Speed distribution on low volume roads in Italy: from inferences to rehabilitation design criteria

Low volume roads (LVRs) can be defined as facility lying outside of built-up areas and having a traffic volume of less than 400 AADT (average annual daily traffic). Although the lower use, related to their location, the low volume roads play an important social and economic role and sometimes represent a wide part of regional and national road network. Regarding their geometric and structural features usually they have not changed since their building, and an improvement according to the current design standard can be uneconomical because the needs are great and the funds insufficient. To this purpose less restrictive design criteria can be used. Design practises for low volume roads should be well addressed in respect to those of the high-volume roads. The current speed in low volume roads appears a crucial parameter in reconstruction/rehabilitation design. The present paper is focused on the analysis of the speed distribution in low volume roads in comparison to the design speed, in order to establish fitting design criteria in rehabilitation. To this purpose an experimental investigation was carried out in a low volume road sited in the Provincia of Reggio Calabria, southern Italy. The speed distribution was assessed in 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, speed distribution can be predicted based on geometric features. Further, based on operating speeds, it was possible to derive information possibly relevant in terms of rehabilitation design criteria.