MULTILEVEL APPROACH TO THE DESIGN OF A FREEWAY CONTROL SYSTEM

THE DEFINITION IS PRESENTED OF THE FUNCTIONAL AND OPERATIONAL REQUIREMENTS FOR FREEWAY CONTROL SYSTEMS AND THE ACTUAL DESIGN AND INSTALLATION OF A PROTOTYPE. THE SPECIFICATIONS PROPOSED FOR DESIGNING THE PROTOTYPE CONTROL SYSTEM ARE (1) THE OPTIMAL USE OF ACCEPTABLE FREEWAY GAPS BY MERGING RAMP VEHICLES AND (2) THE PREVENTION OF CONGESTION. THE UNDERLYING PHILOSOPHY IS THAT MINIMIZING INTER-VEHICULAR INTERFERENCE AT ENTRANCE RAMPS REDUCES THE PROBABILITY OF REAR-END COLLISIONS IN MERGING AREAS DUE TO FALSE STARTS REDUCES THE TENSION ON A MERGING DRIVER, AND PREVENTS SHOCK WAVES FROM DEVELOPING ON THE FREEWAY NEAR ENTRANCE RAMPS. THE THEORY BEHIND THIS IS BASED ON UTILIZING GAP AVAILABILITY AND GAP ACCEPTANCE MODELS. ANOTHER THEORY SUGGESTS THAT THE PREVENTION OF CONGESTION ULTIMATELY RESULTS IN MOVING MORE TRAFFIC FASTER. THEORETICALLY, CONGESTION IS PREVENTED IF DEMAND NEVER EXCEEDS SOME SERVICE VOLUME. THE APPROACH TAKEN IN THE DESIGN OF THE FREEWAY CONTROL SYSTEM PROTOTYPE IS BASED ON THE MULTI-LEVEL CONCEPT. THE FREEWAY IS VIEWED AS A SINGLE ENTITY WITH THE CONTROL LAW BEING SPLIT INTO SEVERAL DEGREES OF SOPHISTICATION OR LEVELS, WITH THE LOWER LEVELS DIRECTED TOWARD RECOGNIZING THE INFLUENCE OF SHORT-TERM FACTORS (GAP AVAILABILITY FOR MERGING RAMP VEHICLES) AND THE HIGHER LEVELS RESERVED FOR FACTORS THAT INFLUENCE PERFORMANCE ON A LONG-TERM BASIS (FREEWAY CAPACITY REDUCTIONS DUE TO ACCIDENTS, INCIDENTS, OR GEOMETRIC BOTTLENECKS). /AUTHOR/