Capacity Of Weaving Section For The Exclusive Bus Lances On An Urban Expressway

ABSTRACT:To alleviate the urban traffic congestion effectively, the study on bus priority is attracting more and more attention. As one of bus priority measures, bus lanes are gradually installed on urban expressways due to the high effectiveness and low costs. Although the capacity of weaving section for bus lanes on an urban expressway is a critical index in the planning, design and evaluation of weaving section, studies on such capacity are scarce currently. Therefore, the analysis of traffic flow characteristic and the development of estimation method of capacity will be conducted based on the field data in this thesis.Firstly, the literature review on traffic flow characteristic of weaving section, capacity of weaving section without a bus lane, and capacity of weaving section with a bus lane or other special lanes are completed in the thesis. Status quo is summarized. After that, the research contents are determined.Secondly, after conducting the data collection scheme according to the data requirements, the data processing method which combines video traffic detection systems and manual counting is designed according to the characteristics of the collected data. The thesis analyzes the effects of important parameters on vehicle operation from qualitative and quantitative perspectives and the important parameters include weaving length, number of lanes, weaving flow ratio, bus weaving ratio and type of bus lanes. Macroscopic and microscopic characteristics for this type of weaving section are studied by analyzing a large number of field data. The traffic composition and relationships among traffic flow parameters on each non-bus lane are macroscopic characteristics and car following and weaving behavior are microscopic characteristics.Thirdly, the ideal safe gap during merging in weaving section is determined based on the speed of the expressway traffic flow and the merging vehicles. The computing method of desired number of vehicle with lane changing that accounts for the length of the weaving section is proposed based on gap acceptance theory. Besides, the capacity is analyzed according to the characteristics of weaving demand and model assumptions are proposed. Capacity model of this type of weaving section is established based on gap acceptance theory and linear programming method. The maximum of the sum of all flow components from main road and ramp is the objective function in this model, with constraints on the capacity of the basic expressway segment, desired number of vehicle with lane changing of each weaving lane, weaving flow ratio of other vehicles, weaving flow ratio of buses and flow ratio of buses from ramp.Finally, the thesis validates the model by the accuracy of the model and sensitivity analysis of parameters. The errors are calculated with the measured and the calculated values of the model from two sites in different days. Moreover, when each parameter of the model is varied, the variation of the calculated capacity and the calculated maximum throughput of traffic flow of the model are also analyzed. The results indicated that the model established in the thesis is effective.