DESIGNING INTERSECTION CONTROL SYSTEMS (AN APPLICATION OF OF NCHRP PROJECT 3-6)

BASIC STUDIES WERE CONDUCTED AT INTERSECTIONS IN THE CHICAGO, NEW YORK, SAN FRANCISCO, AND TORONTO METROPOLITAN AREAS TO IDENTIFY THE EFFECT OF SPECIFIED REGULATORY DEVICES ON INTERSECTION CAPACITY AND OPERATION, AND ON THE SYSTEM OF TRAFFIC FACILITIES. THE RESEARCH INDICATES THAT: (1) A LOGICAL APPROACH TO THE SELECTION OF INTERSECTION CONTROL IS NEEDED SO THAT ALL TYPES OF CONTROL CAN BE CONSIDERED ON A COMPARABLE BASIS, (2) A PROMISING APPROACH TO MEET THIS NEED IS TO PREDICT THE VALUES OF VARIOUS OPERATIONAL CRITERIA FOR EACH CONTROL AND THEN TO COMBINE THE CONTROLS ON THE BASIS OF SOME COMBINATION OF THESE CRITERIA, (3) THE FIELD PROCEDURE AND REGRESSION ANALYSIS TECHNIQUES CAN BE APPLIED IN A FEASIBLE MANNER ON A LARGE SCALE TO DEVELOP GENERALLY APPLICABLE PREDICTION EQUATIONS FOR THE OPERATIONAL CRITERIA, AND (4) THE PROPOSED PROCEDURE CAN BE DEVELOPED INTO A FORMAT PERMITTING IT TO BE APPLIED WITH LITTLE TECHNICAL KNOWLEDGE. THE PROCEDURE USED EMPLOYS TWO MEASURES OF DELAY. FOR THE PURPOSE OF COMPARISON WITH OTHER CONTROLS, AN AVERAGE HOURLY CONDITION IS USED BASED ON THE HIGHEST 8 HOURS OF TOTAL INTERSECTION VOLUME. IN ADDITION TO THIS, A CHECK IS MADE OF THE PEAK HOUR TO DETERMINE IF THE AVERAGE EXPECTED DELAY TO THE VEHICLE ON ANY APPROACH EXCEEDS A MAXIMUM TOLERABLE LEVEL. THE AVERAGE EXPECTED DELAY OF THE VEHICLE ON THE APPROACH IS STATED IN TERMS OF SECOND PER VEHICLE. RESEARCH RESULTS INDICATE THAT IN MANY CASES WHERE TWO-WAY STOP CONTROL IS BEING USED IN EXISTING CASES UNDER THE GENERAL LEVEL OF CONDITIONS STUDIED, YIELD CONTROL MIGHT BE PREFERABLE. THE PROCEDURE DEVELOPED ALLOWS THE ENGINEER TO PLACE EACH OF SEVERAL INTERSECTION CONTROLS ON A COMPARABLE BASIS SO THAT ONE CAN BE SELECTED WHICH PROMISES THE BEST OPERATION UNDER THE GIVEN CONDITIONS. A GENERAL DISCUSSION WAS MADE OF HIGHWAY RESEARCH AND ITS APPLICATION. SOME OF THE DIFFICULTIES IN APPLYING RESEARCH ARE IDENTIFIED AND A FEW SOLUTIONS SUGGESTED.