The upcoming first edition of Highway Safety Manual (HSM) will introduce safety predictive models both for road segments and intersections. A key issue to allows HSM to become a standard for road owners and managers worldwide is the transferability of the predictive models to different networks. The application of the HSM model calibration procedure to different countries has to be evaluated outlining all the practical and potential application problems. In this study the HSM model calibration procedure has been applied to the Arezzo province road network in order to evaluate the effective transferability of this methodology to a region characterized by a different environment, road characteristics, driver behavior and crash reporting systems as compared to the ones on which the HSM models have been developed. The considered road network is composed by 1?300 kilometers of rural two-lane highways located in the Arezzo province and a three years (2002-2004) accident database has been used. The strong difference between the Arezzo province region and Minnesota, for which HSM model have been developed, causes practical application problems, mainly related to segmentation and overestimation of curvature effects, that be discussed in the paper. Four different approaches to fix the calibration factor have been applied and discussed to understand which is the most effective one. Finally this work points out problems related to the identification of data needs and necessary treatments for the HSM model calibration and application.
Samenvatting