Ants never overtake. Not ever. Instead they form into platoons in which all the ants move at the same speed. Increase the density of ant traffic and the platoons simply join together to form larger groups. This is how the velocity remains the same while the density increases.
Alexander John and colleagues at the University of Cologne in Germany have discovered lessons from ant traffic that can be incorporated in traffic planning. This is just one of the applications gleaned from biomimicry.