The role of time budgets in models of multi-tasking while travelling: A comparison between the MDCEV and eMDC approach

The increasingly widespread use of mobile technologies and connectivity as well as vehicle automation have triggered renewed attention to the issue of productivity and enjoyment of time spent travelling. Rejecting the traditional assumption that travel time is “wasted”, questions of whether improved fruition of time spent travelling can help encourage PT ridership and affect the uptake of autonomous vehicles draw increasing interest. Yet, the investigation of how people spend travel time, especially from a modelling standpoint, is still an emerging field in travel behaviour research. This paper contributes to this area of study by jointly analysing activity engagement and time use while travelling, with a particular focus on multitasking, i.e. conducting activities other than travel. The application of the newly developed extended Multiple Discrete-Continuous (eMDC) model allows the relaxation of the assumption of a defined time budget, allowing the performance of multiple activities at the same time, and permits investigating substitutions and complementarity effects between different activities. The eMDC is found to be more suitable to model multitasking compared to existing approaches because (i) it does not require arbitrarily dropping activities when they are performed at the same time, and (ii) it allows capturing complementarity and substitution effects. By applying the model to the UK Time-Use Survey, we find that social and work activities as well as social and mass media consumption are substitutes while travelling. We also forecast time-use changes under different transport policy scenarios, proving impacts of substitution effects. While eMDC is our preferred approach, we observe that depending on the choice of modelling framework, the results can lead to different conclusions concerning suitability of particular policy measures. Hence, for future applications, testing of different frameworks is advised to assess sensitivity of the conclusions to the implicit modelling assumptions.