# Ergonomics Study of Musculoskeletal Disorders Among Tram Drivers
## 4 Discussion  
### Interpretation of Postural Risk Scores  
REBA and RULA evaluations were conducted for all three anthropometric types. The results yielded consistent scores across models. Each driver received a REBA score of 6, placing them in the moderate risk category (action level 2), indicating the need for further investigation and suggesting that the posture and work environment should be modified in the near future [37]. This score reflects a work scenario where ergonomic interventions are necessary to reduce the likelihood of musculoskeletal disorders. The RULA analysis also returned to a score of 6 for each model, placing the posture in the high-risk category with an action level of 3. This score signals the need for prompt ergonomic assessment and corrective action [8; 27]. According to RULA interpretation \begin{table}
\begin{tabular}{c c c c} \hline  & **TallM** & **MidM** & **SmallW** \\ \hline RULA & 6 & 6 & 6 \\ REBA & 6 & 6 & 6 \\ L4/L5, Nm & 101.67 & 71.12 & 51.35 \\ \hline \end{tabular}
\end{table} 
Table 2: Results for RULA, REBA, and for lumbar moment at L4/L5 for SmallW, MidM, and TallM. Figure 6: (a) RULA score with ErgoFellow 3.0 software, (b) REBA score with ErgoFellow 3.0 software. guidelines, scores of 5-6 indicate a posture that requires investigation and imminent change [36]. The RULA and REBA results are shown in Figure 6.  
Prolonged sitting is recognized as one of the primary risk factors for developing musculoskeletal disorders among public transport drivers [27; 39]. Sitting continuously for more than 30 to 60 min is considered detrimental to musculoskeletal health [23; 29], and tram drivers often remain seated for over two hours without interruption [23; 29]. REBA and RULA scores of 6 reflect problematic static postures that substantially increase the risk of WMSDs [5]. Awkward or sustained positions--such as elevated arms, a twisted neck, or unsupported trunk--result in mechanical stress, including tendon and nerve compression [24]. In tram driving, the combination of constrained movement and long static periods introduces complex ergonomic challenges [17; 40; 41]. The consistency of REBA and RULA scores across SmallW, MidM, and TallM profiles suggests a systemic design limitation in the tram cabin [16; 37]. The current configuration does not adequately accommodate anthropometric variability among drivers, which contributes to elevated ergonomic risk [40]. These findings are consistent with prior studies reporting that professional drivers often experience WMSDs, particularly in the shoulder, neck, and lower back regions [23; 42]. Numerous studies confirm that professional drivers (bus, tram, and truck) are exposed to high postural risks. For example, [PERSON] et al. (2015) reported that 46% of bus drivers fell into the high-risk category based on REBA scores (8-10), while 46% also required ergonomic intervention based on RULA score 6 [38; 43; 44]. Similar results were observed in a study on intercity drivers in Indonesia, where the average REBA score was 6, with 57% of drivers classified as moderate risk and 29% as high risk [42]. That study also found a significant correlation between poor posture (REBA \(\geq\) 4) and the frequency of WMSD symptoms. [PERSON] et al. (2022) confirmed through RULA analysis that the lower back, neck, and shoulders are especially vulnerable to overload in long-duration driving tasks [44]. In summary, both REBA and RULA methods consistently identify seated driving postures as high-risk, demanding ergonomic modifications [44]. For example, [PERSON] et al. reported a RULA grand score of 6 (the highest possible), indicating a critical need for intervention in bus driving environments [43; 45]. These findings align with data from the Nordic Musculoskeletal Questionnaire (NMQ), which show that 24% to 35% of drivers report lower back pain in various studies [40; 42].