  We present a theoretical discussion of the reversible parking problem, which
appears to be one of the simplest systems exhibiting glassy behavior. The
existence of slow relaxation, nontrivial fluctuations, and an annealing effect
can all be understood by recognizing that two different time scales are present
in the problem. One of these scales corresponds to the fast filling of existing
voids, the other is associated with collective processes that overcome partial
ergodicity breaking. The results of the theory are in a good agreement with
simulation data; they provide a simple qualitative picture for understanding
recent granular compaction experiments and other glassy systems.
