This study investigates the impact of pick location height switching on task performance time in manual order picking systems. Drawing on task switching theory, we examine whether switching between ground- and chest-level pick locations increases task performance time, whether switching costs are asymmetric, and whether item weight strengthens possible differences between ground-to-chest and chest-to-ground switches.
We adopt a two-stage approach that combines internal validity and operational generalizability. First, a controlled eye-tracking experiment simulates a simplified order picking scenario to explore the cognitive mechanisms underlying visual search when repeating versus switching pick location heights. Second, we analyze 3,537,973 pick location visits from a German grocery retail warehouse to test the effects of pick location height switching in a real-world operational environment with professional order pickers.
The eye-tracking experiment provides mechanism-oriented evidence that switching between pick location heights increases visual search time and reorientation demands under controlled conditions. The archival field study complements these behavioral insights by showing that height switching is associated with longer task performance time. It further shows that switching costs depend on direction, with ground-to-chest switches being more time-consuming than chest-to ground switches. This directional difference becomes more pronounced as item weight increases.
The findings suggest that warehouse managers should consider not only the frequency but also the direction of height switches when designing picking sequences. Batching and routing algorithms could incorporate switching costs as a weighted parameter, with particular attention to ground-to-chest switches involving heavier items. However, reducing height switches should be balanced against ergonomic risks, as long sequences of ground-level picks may increase repetitive bending and musculoskeletal strain.
This study provides the first empirical evidence on pick location height switching in warehouse operations and extends task switching theory to a new operational context. By combining mechanism-oriented eye-tracking evidence with large-scale field data, we show that height switching is associated with asymmetric switching costs and provide insights into the cognitive and motor reorientation processes that may underlie these effects.
