8292431 Tracking bus cabin ergonomics over time with the bus-ergonomics matrix

<h3>Objective</h3> Musculoskeletal disorders are very common in bus drivers worldwide. This study aimed to develop a tool to allow investigating the contribution of bus-related ergonomic factors in the development and exacerbation of these disorders. <h3>Methods</h3> Drawing inspiration from the job-exposure-matrix approach, we developed a Bus-Ergonomics Matrix (BERM) to classify buses according to their ergonomics. A standardized protocol was used to evaluate 36 ergonomic parameters related to the driver’s workspace, including seat configuration, steering wheel, pedals, and dashboard layout. These parameters were weighted and combined to compute region-specific ergonomic scores (e.g., visual, biomechanical, shoulder girdle, back, upper and lower body) as well as an overall cabin ergonomics score. Scores range from zero to 100, with the higher the score, the more ergonomic the bus. Using Integrated Nested Laplace Approximation (INLA) and measurement data, we predicted ergonomic scores for 705 buses in the Swiss fleet, covering models manufactured between 1970 and 2022. We then assessed individual exposure to ergonomic constraints for 612 bus drivers (13% female, age=47.7 (SD=10.1) years, career duration=11.4 (SD=9.0) years). For this, we crossed-referenced their histories of driven buses with the BERM and estimated annual ergonomic scores. <h3>Results</h3> Drivers reported driving multiple bus models over time, with up to six different buses per year. Ergonomic scores of the Swiss bus fleet improved steadily from 1985 to 2010, especially for the ergonomics of shoulder girdle region. A flat point was reached then, with a negligible improvement over the last decade. Strong correlations were found between global and region-specific biomechanical scores, highlighting consistent exposure patterns across body regions. <h3>Conclusion</h3> The Bus-Ergonomics Matrix provides a unique, objective framework to assess ergonomic constraints in bus cabins, demonstrating improvements over time. Its international applicability makes it a valuable tool for improving drivers’ occupational health globally.