Analysis of safety impact of paved shoulder width on Czech secondary roads




secondary road, paved shoulder, shoulder width, safety, crash, speed


Traffic safety is influenced, among other factors, by characteristics of the roads, which include the width of the shoulder. Shoulder width was noted to have a large effect on crash frequency, as well as on traffic speed. In this paper, we focused on paved shoulders. Previous studies confirmed that increasing the width of the paved shoulder is associated with a decrease in crash frequency. However, wider shoulders may encourage higher driving speed, which is related to an increase of impact speed and crash severity – this issue was hypothesized, but not statistically investigated. Thus, conclusions based on crashes and speeds contradict each other, and there is no simple answer to the question of the safety impact of wide shoulders. To address this gap, we analyzed a sample of two most typical categories of Czech secondary roads, which differ only in the paved shoulder width (S9.5 roads with 0.75m-wide shoulder, and S11.5 roads with 1.75m-wide shoulder) and thus present a suitable example for studying the safety impact of paved shoulder width. We used generalized linear models of crash frequency, and multinomial logistic models of crash severity (separately for single-vehicle and multi-vehicle crashes), as well as a statistical test of differences in speed for the two road categories. The results showed that: Firstly, there were fewer crashes on S11.5 roads compared to S9.5 roads; this was true for both single-vehicle and multi-vehicle crashes. Secondly, single-vehicle crashes on S11.5 roads were more severe compared to S9.5 roads; the change of severity in multi-vehicle crashes was not statistically significant. Thirdly, driving speeds on S11.5 roads were approx. by 7 km/h higher compared to S9.5 roads. These findings support the hypothesis of an association between wider shoulders, higher speeds, and increased crash severity, especially in the case of single-vehicle crashes. As a practical solution, various speed management measures, including widening to a 2+1 road, may be recommended.


AASHTO (2010). Highway Safety Manual. First Edition. Washington: American Association of State Highway and Transportation Officials (AASHTO).

Ambros, J. (2011). Relationship between road width and safety. Young Researchers Seminar 2011, Copenhagen.

Ambros, J., Valentová, V., Gogolín, O., Andrášik, R., Kubeček, J., & Bíl, M. (2017). Improving the Self-Explaining Performance of Czech National Roads. Transportation Research Record, 2635, 62–70.

Ambros, J., Jurewicz, C., Turner, S., & Kieć, M. (2018). An international review of challenges and opportunities in development and use of crash prediction models. European Transport Research Review, 10, 35.

Ambros, J. (2019). Rešerše podkladů k porovnání kategorií dvoupruhových silnic S 9,5 a S 11,5. Unpublished contract report. Brno: CDV – Transport Research Centre.

Ambros, J., Altmann, J., Jurewicz, C., & Chevalier, A. (2019). Proactive assessment of road curve safety using floating car data: An exploratory study. Archives of Transport, 50(2), 7–15.

Ambros, J., Elgner, J., Turek, R., & Valentová, V. (2020). Where and when do drivers speed? A feasibility study of using probe vehicle data for speeding analysis. Archives of Transport, 53(1), 103–113.

Ambros, J., Jurewicz, C., Chevalier, A., & Valentová, V. (2021). Speed-Related Surrogate Measures of Road Safety Based on Floating Car Data. In Macioszek, E., & Sierpiński, G. (Eds.), Research Methods in Modern Urban Transportation Systems and Networks (pp. 129–144). Cham: Springer Nature Switzerland AG.

Andres, J., Mikulík, J., Frič, J., Kafoňková, J., Rücker, J., Motl, J., Kratochvílová, S., Tvarožková, L., Kaniová, K., Plánka, L., Krtička, M., Béreš, V., Zůvala, R., & Tecl, J. (2015). Hloubková analýza dopravních nehod. Brno: CDV – Transport Research Centre.

Babkov, V.F. (1975). Road conditions and traffic safety. Moscow: Mir.

Bassan, S., Zilbershtein, R., & Frischer, B. (2015). Country Report: Israel. 5th International Symposium on Highway Geometric Design, Vancouver.

Bucsuházy, K., Zůvala, R., Doecke, S., & Ambros, J. (2018). Investigation of precrash vehicle speed. Fourth International Conference on Traffic and Transport Engineering, Belgrade, 773–779.

Cafiso, S., D’Agostino, C., & Persaud, B. (2018). Investigating the influence of segmentation in estimating safety performance functions for roadway sections. Journal of Traffic and Transportation Engineering (English Edition), 5, 129–136.

Doecke, S.D., Baldock, M.R.J., Kloeden, C.N., & Dutschke, J.K. (2020). Impact speed and the risk of serious injury in vehicle crashes. Accident Analysis and Prevention, 144, 105629.

Elgner, J. Statistické analýzy – řidiči osobních vozidel. Ministry of Transport, Prague. Retrieved from on June 7, 2021.

