A joint trip timing store-type choice model for grocery shopping,including inventory effects and nonparametric control for omitted variables

In principle, stochastic modelling methods are ideally suited to the analysis and forecasting of discretionary travel; they formalise both the capriciousness and continuity which are empirically typical of recurrent choice. In practice, the development of theoretically justifiable but tractable stochastic models has appeared to be an illusive goal in transportation research and stochastic models have found little favour. Recent statistical results on the nonparametric characterisation of mixing distributions now enable stochastic models to simultaneously represent a much greater variety of behaviour while, at the same time, actually reducing problems over tractability. The consequent case for reappraisal is illustrated by the development and calibration of a new joint timing/choice model for shopping travel. This model has sound theoretical underpinnings, permits complex variation in the frequency and regularity of shopping due to both observed and unobserved characteristics and constraints, and yet is readily calibrated from diary data.