Calibration of the Highway Safety Manual's Accident Prediction Model for Italian Secondary Road Network

Abstract

The forthcoming first edition of the Highway Safety Manual (HSM) will introduce safety predictive models both for road segments and intersections. A key issue for allowing 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 calibration procedure of the HSM model to different countries has been evaluated, with all practical and potential application problems outlined. In this study, the calibration procedure of the HSM model has been applied to the road network of the Italian province of Arezzo to evaluate the effective transferability of this methodology to a region characterized by a different environment and different road characteristics, driver behavior, and crash reporting systems than those on which the HSM models have been developed. The considered road network covers 1,300 km of rural two-lane highways located in the Arezzo province, and a 3-year (2002–2004) accident database has been used. The considerable difference between the road network of the Italian province of Arezzo and the one of Minnesota, for which the HSM model has been developed, causes practical application problems, mainly related to segmentation and over-estimation of curvature effects, which are discussed in the paper. Four approaches to define the calibration factor have been applied and discussed to determine the most effective one. Finally, this work points out the problems related to the identification of data needs and necessary treatments for the HSM model calibration and application.

Integrated American-European protocol for safety interventions on existing two-lane rural roads

“…In particular, the HSM predictive method was assumed as a benchmark by several studies, which calibrated it for different areas [42][43][44][45][46][47][48]. Some of them clearly concluded that locally-derived functions fits better data than the calibration of other functions.…”

Updating the Crash Modification Factors and Calibrating the IHSDM for Indiana

“…Finally, other researchers have examined the applicability of the IHSDM within and outside of the US, as well as its calibration scope (Bansen & Passetti, 2005; Dominguez-Lira, Castro, Pardillo-Mayora, & Gascó n-Varó n, 2010; Donnell, Gross, Stodart, & Opiela, 2009;Koorey, 2010;Marchionna, Perco, & Falconetti, 2012;Martinelli, La Torre, & Vadi, 2009). Donnell et al (2009) provided recommendations on the need to expand the capabilities of the IHSDM's design consistency module to consider low-speed, complex alignments.…”

Assessing the transferability of crash prediction models for two lane highways in Brazil

“…However, the most demanding and challenging part of this effort has been linked to data collection, especially in intersections, due to its complexity. Another point to be highlighted is the fact that several studies began investigating two lane highways, because their importance in rural areas (Banihashemi, 2011;Barber, 2014;Koorey, 2010;Lubliner, 2011;Martinelli et al, 2009;Metha & Lou, 2013;Saito et al, 2011;Silva, 2012;Srinivasan et al, 2011;Sun et al, 2006;Williamson & Zhou, 2012;Xie et al, 2011). A synthesis of the current situation in two lane highways segments is shown in the Table 2.1.…”

“…Also, the calibration procedure was evaluated in Italy. It has been applied to highways in Arezzo and some potential problems related to transferability of this methodology were outlined (Martinelli, La Torre, & Vadi, 2009 …”