THE EFFECT OF CONTROL METHODS ON TRAFFIC FLOW-TRAFFIC MOVEMENTS AT SEVENTEENTH STREET AND CONSTITUTION AVENUE IN WASHINGTON, D.C.

A STUDY WAS MADE TO COMPARE THE TIME OF VEHICLE PASSAGE THROUGH AN INTERSECTION WITH VARIABLE CONTROL METHODS FOR TRAFFIC OF NEARLY CONSTANT VOLUME. DATA WERE TAKEN BETWEEN MORNING AND EVENING RUSH HOURS WHEN THE TRAFFIC WAS NEARLY CONSTANT AT 2,000 VEHICLES PER HOUR. MOVEMENT OF TRAFFIC WAS STUDIED UNDER NO-CONTROL, OFFICER CONTROL, VEHICLE-ACTUATED CONTROL, AND SEVENTEEN DIFFERENT FIXED-TIME CONTROLS. ALL VEHICLES THAT ENTERED AND LEFT THE ZONE OF INFLUENCE OF THE INTERSECTION WERE NOTED BY MEANS OF A GRAPHIC TIME RECORDER. FROM THIS RECORD THE AVERAGE TIME PER VEHICLE WAS DETERMINED. OVER 100,000 VEHICLES WERE TIMED. THE RESULTS ARE TABULATED. FOR THE TRAFFIC VOLUME ENCOUNTERED IN THIS ANALYSIS (ABOUT 2,000 VEHICLES PER HOUR) OPERATION OF THE INTERSECTION WITHOUT CONTROL INCURRED THE LEAST DELAY TO TRAFFIC. OF ALL THE CONTROL METHODS, OFFICER CONTROL PERMITTED THE FASTEST MOVEMENT OF TRAFFIC, CLOSELY FOLLOWED BY THE SHORTEST FIXED-TIME CONTROL, AND TRAFFIC-ACTUATED CONTROL. UNDER FIXED-TIME CONTROL, A VERY MARKED INCREASE IN DELAY FOLLOWED LENGTHENING OF THE CYCLE. IN FACT, FOR CERTAIN OF THE SHORT CYCLES COMPLETELY REVERSING THE PROPORTIONING OF THE CYCLE HAD LESS EFFECT ON THE TIME OF THE AVERAGE VEHICLE THAN DID RETAINING THE SAME PROPORTIONING BUT DOUBLING THE CYCLE LENGTH. THE FLEXIBLE CONTROL METHODS SHOWED EFFICIENCY EQUAL TO OR BETTER THAN THE MOST EFFICIENT FIXED-TIME CONTROL, BUT IT IS BELIEVED THAT BOTH THE OFFICER CONTROL AND TRAFFIC-ACTUATED CONTROL COULD BE MORE EFFICIENT THAN INDICATED HERE. DURING THE COURSE OF A 10-HOUR DAY FROM 8:00 A.M. TO 6:00 P.M. AS MUCH DELAY WAS INCURRED DURING TWO HOURS OF PEAK TRAFFIC AS DURING THE REMAINING EIGHT HOURS. /AUTHOR/