Analysis of Rain-Related Crash Risk on Freeway Pavements in Porous and Dense Asphalt

The present paper analyses the correlation between the number of crashes on freeways and weather conditions on dense asphalt and porous asphalt before and after road modernization operations. Data was collected on 43km of the A3 freeway located in Southern Italy from the road interchange of Tarsia to the road interchange of South Cosenza. Crash data were made available by the Police Station of North Cosenza, with traffic data from the ANAS Compartment in Cosenza, and the rainfall measurements were provided by the ARPACAL centre in Calabria. Data were collected for two periods: before the modernization operations with existing dense asphalt and after modernization using porous asphalt. Porous pavement system is a structural and environmental mindful alternative to a traditional pavement system. Safety analyses were carried out correlating the number of crashes to the rainfall detected using two rain gauges, and the traffic data. The results show a considerable dependence of crash frequency on the intensity of rainfall, both in the presence of porous and dense asphalt. In the first case, the accident rate increases to a rainfall of 0.5 mm/h, and then decreases due to probable greater prudence adopted by drivers in adverse meteorological events. The use of porous asphalt allows a reduction in the accident rate both in adverse meteorological conditions and for light rain, and confirmed that, in terms of risk, the psychological effect on drivers increases with the amount of rain on the road rather than a reduction of adherence on a wet road surface.