Evaluating the Impacts of Ramp Configurations and Influential Factors on Freeway Exit Ramps

The primary objective of the study is to evaluate safety performances of different exit ramps used in Florida. More specific, the research objectives include: (1) to evaluate the impacts of different ramp configurations on safety performance; and (2) to identify the different factors contributing to the crashes happening on the exit ramp sections. 389 sites were investigated throughout Florida by four ramp configurations, diamond, out connection, free-flow loop and parclo loop. Cross-sectional comparisons and crash predictive model were used to quantify the impacts. The result shows that the out connection ramps appear to have the lowest average crash. The predictive model indicates that replacing an out connection exit ramp with a diamond, free-flow, and parclo loop will increase crashes counts by 26.90%, 68.47% and 48.72% respectively. This study will help transportation decision makers develop technical guidelines governing the selection of the optimum design on freeway exit ramps.