This paper outlines work in progress on the development of an agent-based model (ABM) of large-scale events employed to investigate the significance of warning message informativeness in the context of evacuations. Unlike other disaster scenarios where the detail within warning messages has been shown to impact response times and decision-making, the effectiveness of such informativeness in large-scale event settings remains underexplored. Our preliminary results indicate that warning message informativity can have a significant effect on decision and evacuation times but other influences on human behaviour such as environmental or social cues also need to be taken into account.