We can draw the following conclusions from the
literature. First, in spite of their dominance in practice,
pickers-to-parts order-picking systems have
received less research attention compared to partsto-
picker order-picking systems. Less than 30 percent
of the about 140 papers we considered concerns
pickers-to-part order-picking systems. The reasons
for this may have something to do with the complexity
and diversity of picker-to-parts order-picking
systems. Furthermore, parts-to-picker systems
are often fully or partly automated, thus catch the
attention of researchers