Thomas ECHAVEGUREN
Associate professor
Department of Civil Engineering - Faculty of Engineering
University of Concepcion, Chile

Sergio Vargas-TEJEDA
Assistant teacher
Department of Civil and Environmental Engineering - Faculty of Engineering
University of Bio Bio (Concepción, Chile)

ABSTRACT
The geometric design of horizontal curves has traditionally been performed on the model of point mass in most design regulations. However, one wonders whether the traditional design approach contributes to road safety.

Research conducted in Australia, the US and Chile, have shown that in road designs roads with average and low categories the speed of operation exceeds the speed of design in horizontal curves. Given this fact, the question of what is the real safety margin offered by the design of the curve and how it is possible to estimate arises.

In this paper the authors propose a new design approach based on the model of 3 areas, which integrates concepts of friction demand, design friction, real-pavement friction and friction thresholds in the design of horizontal curves.

This integration is performed under a probabilistic based on the reliability theory, to estimate the safety margin offered by various designs approach, recognizing that the speed of operation and the friction are random variables, so that the concept of factor expands security traditionally used in engineering.

In the article the concepts of reliability and how they are applied in the model 3 areas are developed. It is obtained from simulation relations between geometry and the design point that maximizes reliability thereof. Finally, an application is made to illustrate the method developed, constituting an alternative to traditional design methods that delivers more conceptual elements that foster a better design analysis.

KEYWORDS
Road safety, Friction, Friction, Model 3 zones, speed, horizontal curve, Reliability, Design.