Quantified Tree Risk Assessment (QTRA) - Questions & Answers

[Acer ventura]

Unfortunately, in most cases of accidents involving trees and motorcars the driver rarely has time to apply the brakes for two reasons, Field Of Vision (FoV) due to the windscreen and roof and the fact that most car drivers are concentrating on the road so braking distances are only relevant if the object is already on the ground.

 

A car travelling at 30mph is covering 13.4112 meters pre second, the car travelling at 60mph is covering 26.8224 meters per second exactly double, so the faster car would be in the contact area for exactly half the time of the slower car.

 

Hi Jonny

 

We seem to be posting at exactly the same time today. It's not just the chances of a tree/branch hitting the car though, it's also the chances of the car hitting the tree/branch if it falls into their path as well. It's both. That's what would be the contact area. I linked this in an earlier post as a pdf, but have converted it to a picture.

 

 

I'm sorry if I fail to explain the value concept' date=' do you have a value order? Differentiating between children and adults is futile, they are both human beings.

 

Simply, in order of priority (hypotheticaly)

Human life=1

Buildings=2

Race horses=3

Garages with lambouginis=4

Cows, chickens, goats etc ????

 

 

And I dare because this is a debate and all opinions are equal, no?[/quote']

 

Debate's great but are all opinions equal? I can think of some pretty appalling opinions.

 

As for failing to explain, that's part of the price we pay for this kind of communication. Clearly, I've not explained to you how QTRA calculates vehicle occupation well enough. Anyhow, yes I agree distinguishing between the size and age of humans is futile in terms of tree risk and they are all equal. As for value, we use the Value Of Statistical Life (VOSL). Have a look at page 3 of the PN. I'm going to attach it this time.

 

QTRA Practice Note_V4_03_UK_2012_08.pdf

 

Cheers

 

Acer ventura

[JonnyVine]

Acer

Sorry for pulling strings, I have been familiar with the QTRA program for a number of years and do use a variation of the theme myself, I even attempted making a copy of the Mikes ready reckoner years ago!

 

Jonny

[Acer ventura]

Acer

Sorry for pulling strings, I have been familiar with the QTRA program for a number of years and do use a variation of the theme myself, I even attempted making a copy of the Mikes ready reckoner years ago!

 

Jonny

 

Hi Jonny

 

Just so I’ve got this right. What you’re saying here is you’ve been wasting my time, and anyone else’s who is following this thread, by feigning ignorance and asking questions to which you already know the answer, and then pretending you don't understand my replies?

 

Cheers

 

Acer ventura

[Acer ventura]

 

I would like to take a closer look at QTRA but can not even find the PN.

 

There appears to be a stalemate situation regarding Q&A, the Q's are in abundance but sadly the A's have dried up? I am always suspicous when answers are hidden or maybe don't even exist.

 

Many thanks

Jonny

 

Hi Jonny

 

Wow! I mean really, Wow!

 

Cheers

 

Acer ventura

Edited February 17, 2013 by Acer ventura

[daltontrees]

Av, thanks for the worked example with the picture of the manual calculator and the software screen shot. It has illustrated the QTRA system as much as (and in conjunction with) everything else you have said.

[WorcsWuss]

I'll queue jump you because it's an easier answer than getting onto WorcsWuss's calculation of bending moments.

 

Any time David! Don't place too much emphasis on the calculation itself though It's more the justification of 'managing' risk with statistics and probability rather than facts, which I'm interested in.

I can see the value in qtra's output, but I'm just curious as to how it would stand up if, or when, something goes wrong, and someone is killed by a low risk tree? Which it could, because people win the lottery all the time.... What is the next step if qtra throws up an unacceptable risk? What if the qtra has been done wrong?

For what my opinion is worth, from what you've said and i've seen, it seems like a well thought out system which will do what it sets out to do in a straight forward way. But as a 'general public' as far as this is concerned, I like to question the systems which are supposed to protect my family.

[JonnyVine]

Hi Acer

Sorry I havent repied sooner, been away for the weekend fasioning a cudgel.

 

Yes I just felt that Jules was recieving unnecessary for behaving no differently from you.

 

I did thoroughly enjoy your replies anyway so no wasted time

 

Happily the bennefits to QTRA are

1. Easy to use

2. Diverts from a modern cotton-wool society by placing an ammount of risk onto Joe public

 

Unhappy issues are

1. Pompous aggressive global marketting strategy

2. Raises concern (personal communication) among consultants that the aggressive desire for controll of the maket will shade the light from already used and accepted methods before crushing them with its Global boot

[Acer ventura]

Hi Rob, and anyone else who wants to have go (whether you want to do it in privacy behind drawn curtains, or chip in)

 

As you’ve probably already seen, I ended up running a worked QTRA example this weekend, which might have helped, but here’s your Ruff Wood one from scratch. How about approaching this as though we were instructed by West Lancashire Borough Council to assess tree risk in Ruff Wood?

 

For educational purposes I’ve snipped a bit off google maps showing Ruff Wood and pasted it into a word document, which I've attached, because I figured this would be the easiest to add text boxes to and annotate.

 

QTRA Ruff Wood Walkover.doc

 

The site can be virtually assessed for Target values from google maps, including street view, and what you might be able to tell us knowing how the site is used.

 

Ruff Lane, Ormskirk - Google Maps

 

With QTRA, the most cost-effective way of approaching this instruction would be to undertake a ‘Walkover Survey’. I’ll explain more about the details of this process as we go through it, but firstly we would treat the woodland as one compartment (in this case W1). The next part of the tree risk assessment is the most important and that is assessing the Target values. So, have a look at table 1 on page 5 of the QTRA PN and have a go at ranking the Targets in relation to the woodland within one of the six ranges. What you’ll end up with is a painting by numbers picture of the Targets adjacent to the wood, and within it.

 

In relation to traffic counts, you might find this site useful.

 

Traffic counts - Transport statistics - Department for Transport

 

If it does occur to anyone to do so, please don’t ring up Lancashire County Council Highways Department to find out whether they have a traffic count for Ruff Lane. I've already done this and they are going to get back to me. I'll let you know when I find out.

 

Have a look, give it a go, and fire away with any questions you have.

 

Cheers

 

Acer ventura

[Gary Prentice]

Hi Acer,

Thanks for the calculations you posted over the weekend. I briefly read through them but really haven't had the time to think everything over (whilst re-reading the practice note again).

I'll be back when I get all my ducks in a row.

[RobArb]

Thanks Acer, i shall have a go at this later:thumbup: