  The question whether mean field effects exist in heavy-ion collisions at AGS
energies is studied in the framework of A Relativistic Transport (ART) model.
It is found that in central collisions of Au+Au at $P_{beam}/A=$11.6 GeV/c a
simple, Skyrme-type nuclear mean field satisfying the causality requirement
reduces the maximum baryon and energy densities reached in the cascade model by
about 30\% and 40\%, respectively. The mean field affects the inclusive, single
particle observables of various hadrons by at most 20\%. We show, however, that
the mean field causes a factor of 2.5 increase in the strength of the baryon
transverse collective flow.
