THE DEVELOPMENT OF TRAFFIC CONGESTION

THE PATTERN OF TRAFFIC BEHAVIOR IS ANALYZED IN DETAIL ON THE MERRITT PARKWAY DURING A THIRTY-MINUTE PERIOD. THE VARIATIONS IN TRAFFIC DENSITY, TRAFFIC VOLUME AND SPACE MEAN SPEED ARE INVESTIGATED IN THE VICINITY OF A KNOWN BOTTLENECK. THE MATHEMATICAL MODELS THAT HAVE BEEN PROPOSED DESCRIBING TRAFFIC BEHAVIOR UNDER CONGESTED AND NEAR- CONGESTED CONDITIONS ARE REVIEWED. THIS ANALYSIS PARTICULARLY INVESTIGATES THE LIGHTHILL AND WHITHAM KINEMATIC FLOW THEORY. DATA COLLECTED WERE ANALYZED IN THE FOLLOWING WAYS: (1) ANALYSIS BY MINUTE PERIODS, (2) ANALYSIS BY GROUPS OF VEHICLES, (3) ANALYSIS BY INDIVIDUAL VEHICLES, (4) RELATION BETWEEN SPACING AND SPEED, (5) TRAVEL TIME, AND (6) VEHICLE SPEED PATTERNS. IT WAS DETERMINED THAT LIGHTHILL AND WHITHAM'S KINEMATIC FLOW THEORY CONCERNING THE FLOW OF TRAFFIC ON LONG, CROWDED ROADS AND THE BEHAVIOR OF THE HEAVY FLOW AS IT PASSES THROUGH A HIGHWAY BOTTLENECK DESCRIBES FAIRLY ACCURATELY THE BEHAVIOR OBSERVED ON THE MERRITT PARKWAY AT THE TEMPORARY BRIDGE SITE. CONSISTENT RELATIONSHIP GRAPHS BETWEEN TRAFFIC DENSITY, TRAFFIC VOLUME AND SPACE MEAN SPEED CAN BE OBTAINED BY AVERAGING THESE VALUES FOR GROUPS OF FROM FIVE TO NINE VEHICLES. THIS GIVES ONE POINT FOR EACH 30 SECONDS DURING CONGESTED AND CRITICAL PERIODS, BUT YET MAINTAINS A GOOD SMOOTHING EFFECT UNDER LIGHT TRAFFIC CONDITIONS. QUEUES OF VEHICLES SPACED CLOSER THAN FOUR SECONDS APART TEND TO REDUCE THEIR SPEEDS AS THEY NEGOTIATE A BOTTLENECK. A RELATIVELY SMALL INCREASE IN TRAFFIC LOAD ON AN ALREADY HEAVILY LOADED HIGHWAY CAN CAUSE A VERY GREAT CHANGE IN THE OPERATING CONDITIONS FOR ALL TRAFFIC ON THE ROAD. THE AVERAGE TRAVEL TIME OVER QUITE A DISTANCE MAY TRIPLE WITHIN A FEW MINUTES, AND THE HIGHWAY IMMEDIATELY LOSES MUCH OF ITS EFFICIENCY. TO AVOID THIS TRAFFIC CONGESTION AND FACILITATE DETECTION OF LOCATION AND POTENTIAL CAUSES OF BOTTLENECK, A TRAFFIC MONITORING DEVICE TO SENSE THE DEVELOPMENT OF CONGESTION WOULD BE VERY VALUABLE.

• Supplemental Notes:
  • pp 105-140, 15 FIG, 1 TAB, 1 PHOT
• Corporate Authors:

  Pennsylvania State University, University Park

  Bureau of Highway Traffic
  University Park, PA  United States  16802
• Authors:
  • Palmer, M R
• Publication Date: 0

Subject/Index Terms

• TRT Terms: Analysis; Bottlenecks; Data collection; Mathematical models; Queuing; Spacing; Traffic; Traffic congestion; Traffic density; Traffic flow; Traffic flow theory; Traffic simulation; Traffic speed; Traffic volume; Travel time
• Uncontrolled Terms: Traffic analysis
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00227129
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 13 2004 6:47PM