Road Accident Location Methodology
The “Location of accidents” section in ISTAT website is dedicated to road accidents which occurred on primary road networks only, namely highways, main ring roads, tunnels, roads of national interest, and Regional and Provincial roads.
In consulting the charts, it must be borne in mind that the accuracy in filling the forms may affect data mapping. Therefore, differences from year to year on a specific road should be carefully evaluated. Moreover, correctly identifying a road is often difficult, especially in built-up areas, where the name of national roads may change and for new roads.
The website section does not take into account the stretches of roads running through towns with more than 10,000 inhabitants, as these stretches belongs to Municipalities, according to the Highway Code. Considering that it may be difficult to clearly identify whether a stretch of road belongs to a Municipality or to another authority, exactness on the part of the data collector in correctly classifying a road is essential for data accuracy and in order to be able to draw space-time comparison.
For each kilometre of each road, data on number of accidents, fatal accidents, killed and injured occurred in reference year and in the two preceding years are provided.
Data can be consulted at the national level, by Region, Province and, for each road, by kilometre. More detailed data are also available on charts which show the type of accidents and the involvement of commercial/heavy good vehicles – which often cause the crash to be more serious – or of two-wheel vehicles – often suffering the most severe consequences.
In addition, for each road and only by Province, charts provide univariate distribution of accidents according to the following variables: municipality, month, day of week, time, type of accident location.
For each Province, a thematic map shows the number of accidents that have been located.
In 2017, 78,8% of crashes have been correctly located – with the exact identification of road and kilometre – resulting in 85,1% of fatalities.
The percentage of correct locations varies considerably according to road categories and, within the same category, according to roads.
Occasionally, there is a clash between the road where the accident occurred and the province where the accident was reported. In these cases, in the absence of precise information, the accidents are classified as “unspecified” and, though being counted once only, they are linked both to the road and the Province – and, of course, to the relevant Region.
The following indicators are also calculated:
• accident DENSITY= accidents / length of selected road
• mortality index = (fatalities / accidents) * 100
• severity index = [fatalities / (fatalities + injured)] * 100
• accident risk, i.e. the ratio of accidents per kilometre in different geographical areas
• mortality risk, i.e. the comparison of mortality indexes in different geographical areas.