Improved Methods of Representing Travel Time Reliability in SP Experiments
COOK A J, JONES P, University of Westminster, BATES J J , John Bates Services, POLAK J, Imperial College and HAIGH M, AEA Techology, UK
Punctuality (i.e. delays) and service reliability (i.e. cancellations) are central both to the rail industlyÔs performance rbghne, linked to the system of financial rewards and penalties, and to the level of passenger demand on individual routes. They are
Punctuality (i.e. delays) and service reliability (i.e. cancellations) are central both to the rail industlyÔs performance rbghne, linked to the system of financial rewards and penalties, and to the level of passenger demand on individual routes. They are generally considered very important variables in travel decisions, particularly the choice of mode. Over time, a poor reputation for service punctuality and reliability will lead to loss of passenger receipts.
There is, however, very little chance of using them as explanatory variables in a Revealed Preference context, and almost all ÒvaluationÓ of punctuality and reliability has been based on hypothetical data. The rail industry has commissioned several studies in the past using stated preference (SP) techniques to obtain passenger valuations, but the results have been inconclusive. The numbers obtained have varied widely fiom one study to another, results have sometimes been counter-intuitive, and values have often been out of line with qualitative findings: passengers say that punctuality is very important, but estimates fiom SP exercises do not usually support this.
Both aspects of punctuality - the Size of the delay and the frequency of delay - must be taken into account. Diffkrent passengers have different tolerance: some would be more tolerant of frequent small delays, and others would ÔpreferÕ occasional larger delays. Research canied out by the authors suggests that serious doubt attaches to most of the estimates of travel time reliability (i.e. punctuality in the case of rail journeys) obtained fiom SP analysis, because of inappropriate presentation of the concept to respondents.
The authors have been involved in on-going work in this area for the last five years. The current study follows on fiom earlier phases of review and data reanalysis and is designed to develop an improved technique for obtaining passenger valuations of punctuality, in particular.
Association for European Transport