Tree Risk Assessment Qualification (TRAQ) – ISA Best Management Practices

[treeseer]

There is a substantial conflict in approach between QTRA and the Risk BMP here because the Risk BMP has is no mechanism to determine whether the risk from a tree is ALARP. ...To not consider ALARP is to be ‘risk averse’ and worship at the unattainable altar of safety, no matter the cost to the client. Assessing whether a risk is Tolerable and ALARP is about being ‘risk aware’, rather than ‘risk averse’, by not only seeing the elephant in the room but by weighing it.

Anyone got any ideas as to how to square the principles of ALARP with the Risk BMP?

 

Not as the tables are currently structured. One option was to have a 5th category of Very Low (or ALARP?) which would put Moderate in the middle--which seems to be where it belongs! All of the 4-section matrices seem skewed toward fear and action; making 5 sections would seem to allow a middle ground, and a more objective approach.

 

I don't know if this would fix the whole scheme or not. It was proposed multiple times during BMP review but never got traction that I know of.

 

re dead branches over paths, the perception of risk (manipulated and heightened by a smoke-and-mirrors communication approach) still seems to rule in the US/ISA. Pay attention to the man behind the curtain, Dorothy!

[daltontrees]

There is a substantial conflict in approach between QTRA and the Risk BMP here because the Risk BMP has is no mechanism to determine whether the risk from a tree is ALARP. The consequences of not assessing whether the risk from a tree is ALARP are that the costs to the owner/manager of managing the risk from their trees are not considered. Consequently, the Tree Risk Assessment can not only be unbalanced, biased, and risk averse, but also stray into becoming a Tree Risk Management policy decision on the part of the risk assessor, causing unnecessary and disproportionate expenditure on tree work and a loss of tree-related benefits.

 

Ah but the ISA system isn't claiming to be a tree risk management system. I don't see the problem. It has facilities to record mitigation of risk options. After that it's for the risk manager presumably to deal with ALARP. If the client wants the tree risk assessor to to take it further and produce a rissk management recommendation he only has to instruct him to do so. Then in a couple of words the risk assessor can put a price against each mitigation option and the extent of mitigation for each option and recommend to the client the appropriate course of ALARP action.

[Acer ventura]

Betweeness

 

Earlier in thread we bore witness to some apparent flaws in the Risk BMP matrices that are commonplace to many risk matrices. Namely, ‘range compression’ and ‘poor resolution’, with the Likelihood of Failure and Impacting ranges of Unlikely, Somewhat likely, Likely, and Very likely. I’m going to walk you through another common flaw with matrices labelled as ‘Betweeness’ and how it affects the Risk BMP matrices. Firstly, we’re going to look at the Likelihood Matrix and you might want to grab a beverage of choice and clear your head.

 

 

 

Likelihood of Failure and Impacting the Target matrix outputs has four ranges increasing from;

 

Unlikely (Number 1) < Somewhat likely (Number 2) < Likely (Number 3) < Very likely (Number 4).

 

I’ve numbered them to help with what’s coming later. I’ve run this by a few people and it can easily mess with your head, so I’m going to try and explain it as clearly and illustratively as I can in a number of posts. I think the numbers help magnify the ‘betweeness’ better than the gaps that allow jumps across the Likelihood words.

 

 

Risk Gradient - increase in risk rating from bottom left to top right.

 

I’ll look at the risk contours tomorrow.

 

 

Risk Gradient overlaid onto the Risk Matrix.

• The lowest value for each cell is the bottom left corner.
  
• The highest value for each cell is the top right corner.
  

 

Cheers

 

Acer ventura

[Acer ventura]

 

Possible + Medium = Unlikely (Number 1)

 

• ‘Possible’ Likelihood of Failure - “Failure could occur, but is unlikely” is at its highest value in its range.
  
• ‘Medium’ Likelihood of Impacting the Target - “as likely to impact the target as not”- is at its highest value in its range.
  
• We're sat in the top right corner of the 'Unlikely' cell
  

 

 

The smallest increase in Likelihood of Failure takes the range value from ‘Possible’ – ‘Probable’ (“failure may be expected within the review period.”)

 

The smallest increase in Likelihood of Impacting the Target takes the range value from ‘Medium’ – ‘High’ (“…most likely impact the target”).

 

 

Probable + High = Likely (Number 3)

 

• We're sat in the bottom left corner of the Likely cell
  

 

 

Have gone from ‘Unlikely’ (Number 1) – ‘Likely’ (Number 3) Likelihood of Failure and Impacting.

 

 

‘Somewhat likely’ (Number 2) has been jumped.

 

The Likelihood of Failure and Impacting value has gone from ‘Unlikely’ (Number 1) to ‘Likely’ (Number 3), bypassing ‘Somewhat likely’ (Number 2).

 

The top of ‘Unlikely’ (Number 1) is kissing the bottom of ‘Likely’ (Number 3).

 

 

To go directly from ‘Unlikely’ (Number 1) to ‘Likely’ (Number 3) without passing through ‘Somewhat likely’ (Number 2) means the highest value of ‘Unlikely’ (Number 1) is the same value as the highest value of ‘Somewhat likely’ (Number 2).

 

Therefore, the top value of ‘Unlikely’ (Number 1) = the top value of ‘Somewhat likely’ (Number 2).

