This study explores the added value of co-design in addition to other innovation research methods in the process of developing a serious game design document for a road safety game. The sessions aimed at exploring 4 aspects of a location-based game experience: themes, game mechanics, mobile phone applications and locations for mini-games. In total, 72 adolescents between 15 and 18 years participated in five co-design sessions lead by a researcher and a professional game designer. The sessions provided useful input regarding the aspects the authors wished to explore. The sessions were especially useful in gathering input on scoring systems, ways to give instructions about next tasks and organizing level systems. In sum, their study indicates that co-design can be a source of additional ideas on top of other research methods such as state of the art analysis and expert consultation and thus lead to more effective interactive content creation.