ROAD SAFETY ANALYSIS USING ITALIAN GUIDELINES

Safe road design is about providing a road environment which ensures vehicle speeds will be within the human tolerances for serious injury and death wherever conflict points exist. International researchers have thus suggested a variety of approaches to analyze the road traffic safety level as some procedures based on the valuation of the accident rates and accident frequency. The research described in this paper aims to illustrate a network safety approach as suggested by Italian Guidelines in order to identify homogeneous roadway segments where the crash rate (crash frequency over traffic exposure) is higher or lower than on statistically significant thresholds referred to the whole analyzed road path. Three different road safety thresholds are suggested: a) low when the crash rate is of less than lower limit, b) moderate when the crash rate falls between upper and lower limits, c) severe when the crash rate is greater than the upper limit. It’s suggested an additional careful study on the road segments with high crash rate making a comparison between existing and potential infrastructural-geometric-environmental failures to determine potential countermeasures. The study presented here involved a rural road in Southern Italy located on flat/rolling area with a vertical grade of less than 6%, without spiral transition curves between geometric tangent and circular elements, which is provided with controlled access or rather road interchanges and 11 km almost of slow lane for both travel directions. The data set used for this study includes crashes from 2003 through 2010; in particular 301 crashes were observed with 444 injuries and 41 deaths over the total length of the 71.92 km. Analysis showed that homogeneous road segments with high crash rates occurred in 16% of cases, while with medium crash rates in 38% of cases and low crash rates in 46% of cases.