Research On Region Division And Safety Measurement For Traffic Accident Scene On Freeway

Freeway is a kind of main line of road with restricted entrances for automobile to run in different direction and in respective lane. And its mileage is a sign of national and regional economic development level. Freeway has outstanding advantages in transportation efficiency, convenience and comfort. But the growing transportation demand brings great traffic flow. In such background, traffic accidents would occur if mismanagement or lack of safty awareness for traffic participants. Traffic accidents result in accident scenes, which are the basis of accidents reconstruction and causations judgement.After traffic accidents occur, it is necessary to wait for traffic police coming to enclose the accident scenes. Due to sudden changes of traffic flow and speed dispersion, traffic police, irrelevant personnel, damaged vehicles and passing vehicles constitute an extremely complex and dangerous traffic environment. Sections around traffic accident scenes are most dangerous during accident scenes formation and rescission. In order to protect traffic police and irrelevant personnel, and avoid vehicles rushing into accident scenes, Ministry of Transport and Ministry of Public Security have formulated many laws and regulations,which regulate the behavior of scene investigation, equipments and scheme of scene disposal for traffic police. But owing to randomicity of accident locations and high speed of passing vehicles, secondary accidents frequently happen.Occurrence of secondary traffic accidents has single or various causations inluding unsuitable disposal of scenes, negligence of traffic police and hamartia of drivers. Compared with the initial accidents, the secondary accidents inducing more casualty and property loss are more preventable. This paper analyzes the safety factors in accident scenes, studies traffic characteristics around accident scenes, puts forward speed limitation suggestions and conducts reasonable setting of traffic signs in the scenes. Detailed descriptions are as follows.(1) Aiming at the statistical absence of secondary accidents, the concept of the secondary accidents is put forward in this paper, and characteristics factors are regulated. Based on the processes and results of the secondary accidents, classifications and forms of the secondary traffic accidents are proposed. The causations of the secondary traffic accidents including person factors, vehicle factors, road and environment factors and management factors are analyzed. And the relationship between state evolution of various factors and safety of traffic accident scenes is studied. In order to obtain the important degree of various factors and propose effective measurements, the initial traffic accident scenes are regarded as dynamics system. Casualty graph and dynamics flow graph involving variable definition, horizontal equation, auxiliary equation, rate equation, the initial value equation and constant equation, are established. After every parameter is defined, dynamics system model is simulated to analyze the importance of factors.(2) In order to divide the regions for traffic accident scenes and propose the suitable speed limits suggestion, personnel behavior characteristics in accident scenes, passing vehicles speed characteristics and traffic flow characteristics are analyzed. According to drivers cognitive pattern of SOR, drivers disposal information model is established, which is combined with information characteristics in accident scenes and utilized driving reliability theory. Behavior purpose, behavior approach and behavior contence of traffic police are investigated. In order to research onlooker psychology, realize onlooking time and onlooking region, questionnaires are made. The questions involve onlooking tendency, watching time and region. Investigation results are made to statistical graphs and charts. For obtaining speed distribution along accident scenes section, radar speed indicator and traffic flow capturing and processing equipment are applied to detect speed at certain points. Probability distribution of speed sample is achieved by means of maximum likelihood estimation. Time headway sample in normal section, single lane enclosing section and multi lanes enclosing section is analyzed to acquire distributed parameters. Based on the speed and time headway distribution, length model of confluence zone is established in different traffic flow.(3) According to speed distribution and relevant regulations, the regions of traffic accident scenes are divided, speed limits model and simulating models are established. Traffic accident scenes are divided into warning zone, confluence zone, buffering zone, accident zone, diffluence zone and termination zone. Vehicles speed charateristics in various zone and drivers behavior charateristics are helpful to calculate length of each zone. Considering large quantity of information and ability of drivers information disposal, speed limit value model in warning zone and confluence zone are established, which aid to develop the decision support system. The system includes modules according to information classification in accident scenes. To verify models and support system, microscopic simulation software of traffic flow is employed to check index involving standard deviation of speed sample, maximum queue length, traffic capacity and mean speed. Speed limits suggestions are proposed for typical accident scenes of four-lane double way, six-lane double way and eight-lane double way.(4) Based on the ergonomics, classifications and location of traffic signs in each zone are put forward according to analyzing the process of drivers reading signs. Means of traffic signs and characteristics of drivers behaviors are contributed to establish distance model of reading signs. Consequently, preposing distance of traffic sings locations and repeating distances are obtained. Referencing speed limits suggestions, setting locations of signs and proposal chemes are proposed for four-lane double way, six-lane double way, eight-lane double way and simple accident scenes. At the same time, full-lane enclosed accident scenes, special climate, special sections and accident scenes in night are anayzed and traffic signs setting schemes are proposed.Research results are valuable theoretically and practically for regulating disposal scheme of traffic accident scenes, ensuring personal safety of traffic police and irrelevant personnel in accident scenes.