Should terminal station operators take steps against terrorist events by developing security checks or should they rely on open transit systems and smooth pedestrian flows as key factors of security prevention? The authors argue that the necessity to articulate fluidity and security strategies in saturated transport places necessitates a careful approach of the spatial insertion of passenger flow as well as a contextual - and critical - perspective of security governance in stations. The demonstration is developed in two stages. Based on a worldwide census and a critical analysis of these events, this article makes a clear correlation between the increase of terrorist attacks in railway stations and the installation of boarding controls. The study of the different positions of these security devices gives a typology of possible access control perimeters. The case of Paris Nord Station boarding controls is then studied in more detail. There, the security gates destabilise boarding and circulation to the point that they are regularly neutralised in order to limit the crowding problems they create. Yet, the devices remain in place since 2015 Thalys attacks for their performing value and because of the State will make visible and enact a permanent defence to terrorist risk, through space.