An Italian experience on crash modeling for roundabouts

In the last few years a considerable amount of safety models and evaluation tasks have been developed and specifically dedicated to roundabouts. Several safety performance functions (SPFs), indeed, have been implemented for roundabouts worldwide. Since SPFs are developed using crashes, traffic volume and other characteristics of a specific site (or geographical area), their direct transferability to other contexts different from those in which SPFs were calibrated is not always possible and, in any case, it must be done very carefully. A safety performance function cannot be used without a transferability evaluation for sites not included in the geographic area for which it was developed. Starting from these considerations, this paper aims to calibrate a safety performance function for urban roundabouts in Italian context, expanding a sample data already used in a previous work by Giuffrè et al. (2007); this SPF is then compared with other safety performance functions found in literature, testing the transferability