  For single-lane traffic models it is well known that particle disorder leads
to platoon formation at low densities. Here we discuss the effect of slow cars
in two-lane systems. Surprisingly, even a small number of slow cars can
initiate the formation of platoons at low densities. The robustness of this
phenomenon is investigated for different variants of the lane-changing rules as
well as for different variants on the single-lane dynamics. It is shown that
anticipation of drivers reduces the influence of slow cars drastically.
