Differences among Route Flow Solutions for the User-Equilibrium Traffic Assignment Problem
Publication: Journal of Transportation Engineering
Volume 133, Issue 4
Abstract
User-equilibrium (UE) traffic assignment is widely used in travel forecasting models. Analyses of assignment results often require detailed information about route flows. For a given UE model, total link flows are uniquely determined, but there can be many route flow solutions. Our goal is to evaluate the potential disagreement between different route flow solutions for the same UE model. We considered a case study of a UE model for the Chicago region. We examined 1,000 different UE route flow solutions. Out of 127,248 routes used by UE solutions, 53,134 have alternatives. For 51,748 routes (97%) the flow is completely undetermined, meaning that it is zero in one UE solution and equal to the total origin-destination (O-D) flow in another UE solution. Significant differences were also found in the distribution of users of a given link among O-D pairs (“select link analysis”). We conclude that in analyses that require route flows, it is important to make a proper choice of a specific route flow solution, such as the maximum entropy user equilibrium route flow solution.
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Acknowledgments
The writers wish to thank David Boyce for his comments on previous versions of this paper. Financial support from the United States-Israel Binational Science Foundation through Grant No. UNSPECIFIED2002145 is greatly appreciated.
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Information & Authors
Information
Published In
Journal of Transportation Engineering
Volume 133 • Issue 4 • April 2007
Pages: 232 - 239
Copyright
© 2007 ASCE.
History
Received: Jan 9, 2006
Accepted: Oct 3, 2006
Published online: Apr 1, 2007
Published in print: Apr 2007
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