Analysis of road safety: three levels of investigation

A survey for road safety must draw on a wide range of data, for the technician or researcher it is important to be able to access the databases organized and up to date. These data concern sure the incidents, the study area demographics, the current infrastructure data, traffic flows, but other data relate to different study problems. Without well organized bases the collection and analysis of data becomes an expensive phase that can and should be carried out, depending on the available resources, to a different levels of detail. Various levels of detail require the acquisition of different kinds of data. Their treatment may provide different indexes and accidents ratio that can bring different interpretations of the road accident phenomena: the interpretations are related to the consistency of the used data. The survey over a wide area can be carried out by three different levels of analysis. The first is a macroscopic level by aggregated data and with a minimal detail. A second level deepens the investigations that can cover those sub‐areas for which has been possible to detect presence of some accident phenomena. This more detailed investigation (meso-level) needs for focus gather further careful data, analysis and formulation of specific actions only for those safety situations that the second level has highlighted. For these situations, at end, it can upgrade to a more detailed level, and therefore more expensive. This level (micro level) can require a study of every single accident report in the area. The procedure is general and can be applied to the analysis of traffic safety on rural roads or on urban roads. In the work will be considered an example of safety analysis sequence for a town of small / medium size with the analysis and processing of technical steps that were valued necessary.