Chapter 7: The Aggregate–Disaggregate–Aggregate (ADA) Freight Model System

Disaggregate models — defined here as models using observations at the level of the traveller, the travelling group, the business establishment or the shipment — have several advantages over aggregate models (which use groupings of those units as observations, e.g. groupings by geographic zone). Disaggregate models can be based on a foundation in behavioural theory, can include more detailed policy-relevant variables and do not suffer from the aggregation biases of aggregate models. Nevertheless, there are perfectly valid reasons why some of the components of a model system are modelled in an aggregate fashion. In this paper, we propose an aggregate–disaggregate–aggregate (ADA) model system for freight transport.