RELATION BETWEEN NUMBER OF ACCIDENTS AND TRAFFIC VOLUME AT DIVIDED-HIGHWAY INTERSECTIONS

THIS REPORT PRESENTS A GRAPHIC EXPRESSION OF THE ACCIDENT- VOLUME RELATION AT DIVIDED HIGHWAY INTERSECTIONS. THE EXPRESSION WAS PRODUCED BY AVERAGING THE PAST ACCIDENT EXPERIENCE AT 150 INTERSECTIONS. A TOTAL OF 1,811 ACCIDENTS WAS TABULATED IN DEVELOPING THE CHART. USES OF THE CHART INCLUDE: (1) ESTIMATING THE PROBABLE NUMBER OF ACCIDENTS WHICH OCCUR IN A FUTURE PERIOD AND (2) CORRECTING FOR THE INFLUENCE OF VOLUME DIFFERENCES WHEN COMPARING ONE INTERSECTION ACCIDENT RATE WITH ANOTHER. INTERPRETATION OF THE EXPRESSION LED TO THE FOLLOWING CONCLUSIONS: (1) ACCIDENT RATES AT INTERSECTIONS ARE MUCH MORE SENSITIVE TO CHANGES IN CROSSROAD (MINOR ROAD) VOLUME THAN TO CHANGES IN DIVIDED HIGHWAY (MAJOR ROAD) VOLUME, (2) NO DIRECT RELATION EXISTS BETWEEN INTERSECTION ACCIDENT RATES AND THE SUM OF THE TWO ENTERING VOLUMES. THE EXISTENCE OF SUCH A RELATION IS IMPLIED WHEN INTERSECTIONS ARE COMPARED ON THE BASIS OF ACCIDENTS PER MILLION VEHICLES, (3) LOW-CROSSROAD- VOLUME INTERSECTIONS HAVE HIGHER ACCIDENT RATES PER CROSSROAD VEHICLE THAN DO HIGHER-CROSSROAD-VOLUME INTERSECTIONS. THIS EVIDENCE THAT THE CONCENTRATION OF CROSS TRAFFIC, THROUGH THE CLOSING OF LOW-VOLUME CROSS-ROADS AND THE PROVISION OF FRONTAGE ROADS, IS AN EFFECTIVE MEANS OF REDUCING THE NUMBER OF INTERSECTION ACCIDENTS. /AUTHOR/