Friction Reliability Criteria Applied to Horizontal Curve Design of Low-Volume Roads

Abstract

Design of road horizontal curves usually considers geometric characteristics and surface pavement condition by means of friction, superelevation, and speed equations in a deterministic point of view: a unique radius and superelevation are selected, considering a uniform behavior of drivers and pavement surface condition. However, empirical evidence shows that operating speed usually exceeds design speed when design speed is lower than 100 km/h. This means that the aggregated friction demand exceeds the design friction. The friction threshold and variability are not considered in design at the present time. Therefore, the designer does not know the remaining friction available and cannot estimate the margin of safety provided by the design. This problem is important in low-volume roads (LVRs) because the design speed usually considered is lower than 100 km/h. In this paper a methodology to design horizontal curves for LVRs is proposed, considering the variability of skid resistance, pavement texture, driver behavior, and geometric design elements. Critical speed is obtained for two conditions: consistency between design and operational conditions and consistency between friction thresholds considered for the pavement surface and operational condition. For this purpose, a reliability index is estimated by using the Hasofer–Lind method. Results show that a more realistic design is obtained when an aggregated friction demand based on driver behavior is considered. A good design is obtained when design speed ranges around 60 km/h and the standard deviation of curve radius is lower than 20% of the mean radius.

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References

Kanellaidis

Aspects of Highway Superelevation Design. Journal of Transportation Engineering, Vol. 117, No. 6, Nov.–Dec. 1991, pp. 624–631.

Krammes

R.A.

Design Speed and Operating Speed in Rural Highway Alignment Design. In Transportation Research Record: Journal of the Transportation Research Board, No. 1701, TRB, National Research Council, Washington, D.C., 2000, pp. 68–75.

Echaveguren

, and Saez

Estudio de Relaciones Velocidad–Geometría Horizontal en Vías de la VIII Región. Proc., 10th Chilean Congress of Transportation Engineering, Concepción, Chile, 2001, pp. 341–350.

McLean

Speeds, Friction Factors, and Alignment Design Standards. Research Report ARR 154. Australian Road Research Board, Vermont South, Australia, Sept. 1988.

Kanellaidis

, Golias

, and Efstathiadis

Drivers' Speed Behavior on Rural Road Curve. Traffic Engineering and Control, Vol. 31, No. 4, July 1990, pp. 414–415.

McLean

An Alternative to the Design Speed Concept for Low Speed Alinement Design. In Transportation Research Record 702, TRB, National Research Council, Washington, D.C., 1979, pp. 55–63.

Echaveguren

, Bustos

, and de Solminihac

Assessment of Horizontal Curves of an Existing Road Using Reliability Concepts. Canadian Journal of Civil Engineering, Vol. 32, No. 6, Dec. 2005, pp. 1030–1038.

Navin

F.P.D.

Safety Factors for Road Design: Can They Be Estimated? In Transportation Research Record 1280, TRB, National Research Council, Washington, D.C., 1990, pp. 181–189.

Rich

, and Stayed

Evaluating the Safety Risk of Narrow Medians Using Reliability Analysis. Journal of Transportation Engineering, Vol. 132, No. 5, May 2006, pp. 366–375.

10.

A Policy on Geometric Design of Highways and Streets. AASHTO, Washington, D.C., 2004.

11.

Bonneson

J.A.

NCHRP Report 439: Superelevation Distribution Methods and Transition Designs. TRB, National Research Council, Washington, D.C., 2000.

12.

Manual de Carreteras. Volume 3, Part I: Instrucciones y Criterios de Diseño. National Roads Administration, Ministry of Public Works, Santiago, Chile, 2002.

13.

Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400). AASHTO, Washington, D.C., 2001.

14.

Lewis

E.E.

Introduction to Reliability Engineering. Wiley, New York, 1987.

15.

Haldar

, and Mahadevan

Probability, Reliability and Statistical Methods in Engineering Design. Wiley, New York, 2000.

16.

Faber

M.H.

Risk and Safety in Civil Engineering. Swiss Federal Institute of Technology, Zurich, Switzerland, 2003.

17.

Van Gelder

, and de Wit

Structural Reliability Analysis. TU Delf University, Netherlands, 2003.

18.

Hasofer

A.M.

, and Lind

N.C.

An Exact and Invariant First Order Reliability Format. ASCE Journal of Engineering Mechanics, Vol. 100, Feb. 1974, pp. 111–121.

19.

Skidding Resistance. In Design Manual for Roads and Bridges, Volume 7: Pavement Design and Maintenance. HD 28/04. Highways Agency, London, 2004.

20.

De Solminihac

, Bustos

, Echaveguren

, and Caroca

Ecuaciones de Correlación de la Medida de Resistencia al Deslizamiento Entre Griptester y Péndulo Británico. Revista Ingeniería de Construcción, Vol. 19, No. 2, Aug. 2004, pp. 75–82.

21.

Echaveguren

, and Basualto

Análisis de Aceleraciones en la Consistencia de Elementos Simples de Alineamientos Horizontales. Proc., 11th Chilean Congress of Transportation Engineering, Concepción, Chile, 2003, pp. 391–402.