Evidence for Modal Inertia in Multimodal Tours: An Integrated Choice and Latent Variable Modeling Approach

Abstract

In this paper, we aim to answer two main questions in the context of multimodal travel and new modes of transportation, such as autonomous vehicles: firstly, as travelers gain the ability to readily compare modes side by side for each trip, will they become more willing to select the option that best meets their needs in the moment, or will they continue to prefer using a single mode for a whole tour? Secondly, we compare two approaches to estimating mode choice models in the context of a typical workday tour: one in which we enumerate each possible sequence of modes, and one in which we calculate the expected utility given all modes available for each trip separately, and sum over all trips in the tour. We find that the latter approach returns similar estimation results to the former, but is much faster and easier to compute, an advantage that would only grow with more mode alternatives or more trips in the tour. In addition, we discovered a substantial “mode inertia” in our sample: the utility of the mode used for the previous trip is significantly higher for the present trip. This finding indicates that respondents in our sample are more likely to stick with unimodal tours than multimodal ones.