Subjective assessment of fork-lift truck seats under laboratory conditions

A subjective assessment of fork-lift truck seats has been carried out to assess the range of preferred seat dimensions and the acceptability of different seat adjustments to fork-lift truck drivers. Twelve fork-lift truck seats fitted to a fixed bench were assessed by twelve fork-lift truck drivers. For each seat, each driver completed a questionnaire that covered the following areas: eleven seat dimensions, four seat adjustments and other features (arm rests, safety belts and safety wings). The drivers assessed the dimensions of a seat chosen at random, before moving to the adjacent seat in either a clockwise or anticlockwise direction. Before each assessment, they were asked to look forward and backward in the seat as though they were driving a fork-lift truck. In general, significant correlations were obtained between the subjective assessments and objective measurements of the seat dimensions. This enabled preferred seat dimension ranges to be defined. Fork-lift truck drivers ranked the forward-backward and the backrest inclination adjustments as most important. The results showed that although the drivers had previous experience in the use of suspension seats, they did not understand the purpose of the weight adjustment. All adjustments should be easy to find, accessible, easy to move and they should enable a range of adjustments. In addition, clear and simple information on the seat is needed, especially for the weight adjustment. The most recently designed seats generally had dimensions within the preferred ranges compared with the older generation seats, mainly because they had more adjustments. However, the results show that adjustments on fork-lift truck seats could be improved further. Some tentative conclusions are made for the preferred fork-lift truck seat dimensions and adjustment ranges which are based on the evidence from this restricted sample of fork-lift truck drivers. They may be useful for seat and truck designers in the preparation of a standard on fork-lift truck seat dimensions.