  We consider a model in which accelerated particles experience line--elements
with maximal acceleration corrections. When applied to the Schwarzschild
metric, the effective field experienced by accelerated test particles contains
corrections that vanish in the limit $\hbar\to 0$, but otherwise affect the
behaviour of matter greatly. A new effect appears in the form of a spherical
shell, external to the Schwarzschild sphere, impenetrable to classical
particles.
