A comparison of U-line and straight-line performances under stochastic task times

Traditionally, assembly lines are laid out in a straight-line configuration where a worker covers only adjacent stations. In a U-line layout, on the other hand, two or more non-adjacent stations can be physically close to each other, making it possible for a worker to cover nonadjacent stations. This added flexibility increases the decision space for U-line layouts and can result in better balanced lines. This paper examines the impact of stochastic task times on the relative performance of U-line and straight-line layouts. Several analytical and simulation results are presented, and insights are provided to explain the difference in the performance of U-line and straight-line layouts. To summarize our main results, although balanced U-line layouts are at least as productive as balanced straight-line layouts given deterministic task times, they can be less productive given stochastic task times if they are balanced deterministically using mean times.