Elvik, R., Høye, A., Vaa, T., & Sørensen, M. (2009). The Handbook of Road Safety Measures. Second Edition. Bingley: Emerald.

Fanning, R., Veith, G., Whitehead, M., & Aumann, P. (2016). Guide to Road Design Part 3: Geometric Design. Publication AGRD03-16. Sydney: Austroads.

Fitzharris, M., Lenné, M. G., Corben, B., Pok Arundell, T., Peiris, S., Liu, S., Stephens, A., Fitzgerald, M., Judson, R., Bowman, D., Gabler, C., Morris, A., & Tingvall, C. (2020). Enhanced Crash Investigation Study (ECIS) Re-port 1: Overview and Analysis of Crash Types, Injury Outcomes and Contributing Factors. Melbourne: Monash University.

Gaca, S., & Pogodzińska, S. (2017). Speed management as a measure to improve road safety on Polish regional roads. Archives of Transport, 43(3), 29–42.

Gårder, P. E. (2004). The impact of speed and other variables on pedestrian safety in Maine. Accident Analysis and Prevention, 36, 533–542.

Gatti, G., Polidori, C., Galvez, I., Mallschützke, K., Jorna, R., van de Leur, M., Dietze, M., Ebersbach, D., Lippold, C., Schlag, B., Weller, G., Wyczynski, A., Iman, F., & Aydin, C. (2007). Safety Handbook for Secondary Roads. RIPCORD-ISEREST project deliverable 13.

Geedipally, S.R., & Lord, D. (2010). Investigating the effect of modeling single-vehicle and multi-vehicle crashes separately on confidence intervals of Poisson-gamma models. Ac-cident Analysis and Prevention, 42, 1273–1282.

Ghadi, M., & Török, Á. (2019). Comparison of different road segmentation methods. Promet – Traffic & Transportation, 31, 163–172.

Gitelman, V., Pesahov, F., Carmel, R., & Bekhor, S. (2016). The identification of infrastructure characteristics influencing travel speeds on single-carriageway roads to promote self-explaining roads. Transportation Research Procedia, 14, 4160–4169.

Gitelman, V., Doveh, E., Carmel, R., & Hakkert, S. (2019). The influence of shoulder characteristics on the safety level of two-lane roads: A case-study. Accident Analysis and Prevention, 122, 108–118.

Gross, F., Jovanis, P. P., & Eccles, K. (2009). Safety Effectiveness of Lane and Shoulder Width Combinations on Rural, Two-Lane, Undivided Roads. Transportation Research Record, 2103, 42–49.

Gross, F., & Donnell, E.T. (2011). Case–control and cross-sectional methods for estimating crash modification factors: Comparisons from roadway lighting and lane and shoulder width safety effect studies. Journal of Safety Re-search, 42, 117–129.

Haghighi, N., Liu, X.C., Zhang, G., & Porter, R.J. (2018). Impact of roadway geometric features on crash severity on rural two-lane high-ways. Accident Analysis and Prevention, 111, 34–42.

Harwood, D.W., Hutton, J.M., Fees, C., Bauer, K.M., Glen, A., & Ouren, H. (2014). Evalua-tion of the 13 Controlling Criteria for Geometric Design. NCHRP Report 783. Washington: Transportation Research Board.

Hauer, E. (2000). Shoulder Width, Shoulder Paving and Safety. Retrieved from on September 13, 2007.

Hedman, K.O. (1990). Road design and safety. Proceedings of Strategic Highway Research Program and Traffic Safety on Two Continents, Gothenburg, 226–238.

Hermitte, T. (2017). Safety Cube scenarios – Single vehicle accident. Retrieved from on June 24, 2020.

Høye, A.K., & Hesjevoll, I. S. (2020). Traffic volume and crashes and how crash and road characteristics affect their relationship – A meta-analysis. Accident Analysis and Prevention, 145, 105668.

Hussain, Q., Feng, H., Grzebieta, R., Brijs, T., & Olivier, J. (2019). The relationship between impact speed and the probability of pedestrian fatality during a vehicle-pedestrian crash: A systematic review and meta-analysis. Accident Analysis and Prevention, 129, 241–249.

Ivan, J.N., Garrick, N.W., & Hanson, G. (2009). Designing Roads that Guide Drivers to Choose Safer Speeds. Report JHR 09-321. Storrs: University of Connecticut.

Jurewicz, C., Steinmetz, L., Phillips, C., Cairney, P., Veith, G., & McLean, J. (2014). Improving Roadside Safety: Summary Report. Publication AP-R437-14. Sydney: Austroads.

Jurewicz, C., Sobhani, A., Woolley, J., Dutschke, J., & Corben, B. (2016). Exploration of vehicle impact speed – injury severity relationships for application in safer road design. Transportation Research Procedia, 14, 4247–4256.

Kafoňková, J., & Andres, J. (2008). Nové poznatky v oblasti utváření bezpečných pozemních komunikací – silniční kategorie S 9,5 a S 11,5. Silniční obzor, 69, 290–292.

