AN EMPIRICAL CAPACITY MODEL FOR ROUNDABOUTS UNDER HETEROGENEOUS TRAFFIC OF HYDERABAD

Abstract

Roundabouts are generally used as a means of intersection control for moderate traffic flows condition. It is important to measure the performance of existing roundabouts in terms of its ability to handle the present traffic condition. The capacity of an entry flow is found to vary considerably with the vary in geometrics of the roundabout. A study was conducted to collect the data from three different roundabouts in Hyderabad with different geometry and traffic characteristics. A model was developed using empirical analysis based on four geometric parameters of roundabout (Entry Width, Weaving Width Central Island Diameter, and Weaving Length) which are significant for estimating the capacity of roundabout. Each geometric have been tested individually for its influence on capacity, by keeping the traffic flow conditions unchanged. The developed model validated with the site data. A comparative study with some existing empirical models indicated that the capacities of roundabouts are underestimated or overestimated for Indian heterogeneous traffic condition.