Abstract Congestion games have many important applications to systems where only limited knowledge may be available to players. Here we study traffic networks with multiple origin-destination pairs, relaxing the simplifying assumption of agents having complete knowledge of the network structure. We identify a ubiquitous class of networks, i.e., rings, for which we can safely increase the agents’ knowledge without affecting their own overall performance – known as immunity to Informational Braess’ Paradox – closing a gap in the literature. By extension of this performance measure to include the welfare of all agents, i.e., minimisation of social cost, we show that IBP is a widespread phenomenon and no network is immune to it