Masters - Safety Vs Progress

Topics relating to Advanced Driving in cars
hir
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Re: Masters - Safety Vs Progress

Postby hir » Fri Nov 02, 2018 11:10 pm

Horse wrote:Have a look at the picture! It's in a village, a stone wall about 8' high, 'vehicle'-sized aperture with huge fuggoff wrought iron gates just visible, with a nice weed-free gravel driveway. The wall is set back no more than a metre from the edge of the road.

In other words, it would be reasonable to expect a Range Rover to emerge. And, as you can see, the Range would have to nose out for the driver to get any view.

So what? You ask.

Well,

1. The picture is to show us the limit point, so if we're concentrating on that and planning for the right hand bend, then where would we position for view?

2. Yes, I do bang on about the SH. And this is a classic example of where someone has progressed to a very high standard of driving - but can still apparently be blissfully unaware. So what do you suggest, that I shut up, encouraging that blissful ignorance?






It just depends what one means by Limit Point.

Definition: The Limit Point is the furthest distance on the surface of the road seen to be clear and likely to remain so.

This isn't a totally satisfactory or useful definition when looking at the photo of the church. If I've understood correctly, the question that seems to be at issue in this discussion is... is the Limit Point in front of the church, or at the point of the entrance on the left? Some say it can't be at the church because something might pop out of the entrance, so therefore the entrance should be regarded as the true Limit Point, others will say the Limit Point is in front of the church because that's the furthest distance on the surface of the road seen to be clear. The point indicated in front of the church is what I would regard as the physical limit point, in accordance with the first part of the definition. But, as Horse quite rightly points out, there is an entrance on the left with a restricted view into that entrance. And this is where I think we begin to get hung up about Limit Points and trying to define where the Limit Point is. I don't think the term "Surprise Horizon" is a particularly helpful term to use in this context because it confuses the distinction between a "hazard" to be dealt with by IPSGA and the Limit Point which is a technique to get our approach and entry speed correct for a bend.

However, I think we can cut through all of this pointless "is it, isn't it" debate if we regard the church as the physical Limit Point and we then apply IPSGA (not Limit Point Technique) to the potential hazard associated with the entrance on our left. Dealing with the entrance on our left as a hazard in its own right [something might pop out without stopping] means that we should be dealing with it by applying the System, maybe by moving offside to move the car to a place of safety or, if that's not possible, reducing speed to be able to deal with any surprises [ie. IPSGA, pure and simple]. When the entrance on the left is passed and has been safely dealt with we can revert to dealing with the limit point in front of the church and, if appropriate, adjusting our speed in accordance with whatever the Limit Point is telling us.

So, if my understanding of how the term "Surprise Horizon" is being used in this context, then, in my opinion, the entrance on the left is not a "Surprise Horizon", a term which seems to be related to Limit Points, but is in fact simply a "potential hazard" to be dealt with by IPSGA in a similar way to any other hazard.

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GTR1400MAN
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Re: Masters - Safety Vs Progress

Postby GTR1400MAN » Fri Nov 02, 2018 11:27 pm

Horse wrote:
Horse wrote:https://www.linkedin.com/pulse/so-whats-masters-david-barnes/


Post #1

In the linked article there are two 'road' pictures and a photo of his report sheet.

Interesting. When I loaded that page earlier I just got text.

Having looked at the image of the church and the hazard/driveway on the left, you can clearly see no-one (advanced or otherwise) goes any where near it , by looking at the muck on the road in the nearside edge. Loads of room for farmer Giles, or more likely city boy Gary, to peek his nose out to see what is coming.

I too looked for the way the sun was shining to make a comment about being able to see a potential exiter, but the photo seems devoid of logical shadows and those on the road (if they are shadows) don't seem to be from what is at the side of the road.
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Horse
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Re: Masters - Safety Vs Progress

Postby Horse » Fri Nov 02, 2018 11:28 pm

SH is, simply, the nearest point at which you can be surprised (without digging out Mind Driving to check the exact wording.
Your 'standard' is how you drive alone, not how you drive during a test.

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Strangely Brown
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Re: Masters - Safety Vs Progress

Postby Strangely Brown » Sat Nov 03, 2018 9:47 am

Horse wrote:
Strangely Brown wrote:
Horse wrote:So what do you suggest, that I shut up, encouraging that blissful ignorance?


