Abstract
Occupants of automobiles experience discomfort after long drives, irrespective of how well designed a seat might be. Previous studies of discomfort during driving have focused either on the seat shape and materials (“static” properties), long-term discomfort (“fatigue” properties), or dynamics (“vibration” properties). These factors have previously not been considered together. This paper reports three studies with objectives to define and test a model for describing long-term discomfort from vibration. Study 1 was an independent measures laboratory trial using an automobile seat, which lasted 80 minutes; Study 2 was a repeated measures laboratory trial using a rail passenger seat, which lasted 60 minutes; Study 3 was a repeated measures field trial in a people carrier automobile, which involved 70 minutes of travelling. The findings showed that discomfort accrues with time but that more discomfort is experienced when subjects are also exposed to whole-body vibration. Exposure to whole-body vibration accelerates development of discomfort. The relationship between the reported discomfort, the vibration magnitude, and the exposure time can be described using a multifactorial linear model. It is concluded that ignoring parts of the multi-factorial model (i.e., static, dynamic, or temporal factors) will compromise understanding of discomfort in context.
Highlights
Long-term exposure to vibration whilst driving or travelling as a passenger in an automobile has been associated with discomfort, increased prevalence of low back pain, and other musculoskeletal disorders (e.g. [1,2,3,4,5,6,7])
Static factors focused on seat stiffness, but these could include any factor which does not change in response to the dynamic environment of the vehicle
The concept of Ebe’s model is that, when vibration is absent, the total seat discomfort is dictated by the static factors, but if there is a vibration input to the seat, the total seat discomfort comprises a combination of static factors and dynamic factors
Summary
Long-term exposure to vibration whilst driving or travelling as a passenger in an automobile has been associated with discomfort, increased prevalence of low back pain, and other musculoskeletal disorders (e.g. [1,2,3,4,5,6,7]). Ebe and Griffin [3, 4] proposed a qualitative and quantitative model of overall seat discomfort. The approach of their model was to separate discomfort into “static” seat factors and “dynamic” seat factors. Static factors focused on seat stiffness, but these could include any factor which does not change in response to the dynamic environment of the vehicle. Dynamic factors are those which are related to the whole-body vibration caused by the vehicle environment. As the vibration magnitude increases, the relative importance of the dynamic increases
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