Study On The Safety Of Freeway Work Zone Based On Traffic Conflict Technique

With the arrival of large-scale repair and maintenance of freeways in our country, the work zone becomes special section of freeway. Vehicles passing through the section and construction vehicles form a complex traffic environment, and its security situation is not optimistic. This problem is paid more and more attention by traffic engineers. The work zone's duration is short, lacking of traffic accident statistics. In order to overcome these defects, this paper carried out safety research of work zone based on traffic conflict technique.Firstly, the definition of freeway work zone is given, and different forms of work zone and its application conditions are analyzed. The study object of this paper is determined which is work zone with lanes of one-way completely closed. With survey data, the road characteristics, traffic flow characteristics and safety situation of work zone are analyzed. The application of traffic conflict technique for work zone safety evaluation is proposed. And then, the definition of work zone traffic conflict is given, and the mechanism of generation and the effectiveness for safety evaluation are analyzed.Secondly, according to sections of traffic conflict generation, the classification of traffic conflicts is given, and the severity judging methods for rear-end conflict and side conflict are given based on TTC index. The factors of traffic conflicts were analyzed, and on this basis, the survey program of traffic conflict is draw up. With the survey data of Ha-a freeway work zone, the relationship of rear-end conflict, side conflict and theirs influence factors are analyzed in detail.Thirdly, on the basis of relationship analysis of traffic conflicts and influence factors, the independent variables of predication models for rear-end conflict and side conflict are determined through correlation analysis. With negative binomial distribution form, the predication models for two typical conflicts are established with respective influence factors. And then, each section conflict predication model is built by accumulating traffic conflict site existed in corresponding section.According to the established conflict predication model, the conflict predicted value of each section in different traffic condition can be obtained. And combining the indexes of conflict quantity and conflict destroy energy, the grey evaluation model for safety level of each section are built. Using the theory of elasticity analysis, the prominent influence factors of the dangerous section can be determined.Finally, with the case of work zone in Ha-a freeway, the traffic conflict quantity of each section is given according to different traffic condition. The safety level of each section in the work zone is determined. And according to the result of elasticity analysis, the safety improvement measures for dangerous section are given.