QTRA - I'm sorry i don't agree with it!

[RobArb]

Getting back to QTRA:biggrin:

 

oh and another thing... and i am being counter-counter-argumentative here... what reason might I (or anyone) have to be biased? unless i am secretly a sales agent for QTRA.

 

You no, but others....

 

 

Some decent sensible points there - I'm glad we've got away from the idea that QTRA is purposefully deceptive.

 

QTRA in itself, as you state is not wholly or purposefully deceptive, i may have been a bit strong with my wording in the opening post and probably should have chosen my words better:biggrin: but there are people out there that have used QTRA to get the end result they desire, fair enough they may be a minority, but the minority exists. Inexperience also brings about mistakes, the human element added on to a system that could be described as a smoke and mirrors exercise is why i feel that QTRA does have a place, but not one when making a fully informed decision about the risk of a tree.

 

Also i have read (well started to read) the HSE's decision making process on reducing risk and i highlight the section on tolerable risk

 

Tolerability limits for risks entailing fatalities

In practice the actual fatality rate for workers in even the most hazardous industries is

normally well below the upper limit of a risk of death to any individual of 1 in 1000

per annum for workers and of 1 in 10 000 per annum for the public who have a risk

imposed on them ‘in the wider interest of society’ (see paragraphs 131-132).

For example, in 1999/00 the annual fatality rates for agriculture, hunting, forestry and

fishing (but not sea fishing); construction; and mining and quarrying (including

offshore oil and gas) were 1 in 12 984, 1 in 21 438, and 1 in 14 564 respectively. In

traditionally less hazardous industries the annual risk of death for workers is lower

still; for example in the service sector in 1999/00 it was 1 in 388 565.

 

How can it be set as 1/10000 (in QTRA) when there is so much diversity within the figures themselves?

 

[daltontrees]

Have a look at "HSE Reducing risks protecting people" you will get it on internet somewhere. Covers it very well inc the 1:10,000 threshold. Tree survey risk assessment is about protecting public at that threshold, forget industry thresholds and actual stats. But of course I have to do a risk assessment for surveying trees which in theory involves examining tree with binoculars to check it is safe enough to survey.

[Amelanchier]

Also i have read (well started to read) the HSE's decision making process on reducing risk and i highlight the section on tolerable risk

 

Tolerability limits for risks entailing fatalities

In practice the actual fatality rate for workers in even the most hazardous industries is

normally well below the upper limit of a risk of death to any individual of 1 in 1000

per annum for workers and of 1 in 10 000 per annum for the public who have a risk

imposed on them ‘in the wider interest of society’ (see paragraphs 131-132).

For example, in 1999/00 the annual fatality rates for agriculture, hunting, forestry and

fishing (but not sea fishing); construction; and mining and quarrying (including

offshore oil and gas) were 1 in 12 984, 1 in 21 438, and 1 in 14 564 respectively. In

traditionally less hazardous industries the annual risk of death for workers is lower

still; for example in the service sector in 1999/00 it was 1 in 388 565.

 

How can it be set as 1/10000 (in QTRA) when there is so much diversity within the figures themselves?

 

 

What do pages 131-132 say?

[RobArb]

I'll have too look it up again when I get in:biggrin:

 

My photographic memory isn't that good:001_rolleyes:

 

Sent from my Galaxy S2

[daltontrees]

Sorry guys, |I don't seem to be able to leave this subject alone. Barring any retorts, I will try and make this my last contribution on QTRA (but not oin the subject of the quantification of tree risk).

I think we all agree it is impossible to quantify tree risk with any degree of precision OR accuracy. If you accept the rough-and-ready notion that likelihood of harm equals likelihood of failure x likelihood of target present x severity of harm it is clear that none of these components can be measured, predicted, whatever, and that the multiplication of errors means that any calculation could result in a flawed probability. Notwithstanding, with a bit of observation and professional judgement a decent stab at them can (and in my opinion should) be made.

If I have any point it is that a systematic attempt is better than a finger in the air and that having put a system in place and implemented it in good faith is all that the law can expect of anyone. So, in conclusion, from what I know of QTRA it sems like a decent effort at going that little bit further, but in my newly enightened view can't achieve any useful additional kudos in the courts for having discharged the tree owner's duty of care. Maybe in 100 years we will have enough statistical evidence to show that the use of QTRA has measurably saved lives, but I am inclined to think that it's precision is a distraction from it's accuracy, if any, as compared with sound tree-by-tree judgement.