DEVELOPMENT OF CAPACITY ESTIMATION METHOD FROM STATISTICAL DISTRIBUTION OF OBSERVED TRAFFIC FLOW

The objective of this study is to present a quantitative method for highway capacity determination by evaluating alternative approaches in developing capacity from the statistical distribution of observed traffic flow. Extremely long headways are considered to be unreasonable for sufficient demand and for the maximum flow rate defining capacity. Therefore, the longer headways are removed from measured data. To determine the threshold which defines "long headways" confidence intervals of 90%, 95%, and 99% from headway distribution have been used. Further, cumulative distribution of volumes were evaluated at their 85, 90, and 95 percentiles. Then the composite evaluation of headways corrected by the "long headway" and volume distribution percentiles is performed. The result revealed that maximum flow rate is between 2,130 pcphpl (passenger cars per hour per lane) and 2,315 pcphpl. Compared to the capacity of 2,200 pcphpl used in the Korea highway capacity manual, capacity appears to correspond to a confidence headway interval of 95%. The study suggests that the rational capacity estimation alternative is to take the 95% of cumulative distribution of observed traffic flows at 95% confidence headway interval eliminating 5% of long headways (i.e., 95-95 Rule).

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 299-309
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00795388
  • Record Type: Publication
  • Report/Paper Numbers: E-C018
  • Files: TRIS, TRB
  • Created Date: Jul 26 2000 12:00AM