The chapter discusses the nature of scenario building process in general and how scenarios contributed to the design process in the case of an educational project on inner-city public transportation design. Scenario building is widely used as a resourceful method to explore and foresee the experiential aspects of user-product interaction in the product design process. Traditional ergonomics uses scenarios as part of evaluating and modelling the human performance in work conditions. Accident scenarios and task analysis are used both to analyse the efficiency of workplaces and to foresee possible failure conditions in order to increase human performance. Scenario building is mainly used as a method in the concept generation phase of the design process. Initial research phase which supports scenario building involves exploring existing situations and conditions by focusing on real contexts in which people use the product or service under consideration.