Speed Factors on Low-Volume Roads for Horizontal Curves and Tangents

Gianluca Dell'Acqua,Francesca Russo

doi:10.3846/bjrbe.2010.13

Abstract

Many studies on driver speed behavior are found in the scientific literature today, and various researchers have addressed roadway alignment consistency for travel safety in context with current operating speeds. Experimental analysis was conducted on low-volume roads in Southern Italy without spiral transition curves between geometric tangent and circular elements on the horizontal alignment. All selected roads are located in areas with level terrain and vertical grades less than 6%. This study will illustrate a methodology, widely employed in the literature, to evaluate at each circular curve transition segment length, the applicable deceleration and acceleration rates. These results were then used to develop four equations for speed prediction models on tangents and curves. These regression equations were developed using a traditional Ordinary-least-squares method involving speed values not surveyed in transition zones. The goal of this research study is to plot continuous speed profiles to illustrate complete driver speed behavior on twolane rural roads and to individualize critical roadway sections to improve driver safety.

Highlights

Many studies in the scientific literature dealt with roadway safety to evaluate how the human, infrastructural and environmental factors can influence an unexpected event
The study of driver speed behavior on two-lane rural roads was divided into two phases for the purposes of this study: the first phase dealt with the identification of transition zones and the estimation of deceleration/acceleration rates at each circular element, while the second one dealt with the calibration and validation of operating speed prediction models on tangents and curves to trace a complete operating speed profile
The study of transitions relied on a methodology based on the operating speed profiles

Summary

Introduction

Many studies in the scientific literature dealt with roadway safety to evaluate how the human, infrastructural and environmental factors can influence an unexpected event. Some researchers have shown how the collisions tend to occur disproportionately at certain roadway segments (Gibreel et al 1999). This implies that in addition to driver error, road characteristics play a major role in collision occurrence. The crashes were defined in the literature as the result of bad decisions by the driver made in an environment created by the engineer. The road traffic safety has thence become a priority field worldwide and one of the major factors describing the transport system’s state with its positive and negative changes (Ratkevičiūtė et al 2007)

Methods

Results

Conclusion