Effects Of Operation Mode On Traffic Safety In Multi-Lane Freeway Diverge Segment

The corridor-type freeways of China mostly are the multi-lane freeways with 6 lanes and above in dual directions. In more flexible operation way, they can restrict trucks from the left lanes. On the one hand, this has increased traffic efficiency; and on the other hand, trucks on the right lanes have the barrier effect and conflict with the vehicles changing lanes, easily causing traffic accidents. In the diverging area, there are many compulsory lane changes and the truck barrier effect is very remarkable. Therefore, it is significant to research the impact of this on traffic safety.The basic conception of operation modes is defined. Traffic volume, time headway and speed parameters under the lane restriction strategy are statistics, and the features of traffic flow are analyzed. On basis of the data flow cluster analysis technology, the traffic flow status are identified and the generation and effect of the truck barrier effect has been verified.The geometric features, operation features and performance indices of the diverging area are studied. The diverging area and the diverge-affected area are distinguished; and the diverging area is divided into four stages on basis of length, i.e. advance notice, preparation, implementation and restoration; moreover, the effect of the width of the diverging area on the operation of the freeway is analyzed. According to the minimum frequency of compulsory lane changes and nature of lane change, the diverging area is classified into 4 basic structure types, and 3 frequent multiplex diverging areas are produced from the combination of them. This Thesis brings forward that, at certain diverging quantity, the maximum traffic volume of straight driving can be regarded as the traffic capacity of the diverging area, which is calculated on basis of the gap-acceptance theory. In addition, and density is taken as the criterion to judge the service level of the diverging area. Diverging action has been observed and the index of diverging strength, diverging length, diverging speed which describing diverging difficulty has been established and conducted.From the macro and micro angles, this thesis has portrayed the traffic flow model of the diverging area. It has introduced traffic flow phase transition characteristics as well as the hydrodynamic model and dynamic model of traffic flow; and it also has discussed the dynamic mechanism, chaos phenomena and stability criteria. The dynamic mechanism, affecting factor and architecture of the driving behavior are restisting and driving behavior model has been classified into three modes, i.e. behaviorism, symbolicism and connectionism. With compulsory lane change as the main behavior feature of the diverging area and on basis of the bounded rationality rule and prospect theory, this thesis establishes the lane change model and has simulation test on the model with cellular automaton.This thesis evaluates the traffic safety of the diverging area with traffic conflict technology. It has analyzed the formation mechanism and characteristics of the traffic conflict in the diverging area. On basis of the potential, severe, continuous, dynamic and limited features of traffic conflict, this thesis has brought forward the index demand and has established the indices for four conflicts, i.e. instant conflict, accumulative conflict, average conflict and statistic conflict. In order to verify the accuracy of the model, this thesis has formulated traffic conflict observation, statistic and correction method. By introducing the lane change stage model and Newell car-following model, this thesis has calculated the traffic conflict in changing lanes and calibrated model parameters. Respectively based on regression analysis, neural network and fractal theory, this Thesis has integrated the traffic safety evaluation indices in respect of traffic conflict, traffic stability, etc..From three aspects, i.e. operation mode selection, upstream speed limit and length setup, this thesis has established the traffic safety countermeasure system for the diverging area. It has described operation mode selection process, and by reference to the Wardorp balance theory, has predicted the distribution of traffic flow on lanes and calibrated traffic flow parameters. Respectively based on utility function and interval probability, this thesis has established the operation mode selection decision model. In consideration of traffic operation uncertainty and with fuzzy inference, this thesis has established the upstream speed limit strategy for the diverging area. With clothoid, this thesis fits the lane change trail of vehicles, further establishes the trail model of continuous multiple lane changes with the repeated game theory and finally obtains the reasonable length of the diverging area.