Modification of SIDRA Model for Capacity Estimation of Urban Roundabouts under Mixed Traffic Condition in Sri Lanka

Abstract

Roundabouts are very popular and used in many countries as a method of intersection control. It facilitates an orderly movement of traffic in a circular motion around a central island in one direction. Design and planning of roundabouts require thorough analysis of its performance. The entry capacity is one important measure of performance of a roundabout. There are several methods to estimate the capacity of roundabouts which have been developed in many countries. However, those methods have been developed for the homogeneous traffic flow conditions in most of the developed countries. The traffic flow condition in most of the developing countries like Sri Lanka is heterogeneous since it consists with motor bikes and three wheelers. Therefore this research aims to determine the effect of the mixed traffic condition in roundabout entry capacity and to develop a method to estimate the entry capacity for urban roundabouts perform under mixed traffic conditions.