This study examines some of the popular demand equations available for assessing future conditions of intercity travel demands and in knowing the passenger's response to a fare hike. Planners need to be able to forecast correctly how a reduction in air fare would affect the passenger demand for airlines and other competing modes such as rails and buses. These demand equations are designed to satisfy three basic properties: homogeneity, summability, and symmetry. The five demand models discussed in this paper are: a double-log demand model, an inequality-constrained double-log demand model, a weighted Stone model, the Rotterdam system of demand equations, and a homogeneous translog demand model. The results of the study indicate that demand equations that are imposed by the homogeneity, summability, and symmetry conditions provide more stable results on the compensated cross elasticities than those equations that do not have such conditions imposed. In general, the market cross elasticities--the traditional means of assessing travel demand--are very unstable; and they vary depending on the choice of functional forms, even when we impose the three basic conditions on their demand equations.

Media Info

  • Media Type: Print
  • Features: References; Tables;
  • Pagination: pp 72-76
  • Monograph Title: Passenger travel forecasting
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00310706
  • Record Type: Publication
  • ISBN: 0309029813
  • Files: TRIS, TRB
  • Created Date: May 21 1981 12:00AM