  Recently it has been shown that the zero-energy eigenstate -- corresponding
to the stationary state -- of a stochastic Hamiltonian with nearest-neighbour
interaction in the bulk and single-site boundary terms, can always be written
in the form of a so-called matrix-product state. We generalize this result to
stochastic Hamiltonians with arbitrary, but finite, interaction range. As an
application two different particle-hopping models with three-site bulk
interaction are studied. For these models which can be interpreted as cellular
automata for traffic flow, we present exact solutions for periodic boundary
conditions and some suitably chosen boundary interactions.