Kröyer, H.R.G. (2015). The relation between speed environment, age and injury outcome for bicyclists struck by a motorized vehicle – a comparison with pedestrians. Accident Analysis and Prevention, 76, 57–63.

Labi, S., Chen, S., Preckel, P.V., Qiao, Y., & Woldemariam, W. (2017). Rural two-lane highway shoulder and lane width policy evaluation using multiobjective optimization. Transportmetrica A, 13, 631–656.

Lamm, R., Psarianos, B., & Mailänder, T. (1999). Highway Design and Traffic Safety Engineering Handbook. New York: McGraw-Hill.

Lord, D., & Mannering, F. (2010). The statistical analysis of crash-frequency data: A review and assessment of methodological alternatives. Transportation Research Part A, 44, 291–305.

Martens, M., Comte, S., & Kaptein, N. (1997). The Effects of Road Design on Speed Behaviour: A Literature Review. MASTER project deliverable 2.

Martensen, H., & Dupont, E. (2013). Comparing single vehicle and multivehicle fatal road crashes: a joint analysis of road conditions, time variables and driver characteristics. Acci-dent Analysis and Prevention, 60, 466–471.

OECD (1999). Safety Strategies for Rural Roads. Paris: Organisation for Economic Cooperation and Development (OECD).

OECD (2006). Speed Management. Paris: OECD.

OECD (2018). Speed and Crash Risk. Paris: OECD.

Ogden, K.W. (1997). Safer Roads: A Guide to Road Safety Engineering. Aldershot: Ashgate.

Papadimitriou, E., Filtness, A., Theofilatos, A., Ziakopoulos, A., Quigley, C., & Yannis, G. (2019). Review and ranking of crash risk factors related to the road infrastructure. Accident Analysis and Prevention, 125, 85–97.

Pokorný, P., Jensen, J. K., Gross, F., & Pitera, K. (2020). Safety effects of traffic lane and shoulder widths on two-lane undivided rural roads: A matched case-control study from Norway. Accident Analysis and Prevention, 144, No. 105614.

Radimský, M., Matuszková, R., Smělý, M., Kosňovský, M., Čepil, J., & Hornoch, O. (2014). Metodika pro navrhování pozemních komunikací v uspořádání 2+1. Brno: Brno University of Technology.

Reed, S., & Morris, A. (2012). Characteristics of fatal single-vehicle crashes in Europe. Inter-national Journal of Crashworthiness, 17, 655–664.

Reurings, M., Janssen, T., Eenink, R., Elvik, R., Cardoso, J., & Stefan, C. (2005). Accident prediction models and road safety impact assessment: a state-of-the-art. RIPCORD-ISEREST project deliverable D2.1.

Ruyters, H.G.J.C.M., Slop, M., & Wegman, F.C.M. (Eds.) (1994). Safety effects of road design standards. Report R-94-7. Leidschendam: SWOV Institute for Road Safety Research.

Shinar, D. (2017). Traffic Safety and Human Behavior. Second Edition. Bingley: Emerald.

Stamatiadis, N., Pigman, J., Sacksteder, J., Ruff, W., & Lord, D. (2009). Impact of Shoulder Width and Median Width on Safety. NCHRP Report 633. Washington: Transportation Research Board.

TRB (2003). Application of European 2+1 Roadway Design. NCHRP Research Results Digest 275. Washington: TRB.

TRB (2011). Modeling Operating Speed: Synthesis Report. Transportation Research Circular E-C151. Washington: TRB.

ÚNMZ (2018). ČSN 73 6101 Projektování silnic a dálnic. Prague: Czech Office for Standards, Metrology and Testing (ÚNMZ).

Usami, D.S. (2017). Increase shoulder width. Retrieved from on March 25, 2020.

Wang, C., Quddus, M.A., & Ison, S.G. (2013). The effect of traffic and road characteristics on road safety: A review and future research direction. Safety Science, 57, 264–275.

Yannis, G., Dragomanovits, A., Laiou, A., La Torre, F., Domenichini, L., Richter, T., Ruhl, S., Graham, D., & Karathodorou, N. (2017). Road traffic accident prediction modelling: a literature review. Proceedings of the Institution of Civil Engineers – Transport, 170, 245–254.

Zegeer, C.V., & Perkins, D.D. (1980). Effect of Shoulder Width and Condition on Safety: A Critique of Current State of the Art. Transportation Research Record, 757, 25–34.

Zůvala, R., Bucsuházy, K., Valentová, V., & Frič, J. (2021). Representativeness of Czech In-Depth Accident Data. Safety, 7, 40.






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How to Cite

Ambros, J., Křivánková, Z., Zůvala, R., Bucsuházy, K., & Frič, J. (2021). Analysis of safety impact of paved shoulder width on Czech secondary roads. Archives of Transport, 60(4), 125-136.


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