Safety evaluation of urban roundabouts in India: a safety performance function-based approach


  • V S Vinayaraj Indian Institute of Technology Bombay, India
  • Vedagiri Perumal Indian Institute of Technology Bombay, India



negative binomial, roundabouts, safety performance function, weaving length


There is a lack of comprehensive research in roundabout safety under non-lane-based traffic conditions, mainly due to the absence of relevant crash data and effective tools for safety evaluation. Safety Performance Function (SPF) is a suitable tool for providing valuable information related to factors which can potentially contribute to the likelihood of increasing traffic crashes. Currently, very limited studies are available to explain the usefulness of SPF in the vicinity of roundabouts, especially at non-lane-based traffic conditions. This study aims to develop an SPF model for assessing the safety evaluation at roundabouts as a whole (intersection level) and the approach level. Data corresponding to crashes in nineteen roundabouts with different geometric and traffic characteristics was used for model formulation. Crash data for five years (2015–2019) was obtained from the State Crime Records Bureau. An SPF model was developed using a negative binomial model with a log-link function based on the number of crashes, traffic characteristics, and geometry characteristics of the roundabouts. The proportion of powered two-wheelers, percentage of heavy vehicles, entry-angle, and weaving-length were all significantly related with higher crash occurrences at roundabouts, according to the findings. In contrast, the number of circulatory lanes, inscribed circle diameter, and presence of road lane marking were negatively associated with the increased crash occurrences at the roundabout vicinity. In addition to this, the overall crash rate significantly varies across roundabout sections due to the asymmetric effects of geometric and traffic characteristics. The developed SPF would best explain the relationship between geometric and traffic characteristics and the crash occurrence rate in non-lane traffic conditions. The findings of this study support the need to relook at design parameters for better movement at the roundabouts, thereby improving the existing facilities to enhance road users' safety, especially in developing countries. The proposed SPF tool would help engineers examine the safety of roundabouts in terms of design adequacy, quantifying the risk factors, and future crash predictions.


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Author Biographies

V S Vinayaraj, Indian Institute of Technology Bombay, India

V S Vinayaraj is a research scholar in the Department of Civil Engineering in the specialization in Transportation Systems Engineering, Indian Institute of Technology Bombay, India. His research mainly focuses on understanding the driver behaviour characteristics, analysing crash data, and safety assessment of roundabouts in disordered traffic conditions. His research interests include vehicle trajectory data analysis, crash data analysis, driver and pedestrian behaviour modelling, and traffic safety. He received his master’s degree in Civil Engineering from SV National Institute of Technology (SVNIT), Surat, India.

CRediT contribution: Conceptualization, Data curation, Formal analysis, Methodology, Validation, Writing—original draft, Writing—review & editing.

Vedagiri Perumal, Indian Institute of Technology Bombay, India

Vedagiri Perumal is Professor in the Department of Civil Engineering, Indian Institute of Technology Bombay, India. His research interests include traffic safety, mixed traffic flow modelling and simulation, traffic monitoring, management and control, traffic facility design and evaluation, and public transit systems design and operations. He has over 40 international journal publications and 100 international and national conference publications. He has received IIT Bombay’s Young Investigator Award in 2013 and Excellence in Teaching award in 2017. He is one of the Recognized Road Safety Auditor in the region. He has successfully completed various national and international research projects.

CRediT contribution: Conceptualization, Supervision, Writing—review & editing.


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How to Cite

Vinayaraj, V. S., & Perumal, V. (2022). Safety evaluation of urban roundabouts in India: a safety performance function-based approach. Traffic Safety Research, 3, 000015.