The Impact of Red Light Cameras (Automated Enforcement) on Safety in Arizona Final Report 550 Prepared by: Dr. Simon Washington and Mr. Kangwon Shin 2004 E 5th St Tucson, AZ 85719 June 2005 Prepared for: Arizona Department of Transportation 206 South 17th Avenue Phoenix, Arizona 85007 in cooperation with U.S. Department of Transportation Federal Highway Administration The contents of the report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Arizona Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Trade or manufacturers’ names which may appear herein are cited only because they are considered essential to the objectives of the report. The U.S. Government and the State of Arizona do not endorse products or manufacturers. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-AZ-05-550 4. Title and Subtitle 5. Report Date The Impact of Red Light Cameras (Automated Enforcement) on August 2005 Safety in Arizona 6. Performing Organization Code 7. Authors 8. Performing Organization Report No. Dr. Simon Washington and Mr. Kangwon Shin 9. Performing Organization Name and Address 10. Work Unit No. Dr. Simon Washington and Mr. Kangwon Shin University of Arizona 11. Contract or Grant No. Tucson, AZ 85721 SPR-PL-1-(61) 550 12. Sponsoring Agency Name and Address 13.Type of Report & Period Covered ARIZONA DEPARTMENT OF TRANSPORTATION 206 S. 17TH AVENUE PHOENIX, ARIZONA 85007 14. Sponsoring Agency Code Project Manager: John Semmens 15. Supplementary Notes Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration 16. Abstract Red Light Cameras (RLCs) have been used in a number of US cities to yield a demonstrable reduction in red light violations; however, evaluating their impact on safety (crashes) has been relatively more difficult. Accurately estimating the safety impacts of RLCs is challenging for several reasons. First, many safety related factors are uncontrolled and/or confounded during the periods of observation. Second, “spillover” effects caused by drivers reacting to non-RLC-equipped intersections and approaches can make the selection of comparison sites difficult. Third, sites selected for RLC installation may not be randomly selected, and as a result may suffer from the regression to the mean effect. Finally, crash severity needs to be considered to fully understand the safety impacts of RLCs. With these challenges in mind this study was designed to estimate the safety impacts of RLCs on traffic crashes at signalized intersections in the state of Arizona and to identify which factors are associated with successful installations. RLC equipped intersections in the cities of Phoenix and Scottsdale are examined in detail to draw conclusions as to the relative success of RLC programs in these two jurisdictions. Both jurisdictions are operating successful installations of RLCs. Factors related to RLC effectiveness appear to include crash type and severity, left-turn phasing, presence of warning signs, approach speeds, and signal timing. Recommendations are made as to under what conditions should RLCs be considered. 17. Key Words 18. Distribution Statement 23. Registrant’s Seal Document is available to the signalized intersections, red light running, red U.S. public through the light enforcement camera, safety, before-and-after National Technical Information study Service, Springfield, Virginia 22161 19. Security Classification 20. Security Classification 21. No. of Pages 22. Price Unclassified Unclassified 139 SI* (MODERN METRIC) CONVERSION FACTORS APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find Symbol LENGTH LENGTH in inches 25.4 millimeters mm mm millimeters 0.039 inches in ft feet 0.305 meters m m meters 3.28 feet ft yd yards 0.914 meters m m meters 1.09 yards yd mi miles 1.61 kilometers km km kilometers 0.621 miles mi AREA AREA 2 2 2 2 in square inches 645.2 square millimeters mm mm Square millimeters 0.0016 square inches in 2 2 2 2 ft square feet 0.093 square meters m m Square meters 10.764 square feet ft 2 2 2 2 yd square yards 0.836 square meters m m Square meters 1.195 square yards yd ac acres 0.405 hectares ha ha hectares 2.47 acres ac 2 2 2 2 mi square miles 2.59 square kilometers km km Square kilometers 0.386 square miles mi VOLUME VOLUME fl oz fluid ounces 29.57 milliliters mL mL milliliters 0.034 fluid ounces fl oz gal gallons 3.785 liters L L liters 0.264 gallons gal 3 3 3 3 ft cubic feet 0.028 cubic meters m m Cubic meters 35.315 cubic feet ft 3 3 3 3 yd cubic yards 0.765 cubic meters m m Cubic meters 1.308 cubic yards yd NOTE: Volumes greater than 1000L shall be shown in