Developing and testing guidelines for ergonomic assessment tools

Research Trainee: Andrew Comai, PhD Student, Dept. of Environmental Health Sciences at the University of Michigan

Faculty Researcher: Thomas J. Armstrong, PhD, Professor of Industrial and Operations Engineering and Biomedical Engineering at the University of Michigan

The primary goals of this project were to: 1) Determine the agreement between evaluators using different ergonomic assessment tools in different manufacturing sites, and 2) Develop basic application guidelines for different ergonomic assessment tools.

There are various ergonomic assessment systems used to describe worker exposure to risk factors for a given work station or activity. The project sought to develop basic guidelines for evaluators using different ergonomic assessment tools. Field trials are needed to compare the tools in different settings and develop guidelines on when and how each tool should be applied. This project compared several ergonomic risk factor assessment systems in real work environments using worker/evaluators.

Four evaluators were trained in the use of Rapid Upper Limb Assessment (RULA), Strain Index, and The Hand Activity Level Threshold Limit Value. One checklist, the UAW GM Risk Factor Checklist used in Delphi and General Motors was well known to the evaluators. For the most part evaluators, were not accustomed to the other checklists. The evaluators were deployed to three manufacturing facilities and asked to collect data on 10-15 jobs at each plant. The facilities selected for study varied in their work organization and product. At the time each job was analyzed with paper checklists, a video was taken. After each data collection a full day focus group was conducted to review video tapes and discuss how each evaluator scored jobs using each tool. The data collected and the discussions from focus groups demonstrate a learning effect as the evaluators became more comfortable with the tools.

In all, 336 ergonomic assessments on 28 jobs were conducted at 3 manufacturing facilities. Statistical analysis of data was performed with SAS:

  • The average Strain Index was 24.7±40.6 out of a possible score of 1,053. Average plant scores for plants 1, 2 and 3 were 8.6±60.0, 13.5±38.1 and 6.8±8.6 respectively.
  • The average RULA was 6±1.3 out of a possible score of 8. Average plant scores for plants 1, 2 and 3 were 5.3±1.4, 6.2±1.1 and 6.4±1.1 respectively.
  • The average HAL was 5.7±2.3 out of a possible score of 10. Average plant scores for plants 1, 2 and 3 were 7.5±2.4, 6.0±1.8 and 4.0±1.5 respectively.
  • The average Peak Force was 3.5±2.1 out of a possible score of 10. Average plant scores for plants 1, 2 and 3 were 2.7±1.8, 3.2±1.8 and 4.5±2.3 respectively.

Much of the variation that is captured by plant level statistics can be explained by a few jobs with special characteristics. The data collected and the discussions from focus groups demonstrate a learning effect as the evaluators became more comfortable with the tools.

 

Research trainee’s current position:
Andrew Comai is currently an Industrial Hygienist at UAW.