PREDICTING TRAFFIC ACCIDENTS FROM ROADWAY ELEMENTS ON URBAN EXTENSIONS OF STATE HIGHWAYS

THE OREGON STATE HIGHWAY DEPARTMENT DEVELOPED EQUATIONS THAT CAN BE USED TO PREDICT ACCIDENTS ON THE URBAN EXTENSIONS OF THE STATE HIGHWAY SYSTEM FROM ROADWAY ELEMENTS SUCH AS ADT, COMMERCIAL AND RESIDENTIAL UNITS AND DRIVEWAYS, INTERSECTIONS, SIGNALIZED INTERSECTIONS, INDICATED SPEED, PAVEMENT WIDTH, EFFECTIVE LANE WIDTH, AND THE NUMBER OF LANES. THE STUDY UTILIZED A SAMPLE OF 426 SECTIONS WITH A TOTAL LENGTH OF 186.4 MI. DATA WERE ANALYZED BY SUBGROUPING THE SECTIONS BY NUMBER OF TRAFFIC LANES AND ADT GROUPINGS. WITHIN THESE GROUPS ADDITIONAL SUBGROUPS OF URBAN EXTENSIONS WERE STUDIED FOR SUBURBAN, CORPORATE, BUSINESS, RESIDENTIAL AND MIXED CULTURE SECTIONS. THE ANALYSIS USED MULTIPLE CORRELATION TECHNIQUES WITH THE END RESULT OF THE ANALYSIS BEING A SERIES OF EQUATIONS WHICH INDICATED THE RELATIONSHIP OF THE VARIOUS ROADWAY ELEMENTS TO ACCIDENT RATES ON URBAN AND SUBGROUPS OF URBAN EXTENSIONS OF HIGHWAYS IN OREGON. THE MORE IMPORTANT CONCLUSIONS WHICH CAN BE DRAWN FROM THE STUDY ARE: (1) MOTOR VEHICLE ACCIDENT RATES ARE RELATED TO CERTAIN PHYSICAL FEATURES OF URBAN EXTENSIONS OF THE HIGHWAY SYSTEM. (THIS RELATIONSHIP IS STRONG ENOUGH IN THE HIGHER ADT RANGES TO MAKE IT POSSIBLE TO PREDICT ACCIDENT RATES WITH A REASON- ABLE DEGREE OF ACCURACY ON THE BASIS OF KNOWN PHYSICAL FEATURES). (2) ACCIDENT RATES ON LOW VOLUME ROADS DO NOT HAVE A STRONG RELATIONSHIP WITH ANY ROADWAY FEATURE. (3) MOTOR VEHICLE ACCIDENT RATES INCREASE WHEN: (1) THE NUMBER OF COMMERCIAL UNITS ADJACENT TO THE SECTION INCREASES, (2) THE NUMBER OF TRAFFIC SIGNALS INCREASES, (3) THE NUMBER OF INTERSECTIONS INCREASES, (4) THE INDICATED SPEED DECREASES, (5) THE AVERAGE DAILY TRAFFIC INCREASES, AND (6) THE PAVEMENT WIDTH INCREASES. /AUTHOR/