Road performance evaluation using geometric consistency and pavement distress data

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 the context of current operating speeds. An experimental analysis of low-volume roads without spiral transition curves between geometric tangent and circular elements on the horizontal alignment was conducted in southern Italy. All selected roadways are located in areas with level terrain and vertical grades of less than 6%. This study is a continuation of a 2009 research project that developed procedures to predict speed factors for horizontal curves and tangents on low-volume roads. The present research focuses on the design of continuous operating speed profiles that reproduce real driver speed behavior at each section of the horizontal alignment with variables that now include the pavement deterioration condition. Four new regression equations were developed to predict the operating speed on tangent and circular curve elements by using speed factors and geometric variables. These models were developed by a traditional ordinary least-squares method involving speed values not surveyed in transition zones. The aim of this refined study is to illustrate the roadway factors influencing optimal and safe driving performance.