# Ergonomics Study of Musculoskeletal Disorders Among Tram Drivers
## 4 Discussion
### Practical Implications and Design Recommendations  
The study highlights the importance of integrating adjustable components into tram cabin design, such as seat height, lumbar support, and control positioning. Procurement specifications for public transportation vehicles should explicitly require ergonomically adaptable workspaces. By aligning vehicle design with anthropometric diversity, operators can reduce the risk of WMSDs and improve driver comfort and performance. These findings reinforce the need for future tram designs to incorporate adjustability features as a standard requirement. Designing solutions that allow adaptation for the seat, pedal, and control panel can significantly improve ergonomic fit and accommodate a broader user base. Such criteria should be integrated into rolling stock procurement to ensure compatibility with anthropometric diversity. The findings of this study emphasize the critical role of anthropometric compatibility in the ergonomic design of tram driver cabins. Through the application of RULA and REBA tools, as well as the biomechanical modeling of lumbar loading, it was demonstrated that current driver workstations impose moderate to high musculoskeletal risk across all three representative morphotypes (SmallW, MidM, and TallM). Identical REBA and RULA scores (score 6) indicate that key body regions--particularly the lumbar spine, neck, and shoulders--are under considerable static and postural strain during typical tram operation. This study represents a preliminary ergonomic analysis based on three representative morphotypes (SmallW, MidM, and TallM), selected to illustrate potential mismatches at the lower, middle, and upper ends of the anthropometric spectrum. Although these models do not cover the full diversity of the population, they provide a foundation for methodological validation. Future research will include a broader range of body types and measurements from actual participants to improve the representativeness and applicability of the results. In line with ergonomic design principles, it is widely recommended that workplaces be designed to accommodate at least 90% of users--typically ranging from the 5 th to the 95 th percentile--in order to ensure inclusivity, safety, and comfort across the working population. This approach helps minimize the exclusion of both smaller and larger individuals and reduces the risk of work-related musculoskeletal disorders [3; 47; 51]. While this study included three morphotypes corresponding approximately to key percentiles (SmallW \(\approx\) 5 th percentile female, MidM \(\approx\) 50 th percentile male, TallM \(\approx\) 95 th percentile male), future research will expand to a more detailed percentile-based design analysis to support broader design applicability. Additionally, the calculated lumbar moments at the L4/L5 intervertebral level (51.35 Nm for SmallW, 71.12 Nm for MidM, and 101.67 Nm for TallM) confirm that taller and heavier drivers experience significantly greater mechanical loading. This loading increases the risk of disk herniation and long-term spinal degeneration, especially in professions involving prolonged sitting without adequate support. As previous studies have shown, unsupported or improperly flexed postures considerably elevate the pressure on intervertebral disks, particularly at the L4/L5 level, which is already anatomically predisposed to biomechanical stress. The focus of this study was on evaluating the current tram driver workspace and exploring how minimal adjustments, especially those under the driver's control, could contribute to reducing the risk of work-related musculoskeletal disorders (WMSDs). While general recommendations for system-level changes were beyond the scope of this preliminary analysis, future work will address procurement-level guidelines and provide more comprehensive design recommendations aligned with anthropometric standards such as ISO 3411, ISO 7250-1, and DIN 33402-2 [47; 50; 52].