ON THE AUSTRALIAN ROAD CAPACITY GUIDE

PROGRESS IS REVIEWED ON THE AUSTRALIAN ROAD CAPACITY GUIDE, THE FIRST PART OF WHICH (ON SIGNALIZED INTERSECTIONS) WAS PUBLISHED DURING 1968. SOME OF THE PRINCIPAL FINDINGS FOR SIGNALIZED INTERSECTIONS WERE AS FOLLOWS. THE CAPACITY OF AN INTERSECTION APPROACH IS CLOSELY RELATED TO THE NUMBER OF LANES, AND THE WIDTH OF THESE LANES HAS COMPARATIVELY LITTLE EFFECT OVER A RANGE FROM APPROXIMATELY 10 TO 13 FEET. CAPACITIES ARE CALCULATED (IN THROUGH-CAR UNITS PER HOUR) BY ADDING THOSE FOR EACH INDIVIDUAL LANE. ON APPROACHES WITH THREE OR MORE LANES IT WAS FOUND THAT THE UTILIZATION OF THE CURB LANE WAS USUALLY POOR, AND FORMULAS FOR ESTIMATING THIS USAGE HAVE BEEN DERIVED IN TERMS OF THE LOCATION OF PARKED VEHICLES, THE DEGREE OF ENFORCEMENT OF NO-STOPPING BANS, AND THE PROPORTION OF TURNING VEHICLES. THE PAPER LISTS THE EQUIVALENTS FOUND FOR TURNING VEHICLES AND TRUCKS. FOR OPPOSED RIGHT-TURNERS (EQUIVALENT TO AMERICAN LEFT-TURNERS), THE EQUIVALENT IS A FUNCTION OF THE AMOUNT OF ONCOMING TRAFFIC AND THE SIGNAL SETTINGS. NO CORRELATION WAS FOUND BETWEEN CAPACITY AND CITY POPULATION. THE LOST TIME PER CHANGE OF PHASE WAS FOUND TO BE 1/2 SECOND LESS THAN THE INTER-GREEN TIME OR 2-1/2 SECONDS PLUS THE TRAVEL TIME THROUGH THE INTERSECTION OF THE LAST VEHICLE, WHICHEVER IS GREATER. THESE CONCLUSIONS WERE ARRIVED AT AFTER COLLECTING AND ANALYZING DATA FROM 220 INTERSECTIONS IN ALL AUSTRALIAN STATES. NEW APPROXIMATIONS HAVE BEEN OBTAINED FOR THE AVERAGE DELAY, THE AVERAGE NUMBER OF VEHICLES LEFT IN THE QUEUE AT THE END OF THE GREEN, AND THE PROBABILITY OF CLEARING THE QUEUE, AT FIXED-TIME SIGNALS WITH RANDOM ARRIVALS. A FORMULA IS ALSO GIVEN FOR THE LOAD FACTOR. OVERTAKING STUDIES HAVE BEEN CARRIED OUT IN BOTH NEW SOUTH WALES AND VICTORIA. THESE STUDIES SHOWED THAT A SMALL PROPORTION OF DRIVERS WILL NOT OVERTAKE, EVEN WHEN THE VEHICLE IN FRONT IS TRAVELING AT ONLY 20 MPH. /AUTHOR/