m3. MASS MASS oz ounces 28.35 grams g g grams 0.035 ounces oz lb pounds 0.454 kilograms kg kg kilograms 2.205 pounds lb T short tons (2000lb) 0.907 megagrams mg Mg megagrams 1.102 short tons (2000lb) T (or “metric ton”) (or “t”) (or “metric ton”) TEMPERATURE (exact) TEMPERATURE (exact) ºF Fahrenheit 5(F-32)/9 Celsius temperature ºC ºC Celsius temperature 1.8C + 32 Fahrenheit ºF temperature or (F-32)/1.8 temperature ILLUMINATION ILLUMINATION fc foot candles 10.76 lux lx lx lux 0.0929 foot-candles fc fl foot-Lamberts 3.426 candela/m2 cd/m2 cd/m2 candela/m2 0.2919 foot-Lamberts fl FORCE AND PRESSURE OR STRESS FORCE AND PRESSURE OR STRESS lbf poundforce 4.45 newtons N N newtons 0.225 poundforce lbf lbf/in2 poundforce per 6.89 kilopascals kPa kPa kilopascals 0.145 poundforce per lbf/in2 square inch square inch Table of Contents EXECUTIVE SUMMARY .............................................................................................. 1 I. STUDY OBJECTIVES AND RESEARCH PROCESS .......................................... 7 II. LITERATURE REVIEW AND DATA SUMMARY .............................................. 9 LITERATURE REVIEW............................................................................................................................. 9 THE EFFECTIVENESS OF ENGINEERING COUNTERMEASURES ..................................................................... 9 THE EFFECTIVENESS OF RLC PROGRAMS .............................................................................................. 11 DATA SUMMARY ACROSS CITIES.......................................................................................................... 15 GENERAL RLC ENFORCEMENT PROGRAM DESCRIPTION ........................................................................ 15 CRASH DATA ........................................................................................................................................ 17 SITE SPECIFICS AND SIGNAL PHASING.................................................................................................... 18 SITE PUBLICITY AND SUPPLEMENTAL ENFORCEMENT CAMPAIGNS ......................................................... 20 DATA SUMMARY WITHIN CITIES.......................................................................................................... 21 CITY OF SCOTTSDALE ........................................................................................................................... 21 CITY OF PHOENIX................................................................................................................................. 32 III. EVALUATION METHODOLOGIES AND RESULTS....................................... 41 TARGET CRASHES AND TARGET APPROACHES ........................................................................... 41 STUDY DURATION ..................................................................................................................... 42 BASIC CONCEPT OF 4-STEP FOR BEFORE-AFTER STUDY.............................................................. 43 ANALYSIS METHOD 1: SIMPLE OR NAÏVE BEFORE-AFTER STUDY WITH RATIO OF DURATIONS .... 48 RATIO OF DURATION ................................................................................................................. 48 PREDICTION IN SIMPLE BEFORE-AFTER STUDY WITH RATIO OF DURATION........................................... 48 ANALYSIS RESULTS: CHANGE IN SAFETY AND INDEX OF EFFECTIVENESS ............................................ 50 ANALYSIS METHOD 2: BEFORE-AFTER STUDY WITH CORRECTION FOR TRAFFIC FLOW.............. 52 CORRECTION IN 4-STEP FOR THE CORRECTION OF TRAFFIC FLOW..................................................... 52 DEVELOPING SPFS FOR PREDICTING THE SAFETY EFFECTS OF CHANGES IN TRAFFIC VOLUMES ............. 55 PREDICTION IN BEFORE-AFTER STUDY WITH CORRECTION FOR TRAFFIC FLOW.................................... 68 ANALYSIS RESULTS: CHANGES IN SAFETY AND INDEX OF EFFECTIVENESS ........................................... 73 ANALYSIS METHOD 3: BEFORE-AFTER STUDY WITH COMPARISON GROUP ................................. 74 CORRECTION IN 4-STEP FOR COMPARISON GROUP METHOD ........................................................... 74 PREDICTION WITH COMPARISON CRASHES.................................................................................... 78 ANALYSIS RESULTS: CHANGES IN SAFETY AND INDEXES OF EFFECTIVENESS........................................ 80 ANALYSIS METHOD 4: EMPIRICAL BAYES’ BEFORE-AFTER STUDY............................................. 81 OVERVIEW OF REGRESSION-TO-MEAN BIAS