Showing papers on "Traffic wave published in 1973"

Multiple ramp control for a freeway bottleneck

Abstract: MANY CURRENT APPROACHES TO FREEWAY CONTROL USE DETERMINISTIC MODELS OF TRAFFIC FLOW BASED ON THE CONTINUOUS FLOW-DENSITY CURVE. THIS PAPER PROPOSES A CONTROL STRATEGY BASED ON A TWO-STATE TRAFFIC FLOW PATTERN WITH THE PRIMARY CONTROL PARAMETER BEING THE PROBABILITY OF TRANSITION FROM UNCONGESTED FLOW TO CONGESTED FLOW. THE OBJECTIVE OF THE CONTROL IS TO MAXIMIZE THE REWARD ASSOCIATED WITH FREE FLOW. TRIAL SOLUTIONS INDICATE THAT FEASIBLE NUMERICAL VALUES FOR OPTIMUM CONTROL CAN BE EASILY OBTAINED, AND THESE WILL BE DEPENDENT ON THE LENGTH OF THE PEAK PERIOD. THE APPROACH SHOULD HAVE DIRECT APPLICABILITY TO EXISTING SURVEILLANCE AND CONTROL HARDWARE.

Microscopic analysis of traffic flow patterns for minimizing delay on signal-controlled links

Abstract: AN OPTIMAL SCHEME FOR COORDINATION OF CONSECUTIVE SIGNALS ALONG ARTERIAL ROUTES OR NETWORKS REQUIRES A MICROSCOPIC ANALYSIS OF THE TRAFFIC FLOW PATTERSN ON EVERY LINK OF THE SYSTEM. SUCH AN ANALYSIS WAS CARRIED OUT FOR TWO-WAY LINKS ON A MAJOR ARTERY IN DOWNTOWN TORONTO. ACCURATE PLATOON PROFILES WERE OBTAINED VIA THE DIGITAL COMPUTER SYSTEM CONTROLLING TRAFFIC LIGHTS THROUGHOUT THE METROPOLITAN AREA AND ITS ASSOCIATED VEHICLE-DETECTOR SYSTEM. INDIVIDUAL LINK DELAY FUNCTIONS WERE CALCULATED SUBJECT TO THE PARTICULAR CHARACTERISTICS OF EACH SIGNALIZED TRAFFIC LINK. THESE FUNCTIONS WERE THEN COMBINED IN PARALLEL ACCORDING TO THE PRINCIPLES OF THE BRITISH TRRL COMBINATION METHOD. THE OPTIMAL SETTINGS DERIVED ARE SHOWN TO DEVIATE SUBSTANTIALLY FROM THOSE ESTABLISHED BY CONVENTIONAL COORDINATION METHODS. THE RESULTANT IMPROVEMENT IN DELAY TO TRAFFIC WAS CONFIRMED BY DIRECT FIELD OBSERVATIONS.

For and against semi-actuated traffic signal control

Abstract: IT IS ARGUED THAT SEMIACTUATED SIGNALS SHOULD ONLY UNDER THE MOST INFREQUENT CIRCUMSTANCES BE INSTALLED FOR "ISOLATED" INTERSECTIONS, I. E., HALF A MILE OR MORE FROM THE CLOSEST SIGNAL-CONTROLLED INTERSECTION ON THE MAJOR STREET. THE ARGUMENT IS BASED BOTH ON THE CHARACTERISTICS OF SEMIACTUATED CONTROL AND THEIR EFFECT ON TRAFFIC FLOW, AND ON THE ADVANTAGES OF FULLY ACTUATED CONTROL IN OPTIMIZING FLOW. GREEN PHASE TIMING UNDER TWO TYPICAL SITUATIONS IS PRESENTED FOR THE CASE OF FULL ACTUATION. WHEN THE INTERSECTION IS PART OF A SYSTEM, I. E., LESS THAN HALF A MILE APART, THEN SEMI-ACTUATED CONTROL MAY BE ADVANTAGEOUS FOR THREE SITUATIONS THAT ARE DESCRIBED BRIEFLY.

A model for dynamic traffic assignment in congested networks with shock waves

Abstract: A mathematical formulation of a dynamic, deterministic traffic assignment algorithm particularly applicable to congested networks is specified. The model lies between the traditional stochastic simulation models, and the static, multicommodity flow formulations of the traffic assignment problem in level of detail. The following properties make the model appear to be useful for the investigation of time varying flows in congested networks of moderately large size. Exogenous demand for travel between trip origins and destinations are treated as piecewise- constant functions of time. These demands are transformed via flow-density relations, which are assumed known for each network link, into piecewise constant functions of distance ("flow packets") which approximate the time and space-varying distributions of vehicle density on network links. The increased densities characteristic of congestion are propagated backward resulting in increased travel times, not only on the under-capacity links, but also on the upstream links feeding them. The model forces the distribution of flows to approach those of "user optimized" flows at any instant by dynamically reassigning flow elements to their shortest-time paths whenever these elements reach nodes which intersect alternative partial paths to their destinations.