To investigate perpetrators of aggression on public transport aims to gain research insights into the causal chain leading to the emergence of violent incidents on public transport so that a structural approach to aggression can be developed on public transport. The research aims to identify the motivational and inhibitory factors that play a role in the establishment and the further development of a violent incident on the one hand and the de-escalation, and the control of the conflict on the other hand. Attention is given to the distal and proximal causes of aggression.