  Several observables of unbound nucleons which are to some extent sensitive to
the medium modifications of nucleon-nucleon elastic cross sections in
neutron-rich intermediate energy heavy ion collisions are investigated. The
splitting effect of neutron and proton effective masses on cross sections is
discussed. It is found that the transverse flow as a function of rapidity, the
$Q_{zz}$ as a function of momentum, and the ratio of halfwidths of the
transverse to that of longitudinal rapidity distribution $R_{t/l}$ are very
sensitive to the medium modifications of the cross sections. The transverse
momentum distribution of correlation functions of two-nucleons does not yield
information on the in-medium cross section.
