Speed Distribution on Low-Volume Roads in Italy

Abstract

Low-volume roads can be defined as facilities outside built-up areas with a traffic volume of less than 400 annual average daily traffic. Although of lower use because of their location, low-volume roads play an important social and economic role and sometimes represent a large part of the regional and national road network. Regarding their geometric and structural features, they usually have not changed since they were built, and improvement according to current design standards can be uneconomical because the needs are great and the funds insufficient. To this purpose, less restrictive design criteria can be used. Design practices for low-volume roads should be as well addressed as those for high-volume roads. The current speed on low-volume roads appears to be a crucial parameter in reconstruction or rehabilitation design. The present study is focused on analysis of the speed distribution on low-volume roads in comparison with the design speed in order to establish fitting design criteria in rehabilitation. An experimental investigation was carried out on a low-volume road in the province of Reggio Calabria, in southern Italy. The speed distribution was assessed for different conditions of horizontal and vertical alignment in order to understand and possibly quantify the influence of road geometric features. Results demonstrated that under specific conditions, the speed distribution can be predicted on the basis of geometric features. Further, on the basis of operating speed, it was possible to derive information that could be relevant in terms of rehabilitation design criteria.