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Analysis of criticalities and trends
Time series of road accidents in Piedmont allow identifying and analysing rural road segments which require a primary focus and which show interesting trends.
Road segments which below are identified as critical are those which show the co-presence of two features: a high number of accidents and the persistence of this feature over time.
In order to measure the level of criticality of each segment the two just mentioned features have been measured by the means of an index, labelled "criticality index", computed as the product between the number of accidents happened outside urban areas on the segment in the last available years (2004 and 2006) and its autocorrelation coefficient with a unitary lag (computed over the entire period 1991-2004 and 1991-2006). A further description of the computation underlying the criticality index is available.
The analysis about criticality has thus been made referring to two moments in time and it is thus possible to acces the pages about the analysis in 2004, in 2006 and in 2007. Each page allows accessing three kinds of data plot in three maps the description of which follows below.
The first map ("Criticality") of the chart below presents the first 90 road segments in Piedmont ranked according to their criticality: in other words they are those with highest values of the criticality index then further categorised in three classes of thirty cases, from the ones with higher criticality (the first thirty, labelled "alta") to the intermediate ones (from position 31 to 60, labelled "media") and to lower ones (from 61 to 90, labelled "bassa"). Besides graphic visualisation, it is possible to download the list of road segments by level of criticality ordered by province in 2004, 2006 and 2007 (.csv file).
The second map ("Criticality index") presents the value of the criticality index of each rural road segment in Piedmont for which it is possible to compute the index. The data is provided in order to allow checking and comparing different road segments.
Finally, in the third map ("Acc. difference 2004-2003 and Acc. difference 2006-2005") of the graph is represented the trend of the number of accidents in the last two available years (2004 and 2003, 2006 and 2005): a negative value (road segments coloured in green) means a decrease in the number of accidents, and viceversa for a positive value (red colour).
