Adolf D May

Experimentation with Manual and Automatic Ramp Control

THE PLANNING, OPERATION AND EVALUATION OF A SERIES OF EXPERIMENTS WITH FREEWAY RAMP CONTROL UNDERTAKEN FOR THE PURPOSE OF IMPROVING NETWORK OPERATIONS IS DESCRIBED IN THIS PAPER. THE DEVELOPMENT OF THE CONTROL PLAN INCLUDED THE IDENTIFICATION OF THE CRITICAL SECTION, DETERMINATION OF THE PERIOD OF TIME AND DEGREE OF CONTROL, ESTIMATION OF THE REDISTRIBUTION OF TRAFFIC, AND RE-EVALUATION OF SYSTEM OPERATIONS. A COMPREHENSIVE SET OF MEASUREMENTS WAS OBTAINED FOR THE NETWORK, INCLUDING EXPRESSWAY AND MAJOR ARTERIALS, FOR THREE WEEKS WITHOUT CONTROL AND FOR THREE WEEKS WITH FREEWAY RAMP CONTROL. THE RAMP CONTROL CONSISTED OF PARTIALLY CLOSING ONE ON-RAMP AND METERING TRAFFIC AT A SECOND ON-RAMP. THE EFFECT ON THE NETWORK OF THE FREEWAY RAMP CONTROL WAS EVALUATED ON THE BASIS OF VEHICLE- MINUTES AND VEHICLE-MILES OF TRAVEL FOR EACH LINK, ROUTE, AND FOR THE TOTAL NETWORK. THE RESULTS INDICATE THAT TRAVEL TIME ON A NETWORK BASIS WAS REDUCED BY FREEWAY RAMP CONTROL. THE INITIAL EXPERIMENTATION WITH MANUAL CONTROL OF RAMP TRAFFIC, AND A THEORETICAL STUDY OF PEAK PERIOD CONTROL OF AN EXPRESSWAY CLEARLY INDICATED THE DISTINCT ADVANTAGE OF RAMP CONTROL UTILIZING TRAFFIC-ADJUSTED METERING AS COMPARED WITH TIME-CLOCK COMPLETE RAMP CLOSURE. AN AUTOMATIC RAMP METERING DEVICE WAS DEVELOPED AND EVALUATED.