United States Department of Transportation
i
Evaluation of Innovative Alternative Intersection Designs in the Development of Safety Performance Functions and Crash Modification Factors
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2020-03-01
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[PDF-11.84 MB]
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Edition:Final Deliverable 2018-2020
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Abstract:Many alternative intersections aim to reduce conflict points by separating turning vehicles (left-turning vehicles in most cases) at intersections. In order to investigate the safety effects of alternative intersections, data were collected from 27 states, including Arizona, Colorado, Florida, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Missouri, North Carolina, New Jersey, New Mexico, New York, Nevada, Ohio, Oregon, Pennsylvania, Tennessee, Texas, Virginia, Utah, Wisconsin, and Wyoming. The ten alternative intersections that were investigated in this project included continuous green T-intersections, median U-turn intersections (Types A, B, and partial), continuous flow intersections, jughandle intersections (Types 1-3), restricted crossing U-turn intersections, and diverging diamond interchanges. It was shown that the restricted crossing U-turn intersections are the most effective to minimize the equivalent property damage only (EPDO), fatal-and-injury, and angle crashes. The median U-turn intersections (Type A and Type B) are the best for reducing total and rear-end crashes, respectively. For minimizing left-turn crashes, implementing jughandle (Type 1) is the most effective, and the continuous flow intersection is the most effective for minimizing non-motorized crashes. It was also shown that converting conventional diamond interchanges to diverging diamond interchanges could significantly decrease the total, fatal-and-injury, PDO, rear-end, and angle crashes by 14%, 44%, 8%, 11%, and 55%, respectively. Fifty intersections were identified as the top 1% intersections with the highest crash risk in FL. It was found that rear-end crashes are the most frequent, ‘most problematic’ crash type, followed by left-turn crashes. For each hotspot intersection, two different alternative intersections were suggested to minimize (1) the most problematic crash type and (2) overall EPDO. In addition to exploring the safety effects of the alternative intersections, it was shown that signalization is effective in reducing severe crash types (e.g., angle, left-turn); whereas it significantly increases rear-end crashes by 66% to 195%. Also, it was found that signalization significantly increased the number of rear-end crashes for elderly drivers.
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