  By means of a novel variational approach and using dual maps techniques and
general ideas of dynamical system theory we derive exact results about several
models of transport flows, for which we also obtain a complete description of
their limit (in time) behavior in the space of configurations. Using these
results we study the motion of a speedy passive particle (tracer) moving
along/against the flow of slow particles and demonstrate that the latter case
might be more efficient.
