Roundabout Capacity Estimation Model Considering Driver Behaviour on the Exiting and Entry Flows

  • Marijan Žura University of Ljubljana, Faculty of Civil and Geodetic Engineering
Keywords: roundabout, capacity, driving behaviour, entry flow, exiting flow, gap acceptance theory


Roundabout capacity estimation has been the subject of several types of research in recent decades. Most of the analyses are based on the empirical or analytical models (e.g. gap acceptance theory) considering various kinds of conflicting flows, namely entry, circulating, and exit-ing flow. The drivers on the exiting flow either obey the traffic rule (use the right-turn indicator) or disobey the traffic rule (do not use the right-turn indicator). Accord-ing to the reviewed literature, the impact of these driv-ers on the roundabout capacity has not been studied to a greater extent. Therefore, this study aims to develop an analytical roundabout capacity estimation model that also takes into account a share of exiting flow. It extends Brilon-Wu’s model, by including the impact of exiting drivers who disobey the traffic rule on the gap accep-tance of the entering drivers. The proposed model was validated using the quasi-observation data generated by a microscopic model. The results obtained by our model were compared with Bovy’ and Yaps’ empirical models as well as Brilon-Wu’s analytical model for a single-lane roundabout. Using the RMSE and regression analysis, it is proved that the proposed model outperforms the exist-ing models in terms of estimating the capacity and delays of roundabouts.


Yap YH, Gibson HM, Waterson BJ. An international review of roundabout capacity modelling. Transport Reviews. 2013;33(5): 593-616. doi: 10.1080/01441647.2013.830160.

Çalişkanelli P, Özuysal M, Tanyel S, Yayla N. Comparison of different capacity models for traffic circles. Transport. 2009;24(4): 257-264. doi: 10.3846/1648-4142.2009.24.

Pilko H, Mandžuka S, Barić D. Urban single-lane roundabouts: A new analytical approach using multi-criteria and simultaneous multi-objective optimization of geometry design, efficiency and safety. Transportation Research Part C: Emerging Technologies. 2017;80: 257-271. doi: 10.1016/j.trc.2017.04.018.

Raff MS, Hart JW. A volume warrant for urban stop signs. Saugatuck, Connecticut: Eno Foundation for Highway Traffic Control; 1950.

Ashworth R. The capacity of priority-type intersections with a non-uniform distribution of critical acceptance gaps. Transportation Research. 1969;3: 273-278. doi: 10.1016/0041-1647(69)90158-0.

Siegloch W. Die Leistungsermittlung an Knotenpunkten ohne Lichtsignalanlagen (Capacity calculations for unsignalized intersections). Series Strassenbau und Strassenverkehrstechnik; 1973. p. 173.

Kimber RM. The Traffic Capacity of Roundabouts. Wokingham, Berkshire: UK Transport and Road Research Laboratory. TRRL Report LR 942, 1980. p. 43.

Ahmad A, Rastogi R. Regression model for entry capacity of a roundabout under mixed traffic condition–an Indian case study. Transportation Letters. 2017;9(5): 243-257. doi: 10.1080/19427867.2016.1203603.

Hagring O. Derivation of capacity equation for roundabout entry with mixed circulating and exiting flows. Transportation Research Record: Journal of the Transportation Research Board. 2001;1776(1): 91-99. doi: 10.3141/1776-12.

Mereszczak Y, et al. Incorporating exiting vehicles in capacity estimation at single-lane U.S. roundabouts. The National Roundabout Conference Proceedings, 22-25 May 2005, Vail, Colorado. 2005.

Fortuijn LGH. Turbo roundabouts: Estimation of capacity. Transportation Research Record; 2009. p. 83-92. doi: 10.3141/2130-11.

Yap YH, Gibson HM, Waterson BJ. Models of roundabout lane capacity. Journal of Transportation Engineering. 2015;141(7): 04015007. doi: 10.1061/(ASCE)TE.1943-5436.0000773.

Suh W, et al. Impact of including exiting vehicles in single-lane roundabout capacity models. Transportation Research Record. 2015;2517: 87-95. doi: 10.3141/2517-10.

HCM. Highway Capacity Manual. 5th ed. Washington, DC: Transportation Research Board; 2010. p. 326.

Perme S. Roundabout capacity with incorporating of exiting flow. M.Sc. thesis. University of Ljubljana, Faculty of Civil and Geodetic Engineering; 2013.

Perme S, Maher T. New method for the calculation of roundabout capacity considering exiting flow impact. Gradbeni vestnik. 2016; p. 253-260.

Troutbeck RJ. Current and future Australian practices for the design of unsignalized intersections. In: Brilon W. (ed.) Intersections without Traffic Signals. Berlin, Heidelberg: Springer; 1988. p. 1-19. doi: 10.1007/978-3-642-83373-1_1.

Brilon W, Wu N, Lemke K. Capacity at unsignalized two-stage priority intersections. Transportation Research Record. 1997;(1555): 74-82. doi: 10.1016/s0965-8564(98)00047-0.

Wu N. A universal procedure for capacity determination at unsignalized (priority-controlled) intersections. Transportation Research Part B: Methodological. 2001;35(6): 593-623. doi: 10.1016/S0191-2615(00)00012-6.

Wu N. A new model for estimating critical gap and its distribution at unsignalized intersections based on the equilibrium of probabilities. 5th Inte rnational Symposium on Hi ghway Capacity and Quality of Service, 25-29 July 2006, Yokohama, Japan. 2006; p. 10.

Wu N, Brilon W. Total capacity of roundabouts analyzed by a conflict technique. Transportation Research Record. 2018;2672(15): 9-22. doi: 10.1177/0361198118788171.

Gass SI, Harris CM. Erlang distribution. In: Gass SI, Harris CM. (eds.) Encyclopedia of Operations Research and Management Science. New York, NY: Springer; 2001. p. 261. doi: 10.1007/1-4020-0611-X_298.

Brilon W, Koenig R, Troutbeck RJ. Useful estimation procedures for critical gaps. Transportation Research Part A: Policy and Practice. 1999;33(3–4): 161-186. doi: 10.1016/s0965-8564(98)00048-2.

PTV. PTV VISSIM 11 User Manual. Karlsruhe, Germany: PTV Planug Trasport Verker AG; 2019. p. 265-297.

Bethea RM, Duran BS, Boullion TL. Statistical Methods for Engineers and Scientists. 3rd Ed. Routledge Taylor & Francis Group; 1995.

How to Cite
Žura M. Roundabout Capacity Estimation Model Considering Driver Behaviour on the Exiting and Entry Flows. Promet [Internet]. 2022May31 [cited 2024Jun.21];34(3):397-05. Available from: