Strategy for health and safety management at an automobile company: From the prevention of low back pain to Toyota's verification of assembly line (TVAL)

Abstract

This paper reports on a strategy to improve and renovate assembly lines, including countermeasures to prevent low back pain during the past two decades at Toyota Motor Co. Since 1975, there have been problems with low back pain at Toyota's vehicle assembly lines. To deal with these low back pain problems, it was necessary to determine their causes and to quantitatively evaluate the burden on workers. For this purpose, functional burden indexes were developed, that is, a posture burden point and a weight burden point were determined to assess the load on the low back, and a low extremity point and a squatting posture point were determined to assess the burden on the leg. The functional burden index, however, could be applied only to specific human functions, not to human functions in general. Since there are about 400 kinds of working patterns in vehicle assembly lines, comprehensive burden index was required to estimate overall burden of such work. Thus, we developed Toyota's Verification of Assembly Line (TVAL), an index for assessing the physiological stress of an assembly line work, in which an equivalent bicycle ergometer workload is calculated from electromyograms taken of 20 different muscles under actual working conditions. At present, TVAL is used to measure physiological burden of assembly work in order to give priority to improvements, and to objectively demonstrate the effects of such improvements at Toyota.