The purpose of this study is to evaluate the safety performance of four exit ramp types and the major contributing factors on motorcycle crashes and injury severity of motorcycle riders. A six-year crash data were collected in Florida, and a web-based survey (234 samples) was conducted. 573 crashes were found at 419 exits, including 178 diamond exits, 71 directional exits, 85 loop exits and 85 outer connection exits. For a diamond exit, both the survey and crash data showed that this type was safer and more preferable by motorcycle riders; while a loop exit was the most dangerous exit due to the sharp curve and a certain length of curve with limited visibility. For a directional exit, longer ramp lengths and the reverse curvature are the major factors causing motorcycle crashes. For an outer connection exit, the riders rated it as a safe type; however, the data showed higher average crash frequency and rate than those at diamond exits or directional exits. The possible reason could be the unexpected curvature in the middle of the ramp, which could be dangerous if the rider is not familiar with the exit ramp location or doesn’t pay attention to the ramp curvatures. The crash predictive model was developed, and the result indicated that if all remained the same, a directional exit, a loop exit, or an outer connection exit will have 16%, 27%, and 42% more crashes than a diamond exit, respectively. The findings from this study can help policy-makers and engineers to develop and apply effective countermeasures to reduce motorcycle crashes and injury severity levels for different exit ramp types.
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