Consistent Route Flows and the Condition of Proportionality

User equilibrium (UE) static deterministic traffic assignments are widely used in travel forecasting practice. Forecasting analyses that are based on route flows are also quite common, even though it is well known that route flows are not uniquely determined by the UE conditions, unless an additional condition is imposed, such as the condition of proportionality. The purpose of the research described here is to examine the nature and magnitude of the differences in route flows in a practical setting, by applying several assignment tools that are commonly used in practice, as well as a research assignment tool (TAPAS), to a case study based on the network of the Chicago region. Select link analyses from the various solutions are compared with each other, showing that the differences in the results are practically meaningful. The findings show that TAPAS can produce a solution that satisfies the condition of proportionality nearly perfectly. Implementations of the Frank-Wolfe algorithm produce solutions that reasonably satisfy proportionality, but satisfactory levels of precision (UE convergence) require substantial computation times. Alternative commercially available assignment tools provide quick precision, but their solutions seem to deviate considerably from the condition of proportionality in the cases examined so far.


  • English

Media Info

  • Media Type: DVD
  • Features: Figures; Maps; References;
  • Pagination: 23p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01155140
  • Record Type: Publication
  • Report/Paper Numbers: 10-1526
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 10:40AM