Age-Related Differences in Appropriate Local Lighting Conditions for Visual Inspection of Machines and Equipment such as Railroad Vehicles

Abstract

Many visual items are inspected during railway vehicle inspections, and local lighting devices such as handy lights are used for checking areas insufficiently illuminated by general lighting. LEDs have replaced conventional incandescent bulbs and fluorescent lights as local lighting sources. However, it is difficult for workers aged over 50 years to see with LED lighting. Therefore, local lighting conditions suitable for different age groups need to be identified. Visual inspections roughly detect two types of abnormalities: those based on two-dimensional information such as color and black-white contrast, and those based on three-dimensional information, such as deformations and dents, among others. This survey examined lighting conditions suitable for detecting two-dimensional black-white contrast and color differences by people of different age groups. The results indicated that luminance around 5000 lx was appropriate for all workers regardless of age. In contrast, lighting conditions suitable for discriminating specific colors differed according to age because of aging-related changes in visual functions. Warm color lights are appropriate for participants aged over 50 years.