Analysis On Traffic Safety Risks Of Freeway Tunnel Group

In recent years,freeway construction expanded gradually to central and west China.To shorten the distance and have less impact on the ecological environment,tunnel construction has been widely applied to cross mountains.Therefore lots of tunnel groups have been formed with big amount of tunnels.However,it was noticed that a large number of traffic accidents with heavy casualties occurred in tunnel group sections,traffic safety problem in tunnel group is critical.Study objects in most of research were mainly focused on single tunnel,but only a few were focused on tunnel group for systematic research.Based on this,the paper has taken freeway tunnel group as research object,and carried out the research in sequence of "traffic safety features analysis-traffic safety risk factors identification-traffic safety risk analysis".Following contents have been included:Firstly,traffic safety features of freeway tunnel group have been analyzed.Based on analysis of the freeway tunnel group’s structure,investigation plan of freeway tunnel group has been made.The investigation plan has considered both overall scale and local features of freeway tunnel group,traffic safety features could be fully obtained in all aspects.The investigation has covered traffic flow,environmental lighting and historical traffic accidents.Through investigation and survey,the data of traffic flow variation,environmental lighting variation characteristics and traffic accident features of freeway tunnel group have been statistically analyzed.The work could provide theoretical and data support for further research.Secondly,by using improved association rule algorithm,traffic safety risk factors of freeway tunnel group have been identified.With character of multi-level and multi-dimension,traffic safety risk factors of freeway tunnel group were correlated with each other.Therefore,risk factors identification method based on association rules has been proposed.Compared to traditional methods,this method needn’t to emphasis the correlation of different risk factors,and solved the problem of missing important association rules.The research has also realized the indepth mining of traffic safety risk factors of freeway tunnel group.The results showed that unsafe speed and rear-end accidents were key factors of increasing traffic safety risk in freeway tunnel group.It provided a research basis for the safety risk analysis of freeway tunnel group.Thirdly,traffic safety risk of freeway tunnel group has been analyzed based on speed distribution rule.Considering the correlation of speed distribution features and traffic safety risk,on the basis of comprehensive analysis of the relationship between speed and traffic safety risk,traffic safety risk analysis index system and risk analysis model of freeway tunnel group have been constructed based on speed distribution rule.The model has integrated speed coordination,relative accident risk level and traffic accident rate,and analyzed traffic safety risk of freeway tunnel group in multiple ways.The research showed that vehicle speed changed greatly in some sections of the freeway tunnel group,and speed varied for different vehicle types,which could bring high safety risk.These findings could provide theoretical reference for the speed management in freeway tunnel group.Finally,traffic safety risks of freeway tunnel group have been analyzed based on traffic conflicts.Considering the correlation of traffic conflicts and traffic safety risks,the risk index of traffic conflicts was determined as traffic safety analysis index of freeway tunnel group.The risk factors of traffic safety have been screened by quantitative and correlative analysis.Followed by using Bayesian network theory and D-S evidence theory,a bottom-up traffic safety conflicts analysis model has been proposed.The model could realize traffic safety conflicts analysis at three levels: tunnel section,tunnel unit and tunnel group.The research results showed that traffic conflicts varied in different sections of the freeway tunnel group,especially at entrance and exit of each tunnel.The research could also provide theoretical reference for traffic conflicts risk control of freeway tunnel group.