Amending the Incentive for Strategic Bias in Stated Preference Studies

Abstract

Stated preference (SP) methods have been used extensively in transport research and elsewhere, both to forecast demand and to value the importance attached to different product features and travel attributes. Before introducing new or refurbished rolling stock as part of their franchises, British Train Operating Companies (TOCs) have often carried out SP surveys to investigate passenger preferences and to test whether the improvement of the fleet and services is enough to recover the cost through increased fares and patronage and thus to evaluate the costs and benefits of this investment. The rolling stock value derived from SP results is used not only for welfare appraisal and pricing but also for rail demand forecasting. Alongside the broader acceptance and wider application of SP methods, some practitioners have argued for greater openness in discussing what they have seen as significant concerns surrounding SP. The issue of the strategic biasing of SP responses was specifically addressed by examining the incentive compatibility of SP responses related to task complexity and the presence of specific antibias warnings in the questionnaire. Methods to amend incentive to bias were suggested. Adding cheap talk script reduces the overestimation of valuation of improved rolling stock in the case study; however, bias may remain. Adding more attributes to the SP experiment does not show a significant impact on the estimation bias, but contributes to a higher error variance in responses.

Price Elasticity of Demand on the High-Speed Rail Lines of Spain: Impact of the New Pricing Scheme

“…Similarly, the remaining elasticities confirm the expectations, an increase in cost is likely to increase the demand for competing goods or services. However, in spite of these unquestionable achievements, cross elasticities are nonetheless beset by bias in the answer due to the fact that the same person answered several questions about his journey (45).…”

Road user charging in rural areas: Upper Derwent valley, UK

“…As was expected, willingness to pay the road user charge is higher at the point of destination as respondents who have recently visited the site have a higher utility and value the valley more. Those two values are also subject to the sample limitations and common stated preference bias (Lu et al, 2008). Both values are near the £2-3 margin that was found to be the most probable and preferable fee by the stakeholders interviewed for this case study.…”

“…An additional interesting finding about the road charging fee level was a small peak of responses at the value of £5. There is no clear reason to explain this apart from questionnaire bias (Lu et al, 2008) and a potential response influence by the London congestion charge (£5) which was introduced a few months earlier and was widely covered by media at a national level. Respondents were possibly influenced by the maximum toll value used in the SP survey (£5), which was asked before this willingness to pay (WTP) question.…”

The Combination of a Fuzzy Analytical Hierarchy Process and the Taguchi Method to Evaluate the Malaysian Users’ Willingness to Pay for Public Transportation

“…One of the ways to measure the quality and improvement of public transportation is using discrete choice models. In this aspect, the MNL framework, which is mainly used for discrete models, can be utilized in assessing the WTP choice behavior among the public transportation users, in which the different transport modes become the variables in the assessment [23][24][25][26]. Other than MNL, nested logit and error components logit were also applied in previous studies [2,27].…”