  The purpose of this paper is to study optimality of circular
neighbor-balanced block designs when neighbor effects are present in the model.
In the literature many optimality results are established for direct effects
and neighbor effects separately, but few for total effects, that is, the sum of
direct effect of treatment and relevant neighbor effects. We show that circular
neighbor-balanced designs are universally optimal for total effects among
designs with no self neighbor. Then we give efficiency factors of these
designs, and show some situations where a design with self neighbors is
preferable to a neighbor-balanced design.
