Recognising car-dependence problem as a pressing problem, travel mode choice has become an important area in transport policy. A lot of money and efforts have been put to use on promoting demand management measures to reduce car-use, however, the results have often been disappointing. Structural interventions seem to be effective since they offer material incentives and physical enforcement. On the other side, psychological interventions lack of those characteristics so that they are prone to be ineffective. However, their effectivenesses may be enhanced if more consideration and emphasis is given to the support of social incentives derived from social-psychological considerations of human behaviour. Given the fact that behavioural change does not take place in a social vacuum, broader society and its social values have important roles to play. Social-psychological aspects (e.g. social norms, altruism, social learning, expectation of others, etc), may influence mode choice decision making and behaviour of travellers. These aspects exist in our daily life but we are often unaware and underestimate them, and then leave them unconsidered, especially in the study of travel behaviour. Better understanding of their influences on travellers� behaviour may give useful informed insights for utilizing them to encourage behavioural change. The study aims to investigate about what aspects are influential and how they influence travellers� decision making and behaviour, and furthermore, to find out the possibility of utilizing them to enhance policies on behavioural change. Empirical data from behavioural surveys and laboratory experiments will be collected and used to understand the relationships between these aspects and their influences on behaviour. Models that are sensitive to social-psychological factors will be developed.