Research On Road Traffic Flow Characteristics In Fog And Haze Weather

With the development of China's roads and the increase in the number of cars,and the demand for transportation continues to increase,the road traffic pressures are becoming increasingly severe.Among the important factors affecting the operation of road traffic,besides the factors of people,vehicles and roads,environmental factor is also an important factor affecting traffic.In recent years,due to the influence of bad weather,traffic accidents have frequently occurred,and traffic has been interrupted,and so on.Especially with fog and haze weather frequently occurred,the traffic environment has been extremely deteriorated,visibility has deteriorated,and wet roads which have caused road safety problems.Therefore,this thesis establishes a traffic flow model for roads with fog and haze weather,studies the characteristics of road traffic flow under fog and hazy weather,and provides a basis for road traffic control under fog and hazy weather.Firstly,it analyzes the domestic and foreign research results on the impact of road traffic with bad weather and lays the foundation for the thesis.From the analysis of the influence factors of fog and haze weather,combined with the definition of fog and haze and the scope of visibility,a fuzzy set is used to introduce the risk index of different haze visibility into the single lane and double lane cellular automata model,and the traffic flow characteristics of the fog and haze weather are studied.In the numerical simulation,the driving environment under different visibility of fog was simulated,and the space-time characteristics,density-velocity relationship and velocity-time relationship were analyzed under visibility of fog and haze weather in a single lane.Relationship curve about the traffic density and lane changing frequency was also analyzed in two-lane traffic under fog and haze weather.By analysis,compared with the sunny days,the impact of the visibility conditions on the fog and haze slightly has a weaker impact on traffic,and the medium and heavy impacts on fog and haze are more likely to cause traffic congestion.Secondly,in the low-visibility environment with fog and haze,due to the driver's poor vision,the road information cannot be obtained accurately during the driving process,and it is very easy to cause rear-end collision traffic accidents.Therefore,the safety speed limit of the vehicle is particularly important.Based on the above problems,this thesis establishes a speed limit traffic flow model with low visibility under fog and haze,and analyzes and obtains the safety speed limit values under different density of low visibility,and compares it with the speed limit standard to verify the correctness of the model.At the same time,based on the speed limit model,the influence of parking line-of-sight is taken into account,and on the basis of the speed effect of the preceding vehicle,a car-following model based on parking distance is established for fog and haze weather,and the numerical simulation is performed,and space-time characteristics,headway fluctuations,and head-to-head spacing maps after rate limiting are obtained.Finally,the relative difference between the average expected speed of fog and haze weather and sunny days was-6.3%,which was similar to the measured data of-5.6%,which verified the correctness of the model.Finally,for the low-visibility real traffic situation,there is a phenomenon in which the driver always tries to go along with the adjacent vehicle.The distance difference and speed difference between the leading vehicle of the adjacent vehicle and the current vehicle are introduced in the form of a random slowing down probability.In the model,a two-lane traffic flow model was established to consider the influence of adjacent vehicles under fog and haze weather,and the impact characteristics of adjacent vehicles on traffic flow under low visibility were studied.The numerical simulation was carried out to obtain the velocity distribution and the time-distance distribution of the vehicle head under the influence of the adjacent roads in fog and haze weather.