Thurston introduced train tracks and geodesic laminations as tools to
study surface diffeomorphisms and Kleinian groups. We'll start the
talk with a relaxed introduction to these. Then, in analogy with the
end invariants of Kleinian groups and Teichmüller geodesics, we will
define the end invariants of an infinite splitting sequence of train
tracks. These end invariants determine the set of laminations that
are carried by all tracks in the infinite splitting sequence. If
there is time, we'll use these ideas to sketch a new proof of
Klarreich's theorem, determining the boundary of the curve complex.