Sébastien Motsch - Arizona State University Fundamental diagram is at the core of traffic modeling. Understanding how the density influences the flux is of primary importance to optimize traffic efficiency. In this talk, we explore such fundamental diagrams experimentally and analytically for pedestrian and ant dynamics. For pedestrians, we introduce a so-called bi-directional fundamental diagram to relate the pedestrian fluxes to both the co- and counter-moving pedestrian densities. Such bi-directional diagram generates complex dynamics as the model is not always hyperbolic. As for the ants, despite their behavioral simplicity, their fundamental diagram is remarkable since no traffic jams are observed even at high density. Studying ants' individual behavior (i.e. number of contacts, traveling time) give some insights on how they manage such a tour de force.