This paper presents a study, including a literature survey, whose objective is to define model structures which can be used to predict the long-term impact of carpool policy measures in The Netherlands. The models used are extensions of the Dutch National Model System (NMS). With respect to the impact of policy measures, the study is mainly concerned with: (1) the number of poolers, the number of pools, and the vehicle occupancy; (2) the net change in car distance travel by zone, which influences emissions, and by link and time of day, which influences congestion; and (3) the use of other modes, especially public transport. Carpooling is here defined as the regular shared use of a passenger car or minibus. Some remarks are made about the classification of carpoolers. The following types of estimation methods and models for carpooling are discussed: (1) the transfer of key figures on carpooling potential, derived from other areas or firms; (2) trip table analysis; (3) mode choice models; (4) mode choice models combined with supply models; and (5) carpool formation models. The structure of an envisaged carpooling model for The Netherlands is outlined, and some of its components are identified. Several conclusions are presented.
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