Study On Safety Risk Factors Of Highway Based On Traffic Flow Parameters

With the rapid development of national economy,people's demand for long-distance travel is increasing rapidly.While the highway brings convenience to people's travel,the traffic safety problems caused by it cannot be ignored.Therefore,it is very crucial to study the traffic safety of highway.For the existing works on this topic,the evaluation indexes of traffic safety are mostly based on the number of accidents,and the traffic risk hidden in the traffic flow cannot be identified in time.Besides,it is difficult to reflect the differences in micro-individual behavior.Because different traffic flow states correspond to different levels of safety,the impact of people,vehicles,roads,environment and other factors on traffic operations will be reflected in traffic flow characteristics to varying degrees.Therefore,based on the characteristics of highway traffic flow,this paper selects the macro risk and rear-end risk parameters from the perspective of traffic flow,combining quantitative methods with qualitative methods to study highway traffic safety.The main content of the paper includes analysis of traffic flow characteristics of the highway,research on macro risk based on vehicle speed dispersion,rear-end risk analysis of different vehicle combinations,and research on the application of highway traffic risk improvement.Firstly,the paper analyzes the safety of highway traffic flow qualitatively and then decides to study the highway safety risk from two aspects of speed characteristics and car-following characteristics.In order to quantitatively study the characteristics of the highway traffic flow,this paper analyzes from the macro and micro perspectives based on the measured traffic flow data.At the macro level,the time and spatial distribution characteristics of traffic volume,cart proportion,speed,and other parameters are analyzed.The statistical characteristics and variation rules of different vehicle speeds,vehicle speed difference,vehicle spacing,rear vehicle speed and vehicle spacing,vehicle spacing and vehicle speed difference,rear vehicle speed and rear vehicle distance,rear end time distance,and vehicle speed difference are analyzed from the micro levelIn terms of macro risk,the paper selects the standard deviation of speed or the coefficient of the standard deviation of speed as the macro risk indicator.Firstly,taking the carriageway as the research object,and using mathematical statistics theory and SPSS software,the paper determines the relationship between the ratio of the carriage and the coefficient of standard deviation of speed,and studies the proportion of the corresponding car in the highest speed discrete risk state,and studies the range of the corresponding carts under different traffic state hazards.Then,the relationship between the standard deviation of each lane's speed and the average speed is determined by taking the overtaking lane and the lane of the highway as the research objects,and the difference of standard deviation of speed between any two average speed levels is also studied.In terms of the micro-risk,the paper aims to study the rear-end risk of different vehicle combinations(cars-cars,cars-carts,carts-cars,carts-carts).Firstly,through calculating the minimum safe vehicle spacing between the four vehicle types in different vehicle speeds and vehicle speed differences,the difference in driving safety between different vehicle combinations is indirectly reflected.Secondly,based on the microscopic traffic flow data such as the following speed,vehicle speed difference,rear end distance and vehicle spacing,the safety differences reflected by the traffic flow characteristics of different vehicle combinations are studied.Then,descriptive analysis and statistical test are carried out on TTC value,DRAC value and rear-end risk intensity grade(based on TTC value division)of different vehicle combinations,and the results show that the cars-carts combination has the highest risk of driving,and the carts-cars has the lowest driving risk.Besides,the risk of rear-end collision between the carts-carts combination is greater than that of the car-car combination when the TTC value is less than 2s.Then,the non-parametric test is carried out on the TTC index and DRAC index of any two vehicle combinations,and the results show that the difference in rear-end risk between different vehicle models is independent of the evaluation index used.On this basis,the differences in rear-end risk intensity distribution of the four types of vehicle combinations are studied under different vehicle speed levels.Finally,the paper studies the improvement of highway traffic safety from two perspectives:reducing speed dispersion and preventing rear-end accidents.In order to improve the traffic safety of highway,some suggestions are also proposed,such as real-time control of the cart,lane management,vehicle speed control,minimum safety vehicle distance warning,and vehicle distance auxiliary facilities design.