Calibration of the Highway Safety Manual and the SafetyAnalyst Methodologies for Ontario Highways

Abstract

SafetyAnalyst and the Highway Safety Manual (HSM) are two tools that are expected to revolutionize highway safety analyses. A key issue that allows SafetyAnalyst and HSM to become the new standards in road safety engineering is the calibration of their safety performance functions (SPFs) across time and jurisdictions. In this study, the methodologies of SafetyAnalyst and HSM are calibrated for Ontario to evaluate the effective transferability of their SPFs to local topographical conditions. A SafetyAnalyst calibration has been completed for Ontario highways and freeways, intersections, and ramps for six years (1998-2003) of traffic and accident counts. A data set which consists of 78 kilometres of rural two-lane two-way highways and 71 three- and four-legged stop controlled intersections located in the eastern and central regions of the Ministry of Transportation of Ontario (MTO) with six years (2002 to 2007) of traffic volume and collision counts has been used to evaluate the HSM SPFs to Ontario data. Several goodness-of-fit (GOF) measures are computed to assess the transferability and suitability of the crash models for applicability in Ontario. The study suggests that while most of the SafetyAnalyst SPFs for highways and ramps are not adaptable to Ontario data, the recalibrated SafetyAnalyst SPFs for intersections and also the recalibrated HSM Part C predictive models for two-lane rural highways and intersections provide satisfactory results in comparison to the crash models developed specifically for Ontario. Finally, this research highlights the substantial need for future improvements in data quality for more reliable safety performance estimations and evaluations.