Analysis of Crashes Occurring on Florida Six-Lane Roadways

This paper describes how the safety characteristics of roadways with six or more travel lanes in the State of Florida have raised concerns because the annual crash rates are higher than those on 4-lane roadways. This study was designed to build a crash prediction model to preliminarily assist researcher in revealing roadway geometrics and traffic characteristics on six-lane highways that influence crashes. Crash frequency was used as the dependent variable in a Zero-Inflated Negative Binomial (ZINB) crash prediction model that was developed. The model indicated that section AADT, number of access points, percentage of trucks in the traffic stream, and the width of the sidewalk had positive correlation with the crash frequency. In addition, the model showed that median width, shoulder width, surface width, roadway curvature, and posted speed limit were negatively correlated with the crash frequency. The additive change in the expected crash frequency caused by each independent variable was also determined while holding all other variables in the model at their mean values. The results showed that section AADT was the most positively correlated variable with crash frequency while the posted speed limit was the most negatively correlated based on the variable levels that were analyzed.