  We present a model of ant traffic considering individual ants as
self-propelled particles undergoing single file motion on a one-dimensional
trail. Recent experiments on unidirectional ant traffic in well-formed natural
trails showed that the collective velocity of ants remains approximately
unchanged, leading to absence of jamming even at very high densities [ John et.
al., Phys. Rev. Lett. 102, 108001 (2009) ]. Assuming a feedback control
mechanism of self-propulsion force generated by each ant using information
about the distance from the ant in front, our model captures all the main
features observed in the experiment. The distance headway distribution shows a
maximum corresponding to separations within clusters. The position of this
maximum remains independent of average number density. We find a
non-equilibrium first order transition, with the formation of an infinite
cluster at a threshold density where all the ants in the system suddenly become
part of a single cluster.
