Traffic Circulation Efficiency of Elliptical Roundabouts

Fathullah, Hardi S. and Majid, Hirsh M. and Ahmed, Chro H. and Sourkan, Sulleyman H. and Ismael, Karzan S. and Abdulsamad, Balen Z. (2023) Traffic Circulation Efficiency of Elliptical Roundabouts. ARO-THE SCIENTIFIC JOURNAL OF KOYA UNIVERSITY, 11 (2). pp. 65-72. ISSN 2410-9355

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This paper investigates the impact of geometry of central island of roundabout on operational performance in terms of delay and capacity measures. A roundabout with an elliptical central island having major and minor axes of 63 and 44m respectively was selected as a case study. Using SIDRA Intersection software two simulation models are developed while considering two geometric shapes of central island; one with an elliptical shape and the other with a circular shape. The peak traffic volume of each approach was assigned to both models as a preliminary simulation then twelve scenarios were generated by assigning identical lane volumes starting from a value that gave level of service A and increasing gradually to level of service F. In each scenario 100% of the volume assigned to an approach while the other was assigned with 75% of it and this process was reversed for every run. The results revealed that at high degree of saturation, the elliptical roundabout generally possessed a higher performance especially in term of delay and capacity compared to the circular roundabout. Furthermore, a parametric study was carried out through running eight more simulation scenarios to examine the impacts of heavy vehicle percentage (HV%) on the roundabout operational performance. The (HV %) started from 2% and increased to 12% with alternate approach virtual volume, and the results showed that performance of the elliptical roundabout was higher than the circular roundabout. However it was more susceptible to increase of HV% in term of control delay and capacity.

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Additional Information: AASHTO., 2011. A Policy on Geometric Design of Highways and Streets. American Association of State Highway and Transportation Officials, Washington DC. Akçelik, R., 2011. An Assessment of the Highway Capacity Manual 2010 Roundabout Capacity Model. In: International Roundabout Conference. Transportation Research Board, Carmel, Indiana, USA. Akçelik, R., 2011. Some Common and Differing Aspects of Alternative Models for Roundabout Capacity and Performance Estimation. In: International Roundabout Conference. Carmel, Indiana, USA: Transportation Research Board. Akçelik, R., 2017. An Assessment of the Highway Capacity Manual Edition 6 Roundabout Capacity Model. In: 5th International Roundabout Conference. Transportation Research Board, Green Bay, WI, USA. Akçelik, R., 2018. SIDRA Intersection 8.0 User Guide. Akçelik and Associates Pty Ltd., Greythorn, Australia. Akgelik, R., and Besley, M., 2005. Differences between the AUSTROADS roundabout guide and AUSIDRA roundabout analysis methods. Road and transport Research Journal, 14(1), pp.44-64. AL Momani, M., 2009. A Comparison of Traffic Flow Performance of Roundabouts and Signalized Intersections using MITSIMlab. Master’s Thesis, Near East University. Graduate School of Applied Sciences, Nicosia. Davies, C, 2011. A Brief History of Roundabouts: Once Bitten Twice Shy. Canada: Miovision. Hatami, H., and Aghayan, I., 2017. Traffic efficiency evaluation of elliptical roundabout compared with modern and turbo roundabouts considering traffic signal control. PROMET-Traffic and Transportation, 29(1), pp.1-11. DOI: Mabuchi, T., and Nakamura, H., 2007. Performance evaluation of roundabouts considering traffic conflicts. J East Asia Sociesty for ransportation Studies, 7, pp.2412-2424. Mohamed, A.I., Ci, Y., and Tan, Y., 2022. Mega elliptical roundabouts versus grade-separation interchange. Proceedings of the Institution of Civil Engineers Transport, 175(6), pp.323–343. DOI: Mohammed Ali, H.K., and Majid, H.M., 2023. Comparative evaluation of roundabout capacities methods for single-lane and multi-lane roundabout. Journal of Engineering, 29(3), pp.76-97. DOI: Moran, J., 2009. Defining Moment: The British Invent the modern Round About, 1966. FT Magazine Europe. Qu, X., Ren, L., Wang S., and Oh E., 2014. Estimation of entry capacity for single-lane modern roundabouts: Case study in Queensland, Australia. Journal of Transportation Engineering, 140(7), pp. 1-5. DOI: Sisiopiku, V.P., and Oh, H.U., 2001. Evaluation of roundabout performance using Sidra. Journal of Transportation Engineering, 127(2), pp.143-150. DOI: 2(143) TRB, 2010b. National cooperative highway research program and United States, federal highway administration 2010. In: Roundabouts: An Informational Guide. Washington, DC: Transportation Research Board. Tracz, M., and Chodur, J.,2012. Performance and safety roundabouts with traffic signals. Procedia-Social and Behavioral Sciences, 53, pp.788-799. DOI: WSDOT., 2021. What is Roundabout? Available from: htm#:~:text=A%20modern%20roundabout%20 is%20a,exit%20at%20their%20desired%20street [Last accessed on 2023 Aug 15]
Uncontrolled Keywords: Circular roundabout, Elliptical roundabout, Heavy vehicle percentage, Performance evaluation, Traffic simulation
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: ARO-The Scientific Journal of Koya University > VOL 11, NO 2 (2023)
Depositing User: Dr Salah Ismaeel Yahya
Date Deposited: 25 Sep 2023 09:45
Last Modified: 25 Sep 2023 09:45

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