VARIANCES AND COVARIANCES FOR ORIGIN-DESTINATION FLOWS WHEN ESTIMATED BY LOG-LINEAR MODELS

An expression is derived for the variances and covariances of the logarithms of origin-destination flows when estimated by one of a family of log-linear models. Among this family is the Furness growth factor model, the gravity model, the Willumsen model and the Van Zuylen-Bell model. Variances and covariances for the logarithms of the parameters incorporating prior information and for the values of the constraints with which the fitted values must conform are transformed linearly into approximate variances and covariances for the logarithms of the fitted values. Additional error due to misspecification of either the model or the constraints is not taken into account. Depending on the model, the prior information parameters may correspond to values of a deterrence function or to a base year trip matrix, while the constraints may represent design year trip and end totals or traffic counts. As an illustration, the expression is applied to an example involving Willumsen's model. (Author/TRRL)

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/01912615
• Corporate Authors:

  Pergamon Press, Incorporated

  Headington Hill Hall
  Oxford OX30BW,    
• Authors:
  • Bell, MGH
• Publication Date: 1985-12

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 497-507
• Serial:
  • Transportation Research Part B: Methodological
  • Volume: 19B
  • Issue Number: 6
  • Publisher: Elsevier
  • ISSN: 0191-2615
  • Serial URL: http://www.sciencedirect.com/science/journal/01912615

Subject/Index Terms

• TRT Terms: Covariance; Estimating; Logarithms; Mathematical models; Origin and destination; Traffic flow; Variance
• Subject Areas: Highways; Planning and Forecasting;

Filing Info

• Accession Number: 00466010
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• Files: ITRD, TRIS
• Created Date: Mar 31 1988 12:00AM