TITLE:
Incorporating the Multinomial Logistic Regression in Vehicle Crash Severity Modeling: A Detailed Overview
AUTHORS:
Azad Abdulhafedh
KEYWORDS:
Multinomial Logistic Regression, Odd Ratio, The Independence of Irrelevant Alternatives, The Hausman Specification Test, The Hosmer-Lemeshow Test, Pseudo R Squares, Crash Severity Models
JOURNAL NAME:
Journal of Transportation Technologies,
Vol.7 No.3,
July
4,
2017
ABSTRACT: Multinomial logistic regression (MNL) is an attractive statistical approach in modeling the vehicle crash severity as it does not require the assumption of normality, linearity, or homoscedasticity compared to other approaches, such as the discriminant analysis which requires these assumptions to be met. Moreover, it produces sound estimates by changing the probability range between 0.0 and 1.0 to log odds ranging from negative infinity to positive infinity, as it applies transformation of the dependent variable to a continuous variable. The estimates are asymptotically consistent with the requirements of the nonlinear regression process. The results of MNL can be interpreted by both the regression coefficient estimates and/or the odd ratios (the exponentiated coefficients) as well. In addition, the MNL can be used to improve the fitted model by comparing the full model that includes all predictors to a chosen restricted model by excluding the non-significant predictors. As such, this paper presents a detailed step by step overview of incorporating the MNL in crash severity modeling, using vehicle crash data of the Interstate I70 in the State of Missouri, USA for the years (2013-2015).