A Study on Capacity of Weaving Sections

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This study discusses capacity of weaving sections based on several observations on the Metropolitan Expressway. The study is divided into two parts : a macroscopic analysis of traffic flow conditions such as flow, speed, and density of traffic in a weaving section, and a microscopic analysis of each vehicle motion in order to develop a simulation model which can reproduce weaving capacity.For the macroscopic analysis, we first show that capacities of some weaving sections are lower than those of simple section by at most 26% and that the capacities vary depending on highway geometry and traffic conditions such as weaving lengths and volume ratios. Secondly, we compare values of weaving influence factor estimated by the 1965-HCM (Highway Capacity Manual) with the observed values. The estimates were found to be slightly smaller than the observed values. Thirdly, we examine applicability of four different existing methods for predicting weaving speed ; those are the 1985-HCM, JHK, PINY, a … More nd Leisch methods. The 1985-HCM method gives the best agreement with the observed speed but the PINY and Leisch methods tend to underestimate the speed.For the microscopic analysis, using vehicle trajectory data obtained from observations, microscopic variables such as relative position and relative speed of weaving vehicles are analyzed. Based on these data, a simulation model estimating weaving capacity was developed. It is considered that weaving vehicles are always selecting an optimum acceleration and the required time for lane changing corresponding to the aimed gap, and they adjust these variables until the weaving is completed. In this model, every vehicle momentarily updates such particular maneuvers precisely by predicting its condition at the moment the weaving is completed. The simulation model was validated at two congested weaving sections on the Metropolitan Expressway. As a result, the simulated values f capacity and speed fit well with the observed ones. Finally capacities at the weaving sections under various traffic and geometric conditions were discussed. Less