Study On Capacities Of Diverging And Mergeing Are Of Urban Expressways

Urban expressways had played an important pole in the city transportation systems in release traffic press of city center and partake traffic volume that passed through. But,under the rapid increased traffic demands, unvarying traffic jam has occurred in expressway system and resulted the fall of expressways'function. This paper based on the data collected from expressways of Beijing and shanghai, studied the traffic characters, capacity and the factors that influenced capacity of diverge and merge area by the numbers, to provide theories base and analysis foundation for plan, design and manage of diverge and merge area so that ensure expressways'safe, efficient, comfort. At first, the paper systemic reviewed the studied statuses in capacity of diverge and merge area inboard and outboard, especially anatomy the capacity study methods in German and in Highway Capacity Manual of America. On this base, confirmed the paper's study method and technical means is: based on engineer application, based on data collected field test and analysis methods of American HCM, with theoretic and practice methods, analysis the capacity of diverge and merge area. Through field survey on expressway of Beijing and shanghai, differentiated the form of diverge and merge area into nine type; then analysis the traffic characters of diverge and merge influence area based on data from field test, compared the difference of volume on different lanes, different sites, different time, speed on different lanes, different sites and different volumes of diverge and merge influence area, confirmed the correctness of study methods that based on HCM; Then, this paper confirmed the capacity values of diverge area by built speed-flow statistical model and by statistic saturated head time and the capacity values of merge area by built speed-flow statistical model and by measured capacity after speed break with timing serial method; At last, the paper confirmed the factors which affected the capacity of diverge and merge influence area by analysis the traffic characters of diverge and merge influence area; referred to the analysis methods of HCM and modified the formula that used to calculate density and speed with data from field test, constituted the analysis methods and programs that suited to analysis the factual traffic status of diverge and merge area of Chinese urban express, and proved the modified formula is more accurate in predict density and speed of diverge and merge area in China.