A THEORY OF TRAFFIC FLOW FOR EVALUATION OF GEOMETRIC ASPECTS OF HIGHWAYS

AN ANALYTIC APPROACH IS DEVELOPED WHEREBY THE VARIOUS ASPECTS OF A HIGHWAY (SUCH AS CURVES, GRADES, LANE WIDTH, TRAFFIC CONTROL DEVICES, TYPE AND CONDITION OF SURFACING) CAN BE EVALUATED QUANTITATIVELY UNDER VARYING TRAFFIC DENSITY AND WEATHER CONDITIONS PROVIDING A RATIONAL BASIS FOR GEOMETRIC DESIGN. IN THE PRESENT ANALYSIS IT IS POSTULATED THAT TRAFFIC REACTS TO A MOTIVATING PRESSURE POTENTIAL IN A PATTERN THAT DETERMINES THE BEHAVIOR OF ANY PARTICULAR VEHICLE TRAVERSING A GIVEN SECTION OF ROADWAY. THIS CONCEPT CAN BE EXPRESSED QUANTITATIVELY IN A MANNER ANALOGOUS TO THAT USED IN DESCRIBING ONE-DIMENSIONAL VISCOUS FLOW IN A COMPRESSIBLE FLUID. SOLUTION OF THE RESULTING DIFFERENTIAL EQUATION YIELDS A PARAMETER WHICH IS A NUMERICAL MEASURE OF THE SALIENT CHARACTERISTICS OF A ROAD. PROCEDURES ARE THEN PROPOSED TO DETERMINE THIS PARAMETER, USING MEASURABLE VEHICULAR VELOCITIES, WHICH ELIMINATE THE NEED FOR EVALUATING THE MOTIVATING PRESSURE POTENTIAL.