You could just answer the question: What speed would you consider safe there?

Personally, I don't believe that anyone living in that property would ever drive straight out so simply moving slightly away on approach would be quite sufficient. That still leaves room to reposition nearside for the RH bend.


The "4mph?" seemed like a rhetorical question, and even if actually intended as a genuine question there isn't a single answer.

For example, which way is the Sun shining? If from the left, the there could well be a shadow preceding the vehicle.

I'm impressed by your confidence that no-one would ever pull out without checking. If that was repeated at all give way junctions, it'd be a miracle. And even if they check, crashes still happen - people make mistakes. What other assumptions do you make? :)


I try not to make assumptions. I try to make judgements based on what can be seen, what cannot be seen and the circumstances that may reasonably be expected to develop. In this case, I agree, it is certainly possible that someone may drive straight out without checking. I also think that it is rather more improbable. If the users of that or any similar property were to so habitually then I would expect them to have come to grief long before now. So, as I said, I would likely move away slightly and then reposition nearside for the corner. Speed would probably already be reduced for the confined environment and considering further reduction for the corner.

So just how far would you slow for that entrance? 40? 30? 20? less? After all, even if they check, crashes still happen, people make mistakes.

hir
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Re: Masters - Safety Vs Progress

Postby hir » Sat Nov 03, 2018 9:49 am

Horse wrote:SH is, simply, the nearest point at which you can be surprised (without digging out Mind Driving to check the exact wording.


... and should therefore be dealt with by using IPSGA, not Limit Point Analysis.

Roadcraft says... "... Limit Point [analysis] gives you a systematic way of judging the correct speed to use through the bend"

So, Limit Point Analysis is a simple technique for gathering information about a bend and moderating one's approach, entry and transition speeds through said bend. It is not a suitable tool for dealing with a "surprise horizon" consisting of a residential entrance into which we can't see.

If there is a potential "surprise horizon" hazard ahead, for example the blind residential exit already noted, or a warning of a junction ahead, one should deal with that potential "surprise horizon" hazard by using IPSGA. Instead of a closed-view residential entrance as per the example quoted, let's assume we have warning of a closed-view nearside road junction ahead. We can't see into the junction, we don't know if there is anyone in the junction or approaching it. Why would we start thinking about Limit Point Analysis for this "surprise horizon" when we can, and would, deal with the potential "surprise horizon" hazard using IPSGA?

Carbon Based
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Re: Masters - Safety Vs Progress

Postby Carbon Based » Sat Nov 03, 2018 10:38 am

dvenman wrote:I was more interested - at a quick glance - at the interaction between David and Carol. I'm going to have to dig a little deeper...

Did you find this:
https://mcskillsasia.wixsite.com/home

Triquet
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Re: Masters - Safety Vs Progress

Postby Triquet » Sat Nov 03, 2018 1:30 pm

Whatever. Yesterday I went through here, which was further decorated with four pedestrians and a random dog. I was down to 5 mph.

https://www.google.co.uk/maps/@53.56649 ... 8192?hl=en

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Horse
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Re: Masters - Safety Vs Progress

Postby Horse » Sat Nov 03, 2018 5:05 pm

hir wrote:
Horse wrote:SH is, simply, the nearest point at which you can be surprised (without digging out Mind Driving to check the exact wording.


... and should therefore be dealt with by using IPSGA, not Limit Point Analysis.

Limit Point Analysis is a simple technique for gathering information about a bend and .. is not a suitable tool for dealing with a "surprise horizon" consisting of a residential entrance into which we can't see.


I never said otherwise. My comment in relation to SH and the annotated photo was in relation to use of 'thirds'. No confusion on my part.
Your 'standard' is how you drive alone, not how you drive during a test.

hir
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Re: Masters - Safety Vs Progress

Postby hir » Sat Nov 03, 2018 9:38 pm

Crrr003 wrote: Do you remember the thread about 1/3 or 2/3s rule for acceleration between hazards?


