UKTC Archive

RE: Windshield/Drive-by | Speed Limit

Subject: RE: Windshield/Drive-by | Speed Limit
From: David Evans
Date: Dec 01 2019 08:48:30
<<David from your writings I have learned that TRAQ, QTRA, and PTI are no 

Hi Michael

I've not said they're all 'no good'.

They all have some value, but as you know they all have substantial issues in 
their construction and in their application by the assessor.  PTI doesn't 
even assess risk - which, if you think about it is rather odd when you're 
taking all that time and effort to inspect a tree.  It's why I put so much 
work into getting VALID going because I thought the whole thing could be done 
so much better.  As well as being so much easier on the assessor and duty 

<<Can you please tell us exactly what is reasonable, practical and 
proportionate for one single example?>>

I'm not being pedantic here but it's not 'practical'.  It's 'reasonably 
practicable'.  The term has a very particular meaning in risk management.

At the risk (acceptable) of enraging the usual suspects, it's all set out in 
the Tree Risk-Benefit Management Strategies on the Risk Management page of 
VALID's website here.

Have a look at the Government one, which is the most comprehensive.  The 
single most important document is the Policy.  It's a position statement.  
Everything flows from the Policy.  In the unlikely event of a claim being 
made, it sets out the ground on which a duty holder would mount their defence.

Kew Gardens Questions
Have a read of the Active and Passive Assessment Note in the Strategy, and 
the three levels of Active Assessment - Basic, Detailed, and Advanced.   This 
answers most of your questions.   How frequently Kew would carry out an 
Active Assessment is their call - VALID proposes a 5 yearly Active Assessment 
frequency in high use zones as being reasonable, proportionate, and 
reasonably practicable.

Really importantly, Active Assessment is forever being topped up by Passive 
Assessment, which is happening all of the time.  One of the things I've been 
doing in Tasmania is putting all their Highways Inspectors through a one day 
'Tree Risk & Obvious Trees Defects' course.  If Kew were to follow what the 
Tasmanian Government have done, then all of their outdoor staff would be 
trained to recognise obvious tree defects.  They'll then be carrying out 
thousands of 'free' Passive Assessments each week.  As such, I'd have thought 
they could make a very strong case to manage their risk by Passive Assessment 
alone, and carry out Advanced Active Assessments on those few trees that 
they're monitoring, at whatever period of time has been specified.

<<exactly how many minutes and seconds per tree>>

<<Further can you please tell us the exact risk vs. benefit for the massive 
*Quercus castaneifolia*.>>

Sorry, I can't on both counts.  VALID doesn't do 'exact'.  There's way too 
much uncertainty in tree risk assessment to be exact.  I'd have to see the 


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