The gantry system has been widely employed within rice seedling centres in Taiwan to transport planting boxes. The objective of this study was to develop a computer model to simulate this process by evaluating two transport activities in four seedling centres in Taiwan. In the "rst, the seeded boxes are moved to the "eld for sprouting. In the second, boxes of seedlings are moved from the "eld for transplanting. The throughput performance and worker e$ciency of each centre was measured and compared. Variables include "eld shapes, operation methods, and number of labourers. The predicted values agree well with observed values.
The model shows that a poor allocation of labour force leads to an imbalanced workload, restrictions in the work#ow and decreased system throughput. Optimum operating e$ciency occurred in simulation where seven labourers worked on both sides of a gantry, in "elds 7)6 m in width. Peak simulated throughput reached 3716 seeded boxes per hour moving into the nursery "eld and 2155 boxes of seedlings per hour moving out of the "eld. Installation costs were higher for the longer gantry operations. With "elds of identical size, hardware cost for the 200 m gantry was 39)5% higher than for the 100 m gantry, and 47% higher than the 50 m gantry.