An Estimation Method of Roundabout Entry Capacity Considering Pedestrian Impact

Entry capacity is one of the most important indices for performance evaluation of roundabout. In addition to circulating vehicles, pedestrian flow is another key conflicting stream which has significant impact on entry capacity. The pedestrian impact is considered by an adjustment factor in the existing method (Brilon et al., 1993) which was developed based on the roundabouts under the design with physical splitter island, crosswalk and distance of one-vehicle length between crosswalk and yield line. Some of them such as the physical splitter island and the distance between crosswalk and yield line cannot be always satisfied due to space limitation in some places, which are considered to have significant impact on entry capacity. Moreover, it is supposed that several other influencing factors also strongly affect entry capacity, e.g., pedestrian approaching side and queuing vehicles in circulating roadway due to pedestrians across downstream exits. Therefore, a theoretical model was developed in this study to estimate roundabout entry capacity considering pedestrian impact and these influencing factors, i.e., physical splitter island, pedestrian approaching side, distance between crosswalk and yield line and queuing vehicles in circulating roadway. Through conducting sensitivity analyses it was found that the impacts of the influencing factors on entry capacity can be expressed by the proposed model. Parameters in the proposed model which is used to reflect influencing factors should be calibrated and modified by empirical data in future.