Study on Saturation Flow Rates for Signalized Intersections

Past research has indicated that the effectiveness and efficiency of traffic control of signalized intersections strongly depend on the accurate calculation of saturation flow rate, particularly when demand approaches capacity. Minimal work has been done in the past on calibration of the parameters for saturation flow rate used in traffic control of signalized intersections. This paper discusses a saturation flow study conducted in Nanjing City, the Capital of Jiangsu Province, which lies in the east of China. Using linear regression analysis, average time headway of saturation flow rate for nine signalized intersections has been studied. Base saturation flow rate and heavy vehicle equivalency factor have been calculated. The results confirm that the methodology for saturation flow rates, put forward by Highway Capacity Manual (HCM) can also be used in China. However, parameters should be systematically calibrated, based upon widespread study, before they can be used effectively in the practice of traffic control in China.