A lattice model for active - passive pedestrian dynamics: a quest for drafting effects

We study the pedestrian escape from an obscure room using a lattice gas model with two species of particles. One species, called passive, performs a symmetric random walk on the lattice, whereas the second species, called active, is subject to a drift guiding the particles towards the exit. The drift mimics the awareness of some pedestrians of the geometry of the room and of the location of the exit. We provide numerical evidence that, in spite of the hard core interaction between particles - namely, there can be at most one particle of any species per site - adding a fraction of active particles in the system enhances the evacuation rate of all particles from the room. A similar effect is also observed when looking at the outgoing particle flux, when the system is in contact with an external particle reservoir that induces the onset of a steady state. We interpret this phenomenon as a discrete space counterpart of the drafting effect typically observed in a continuum set - up as the aerodynamic drag experienced by pelotons of competing cyclists.