  We study an assembly line balancing problem that occurs in sheltered worker
centers for the disabled, where workers with very different characteristics are
present. We are interested in the situation in which parallel assembly lines
are allowed and name the resulting problem as parallel assembly line worker
assignment and balancing problem. We present a linear mixed-integer formulation
and a four-stage heuristic algorithm. Computational results with a large set of
instances recently proposed in the literature show the advantages of allowing
alternative line layouts.
