Katherine J. Gregersen

Project title: Cost-Effectiveness of Driver Seat Alternatives for King County Metro Buses

Degree: MPH | Program: Environmental and Occupational Health (EOH) | Project type: Thesis/Dissertation
Completed in: 2015 | Faculty advisor: Peter W. Johnson


Background: Low back pain (LBP) is a leading cause of occupational disability and a large contributor to worker compensation costs among bus drivers in the transportation sector. In King County Metro, the mass transit provider in Seattle, Washington, LBP in drivers is frequently attributable to whole-body vibration (WBV) exposures that occur when a vehicle encounters bumps in the road. To reduce WBV exposures and mitigate some of the bus driver LBP cases, engineering controls, such as improved seats for drivers, may be used. This predictive cost-utility analysis (CUA) aimed to determine whether alternatives to currently installed, industry-standard, passive air-suspension driver seats could be cost-effective interventions to reduce LBP and neck pain worker compensation claims at the agency. The three strategies evaluated were: installation of an active-suspension driver seat, frequent passive-suspension driver seat replacement, and installation of a static driver seat. Methods: The CUA was performed from the perspective of the worker compensation payer, King County Metro. A decision-analytic Markov model was developed to simulate the likelihood of a driver filing a LBP or neck pain claim using a 15-year worker compensation claim database from King County Metro. Back and neck claims were classified by their likelihood of WBV-relatedness and severity. Using employee data from King County Metro, rates and costs of back claims and neck claims were determined. Expected reductions in claim rates were determined from the epidemiologic literature on WBV and LBP and previous research on seating interventions. Utilities for back pain and neck pain were taken from relevant health-related quality of life literature. One-way, multi-way, and structural sensitivity analyses were used to test result robustness. Results: The active-suspension seat was dominant over the existing passive-suspension seat; it was found to improve driver health through reduction in WBV exposures as well as reduce costs to King County Metro. The static seat was found to be cost saving but since it would not reduce WBV exposures, was not predicted to result in quality of life benefits for drivers. Frequent passive-suspension seat replacement did not appear to be cost-effective in comparison to the other seating interventions, with an incremental cost-effectiveness ratio of $1,383,188 per Quality-Adjusted Life Year. In the sensitivity analyses, the results were sensitive to the rate of claim reduction and robust to claims costs and utility inputs. Conclusion: These findings imply that frequent seat replacement would likely result in a substantial cost increase to King County Metro, while the adoption of active-suspension seats may both improve driver health and reduce claims costs at the agency. The adoption of static suspension seats would likely result in cost-savings from seat cost and seat maintenance costs. However, it is anticipated that these seats would not improve driver health. URI