Microscopic models provide an understanding of traffic operations at the level of passage of individual vehicles. Roadway performance can be ascertained by understanding how vehicles interact with each other. Cowan's M3 headway distribution models were calibrated for the curb and median lanes of two-lane mainline freeway segments, using data captured at 14 sites. Calibration of the relationship among Cowan's M3 parameters, proportion of headways greater than a minimum of 1 sec, and flow rate yielded exponential decay equations for each lane. The M3 models provide a source of vehicle arrivals for gap acceptance models, which may be used to quantify the ability of drivers to change lanes, for example. It was found that the parameters calibrated for each lane are suitable for use at any mainline site, independent of site-specific conditions. The proportion of small headways was found to be higher in the median lane than the curb, for all flow rates, and for both lanes lower than their respective equivalents on arterial roads with intersections. The largest bunched headway was considered to be between 2 and 3 sec. The models predicted bunching between 85% and 93% of median lane vehicles, and between 75% and 90% of curb lane vehicles, at capacity. The lesser amount of curb lane bunching reflects its use as a slower vehicle lane with greater stream friction.


  • English

Media Info

  • Features: Figures; References;
  • Pagination: p. 19-25
  • Monograph Title: Traffic flow theory and characteristics with applications for intelligent transportation system technologies
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00715621
  • Record Type: Publication
  • ISBN: 0309062039
  • Files: TRIS, TRB
  • Created Date: Jan 19 1996 12:00AM