Modelling of human behaviour during emergencies is an important issue to be investigated to improve the safety of transportation infrastructures. This behaviour can be influenced by both the environment (i.e. social influences) and characteristics of the users of infrastructures. The main aim of this paper is to investigate the social influences that push a user to manifest a herding behaviour during evacuations. A behavioural model based on discrete choice models is proposed by using data collected through an on-line survey. This approach is able to highlight the heterogenic tastes of decision makers that may influence this choice in exit behaviour. The results show that decision makers are influenced by both people close to the exit and their socio-economic characteristic.