Study On The Safety Mechanism And Support Technology Of Sections With High Ratio Of Bridges And Tunnels Of Mountainous Freeway

Due to the fact that the freeways in the central and western regions of China mostly travel through the mountains,in the process of construction,,Freeway with high ratio of tunnels and bridges gradually emerge,which are composed of special structures such as bridge beam groups,tunnel groups and bridge-tunnel groups,which creates a special operating environment for drivers and vehicles,which is easy to lead traffic accidents due to the coupling of human-vehicle-road-environment and other factors?At present,there are many studies on the environment and safety characteristics of single tunnel at home and abroad,but lack of systematic research about safety guarantee technology on freeway with high ratio of bridges and tunnels.The research results can not meet the requirements of driving safety in freeway with high ratio of bridges and tunnels.It is necessary to study the accident characteristics and safety guarantee technology of freeway with high ratio of bridges and tunnels.The basic distribution law of accidents,the distribution law of types of accident structures and the spatial distribution law of tunnel accidents were studied.The factors that influenced the accident severity of freeway with high ratio of bridges and tunnels were analyzed based on the binomial logistic theory,the factors which had a significant impact on the severity of the accident were screened out.The logistic model of the influence factors of freeway with high ratio of bridges and tunnels was established.The study would provide theoretical basis for the research of driving safety guarantee technology of freeway with high ratio of tunnels and bridges.The relationship between the linear index(mainly including plane linear index,vertical linear index,tunnel length,bridge length)and the accident rate of freeway with high ratio of bridges and tunnels was analyzed.The 12 indexes of circle curve radius,transition curve radius,straight line length,circle curve length,transition curve length,vertical curve radius,longitudinal slope,longitudinal slope length,tunnel length,bridge length and annual average daily traffic volume AADT,were taken as independent variables,the accident number of prediction unit was taken as dependent variable,and based on the negative binomial distribution theory,the accident prediction model freeway with high ratio of bridges and tunnels under different road section unit conditions was established.The change law of driver's visual when passing through the typical section with high ratio of bridges and tunnels was studied.Linear regression was used to analyze the trend of pupil area change,and the magnitude of visual change was represented by the slope of curve.The Kruskal-wallis H multi-group rank sum test of non-parametric test was used to test the pupil area data of the open section,tunnel entrance,tunnel interior and tunnel outlet,to explore whether there are significant differences in the pupil area values of drivers in the four sections.Both the theory and real vehicle test were carried out for the repeated effects of the driver's load on the section with high ratio of bridges and tunnels.The maximum instantaneous velocity ^V?(t)of pupil area was used as the evaluation index to describe the visual load change rule of the driver at the entrance and exit of the tunnel.Based on the maximum transient velocity of pupil area(MTPA)and the duration of visual shock(t _C),the evaluation system of visual comfort for drivers at tunnel entrances and exits was established.According to this evaluation index system,the driver's visual load degree of tunnel entrance and exit could be determined,and the influence degree of tunnel entrance and exit on driving safety would be judged.Finally,the guarantee technology of driving safety of sections with high ratio of bridges and tunnels of freeway in mountainous area was studied.Aiming at the safety guarantee of the tunnel entrance,it was proposed to set up a combined visual illusion deceleration line in front of the tunnel entrance,so as to reduce the speed of vehicles entering the tunnel.The safety distance model between the visual illusion deceleration line and the tunnel entrance was established,and the safety distance between the visual illusion deceleration line and the tunnel entrance was obtained.UC-win/road simulation experiment was used to evaluate the effect of speed control.Based on the risk sources of sections with high ratio of bridges and tunnels of mountainous freeway studied above.The impact from road and environment on the safety of drivers and vehicles was studied,the evaluation system of driving safety of sections with high ratio of bridges and tunnels of mountainous freeway was constructed,and the evaluation method of driving safety in sections with high ratio of bridges and tunnels was put forward.In this paper,the driving safety characteristics of freeway with high ratio of bridges and tunnels are comprehensively analyzed from the perspective of human-vehicle-road-environment.The results of this study have a certain guiding role in the engineering design and operation safety risk prevention and control.