UKTC Archive

When tree risk assessment becomes like adding up hopeless hedgehog cakes

Subject: When tree risk assessment becomes like adding up hopeless hedgehog cakes
From: David Dowson
Date: Aug 13 2021 10:55:52
Hi All

With reference to the Lantra highways course, to be simply looking at how a 
risk posed by trees may be determined e.g. the table, is not the whole 
picture and is lacking the understanding of the purpose of the risk section, 
who the target audience is and the purpose to which the answer has to be 
utilised. The method is labelled as an example, nothing in stone about it 
what so ever. One also is not aware of the what is explained in the class 
teaching sessions about using numbers and the difficulty with using them. One 
is being very selective to pass comments by only picking on a table used as 
an example.

Whatever any one says risk posed by trees cannot be quantified. The best one 
can do is called 'estimated accuracy risk'. This reflects the uncertainty of 
the accuracy of the estimate.  Risk in relation to trees relies very heavily 
on the individual's experience and knowledge (Heuristic method) to arrive at 
any kind of answer that includes the two unknown elements i.e. if and when 
will the part fail and if it does will it hit a target.

The use of any format, which is essentially a list, is 'better than nothing' 
as it engages the individual with the thinking and forms a defendable 
position. Research shows that when using a list for any purpose the user will 
make less mistakes than if they don't use a list. Some lists are better than 

The objective for a highway authority is to enable a decision to be taken 
regarding the safe retention of a tree(s) or not and then to make 
contingencies in terms of costs, time, or human resources and to prioritize 
them. If a simple table assists with that process for lay person highway 
engineers, which is the target audience, one might conclude that it is very 

Dave D

Dave Dowson
Chartered Arboriculturist
Arb Assoc Registered Consultant
Tree Life A/C Ltd
Tel/ Fax: 01162XXXXXX
Braemar Court, 1319 Melton Road, Syston, Leicester, LE7 2EN<>

Tree Life Arboricultural Consultancy Ltd, Braemar Court, 1319 Melton Road, 
Syston, Leicester LE7 2EN.  Registered in England 4268200. Vat Registered 695 
5876 60

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