The knowledge about work task which has to be assessed is required. For staff members this knowledge is available mostly. For users without this knowledge a workstudy must be carried out before.
The risk assessment contains

• the description of essential task requirements and working conditions and
  
• the quantification of stress level by a risk score.
  

This risk score reflects the degree of likelihood for musculoskeletal overload. The higher the score the higher the risk. The probability of musculoskeletal overload refers to a general population of healthy and normal trained workers.
The user has the option to choose between two tools

• Key Indicator Method (short form: KIM)
  
• Manual Handling Assessment Charts (short form: MAC)
  

which are both applied in Europe.

On quality reasons the special instructions for both tools (KIM and MAC) must be considered carefully.

Goals

• Description of essential task requirements and working conditions
  
• Quantification of stress level
  
• Objective risk assessment – calculation of a risk score
  
• Indication of intervention points (redesign and/or medical care)
  

Target user population, preconditions for application

• Good knowledge about work which has to be assessed
  
• Basic knowledge in Occupational Safety and Health (OSH)
  
• no special ergonomic training
  
• common sense
  

Effort

If there are sufficient informations and knowledge about the work task, only a few minutes.
If there are no sufficient informations, a work and motion study must be carried out before. In that case the effort depends on complexity of task, degree of repetition and working conditions. On average it takes about 20 minutes.

Tools

For risk assessment on screening level two valid methods are available:
Key Indicator Method (KIM) or Manual Handling Assessment Chart (MAC)
Both methods

• are developed with special reference to Council Directive of Manual Handling of Loads
  
• are based on a biomechanical, physiological and psychopyhsiolgical basics
  
• are tested concerning validy and reliability
  
• are applied for several years
  

Both methods gives comparable results.

Both method are tools for bottle neck risk assessment - not for assessment of strain and stress at a complete working day or life. No or only limited application is possible, when tasks are complex or changing frequently .

Remarks

Risk Assessment on screening level defines features of physical work load, shows bottle neck situations and gives hints for actions.
Principle: Important task features are classified by means of a rating scale and followed to a risk score.
Analogous to Level I, different stress features on MHL are taken into consideration:

• Biomechanical strain of bones, joints, and muscles resulting from aktion forces and restricted postures
  
• Muscle fatigue as a result of intensive, frequent or persistent force generation
  
• Stress of cardiovascular system due to high physiscal workload
  
• Handicaps because of characteristics of load (bulky, slippery, very large)
  
• Risk of accident because of characteristics of load (very heavy, hot, sharp, moveable)
  
• Risk of accident because of characteristics of working environment (floor uneven or slippery, restricted area for workers movement, obtacles, insufficient illumination)
  

The risk score reflects the degree of likelihood for musculoskeletal overload. The higher the score the higher the risk. The probalbility of musculoskeletal overload refers to a general population of normal trained and healthy workers.
For assessing the indivudal risk of a single worker further factors must be taken into account. The worker may be at risk if he/she:

• is physically unsuited to carry out the task in question,
  
• is wearing unsuitable clothing, footwear or other personal effects,
  
• does not have adequate or appropriate knowledge or training.
  

With a view to multi-factor analysis, reference may be made simultaneously to the various factors listed in Annexes I and II.

Advices for users

Exact measurement of input data are theoretical possible. In practice some features can be measured easily, severeal features are not measureable. The load weigth can be measured with a spring balance, the number of handlings can be counted. Complicated and expensive, however, is the measurement of action force, frictional resistance or body postures.
For an equivalent level of accuracy the principle of calculated fuzziness are used: All features are classified by use of specific ratings scales from minimum to maximum value. For screening level, a sufficient accuracy is reached in this way.
For interpretation of the risk score this limited accuracy must be taken into account. The focal points are the bottle necks and risk areas – not the discrete risk score. In this way for most of tasks sufficient risk assessments are available. In some situations a risk assessment on this level will be not successful. In that case there are two possibilities:

• If there are an unclear situation or not acceptable results, further informations as subjective estimation of work load by workers or complaints must be considered, discussed, and interpreted together.
  
• If there is a need for higher accuracy and detailed risk assessment, a differentiated analysis corresponding to Level III must be carried out.
  

To avoid errors all scores must be evaluated critically. The results should be compared with experience, the subjective stress felt by the worker, with informations on complaints or absence.
When risk assessment on screening level are carried out, there is a possibility of assessment error or misinterpretation. Potential sources may be insufficient knowledge about work, which has to be assessed, subjective misinterpretations, incorrect input data, calculation errors.