trafficmanagement control program in special weather conditions.