Study On Strategies Of Inputting Control Signal For Freeway In Foggy And Rainy Weather Based On CAM

Freeway has become the skeleton of road traffic system because of its characteristics of high driving speed and large traffic flow.While playing the role of large capacity,rapid and convenient at the same time,freeway presents many disadvantages.Especially,the phenomenon of incident traffic accidents and traffic jams have become one of the focus of social in the foggy and rainy of bad weather.It has become the serious problem of freeway management that how to take the reasonable control measures to reduce the accident rate and guarantee the freeway traffic safety and improve actual capacity according to different bad weather and actual traffic demand.In the aspect of theory,although there are some researches about management and control of the traffic on freeway in foggy and rainy weather,point of,these are the qualitative or easy quantitative control measures.Building the traffic flow model and studying of strategies of inputting control signal have not been discussed.In addition,the studied object hardly has been related to the management and control of traffic on freeway under bad weather.Based on this,this paper tries to build a cellular automaton model(CAM)of a section of freeway in foggy and rainy weather by possible accidents.Through simulating traffic flow characteristics of freeway in foggy and rainy weather,we want find the best strategies of inputting control signal to improve the capacity of freeway and reduce the accident rate.It can provide decision support for specific traffic management.The main work in this paper could be summarized as the following aspects:(1)Analyzing freeway traffic system in foggy and rainy weather.The paper analyzed freeway traffic system components and main influence factors.Then the paper studied essential feature of foggy and rainy weather and the influence of the feature to freeway traffic flow on this basis.(2)Setting up CAM of study object.Based on the symmetric two-lane Nagel-Schreckenberg(STNS)model,This paper extends the research object to three lanes.Combining the essential feature of study object and drivers' psychological and behavior characteristics in foggy and rainy weather,the paper initial builds a one-way three lanes freeway CAM which maybe happen rear-end accidents in foggy and rainy weather(3)The strategies of inputting control signal for freeway in foggy weather.Through analyzing the impact of visibility to the driver's sight,visibility is introduced as the main parameter.By adjusting the upstream traffic flow and VSL(Variable Speed Limits)value,experiments are made.And then the paper get the corresponding optimal upstream traffic volume and speed limit of different visibility under the simulation experiment conditions.Traffic safety can be ensured and traffic congestion can be suppressed in this way.In addition,the purpose of reducing vehicle total transit time and improving the road actual capacity can be achieved.(4)The strategies of inputting control signal for freeway in rainy weather.Through analyzing the relationship between rainfall intensity and visibility and road friction coefficient,visibility and road friction coefficient are introduced as the main parameters.By adjusting the upstream traffic flow and VSL value,experiments are made.And then the paper get the corresponding optimal upstream traffic volume and speed limit in rainy days under the simulation experiment conditions.The conclusion provides some scientific and reasonable decision support for freeway in rainy days.