Interchange or transfers for passengers in large multimodal public transport networks are more or less inevitable. A zone based fare system has the potential to ensure that there is no financial penalty for interchange. In South East Queensland (SEQ), Australia, there is a zone based fare system in place which does not penalize transfers within the same zone but does charge a full fare for an inter-zone transfer in a single journey. This research investigates the interchange effects from an analysis of passengers' travel patterns using the smart card data from the automated fare collection system in place in SEQ. Latent class nested logit models are estimated with social demographic characteristics to measure transfer behaviour and are used to investigate the opportunity for better interchange policies to increase the network effect in the SEQ network. The results identified passengers' heterogeneous preferences towards travel alternatives with markedly different market segments. The empirical results identified passengers categorised into four segments of employees, students, wealthier people and seniors. The findings suggest that public transport network effects are most important to the employee segment with student and senior segments being more likely to choose direct alternatives over alternatives involving interchange. In order to enhance the public transport network effects, two policies to encourage transfers by passengers are investigated using simulations with the policy implications identified.