The Development of Ergonomic Guidelines for Railroad Hand Switch Operation

Abstract

Injury statistics and worker perceptions of relative task difficulty and frequency suggest that the operation of hand switch stands/switches may be a problem task in the railroad industry (Kuciemba, Page, and Kerk, 1988). Injuries associated with this task are mostly over exertion in nature, 43% of which occur to the lower back. This paper describes how we developed ergonomic guidelines specifically to address hand switch operation. These guidelines could be applied to: identify switches that may pose excessive risk of injury when operated, evaluate maintenance procedures, and assist in developing switch stand design alternatives. The guidelines specifically define hand forces across the range of switch lever motion encountered when operating the switch stand. There are two sets of guidelines, lower guidelines and upper guidelines. The lower guidelines are defined by the back compression and static strength criteria NIOSH (1981) uses to define their Action Limit, along with a stability criterion. The upper guidelines are defined by the same two criteria NIOSH (1981) uses to define their Maximum Permissible Limit, along with the stability criterion. We videotaped 20 workers operating 50 different switches at 3 different rail yards to classify worker methods into general categories. Then the postures associated with each of the general methods were recreated using 5th and 95th percentile workers, photographed, and digitized for use in the University of Michigan 3D Static Strength Prediction ProgramTM. For each posture, we then calculated the maximum hand forces that separately satisfied the lower and upper criteria. The maximum hand forces under the two sets of constraints define our guidelines.