UKTC Archive

Re: Windshield/Drive-by | Speed Limit

Subject: Re: Windshield/Drive-by | Speed Limit
From: Wayne Tyson
Date: Dec 02 2019 07:45:56
The bane of scientific experiments is too many variables. Trying to reduce
such complexity into a formula may be impossible. The test, I suspect, of
any predictive tool, is not the authorities' opinions, so much as it is
feedback on what actually happens (predictive value).


On Sun, Dec 1, 2019 at 10:22 PM David Evans <> wrote:

<<David, after re-reading your website I am still left asking how do you

1) It's not reasonable
2) It's not proportionate
3) It's not reasonably practicable>>

Hi Michael

I'm a bit baffled about what you're after here.  You first asked me...

<<Can you please tell us exactly what is reasonable, practical and

Which is written up in VALID's Tree Risk-Benefit Management Strategies,
and you seem to be struggling with this*.  If you want to know more,
there's always Chapter 2 & 3 of the NTSG's Common Sense Risk Management of
Trees, which expands on it in more detail.  Or Professor David Ball's
"Public Safety & Risk Assessment".  I'm pretty certain I can't explain it
any further than what already I've set out.

Now, you appear to be asking why Jeremy's highways stuff isn't?

As for the rest.

<<I have no idea why you propose 5 years, not 4 or 6 or 7 years 2 months.>>

5 Years Active Assessment frequency is a serving suggestion based on a
number of points.  Not least the 'proportionate' factors that the overall
risk from tree failure is extremely low.  The "prospects of reducing the
risk from tree failure below the current level are remote and comparable to
finding a microscopic needle in a gargantuan haystack" - Professor David
Ball (part for the risk advisory team to NTSG)

In application, Kent County Council (who were the first local government
organisation to host VALID training) is one of the main Highways
Authorities in the UK, and they carry out a 5 yearly assessment.
Birmingham City Council is the largest municipality in Europe, and they
carry out a 5 yearly assessment.  Whilst putting VALID together, when
canvassing local governments, urban forestry academics, and solicitors
representing local government in the UK, New Zealand, Australia, and the
US, there seems to be a general agreement that a 5 year Active Assessment
frequency is 'reasonable' and 'proportionate'; particularly when it's being
topped up by Passive Assessment.   Hence, the Tasmanian Government are
going to adopt a 5 year Active Assessment frequency on their roads.  It's
why I'm proposing 5 years instead of 7 years 2 months.  Up to now, there's
been no benchmark for this.  I'm suggesting one that seems to be widely
agreed.  Have you got a better suggestion?

However, it's up to the duty holder to agree a frequency of assessment and
they can go for whatever they want.  They could even go for your fatuous 7
years 2 months if they chose.  It's their call.  But if as a profession we
can get some kind of consistency, then when a legal claim is inevitably
made we're in a better position to justify this frequency of assessment
rather than be held hostage by highly questionable expert witness
testimony, resulting in equally questionable court Judgments.  The court
looks to our profession to set standards.  It's not the other way around,
as some might claim.

<< In the case of KEW we know the number of visitors per year and the
number of hours workers have been on the grounds.  We wold know similar
numbers for many roads and public places, but we don't know for many other
places, thus how do you determine under VALID your three criteria.>>

I really have no idea what you're asking here.  But it looks like you
might've been confusing risk management with risk assessment from the get


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