The publication of the Highway Safety Manual (HSM) in 2010 established crash frequency prediction as the essential safety measure for safety studies. However, given that the models were developed using a single state’s data, the HSM recommends calibration of the prediction models using data from the jurisdiction where they will be applied. This calibration process has been conducted in several states and many questions have been raised as a result. This paper is intended to investigate different definitions and criteria for the calibration factors, and provide recommendations for practitioners on which definition to use. In addition to the calibration factors in the HSM and previously published definitions, two other calibration factor equations are proposed and compared using multiple goodness of fit measures. Whereas each definition may outperform others in certain measures, in this study, it is recommended to use the definition that maximizes the likelihood between predicted and observed crashes. The idea is to follow the same concept in both state-specific safety performance functions development and calibration process, which is maximizing the likelihood of predicted and observed crashes.
Highway Safety Manual Calibration: Assessing Alternate Definitions of the Calibration Factor
Transportation Research Record: Journal of the Transportation Research Board
Transportation Research Record: Journal of the Transportation Research Board ; 2672 , 30 ; 99-108
2018-07-07
Article (Journal)
Electronic Resource
English
Calibration of Highway Safety Manual Safety Performance Function
Transportation Research Record | 2012
|Highway Safety Manual Calibration: Estimating the Minimum Required Sample Size
Transportation Research Record | 2021
|Calibration of Highway Safety Manual Predictive Models for Oregon State Highways
Online Contents | 2011
|Calibration of Highway Safety Manual Predictive Models for Oregon State Highways
Transportation Research Record | 2011
|