The Effect of Geometric Factors on Saturation Flow at Selected Intersections of Kathmandu

Abstract

The main objective of intersection design is to facilitate the convenience, comfort and safety of people traversing the intersection by enhancing the efficient movement of road users. The intersections on urban roads in Nepal generally cater heterogeneous motorized traffic, along with slow-moving traffic including pedestrians. It is therefore necessary to consider saturation flow for mixed traffic conditions to evaluate the overall operation of signalized intersections. This study focuses on analyses of saturation flow rate conducted at signalized intersections with mixed traffic conditions in selected intersection of Kathmandu, Nepal. Studies were carried out at 19 signalized junctions in Kathmandu with varying geometric factors such as width of road (w), gradient of road (g), and turning radius (r) for right turning vehicles. Saturation flow rate at first was computed as per Highway Capacity Manual (HCM: 2000). Then geometric factors, which affect the saturation flow, have been considered and accordingly a new model has been proposed for determining saturation flow. It has been shown that by the introduction of the suggested adjustment factors, the saturation flow rate can give better picture of the field conditions, especially under heterogeneous traffic conditions of an urban area.