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Accident Ratios (1)


Heinrich's analysis of 75,000 industrial accident reports found, amongst other things (e.g. 88% of the accidents were due to ‘unsafe acts’ and 10% to ‘unsafe conditions’), that lost time injuries had been preceded by 329 similar accidents (i.e. involving similar unsafe acts or conditions), 300 accidents out of every 330 had resulted in no injury and 29 in just minor injury.

 

 

                  

Later studies reported similar findings...

                           
1
Disabling injury
100
Minor injuries
500
Property damage accidents
Bird (1969)

 

(Whilst not strictly relevant for purposes here, an HSE/APAU (see HSG96) case study provides additional insight into property damage accidents. In an eighteen week period on a construction site employing 120 workers, 3570 such accidents were recorded).                                     

 

1
Serious or disabling
10
Minor injuries
30
Property damage accidents
600

Incidents with no visible injury or damage

(near-miss accident)

Bird (1974)

 

 

1
Fatal or serious injury
3
Minor injuries with up to 3 days lost time
50
Injuries requiring first aid
80
Property damage accidents
400
No injury or damage
Tye/BSC 1976

 

The actual figures above (often displayed in pyramids) relate only to the Organisations/populations that provided the data from which the ratios were determined; ratios for other Organisations can only be generated from their own data.

                                       

 

 

Comment:         

Whilst the sum total of an Organisation's accidents is essentially unique, the distribution of outcome variables is not. In main stream sectors, the number of accidents that result in property damage has always exceeded those that result in injury. As for accidents that result in neither injury nor damage (the near-miss accidents), they have always massively exceeded the combined total of both property damage and injury accidents. Consequently, an informed glance at an Organisation's accident data can reveal much about its general reporting culture.

(An additional and quite alarming variable exists to corrupt analysis for the unwary but that discussion will continue in the members only area).

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Industry tends to focus most of its efforts on reducing the number of injuries that, relatively speaking, appear infrequently at the top of the pyramid; severity of outcome tends to be the driver. Whilst they must be investigated, the priority given to them has resulted in reduced attention lower down the pyramid. The belief, prevailing for many years, is that accident prevention capability is measurable via injury statistics; however, it is a belief fuelled by a misunderstanding of terms.

The accident and the injury are two distinct...Read More