THE DENSITY FACTOR IN TRAFFIC FLOW

EQUATIONS ARE GIVEN FOR THE RELATIONSHIP BETWEEN DENSITY, SPEED AND VOLUME TO CALCULATE TRAFFIC FLOW. THE FULL SIGNIFICANCE OF THE DENSITY CONCEPT DID NOT BECOME APPARENT IN TRAFFIC ANALYSIS UNTIL IT WAS REALIZED THAT BOTH TRAFFIC MOVEMENT AND VEHICLES COULD BE TREATED AS TRAFFIC EVENTS. CASUAL OBSERVATION OF THE FLOW OF TRAFFIC INTO AND OUT OF A SELECTED AREA OF ROADWAY REVEALS THAT WHEN A CRITICAL DENSITY OF EVENTS IS EXCEEDED, TRAFFIC QUICKLY SLOWS TO A HALT. A FIGURE IS PRESENTED THAT SHOWS THAT MAXIMUM VOLUME IS REACHED AT A CERTAIN SPEED AND THEN DECREASES. RECENT DEVELOPMENTS OF THE DENSITY COMPUTER, WHICH SENSES THE NUMBER AND SPEEDS OF VEHICLES AT A POINT AND AUTOMATICALLY COMPUTES THE DENSITY OF VEHICLES PER MILE PRESENTS THE FIRST COUNTING DEVICE. THIS DEVICE DOES NOT GIVE THE DENSITY OF VEHICLES WITHIN A GIVEN AREA WHICH IS THE BASIS OF THE DENSITY THEORY, BUT CALCULATES THE DENSITY FROM THE NUMBER OF VEHICLES AND THEIR SPEEDS SENSED AT A POINT. THE DENSITY COMPUTER SHOULD BE VALUABLE FOR OBTAINING RESEARCH DATA ON HIGHWAY CAPACITY. A MEASURE OF CAPACITY MUST INCLUDE VOLUME, SPEED AND DENSITY. AN EQUATION IS PRESENTED THAT WILL OBTAIN A CAPACITY INDEX INCLUDING BOTH THE ROADWAY AND THE VEHICLE. IT APPEARS THAT IT MAY BE MORE EFFECTIVE TO USE THE DENSITY- VOLUME RELATIONSHIP RATHER THAN THAT OF VOLUME AND SPEED IN SOLVING CERTAIN TRAFFIC PROBLEMS. OBSERVING AND RECORDING THE DENSITY OF TRAFFIC EVENTS OVER A LARGE AREA MAY BE ACCOMPLISHED WITH TIME-LAPSE PHOTOGRAPHS TAKEN FROM A PLANE OR HELICOPTER OR FROM VANTAGE POINTS ON THE GROUND. ONCE CRITICAL DENSITY VALUES HAVE BEEN OBTAINED, PROPERLY LOCATED SENSING UNITS USED IN COMBINATION WITH ELECTRONIC COMPUTERS COULD BE USED TO CONTROL THE FLOW OF TRAFFIC OVER A NETWORK OF CELLS.

• Supplemental Notes:
  • Vol 30, No 6, PP 26-28, 30, 2 FIG
• Authors:
  • Greenshields, B D
• Publication Date: 0

Media Info

• Serial:
  • Traffic Engineering, Inst Traffic Engr
  • Volume: 44
  • Issue Number: 1

Subject/Index Terms

• TRT Terms: Analysis; Computers; Density; Highway capacity; Highway traffic; Mathematical analysis; Measurement; Measuring instruments; Traffic; Traffic control; Traffic counts; Traffic density; Traffic flow; Traffic speed; Traffic volume
• Uncontrolled Terms: Traffic analysis
• Old TRIS Terms: Density measurement; Vehicular traffic
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00227127
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 13 2004 6:56PM