When a front-loading fork-lift truck with a forward-facing driver's seat is driven in reverse during the in-plant transport of goods, the driver's upper body is twisted, resulting in elevated strain upon the spine and the back muscles. Where the adoption of unfavourable body postures is combined with vibration exposure, this stress is exacerbated by whole-body vibration.
The use of seats facing perpendicular to the normal direction of travel is intended to counter this stress. The objective of the project was to quantify the differences in body postures associated with use of the sideways-facing seats compared to those with conventional (forward-facing) seats.
The combined stresses of body posture and vibration arising with each driver's seat arrangement were recorded by the German Social Accident Insurance Institutions involved in the project (those for the trade and distribution industry and for the woodworking and metalworking industries) and the IFA. For this purpose, a swivel seat was used that was set facing forwards and sideways, both during routine tasks in the plant and on a defined test track.
The results were interpreted at the IFA.
The stresses arising from unfavourable body postures differ according to which of the two seating arrangements is selected. Where the seat is set facing forwards and travel is backwards, the driver's neck and back are twisted; where the seat is set facing sideways, only the neck is twisted. The series of measurements showed that a seat facing sideways leads to better body postures, particularly with regard to spinal torsion during reversing. Unfavourable spinal torsion was reduced from 54.6% to 1.3%. During forward travel however, use of the sideways-facing seat exacerbated torsion of the neck, since the driver must then turn his or her head in order to look ahead. When the seat is facing forwards, the neck is not subject to this torsion and the body posture is neutral.
A swivel seat results in drivers exploiting the benefits of both seat types, as was observed in the study: reduced torsion during reversing with the seat swivelled into the 90° position, and the neutral body posture during forward travel with the seat in the normal 0° position.
-cross sectoral-Type of hazard:
ergonomics, vibrationDescription, key words:
industrial trucks, body posture, vibration