SIMULTANEOUS-EQUATIONS ANALYSIS OF GROWTH IN BUS ROUTE PATRONAGE IN SAN DIEGO

An analysis of data describing 40 months' operating experience for the San Diego Transit Corporation bus system is discussed. The analysis used a simultaneous-equations model estimated by using a pooled time-series/ cross-sectional data base. The model relates the ridership on a specific bus route in a specific month to various influencing factors, particularly the service and fare policies adopted by the system. It also attempts to capture complex interrelations among the influencing factors. The structure of the overall model is summarized. Detailed results, however, are discussed for only one of the five equations in the system, the principal demand equation. Relatively clear bus fare and gasoline price effects were identified, but the separate influence of each of a range of service quality variables (average bus speed, average waiting time, mean stop spacing, and duration of service) was obscured by multicollinearity. Estimates of demand elasticities with respect to a range of different influencing factors are presented, along with associated confidence intervals. Several general conclusions from the analysis are discussed. The work shows that it is possible to use a transit system's time-series operating data in more sophisticated ways than have been customary: The model proved successful in identifying credible structural equations for both demand and supply relations. However, multicollinearity problems are probably intrinsic to the overall approach, and replications of the method are currently strongly constrained by the lack of appropriate computer software. Some potential uses of a model of this type are also discussed.

Media Info

  • Media Type: Print
  • Features: References; Tables;
  • Pagination: pp 58-63
  • Monograph Title: Urban public transportation planning issues
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00372417
  • Record Type: Publication
  • ISBN: 0309034655
  • Files: TRIS, TRB
  • Created Date: Apr 29 1983 12:00AM