For the first time, Istat makes available data on length of Italian roads by type and province, downloaded from the Open Street Map website, and proposes the calculation of new indicators on road accidents.The focus, in fact, is on the exploitation of existing administrative sources, the scouting of new sources and the analysis of integrated and auxiliary data. The first release refers to 2016.
Nowadays there is a clear information bias as regards the appropriate reference denominators to be placed as basis in construction of statistical indicators linked to road accidents. Resident population is used as a common proxy for exposed at risk in a specific geographical area, but not always an appropriate solution, especially in the light of the seasonal nature of road accidents and concentration, in some periods of the year, in specific locations. Vehicle fleet can be another administrative source that gives a more accurate information, but the characteristic of the phenomenon implies a deductible distortion on measures due to the mobility of road users.
The length of the road network (from Open Street Map) gives for sure a consistent first set of information concerning the different territories. This information is not available from official statistics at national level, although there are archives and detailed road graphs for each municipality, province and region, a harmonized and systematic national road registry has not yet been established.
For the construction of indicators on road accidents, it was necessary to recode the road type classification provided by Open Street Map with the grouping used by ISTAT for the survey of road accidents. For this purpose, the Census Map localities shapes referred to 2011 and the classification of municipalities 2016 have been used.
An upgrade of Census Map localities shapes referred to 2011 to municipalities 2016 was done. The aim was to build a link table with the aggregation of all 8090 local administrative units territory, at 2011, to the 7998 municipalities at 2016, included in the Italian territory.
To build and process synthetic indicators on the dimensions taken into consideration, two standard tools developed in Istat were used: RankerTool desktop and i.Ranker web application. The Ranker tool used provides the possibility of choosing different methods. For the selection of the method to be used, a robustness test and an influence analysis have been carried out by applying the COMIC software (COMposite Indices Creator) for the construction of composite indexes.
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