  The proposal that the interaction between a macroscopic body and its
environment plays a crucial role in producing the correct classical limit in
the Bohm interpretation of quantum mechanics is investigated, in the context of
a model of quantum Brownian motion. It is well known that one of the effects of
the interaction is to produce an extremely rapid approximate diagonalisation of
the reduced density matrix in the position representation. This effect is, by
itself, insufficient to produce generically quasi-classical behaviour of the
Bohmian trajectory. However, it is shown that, if the system particle is
initially in an approximate energy eigenstate, then there is a tendency for the
Bohmian trajectory to become approximately classical on a rather longer
time-scale. The relationship between this phenomenon and the behaviour of the
Wigner function post-decoherence (as analysed by Halliwell and Zoupas) is
discussed. It is also suggested that the phenomenon may be related to the
storage of information about the trajectory in the environment, and that it may
therefore be a general feature of every situation in which such environmental
monitoring occurs.
