Social-psychological aspects are likely to be influential in the dynamics of travellers' mode choice behaviour. The study aims to understand the role of the social-psychological aspects, particularly social interaction, social learning and social influence, on the dynamics of travellers' mode choice decision making and behaviour, and furthermore, to find out the possibility of utilizing them to enhance policies on behavioural change. Social interactions, which may due to an interdependent situation between travellers, social information about other travellers' behaviour and communication between travellers, enable social learning and social influence processes between travellers. A behavioural survey is used to provide initial insights regarding the influence of the social aspects and to set parameter values for further stages of study. Then the study utilizes innovative methodology involving laboratory experiments to capture the role of the social interactions in the dynamics of human subjects' decision I11aking over tilne, which is extended with more individuals, longer repetitions, and various settings in multi-agent simulation experiments. The laboratory experiments found that effects of social interaction and social learning are more visible and significantly observed at individual and group level than at aggregate level. Social interaction produces different effects between different individuals or groups of individuals. Some individuals are positively or negatively influenced, others may not be influenced. Providing more information increases the level of uncertainty as travellers' know what other travellers' doing and they react accordingly by changing their choices, thus producing instable situation. Analyses of group and individual behaviour reveal that people learn individually from their previous experience and socially from other people. It is revealed that confirmation (keeping previous behaviour when the observed individuals also previously chose the same choice) and conformity (following the choice of the majority or plurality) models are likely to exist whenever individuals have access to social information. In long-term, strong reliance on these two social learning mechanisms (confirmation and conformity) has two opposite effects (negative and positive, respectively) as shown in a simulation experiment. Another simulation experiment shows that repeated social interactions between individuals through various domains and the existence of a small number of 'key people' produces a higher level of cooperation. These findings elicit some behavioural, policy and methodological implications and encourage further studies.