How Expressway Geometry Factors Contribute to Accident Occurrence? A Binary Logistic Regression Study

Abstract

Logistic regression and statistical method are combined to analyze accident data from “Traffic Accident Database System” (TADS) in order to find the relationship between expressway geometric factors and accident rate. A total of 2004 observations are used to illustrate the proposed model. A new concept mean angle of deflection (MAD) is also introduced to evaluate the effect of horizontal alignment. Accident rate (the dependent variable) in this study is a dichotomous variable, so a binary logistic regression is found suitable. Totally sixteen variables are proposed and fourteen are used in the model. Eight variables are found significantly associated with accident rate at the 0.05 significance. Each variable is interpreted with the results of SPSS 19.0 and the results provide the references for identifying unsafe locations and taking appropriate counteractive measures for expressways in mountainous areas.