DETERMINATION OF MERGING CAPACITY AND ITS APPLICATIONS TO FREEWAY DESIGN AND CONTROL

THIS PAPER PRESENTS A NEW APPROACH TO THE DETERMINATION OF MERGING CAPACITY AND MERGING SERVICE VOLUMES. FOR THE FIRST TIME IN THE LITERATURE, A METHOD IS PRESENTED OF QUANTITATIVELY DETERMINING THE INFLUENCE OF ENTRANCE RAMP GEOMETRICS ON THE CAPACITY AND LEVEL OF SERVICE OF A RAMP-FREEWAY MERGING AREA. THE PROCEDURE ENABLES THE DESIGN ENGINEER TO EVALUATE RATIONALLY ALTERNATE DESIGNS AND, IF COMPROMISE IS NEEDED, TO SELECT THE ELEMENT OR LOCATION WHERE SUCH COMPROMISE WILL BE THE LEAST OBJECTIONABLE. THE CAPACITY OF A MERGING AREA IS BASED ON THE INTERACTION BETWEEN THE GAP ACCEPTANCE BEHAVIOR OF ENTRANCE RAMP DRIVERS AND THE AVAILABILITY OF GAPS ON THE FREEWAY SHOULDER LANE, WHILE THE SERVICE VOLUMES SUGGESTED ARE DEVELOPED FROM CONSIDERATIONS OF THE RAMP JUNCTION AS A QUEUING SYSTEM. THIS PERMITS THE PROVISION OF A LEVEL OF SERVICE SUCH THAT A RAMP VEHICLE HAS A CERTAIN PROBABILITY OF FINDING THE MERGING AREA EMPTY. ANOTHER MEASURE OF LEVEL OF SERVICE-THE DELAY SUFFERED BY RAMP VEHICLES-IS TREATED AND CHARTS ARE PRESENTED FOR ITS DETERMINATION. THE MERGING PARAMETERS DEVELOPED ARE CLOSELY LINKED TO THE CRITICAL GAP OF THE RAMP-FREEWAY JUNCTION. THROUGH THE STUDY OF MERGING OPERATIONS AT 29 ENTRANCE RAMPS ACROSS THE CONTINENTAL UNITED STATES, RELATIONSHIPS ARE DEVELOPED BETWEEN THE GAP ACCEPTANCE CHARACTERISTIC AND CERTAIN DESIGN CHARACTERISTICS OF AN ENTRANCE TERMINAL. THIS ALLOWS FOR ESTIMATION OF THE CRITICAL GAP AND HENCE FOR THE CAPACITY AND SERVICE OF AN ON-RAMP, BASED ON THE LENGTH OF ACCELERATION LANE, THE ANGLE OF CONVERGENCE AND THE SHAPE OF THE ACCELERATION LANE. APPROPRIATE CHARTS ARE PRESENTED FOR ESTIMATION OF THE MERGING PARAMETERS AND THE INFLUENCE OF DESIGN CHARACTERISTICS. THE APPLICATION OF THE DEVELOPED PARAMETERS TO FREEWAY CONTROL VIA THE GAP ACCEPTANCE MODE OF CONTROL IS ALSO DISCUSSED. /AUTHOR/