Adaptable Assignment
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Adaptable Assignment

  • Published Date:

    1997

  • Language:
    English
Filetype[PDF-25.05 KB]


Details:
  • Resource Type:
  • TRIS Online Accession Number:
    789768
  • NTL Classification:
    NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION ; NTL-PLANNING AND POLICY-Travel Demand ; NTL-PLANNING AND POLICY-Management Systems ; NTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic Flow ; NTL-REFERENCES AND DIRECTORIES-Statistics ;
  • Abstract:
    This paper reports on a practical, simple method for adjusting a vehicle trip table so that the resulting assignments more closely match available traffic counts. "Practical" means that this is not purely a research effort - the procedure described here has been used in several studies as production- ready tool. "Simple" means that no special programming is necessary - the method can be implemented using existing travel modeling software packages. This procedure does not create a trip table directly from only traffic counts, but rather adjusts an existing table. The method discussed here avoids elaborate algorithms in favor of a more easily understood "brute force" approach. The process requires the construction of minimum paths and the summation of the total count and total assigned volume (on links with counts) for each origin-destination (O-D) pair. This information can readily be used to adjust the trips in each O-D pair. By iterating the process many times, dramatic improvements in the root-mean square assignment error can be achieved without unduly distorting the original trip table. This has been implemented as a simple multi-step procedure using the MINUTP software package; it may be possible to apply the procedure using other packages as well. The process results in a "delta" trip table, representing the difference between the original and adjusted trip tables. This delta table can be used by itself in forecasting or as the basis from which a model can be adjusted. This procedure has been used in several cities in New Jersey and Pennsylvania, with satisfactory results. 8p.
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