Capacity analysis of Roundabout

Dr. RAJASHEKAR REDDY DUDIPALA

PROFESSOR
OSMANIA UNIVERSITY

Dr. Rajashekar Reddy Dudipala is presently working as Professor in the Dept. of Civil Engineering, University College of Engineering, Osmania University. He has 20 years of Teaching and research experience. His research areas of interest are Pavement materials and Traffic Engineering. He is Doctoral committee member and member board of studies of various Universities and Engineering Colleges. He is a member State Technical Agency(STA), PMGSY, NRRDA, Govt. of India. Empaneled as National Quality Monitor (NQM) under PMGSY, NRRDA,Govt. of India.

He has published 30 Papers in various International and National Journals and Conferences. He has also done research and consultancy projects in the field of Transportation Engineering.

He is a member of various professional bodies like Fellow of The Institution of Engineers (India), Life member of Indian Society for Technical Education (ISTE). He has delivered guest lecturers and Keynote addresses in various UGC & AICTE refresher courses, conferences, in house training programs. He organized several conferences and workshops on various topics related to Transportation engineering especially Pavement Engineering.

Roundabouts are a form of signalized intersections where the vehicles are forced to move around central island. The geometry of roundabout itself forces the vehicles to slow down before entering and reduces the severity of crashes. Operating cost is lesser than signalized intersections and delay is lesser than unsignalised intersections. The capacity of the roundabout is a function of various factors that have a significant influence on it. The effect of identified traffic and geometric factors are taken for the study. Two types of analysis are available for the capacity estimation of an intersection, namely, analytical methods and empirical methods. Empirical methods rely on field data which develop the relationship between geometric variables and performance measures. However, analytical methods which are based on gap acceptance theory develops the relationship between driver behavior and performance measures, such as capacity and delay. For the present study data is collected for two roundabouts by video recording at Hyderabad city. The gaps in the traffic stream and traffic volume count data were extracted from the video. Critical gap is a traffic parameter that is used in the analytical model, which is more preferred for the capacity estimation. In this study, the critical gaps were estimated for various vehicle types separately and the effect of circulating flow on critical gap was analyzed.The critical gap is a complex variable to estimate, as it cannot be measured directly in the field and whose value changes from driver to driver, time to time, between intersections, type of movement (Right, Left or Through) and vehicle type. A comparison was made between Raff’s method and MaximumLikelihood Estimation (MLE) method of critical gap estimation from the data of two roundabouts .The capacity of the roundabout is estimated using three models were considered to compare the better method.

The objective of this study is to carry the capacity analysis of Roundabout and propose some improvements to the selected roundabouts of Hyderabad, INDIA.

The topic which i choose is important because the developing countries like India because of mixed traffic conditions it is essential to study the factors contributing the capacity of roundabouts and to propose some recommendations