Experimental Analysis on Hairpin Curves


  • Paolo Discetti Dept of Transportation Engineering “Luigi Tocchetti”, University of Naples “Federico II”, Via Claudio 21, I-80125 Naples, Italy




operating speed, driver behavior, mountain roads


The consistency of a highway alignment refers to the conformity of its geometry to driver expectancy and to the improvement of the design consistency and consequently it is necessary to know real speed behavior in order to calculate highway safety. The disparity between design and operating speeds has been shown, in fact several different studies were undertaken to predict the operating speed in different conditions as a function of the alignment features: horizontal and vertical curves, combinations of tangent sections of horizontal and vertical curves; sections prior to or following horizontal curves. In literature however, no studies speak of the operating speed on hairpin curves of mountain roads where driver behavior is influenced by the combination of small radius curves, limited sight distance and the approach to the slope of a tangent. Therefore, a mathematical model was developed specifically for mountain roads using speed data collected on hairpin curve and tangent approaches. The experimental study was carried out using traffic counters capable of recording the following variables during the passage of each vehicle in both directions: vehicle length, instant speed and direction. Video cameras were also used. In this paper the author also investigated the real speed driver behavior by analyzing deceleration and acceleration rates. These rates were calculated for each vehicle and then the 85th percentile of the rate distribution was also calculated. With the availability of acceleration and deceleration rates that respect real driver behavior, it is possible to analyze the defects of existing mountain roads and to evaluate corrective measures that can be implemented.


Babkov, V.; Zamkhayev, M. 1967. Highway Engineering. Moscow: Mir. 535 p. ASIN B0006BT4TQ.

Discetti, P.; Dell’Acqua, G. 2008. Infl uence of Sight Distance on Driver Speed Behavior for Low Volume Roads (08-1519) [CD-ROM], in Transportation Research Board 87th Annual Meeting, compendium of papers, January 13–17, 2008, Washington DC, USA. 13 p.

Dragčević, V.; Korlaet, Z.; Stančerić, I. 2008. Methods for Setting Movement Trajectories, The Baltic Journal of Road and Bridge Engineering 3(2): 57‒64. doi:10.3846/1822-427X.2008.3.57-64

Fitzpatrick, K.; Elefteriadou, L.; Harwood, D.; Collins, J.; McFadden, J.; Anderson, I.; Krammes, R.; Irizarry, N.; Parma, K.; Bauer, K.; Passetti, K. 2000. Speed Prediction for Two-Lane Rural Highways. Report No. FHWA-RD-99-171, Federal Highway Administration.

Lamm, R.; Choueiri, E. M.; Hayward, J. C.; Paluri, A. 1988. Possible Design Procedure to Promote Design Consistency in Highway Geometric Design on Two-Lane Rural Roads, Transportation Research Record 1195: 111–122.

Li, Y.; Zhu, F.; Ai, Y.; Wang, F.-Y. 2007. On Automatic and Dynamic Camera Calibration Based on Traffic Visual Surveillance, in Proc of the IEEE Intelligent Vehicles Symposium. June 13–15, 2007 Istanbul, Turkey. Istanbul, 358–363.

Kanhere, N. K.; Birchfield, S. T.; Sarasua, W. A. 2008. Automatic Camera Calibration Using Pattern Detection for Vision-Based Speed Sensing, Transportation Research Record 2086: 30–39. doi:10.3141/2086-04

Kanhere, N. K.; Birchfi eld, S. T.; Sarasua, W. A.; Whitney, T. C. 2007. Real-Time Detection and Tracking of Vehicle Base Fronts for Measuring Traffic Counts and Speeds on Highways, Transportation Research Record 1993: 155–164. doi:10.3141/1993-21

Krammes, R. A.; Brakett, R. Q.; Shaffer, M. A.; Ottesen, J. L.; Anderson, I. B.; Fink, K. L.; Collins, K. M.; Pendleton, O. J.; Messer, C. J. 1995. Horizontal Alignment Design Consistency for Two-Lane Highways. Report No. FHWA-RD-94-034, Federal Highway Administration.

Misaghi, P.; Hassan, Y. 2005. Modeling Operating Speed and Speed Diff erential on Two-Lane Rural Roads, Journal of Transportation Engineering 31(6): 408–418. doi:10.1061/(ASCE)0733-947X(2005)131:6(408)

Nie, B.; Hassan, Y. 2007. Modeling Driver Speed Behavior on Horizontal Curves of Diff erent Road Classifi cations (07-0782) [CD-ROM], in Transportation Research Board 86th Annual Meeting, compendium of papers, January 21–25, 2007, Washington DC, USA. 16 p.

Oke, S. A.; Bamigbaiye, A.; Oyedokun, O. I.; Charles-Owaba, O. E. 2006. A Mathematical Model to Set Speed Limits for Vehicles on the Highway, Transport 21(4): 278–283.

Ratkevičiūtė, K.; Čygas, D.; Laurinavičius, A.; Mačiulis, A. 2007. Analysis and Evaluation of the Efficiency of Road Safety Measures Applied to Lithuanian Roads, The Baltic Journal of Road and Bridge Engineering 2(2): 81–87.

Taylor, M. A. P.; Young, W.; Thompson, R. G. 1989. Headway and Speed Data Acquisition Using Video, Transportation Research Record 1225: 130–139.

Vorobjovas, V.; Žilionienė, D. 2008. Evaluation of Shoulders Functions on Lithuanian Regional Roads, The Baltic Journal of Road and Bridge Engineering 3(4): 213–218. doi:10.3846/1822-427X.2008.3.213-218




How to Cite

Discetti, P. (2010). Experimental Analysis on Hairpin Curves. The Baltic Journal of Road and Bridge Engineering, 5(3), 148-155. https://doi.org/10.3846/bjrbe.2010.21