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Former Member
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A small improvement in the method for assessment of probability 

1. Risk assessment is an important exercise in any OH&S Management System for taking preventive action and assuring safety of people.

2. The procedure for Risk Assessment is freely available from many sources.For example the following sites provide good guideline. 

http://www.hse.gov.uk/risk/fivesteps.htm

www.uq.edu.au/ohs/pdfs/ohsriskmgt.pdf

3. Risk is defined as the net result of probability and consequence; r=pc.

4. As part of assessment, what is suggested in the procedure for assessing probability is to select from a table such as the following: 

Probability :   (as per www.uq.edu.au/ohs/pdfs/ohsriskmgt.pdf)  

Almost certain                            The most likely and expected result if the hazard – 

                                                event takes place.

 

Quite possible                            Quite possible, would not be unusual, even 50/50  

                                                chance

Unusual but possible                    Unusual but possible sequence or coincidence

Remotely possible                        Remotely possible coincidence

Conceivable but unlikely                Has never happened after may years of exposure,

                                                  but is conceivably possible

Practically impossible.                   Practically impossible, has never happened before 

5 My view

P being one of just two items in the equation, and the assessment having a strong bearing on assurance for people's safety, it is considered desirable to make the assessment a little more objective.It is true that arbitrariness could not be completely eliminated. But it could be reduced to some extent by taking the analysis a bit further.

6. In view of the above, the line of thought is as follows: An assessor is making the assessment at certain point of time.The assessor is making an assessment with respect to certain situation/location. The likelihood of an undesirable event happening would depend on certain factors existing in the situation/location. 

Hence it is felt that the assessor must list the general and specific factors having influence on an accident,    visualize the various states in which the factors likely to exist anywhere, identify each factor-wise the state which is prevalent in the location and, based on the combination of the states of the factors, arrive at conclusion regarding probability.  

7. The following Table is provided herewith as an example: 

   Sl.NoFactors that have influence for an accident          Probability of Occurrence and Numerical value assignable
Will HappenMay HappenEqual ChanceMay not happenWill not happen
                            Numerical value Assignable
54321
                                            State of the Factor
1Occurrence of IncidentsFrequent*NoticeableRareNil
2Occurrence of AccidentEvery Year*Last year*Never
3Condition of work environmentBadNot satisfactorySatisfactoryScope for improvementGood
4Exposure of personsLong *Medium*Short
5Permit system(Hot permit, Height permit etc.,)Does not exist*Exists not followed always*Exists and followed
6SupervisionDoes not existShort periodIntermittentfrequentContinuous
7

Education/

Experience/

Training

Less

Less

Nil

*

Qualified

Minimum

Not trained

*

Educated

Experienced

Trained

8Engineering controlNilExists but Not reliable**Exists and reliable
9Use of PPENot a practice***Completeadherence

* To be described similarly 

8. We can also add ‘weight’ to each factor, assign numerical values for the ‘states’ and arrive at a ‘score’ for the overall assessment.   

9. The above method involving factorization, factor-wise description of the likely scene in general and selecting the scene that exists in the location at the assessment time , it is felt, may be adopted for any other assessments also, by adapting it suitably.  

10. A small step to make the risk assessment a bit more reliable! Or shall we call it a step for ‘process refinement’?  

 

Sam Anbazhagan

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