  One standard approach to describe the collective behaviour of self-propelled
particles is the Vicsek model: point-like self-propelled particles tend to
align their migration directions to the ones of their nearer neighbours at each
time-step. Here we use a variant of the Vicsek model that includes pairwise
repulsive interactions. Confining the system between parallel walls can
qualitatively change its appearance: a laning state can emerge that is
different from the ones previously reported. All lanes show on average the same
migration direction of the contained particles with a finite separation
distance between the lanes. Furthermore, in certain parameter ranges we observe
collectively migrating clusters that arrange in an approximately hexagonal way.
We suggest that the mechanism behind these regular textures is an overreaction
in the alignment mechanism. Considering the more realistic scenario of
non-point-like particles in the presence of confining surfaces is generally
important for the comparison to experimental systems.
