Benefits of small municipalities using jurisdiction-specific safety performance functions rather than the Highway Safety Manual's calibrated or uncalibrated safety performance functions

Abstract

This study compares the performance of uncalibrated and calibrated Highway Safety Manual (HSM) safety performance functions (SPFs) with jurisdiction-specific SPFs. The first edition of the HSM includes a number of SPFs which can be used to identify collision-prone locations on a roadway network. The HSM recommends that these SPFs be calibrated to more accurately reflect a specific jurisdiction's unique roadway characteristics, driver behaviour, etc. and to produce better-fitting results. An alternative approach is the creation of jurisdiction-specific SPFs. This study used negative binomial regression and 5 years of collision data (2005–2009) from the City of Regina, Saskatchewan to develop a set of SPFs. Three intersection categories were investigated: 3-leg unsignalized, 4-leg unsignalized, and 3- and 4-leg signalized. The SPFs provided in the HSM were calibrated using the Regina data, and a set of calibration factors was produced. To compare the different SPFs and find the best-fitting SPFs for the stu...