Traffic Flow Equilibrium Analysis Of Urban Road Traffic System With Bi-directional Flow’s Effect Of Local Road

Abstract:The present study investigates theories and methods for traffic flow equilibrium analysis of urban road traffic system with bi-directional flow’s effect of local road. It is aimed to utilize and evaluate urban branch road network. After making the best use of road resources in branch network, it helps to raise the function of branch road on urban arterial road traffic diversion and alleviate traffic congestion pressure on arterial road, as well as saving urban land use and saving money investment. This study is focused on the traffic flow equilibrium analysis of urban road traffic system with bi-directional flow’s effect of local road. To start with the capability analysis of branch road, equilibrium analysis is performed on urban branch road network, and optimization approach is proposed and investigated for branch network traffic organization, which establish the theoretical basis for rational use of branch network.At first, through the analysis of general influence factors on the capacity of urban road section, two-way traffic characteristic properties of branch road are pointed out. Then, several key influence factors on the capacity of branch road section are selectively analyzed, such as the influence of road width on safe meeting speed, unequilibrium of two-way traffic capacity on bi-directional flow, decision of vehicle meeting behavior on traffic flow speed, etc. Through the modeling analysis of urban branch road traffic capacity using the cellular automation model, the simulation result reflects ability characteristics of urban branch road.Due to the lack of equilibrium analysis method of traffic network with mixed-use local road, a capacity function of local road is proposed based on the local road simulation and characteristics analysis, which is related to the road width, capacity of lane and bi-directional traffic ratio on the local road. Furthermore, based on the capacity function of local road, an equilibrium analysis method is extended to consider traffic network with mixed-use local road, and all-or-nothing assignment method as well as method of successive average are employed to solve the equilibrium analysis model which can accommodate the non-concave character of the capacity function on directional road traffic flow. Example shows that the extended equilibrium analysis method of traffic network with mixed-use local road is valid and caters for application of practice project.Because the two-way traffic flows in the branch road sections of the urban road network is not parted by lanes, there is a big difference in the description of road capacity between the two-way and the one-way branch road sections. Taking into account the random degradation phenomenon of the branch capacity, and through the description of each road section capacity degradation parameters, based on the long term habitual traffic equilibrium model and combined with the features of the two-way branch road sections to expand, traffic flow equilibrium model of branch network based on travel time reliability is constructed. Analysis result shows that under the different reliability requirements, there are differences in the travelers’ choices on the arterial road section and the branch road sections, and the more conservative travelers have a smaller probability of the branch road sections.In order to maximize the efficiency of traffic stream in branch network, approaches for one-way traffic organization in branch network are studied and optimized. From the view of traffic load and road equity and considering bi-directional flow’s effect of local road, a one main and multi servo bi-level programming model is established. The upper model is a multi-objective programming to minimize the portion that road saturation exceeds the anticipant saturation in order to reduce road load and the vehicle detour index to improve equity by using traffic organization scheme as the decision. The link flows and the shortest paths between arbitrary two points in the given one-way traffic organization scheme are determined by a number of low programming. The simulated annealing algorithm is designed to solve the bi-level model and the solution performance is significantly better than the traditional optimal methods which the capacities of local roads are equivalently divided as bi-directional diverged lanes’.Finally, the research ideas and conclusions on traffic flow equilibrium analysis of urban road traffic system with bi-directional flow’s effect of local road are discussed, and the prospect of future research is proposed.