This volume is based on selected papers presented at the triennial IATBR (International Association for Travel Behavior Research) conference in August 2003. We also published the previous four volumes in this series (by Hensher, Mahmassani, Ortuzar, Stopher); the Hensher volume included a paper by Nobel Prizewinner Dan McFadden and sold out its initial printrun.

In aiming to understand and model peoples' out-of-home movements, the academic field of transport planning is confronted with two major challenges. Firstly, leisure travel is increasing in importance and is more complex and variable than work-related travel, being less rigid in temporal and spatial patterns and more influenced by external factors such as social contacts or weather conditions. Secondly, traditional aggregated transport models do not include any information on peoples' social interactions or their personal social networks. In contrast, the recent development and availability of...