Analysis of Horizontal Curves Operating Speed Models for Italian Two Lane Rural Roads

The scientific literature shows the existence of many studies about influences of road features on driver behaviour. Most of researchers focused their attention on the building of mathematical models that should be able to link driving behaviour and road characteristics. Several international research works show that operating speed is an excellent driver behaviour parameter. The road characteristics are represented by curvature change rate of the single curve (CCRs) or by circular curve radius (R). In Italy two-lane rural roads can be divided into two main categories: roads built before and after 2001. The main difference between these two types is that the roads built before 2001 did not include transition curves. A previous statistical analysis (that was carried out at the University of Cagliari, Italy) had demonstrated that the existing international models are representative of driving behaviour on the Italian roads built before 2001; but none of them is applicable to the roads that were built after 2001. For this reason it was decided to proceed with the construction, on the basis of speed data collected, of new models of driving behaviour in Italy. The work is divided into four main steps: 1. construction of a model for roads built before 2001 (although some of the existing ones are applicable to Italian two-lane rural roads, it was decided to construct an ad hoc model because of the close correlation between the model itself and the context in which it has been created); 2. construction of a valid model for the Italian roads built after 2001 (because none of the existing ones is applicable to this type of road); 3. construction of a valid model for both types of roads (roads built before and after 2001); 4. in the conclusions, comparison between the obtained results and some existing international models.