In many studies a relationship between vibration and fatigue has been assumed without supporting research, and often based only on anecdotal evidence. The study of fatigue as it relates to vibration is complex and there is limited research available. However, the literature review has identified a few studies showing a possible association between fatigue and low frequency vibration that is typical of the vibration frequencies experienced by truck drivers. These findings could form the basis of further research in this area.
Past research has associated whole-body vibration exposure with a number of adverse effects on the human body. The effects of vibration on the lower back and spine have been extensively researched and documented. Effects on the gastrointestinal system have received less attention but are considered by some to be significant.
The following points summarise the findings of the literature review:
- There is some laboratory and field research that supports a relationship between low frequency vibration (3 Hz) and increased fatigue or drowsiness. This may have implications for heavy vehicle truck drivers who usually experience vibration levels around this frequency while driving.
- Intermittent and random vibration can have a stimulating or wakening effect.
- Vibration exposure has been found to cause changes to body metabolism and chemistry that could lead to fatigue effects.
- The health effects of whole-body vibration have been extensively researched and adverse effects have been established. Truck drivers shown many of the symptoms of adverse health effects associated with whole-body vibration exposure.
- Typical whole-body vibration exposure levels of heavy vehicle drivers are in the range 0.4 - 2.0 m/s2 with a mean value of 0.7 m/s2 in the vertical (z-axis). Vertical vibration is highest in the frequency range 2 – 4 Hz.
- The average whole-body vibration level experienced by drivers of heavy transport vehicles exceed health, fatigue and comfort limits of the Australian Standard and most exposures are within the Caution zone (for health) according to the current International Standard. Many typical exposures will reach the likely health risk zone of the International Standard. According to these standards, many truck drivers are at risk of incurring adverse health effects from prolonged exposure to vibration.
- There is evidence that truck drivers have back complaints that could be partly attributable to whole-body vibration exposure.
- Comfort limits of both Australian and International Standards are exceeded by most vehicle rides.
Exposure limits and guidelines
The guidelines for health effects of whole-body vibration are well documented in Australian and International Standards. However, there is still much to be learnt about vibration dose/response relationships. In terms of health criteria, the current International Standard is an improvement on the Australian Standard which was based on the 1985 International Standard. The new standard should provide a truer indication of injury risk due to vibration than the older standard.
The various State Occupational Health and Safety Regulations apply to truck drivers and under these Regulations employers are required to ensure that the systems of work and the working environment of the employee are without risks to health and safety. This would also apply to vibration exposure. However, the Australian Standard for whole-body vibration is not cited in State OH&S Regulations. This means that employers and employees would need to comply with guidelines from the most appropriate Standard available. Being the most recent standard, ISO 2631-1997 is likely to be considered most appropriate.
The fatigue limits in the current Australian Standard have been abandoned in the current International Standard because they were not supported by research. Further research is required to establish realistic fatigue limits.
The guidelines for comfort in the International Standard seem to be reasonably well founded (Griffin 1990) and could be useful in rating truck drivers vibration exposures especially if the contribution of vibration in all axes is included in the assessment. Comfort levels could possibly form the basis for fatigue limits although extensive research would be necessary to confirm such a link.
Conclusions and recommendations
There are at present no exposure limits for fatigue and vibration that are accepted by experts in the field. The limits for ?fatigue-decreased proficiency? in the current Australian Standard have been deleted from the new International Standard because they were not supported by research. There is anecdotal evidence that truck rides are often rough, uncomfortable and tiring. However, specific research on vibration and fatigue is limited and many authors have assumed a relationship without reference to supporting research. Some research shows a possible link between constant low frequency vibration and fatigue but more extensive research is required to establish meaningful exposure limits.
There is sufficient evidence that vibration exposure to drivers could be a health hazard particularly with regard to back problems. The relatively high vibration exposure levels combined with long exposure durations and prolonged sitting are likely to contribute to back pain and other health effects.
The current International Standard (ISO 2631 (1997) on whole-body vibration provides useable guidelines for vibration exposures and predicted health effects.
Recommendations for further research
- An extensive experimental study on a possible relationship between vibration and fatigue could be considered, although it is likely that such research would be costly to conduct. Such a study is necessary to establish whether the effects of vibration would be noticeable among all other contributors to fatigue and each factor known to contribute to fatigue would need to be controlled for (e.g. time awake, time on task, rest and sleep, circadian factors).
- There are limited published data on vibration exposure to drivers under Australian conditions. Available data indicates that exposures are likely to be high putting drivers at risk to health. A field survey of vibration levels experienced by heavy vehicle drivers under Australian conditions is recommended. Such data would be necessary to establish standards for trucks sold in Australia. A survey of this type need not be expensive because sufficient data could be obtained from a relatively small representative sample of drivers.
- provide information on typical vibration levels experienced by drivers under a range of operating conditions
- consider the practicality and relevance of exposure limits or guidelines for health, fatigue and comfort
- collect information on factors influencing vibration levels and ways to reduce vibration exposures to drivers
- develop simple and efficient vibration monitoring and reporting methods
Information collected from the survey could also form the basis of an information booklet for the trucking industry.
The report and its recommendations should be referred to the National Occupational Health and Safety Commission for broader dissemination to its key stakeholders and their advice should be sought on possible strategies for filling the gaps identified.
Download Complete Document: Fatig_Trans_8 [PDF: 370 KB]
Type: Research and Analysis Report
Sub Type: Consultant Report
Author(s): N Mabbott, Garry Foster & B McPhee
Topics: Fatigue, Heavy vehicle
Publication Date: 01/06/01