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TopThis progress of MEU has led to changes the specification of a utility function that incorporates travel time variability, and also leads to significant innovations in the way that stated choice (SC) experiments have to be designed to capture travel time variability. In recognition that travel time does vary, a series of arrival times, rather than the extent and frequency of delay, have been considered in recent SC experiments (see, e.g., Senna, 1994; Noland and Small, 1995; Small et al., 1999; Hollander, 2006; Asensio and Matas, 2008; Batley and Ibáñez, 2009). However, in stated preference studies not established on RUM, travel time variability is typically presented as the extent and frequency of delay relative to ‘normal’ travel time (see e.g., Jackson and Jucker, 1982; Small et al., 2005).
In terms of the modelling framework, the mean-variance model and the scheduling model are two dominant approaches in the transport literature; while most stated preference (SP) experiments are similar to Small et al. (1999) (see Table 1) with some slight changes (e.g., some used vertical bars to represent travel times (e.g., Batley & Ibáñez, 2009); some provided 10 travel times instead of five (see e.g., Bates et al. 2001; and some show the departure time explicitly to the respondents (e.g., Holland, 2006). The behavioural paradigm widely used in the MEU model is a mix of Random Utility Maximisation (RUM) and Expected Utility Theory (EUT) (i.e., a linear utility specification with linear probability weighting).