Horse wrote:I don't like the way (from the way I read and [mis?]understood?) it seems to place emphasis on getting from 'Here >>>> there' which may remove caution for 'here>>>danger in between>>> there' IYSWIM or, to use jargon, emphasis on limit point rather than surprise horizon*

* See the second on-road photo in the article, annotated with the limit point - which neatly ignores the (much closer) blind entrance through a high wall.


Horse wrote: My comment in relation to SH and the annotated photo was in relation to use of 'thirds'. No confusion on my part.


OK, then I'm confused.

The Limit Point is, well, it’s the Limit Point. When explaining and identifying what the Limit Point is, which was the purpose of the original narrative and the picture of the church, why would one confuse the issue by saying… “There’s the Limit Point in front of the church, Oh, and by the way, there’s an entrance on the left which you can’t see into”? You wouldn’t. If you’re trying to illustrate where the Limit Point is you simply say… “There’s the Limit Point, in front of the church”. The concealed entrance is irrelevant in the context of explaining where the Limit Point is. Therefore, the writer has… “neatly ignored the (much closer) blind entrance through a high wall”, simply because it’s not relevant to what he wants to convey to the reader. Which is… “This is where the Limit Point is, in front of the church”.

OK, I’m now even more confused.

The “thirds rule” isn’t about “thirds” and it isn’t a “rule”. It’s a misnomer. The word “thirds” implies three equal parts; but that’s not what happens. A better description would be the... “three segments technique for allocating a specific activity to each of three segments of the road ahead”, but that’s such an inelegant mouthful we’ll stick with “thirds rule” for the purpose of this discussion. It’s a technique that is used to divide the road ahead into three segments. These three segments are invariably of different lengths. A different action then takes place in each segment. The misunderstanding appears to be the perception that the road is divided in to three segments from the current position of the car, as it exits a bend, right up to the limit point in the distance with no regard for anything in-between. This misunderstanding would appear to be the source of your comment… “it seems to place emphasis on getting from 'Here >>>> there' which may remove caution for 'here>>>danger in between>>> there'. That is not a correct. That is not how the technique should be applied. The division of the road ahead into three segments is from… “Here >>>> the next hazard/danger”. Which may be the bend at the limit point ahead, if there is no earlier hazard, or it might be an earlier hazard such as the concealed entrance that is illustrated in the photo to which we have been referring. The final, or third, segment always deals with the next hazard, be that at the limit point or before it. If the next hazard (the concealed entrance in the photo, for example) is before the limit point then, once the first hazard is passed, the road will again be divided into three segments through to the next hazard, which, again, may or may not be the limit point.

The misunderstanding seems to be that when applying the "thirds rule" one takes account only of the limit point when segmenting the road. That is not correct... the road is segmented in to three parts only as far as the next hazard.

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Horse
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Re: Masters - Safety Vs Progress

Postby Horse » Sat Nov 03, 2018 11:14 pm

I'm glad that it wasn't me who called it a rule! And it's fairly obvious (to me anyway) that the sections can't be fixed length or equal - one aspect being that the more you accelerate (possibly taking more distance, depending on rate of acceleration) then more space may be needed for braking (depending ... ). If those two lengthen, then the middle shrinks. Where I have issue with it is, yes it's from 'here to next hazard' - but by placing emphasis (whether intentional or not) onto acceleration - it potentially takes emphasis away from other mid-point hazards.

Very simply, it was poor selection of image. To be fair, if he's not an instructor then he may not be thinking 'that' way.

WRT my understanding of the concept, as I said it's only from a couple of online explanations, but I think my concern is the same as for some other techniques/ideas/whatever, and that's that they encourage looking to do rather than looking to don't.

But, to reiterate, I am really not confused in my understanding of limit point and how to use it, I'm quite happy there. Conversely, I don't misunderstand thirds because I don't have really have an understanding of it :) I read about it, tried it, didn't get on with it, so went back to tried and [literally] tested methods! And it wasn't me who introduced it to the thread. I don't confuse SH and LP either (if you want evidence of that, refer back to the Cumbrian lane photo I posted ages ago:
https://2.bp.blogspot.com/-rbfwunUF0Y4/ ... 2Bcrop.jpg (but it would take a while to find that post!) The LP is waaaaay in the distance - but there's a plethora of places where vehicles, pedestrians, or other could emerge.
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Your 'standard' is how you drive alone, not how you drive during a test.


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