This paper explores the creation and use of a long-term global tourism transport model for private and public sector tourism policy makers. Given that technology is unlikely to reduce tourism transport's impact on climate change sufficiently to avoid serious dangers, behavioural change is necessary. The model presented here helps policy makers and the tourism sector evaluate behavioural change measures. Such tools to assess long-term (up to a century) policy impacts do not currently exist. Projecting behavioural change over such long periods is difficult with contemporary economic modelling. This paper's model is founded in psychological economics theory and mechanisms at work in product diffusion. It describes the tourism system based on identifiable mechanisms and not on statistical relations with only current validity. It delivers global numbers of trips and distances travelled per transport mode as a function of transport cost, travel time, population and income distribution. The model is based on theories including product innovation theory (Bass model) and prospect theory (psychological value). It has been successfully calibrated to tourism development between 1900 and 2005 and tested against future low and high growth economic and demographic scenario combinations. Implications for tourism travel and climate change are discussed.