CAPACITY OF SIGNALIZED INTERSECTIONS

THREE METHODS OF ESTIMATING CAPACITY AT SIGNALIZED INTERSECTIONS, DEVELOPED BY THE HIGHWAY CAPACITY MANUAL, ROBERT DIER (TRAFFIC ENGINEER FOR LONG BEACH, CALIF.), AND W. R. BELLIS (DIRECTOR OF RESEARCH, NEW JERSEY DEPARTMENT OF TRANSPORTATION), ARE ANALYZED AND COMPARED TO AN EMPIRICAL VALUE CALLED "AVERAGE LOADED PHASE EXPANDED". (ALE). DATA WERE COLLECTED AT 38 SITES AND GROUPED INTO VARIOUS CATEGORIES OF TRAFFIC CHARACTERISTICS. THE HCM AND DIER METHODS PRODUCED ERRORS IN EXCESS OF PLUS OR MINUS 20% FOR APPROXIMATELY HALF THE SAMPLED SITES, WHILE THE BELLIS PROCEDURE YIELDED SUCH A LARGE ERROR FOR LESS THAN 15% OF CASES. /AUTHOR/