U-shaped assembly line layouts and their impact on labor productivity: An experimental study

The decision to move straight-line assembly systems to U-shaped assembly lines systems constitutes a major layout design change and investment for assembly operations. Proponents of the lean manufacturing and just-in-time philosophies assert that U-shaped assembly systems offer several benefits over traditional straight-line layouts including an improvement in labor productivity. This premise often serves as the fundamental reason why firms consider transforming their assembly systems from traditional straight-lines to U-shaped layouts. Surprisingly, little empirical or experimental data supports this assertion. The purpose of this research is to empirically confirm that U-shaped assembly lines improve labor productivity. Results indicate that labor productivity will improve significantly under certain conditions when switching from a straight-line layout to a U-shaped layout but not in all cases. The research also reveals some limitations of such a layout change when factors such as the number of tasks and cycle times are varied.