Ergonomic Workload Analysis of Based on the Roof Height of Delivery Vehicles

Objective: The purpose of this study is to ergonomically analyze the workload associated with the roof-height of the cargo area in delivery trucks, targeting courier workers operating in logistics terminals.<br/>Background: To promote ground-level park development in apartment complexes as part of efforts to improve residential environments and address traffic safety issues, restrictions are being placed on the entry of delivery trucks based on the roof-height of their cargo areas.<br/>Method: A total of 18 industrial male workers participated in the experiment (high-roof: 9, low-roof: 9). This study considered four independent variables: roof-height (high, low), task (loading, organizing, unloading), work timing (before work, after work), and body parts (neck, shoulder, lower back, knee, whole body). The objective dependent variable, rapid entire body assessment (REBA) score, was analyzed, and the subjective discomfort was assessed using visual analogue scale (VAS) to evaluate perceived discomfort. The entire body movements of the subjects were continuously recorded using a compact camcorder. Before and after the tasks, subjective discomfort in each body part was assessed using a questionnaire. To statistically analyze the significant differences according to the experimental design, a repeated measures ANOVA was performed.<br/>Results: The ANOVA results for the REBA score showed statistically significant differences, with the main effects (roof height: p=0.007, task: p<0.000) and interaction effect (p<0.000). The mean REBA score showed a significantly higher risk for low-roof height compared to high-roof height. The REBA scores for the tasks of organizing and unloading were significantly higher in the low-roof height. The ANOVA results for the subjective discomfort showed statistically significant differences, with all main effects (roof height: p<0.000, task: p=0.001, body part: p<0.000, work timing: p=0.003) and the two-way interaction effect between roof height and work timing (p=0.003). The mean subjective discomfort in the lower back, overall body, and knee was found to be significantly higher. In low-roof height, the mean subjective discomfort significantly increased after work compared to before work. Conclusion: Low-roof vehicles repeatedly expose workers to bending and crouching postures, leading to a high risk of musculoskeletal disorders and increased subjective discomfort, emphasizing the urgent need for ergonomic improvements.<br/>Application: Based on the findings of this study, ergonomic improvements for low-roof vehicles are suggested, which are expected to reduce the physical workload.