IMPROVED METHODS OF REPRESENTING TRAVEL TIME RELIABILITY IN STATED PREFERENCE EXPERIMENTS

Reliability is generally considered a very important variable in travel decisions, particularly the choice of mode. There is, however, very little chance of using it as an explanatory variable in a Revealed Preference context, and almost all "valuation" of reliability has been based on hypothetical data. However, the presentation of reliability in an SP context has proved to be problematic; values are often relatively low and can vary considerably from one study to another. Research carried out by the authors suggests that serious doubt attaches to most of the estimates of reliability obtained from SP analysis, because of inappropriate presentation of the concept to respondents. Formats such as "1 in x journeys are y minutes late" have been shown, using careful de-briefing, to be interpreted very differently by respondents from the way in which the analyst wishes to define them. The authors have been involved in on-going work in this area for the last five years, and have recently developed a carefully conceived computer-based survey vehicle to address the perceived defects of presentation, in the context of rail travel. The interview involves a detailed investigation of the circumstances of the journey, and any attendant time constraints, followed by an initial SP experiment related to flexibility of journey timing. Respondents are then asked for their impression of the existing service in terms of the distribution of delays. This is used within an "educational process" to introduce the concept of reliability and the method of presenting it, as a set of 10 equally likely arrivals relative to the scheduled time: both late and early arrivals are catered for. The second SP experiment is then carried out, to investigate the response to different fares and timetables for two "operators" having different reliability performance. The interview concludes with a simple SP exercise looking at valuations of delays experienced on route. This paper presents both the method of interview and the analysis of the data that has been collected, in some detail. For the covering abstract see ITRD E105584.

Language

  • English

Media Info

  • Features: References;
  • Pagination: p. 37-49
  • Serial:
    • Volume: P434

Subject/Index Terms

Filing Info

  • Accession Number: 00796486
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-86050-325-9
  • Files: ITRD
  • Created Date: Aug 2 2000 12:00AM