Modeling the Operating Speed in Tangents and Curves of Four-lane Highways Based on Geometric and Roadside Factors

Document Type : Research Paper


1 M.Sc. Grad. , Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran

2 Assistant Professor, Department of Civil Engineering, , Imam Khomeini International University, Qazvin, Iran


Operating speed is an index that represents drivers’ speeding behaviors on different highways and shows the comfort and safety levels they experience. Many models had been proposed in previous studies to predict operating speed and most of these works had used geometric, with few of them conducted using roadside variables to predict operating speed. Also, the operating speed study in multilane rural highways had been gained less attention by researchers. In this study, two four-lane rural highways (Kole jub-Borujerd and Borujerd-Khorramabad) had been surveyed for analyzing the operating speed. More than 13,800 spot speed data was gathered in 108 tangent and 30 curve segments. Two linear regression models were developed to predict operating speed in the tangent and curve segments using geometric and roadside factors simultaneously with the acceptable R-squared statistic (0.730 and 0.854 respectively). The results showed that segment length, guardrail median, and flat roadside configuration have a positive effect while slope, accesses density, curvature, and adjacent land use length have a negative effect on operating speed. Moreover, the sensitivity analysis demonstrates that the effect of slope on operating speed in curves is twice comparing to its effect in tangents; while, operating speed in tangents is approximately 2.5 times more sensitive to access density than operating speed in curves. Thus, it can be concluded that not only geometric features affect operating speed but also roadside features affect it. The outcomes of this study can be useful in design and safety planning studies of rural multilane highways.


-Abbas, S. K. S., Adnan, M. A. and Endut, R. (2011) "Exploration of 85th percentile operating speed model on horizontal curve: a case study for two-lane rural highways", Procedia-Social and Behavioral Sciences, Vol. 16, pp.352-363.
-Azarmi, A. (2005) "Accident prevention model for curves in Iran two lane rural roads", Master of Science Thesis, Tarbiat Modares University, (In Persian)
-Bassani, M., Cirillo, C., Molinari, S. and Tremblay, J. (2015) "Fixed and random effect models to predict operating speed percentiles on rural two-lane highways", TRB Transportation Research Board of the National Academies.
-Bella, F. (2013) "Driver perception of roadside configurations on two-lane rural roads: Effects on speed and lateral placement", Accident Analysis & Prevention, Vol. 50, pp. 251-262.
-Boroujerdian, A., Seyedabrishami, E. and Akbarpour, H. (2016) "Analysis of Geometric Design Impacts on Vehicle Operating Speed on Two-Lane Rural Roads", Procedia Engineering, Vol. 161, pp.1144-1151.
-Cafiso, S., Di Graziano, A., Di Silvestro, G., La Cava, G. and Persaud, B. (2010) "Development of comprehensive accident models for two-lane rural highways using exposure, geometry, consistency and context variables", Accident Analysis & Prevention, Vol. 42, No.4, pp.1072-1079.
-D’Andrea, A., Carbone, F., Salviera, S. and Pellegrino, O. (2012) "The most influential variables in the determination of V85 speed", Procedia-Social and Behavioral Sciences, Vol. 53, pp.633-644.
-Eboli, L., Guido, G., Mazzulla, G. and Pungillo, G. (2017) "Experimental relationships between operating speeds of successive road design elements in two-lane rural highways", Transport, Vol. 32, No. 2, pp.138-145.
-Esposito, T., Mauro, R., Russo, F. and Dell’Acqua, G. (2011) "Speed prediction models for sustainable road safety management", Procedia-Social and Behavioral Sciences, Vol.20, pp.568-576.
-Fitzpatrick, K., Carlson, P., Brewer, M. and Wooldridge, M. (2001) "Design factors that affect driver speed on suburban streets", Transportation Research Record: Journal of the Transportation Research Board, No. 1751, pp.18-25.
-Garcia, D. S., Lindau, L. A. and Nodari, C. (2013) "Multivariate operating speed forecasting model based on the geometric elements of two-lane highways", Journal of Traffic and Logistics Engineering, Vol. 2, pp.97-103.
-Gargoum, S. A. and El-Basyouny, K. (2016) "Exploring the association between speed and safety: A path analysis approach", Accident Analysis & Prevention, Vol. 93, pp.32-40.
-Gitelman, V., Doveh, E. and Bekhor, S. (2017) "The Relationship between Free-Flow Travel Speeds, Infrastructure Characteristics and Accidents, on Single-Carriageway Roads", Transportation Research Procedia, Vol. 25, pp.2031-2048.
-Gong, H. and Stamatiadis, N. (2008) "Operating speed prediction models for horizontal curves on rural four-lane highways", Transportation Research Record: Journal of the Transportation Research Board, No. 2075, pp.1-7.
-Gujarati, D. N. and Porter, D.C. (2003) "Basic econometrics. 4th ed.", New York: McGraw-Hill.  
-Hashim, I.H., Abdel-Wahed, T.A. and Moustafa, Y. (2016) "Toward an operating speed profile model for rural two-lane roads in Egypt", Journal of traffic and transportation engineering (English edition), Vol. 3, No. 1, pp.82-88.
-Himes, S. C. and Donnell, E. (2010) "Speed prediction models for multilane highways: simultaneous equations approach", Journal of Transportation Engineering, Vol. 136, No. 10, pp.855-862.
-Islamic Republic of Iran. Vice Presidency for Strategic Planning and Supervision (2012) "Highway Geometric Design Code", Office of Deputy for Strategic Supervision, Department of Technical Affairs, No. 415. (In Persian)
-Mirbaha, B., Saffarzadeh, M. and Noruzoliaee, M. H. (2013) "A model for predicting schoolchildren accidents in the vicinity of rural roads based on geometric design and traffic conditions", International Journal of Transportation Engineering, Vol. 1, No. 1, pp.25-33.
-Praticò, F.G. and Giunta, M. (2012) "Modeling operating speed of two lane rural roads", Procedia-Social and Behavioral Sciences, Vol. 53, pp.664-671.
-Semeida, A. M. (2013) "Impact of highway geometry and posted speed on operating speed at multi-lane highways in Egypt", Journal of Advanced Research, Vol. 4, No. 6, pp.515-523.
-Shallam, R. D. K. and Ahmed, M. A. (2016) "operating speed models on horizontal curves for two-lane highways", Transportation Research Procedia, Vol. 17, pp.445-451.
-Yagar, S. and Van Aerde, M. (1983) "Geometric and environmental effects on speeds of 2-lane highways", Transportation Research Part A: General, Vol. 17, No. 4, pp.315-325.
-Zhu, Z. and Rong, J. (2010) "The impact of the accesses on the operating speed of two-lane highways", In ICCTP 2010: Integrated Transportation Systems: Green, Intelligent, Reliable, pp. 935-942.