Edited June 5, 2014 by Acer ventura

[Acer ventura]

 

Similarly, Likelihood of Failure and Impacting can jump from ‘Unlikely’ (Number 1) to ‘Likely’ (Number 3), without passing through ‘Somewhat likely’ (Number 2) where;

 

• Probable + Low = ‘Unlikely’ (Number 1)
  

jumps directly to

 

• Imminent + Medium = ‘Likely’ (Number 3)
  

Without bothering to pop in and say hello to 'Somewhat likely' (Number 2)

 

Cheers

 

Acer ventura

[Paul Barton]

I'm following so far - the diagrams are very helpful, thanks.

[Acer ventura]

 

Likelihood of Failure and Impacting can jump from ‘Somewhat likely’ (Number 2) to ‘Very likely’ (Number 4), without passing through ‘Likely’ (Number 3) where.

 

• Probable + Medium = ‘Somewhat likely’ (Number 2)
  

jumps directly to

• Imminent + High = 'Very likely’ (Number 4)
  

The top of ‘Somewhat likely' (Number 2) is kissing the bottom of ‘Very likely’ (Number 4).

 

 

To go directly from ‘Somewhat likely’ (Number 2) to ‘Very likely’ (Number 4) without passing through ‘Likely’ (Number 3) means the highest value of ‘Likely’ (Number 3) is the same value as the highest value of ‘Somewhat likely’ (Number 2).

 

Therefore, the top value of ‘Somewhat likely’ (Number 2) = the top value of ‘Likely’ (Number 3).

 

Cheers

 

Acer ventura

[Acer ventura]

What the Likelihood matrix is saying is that the Likelihood of Failure and Impacting is not a progressive increase from;

 

• Unlikely < Somewhat likely < Likely < Very Likely
  
• Number 1 < Number 2 < Number 3 < Number 4
  

We have the top of each Likelihood kissing the bottom of the range above it. With the exception of the top value of ‘Very likely’ (Number 4) which kisses no bottoms.

 

 

However, the top value of ‘Somewhat likely’ (Number 2) is able to jump over ‘Likely’ (Number 3) and kiss the bottom of Very likely (Number 4).

 

The top value of ‘Unlikely’ (Number 1) is able to jump over ‘Somewhat likely’ (Number 2) and kiss the bottom of Likely (Number 3).

 

What this means mathematically is;

 

 

The top value of;

 

‘Likely’ (Number 3) = Top value of ‘Somewhat likely’ (Number 2) = Top value of ‘Unlikely’ (Number 1).

 

All of the ‘Likely’ (Number 3) range share the same top values as the ‘Somewhat likely’ (Number 2) and ‘Unlikely’ (Number 1) ranges.

 

The lowest half of the ‘Somewhat likely’ (Number 2) range, share the same values as the mid-range of ‘Unlikely’ (Number 1).

 

Cheers

 

Acer ventura

[Acer ventura]

What does this mean for the Risk Matrix?

 

 

If the highest values of ‘Unlikely’ and ‘Somewhat likely’ are the same as ‘Likely’. Then whatever the risk rating is for ‘Likely’, is also the highest risk rating for the ‘Somewhat likely’ and ‘Unlikely’ ranges and their respective cells.

 

I’m going to get on and do some proper work and will post the Betweeness example in the Risk Matrix later.

 

Cheers

 

Acer ventura

[Acer ventura]

Not as the tables are currently structured. One option was to have a 5th category of Very Low (or ALARP?) which would put Moderate in the middle--which seems to be where it belongs! All of the 4-section matrices seem skewed toward fear and action; making 5 sections would seem to allow a middle ground, and a more objective approach.

 

I don't know if this would fix the whole scheme or not. It was proposed multiple times during BMP review but never got traction that I know of.

 

Hi Treeseer

 

Thanks for that insight. The ALARP region lies between 1/1 000 and 1/1 000 000 per annum in ToR. I’m not sure how this quantitative range could be nailed down with a qualitative descriptor like ‘Very low’, unless the numerical probability range is the definition of ‘Very Low’. It would also squeeze ‘Low’ into meaning a risk greater than 1/1 000, and a Moderate risk range would have to be even higher than that. Under such circumstances the ‘middle ground’ would only be ‘middle’ relatively. In reality a Moderate risk being significantly higher than 1/1 000 is surely not ‘middle ground’ in comparison to an annual exposure to common risks.

 

Which also feeds back to part of the problem of claiming to take into account the owner/managers Risk Tolerance. Is the owner/manager’s understanding of what a Moderate risk rating means in terms of Risk Management the same as what a Tree Risk Assessment of Moderate risk means? Given what appears to be the case from this thread, I think the likelihood of that being the case is perhaps ‘Extremely unlikely’?

 

Then there’s also the consideration of how the owner/manager figures out whether the risk is ALARP when faced with an ALARP range in numbers, a fee proposal to reduce the risk in numbers, and a risk rating in subjective and ambiguous words.

 

Many trees, of course, evidently have a risk that is lower than 1/1 000 000, given that the annual risk of death from tree failure in the USA is substantially lower than this. Isn’t it a bit higher than the UK’s 1/10 000 000, at around 1/9 000 000? Which begs the question, what sort of 'Low' would be used to describe risks that are less than 1/1 000 000 that are acceptable without the need to consider whether the risk is ALARP?

 

re dead branches over paths' date=' the perception of risk (manipulated and heightened by a smoke-and-mirrors communication approach) still seems to rule in the US/ISA. Pay attention to the man behind the curtain, Dorothy! [/quote']

 

Is the perception about deadwood = unacceptable risk, even if the risk is Low with the Risk BMP, a common cognitive bias over in the USA?

 

Cheers

 

Acer ventura

Edited June 7, 2014 by Acer ventura