Final Report Contract BDV24-977-27 Evaluation of Innovative Alternative Intersection Designs in the Development of Safety Performance Functions and Crash Modification Factors Mohamed A. Abdel-Aty, Ph.D., P.E. Jaeyoung Lee, Ph.D. Jinghui Yuan, Ph.D. Lishengsa Yue, Ph.D. Ma’en Al-Omari, Ph.D. Student Ahmed Abdelrahman, Ph.D. Student University of Central Florida Department of Civil, Environmental & Construction Engineering Orlando, FL 32816-2450 May 2020 DISCLAIMER “The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the State of Florida Department of Transportation.” ii UNITS CONVERSION APPROXIMATE CONVERSIONS TO SI UNITS SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL LENGTH in inches 25.4 millimeters mm ft feet 0.305 meters m yd yards 0.914 meters m mi miles 1.61 kilometers km SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL AREA in2 square inches 645.2 square millimeters mm2 ft2 square feet 0.093 square meters m2 yd2 square yard 0.836 square meters m2 ac acres 0.405 hectares ha mi2 square miles 2.59 square kilometers km2 WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL SYMBOL VOLUME fl oz fluid ounces 29.57 milliliters mL gal gallons 3.785 liters L ft3 cubic feet 0.028 cubic meters m3 yd3 cubic yards 0.765 cubic meters m3 NOTE: volumes greater than 1000 L shall be shown in m3 SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL MASS oz ounces 28.35 grams g lb pounds 0.454 kilograms kg iii T short tons (2000 lb) 0.907 megagrams (or Mg (or "t") "metric ton") SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL TEMPERATURE (exact degrees) oF Fahrenheit 5(F-32)/9 or (F-32)/1.8 Celsius oC SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL ILLUMINATION fc foot-candles 10.76 lux lx fl foot-Lamberts 3.426 candela/m2 cd/m2 SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL FORCE and PRESSURE or STRESS lbf poundforce 4.45 newtons N lbf/in2 poundforce per square 6.89 kilopascals kPa inch SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL LENGTH mm millimeters 0.039 inches in m meters 3.28 feet ft m meters 1.09 yards yd km kilometers 0.621 miles mi SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL AREA mm2 square millimeters 0.0016 square inches in2 m2 square meters 10.764 square feet ft2 m2 square meters 1.195 square yards yd2 ha hectares 2.47 acres ac km2 square kilometers 0.386 square miles mi2 iv SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL VOLUME mL milliliters 0.034 fluid ounces fl oz L liters 0.264 gallons gal m3 cubic meters 35.314 cubic feet ft3 m3 cubic meters 1.307 cubic yards yd3 SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL MASS g grams 0.035 ounces oz kg kilograms 2.202 pounds lb Mg (or "t") megagrams (or "metric 1.103 short tons (2000 T ton") lb) SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL TEMPERATURE (exact degrees) oC Celsius 1.8C+32 Fahrenheit oF SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL ILLUMINATION lx lux 0.0929 foot-candles fc cd/m2 candela/m2 0.2919 foot-Lamberts fl SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL FORCE and PRESSURE or STRESS N newtons 0.225 poundforce lbf kPa kilopascals 0.145 poundforce per lbf/in2 square inch v TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle 5. Report Date Evaluation of Innovative Alternative Intersection Designs in the March 2020 Development of Safety Performance Functions and Crash Modification 6. Performing Organization Code Factors 7. Author(s) 8. Performing Organization Report No. Mohamed A. Abdel-Aty, Ph.D., P.E.; Jaeyoung Lee, Ph.D.; Jinghui Yuan, Ph.D.; Lishengsa Yue, Ph.D. Student; Ma’en Al-Omari, Ph.D. Student; Ahmed Abdelrahman, Ph.D. Student 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Department of Civil, Environmental & Construction Engineering University of Central Florida 11. Contract or Grant No. 12800 Pegasus Drive, Suite 211 BDV24-977-31 Orlando, FL 32816-2450 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Florida Department of Transportation Final Deliverable 2018-2020 14. Sponsoring Agency Code 15. Supplementary Note 16. 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. 17. Key Word 18. Distribution Statement alternative intersections; intersection safety; safety performance functions; crash modification factors; crash modification functions; hotspot identification 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified 455 vi EXECUTIVE SUMMARY Intersections have been of major interest to traffic engineers because there are many conflicts between road users and they pose considerable exposure to safety risk and traffic congestion. In order to alleviate the safety and congestion problems, several types of alternative intersection designs have been suggested and implemented in some states. It would be useful and important to evaluate the alternative intersections that have been implemented in other states and predict their effects when they are implemented in Florida. Many alternative intersections aim to reduce conflict points by separating turning vehicles (left- turning vehicles in most of the 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 include 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. vii Fifty intersections were identified as the top 1% intersection with the highest crash risk. It was found that rear-end crashes are the most frequent, ‘most problematic’ crash type, and left-turn crashes follow. 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 the 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. This study also evaluated the safety benefits of diverging diamond interchanges (DDIs) in comparison to the conventional diamond interchanges. Three methods were adopted to estimate the crash modification factors (CMFs), which are before-and-after with comparison group (CG), Empirical Bayes before-and-after (EB), and the cross-sectional analysis. The studied sample included 80 DDIs and 240 conventional diamond interchanges as comparison sites located in 24 states. Different data types were collected to conduct the analysis. First, multi-year crash data were acquired from the various states. Then, traffic and geometric features were collected, including annual average daily traffic (AADT), speed limits, and the distance between crossovers or ramp terminals.