The Limit Point

[LuckyNumber72]

Hi everyone. Have just started to read Roadcraft as I am starting both ROSPA and IAM training in the near future and just wanted to check I have understood what the limit point is and how to use it to judge speed/corner severity. Here is how I understand it:-

As you approach the corner-

If the limit point is moving towards you quickly you need to slow down.
If the limit point appears to be static you are at the correct speed.

As you enter / during the bend-

If the limit point moves towards you quickly the bend is tightening and you may need to slow down.
If the limit point stays static then it is a constant radius bend.
If the limit point begins to move away slowly the corner is opening up and you can consider accelerating.
If the limit point moves away quickly you are exiting the corner so can accelerate if it is appropriate to do so, at which point you will be looking for your new limit point.

Any feedback would be greatly received. Thanks in advance Luckynumber72.

[mph999]

If the limit point moves towards you quickly the bend is tightening and you may need to slow down.
If the limit point stays static then it is a constant radius bend.
If the limit point begins to move away slowly the corner is opening up and you can consider accelerating.
If the limit point moves away quickly you are exiting the corner so can accelerate if it is appropriate to do so, at which point you will be looking for your new limit point.

Correct.

As you approach a bend the limit point will be stationary. At some point, depending on the severity of the bend it will stay with you, or move away.

A very simple guide ...

Make sure you can stop in the distance between you and the limit point.
As you approach a bend, bearing in mind the point above, ajust your speed so that the limit point moves with you.
Be aware that once in a bend, a stationary or limit point moving away from you, might come back towards you (double apex bend).

[vonhosen]

LuckyNumber72 said:

Hi everyone. Have just started to read Roadcraft as I am starting both ROSPA and IAM training in the near future and just wanted to check I have understood what the limit point is and how to use it to judge speed/corner severity. Here is how I understand it:-

As you approach the corner-

If the limit point is moving towards you quickly you need to slow down.
If the limit point appears to be static you are at the correct speed.

As you enter / during the bend-

If the limit point moves towards you quickly the bend is tightening and you may need to slow down.
If the limit point stays static then it is a constant radius bend.
If the limit point begins to move away slowly the corner is opening up and you can consider accelerating.
If the limit point moves away quickly you are exiting the corner so can accelerate if it is appropriate to do so, at which point you will be looking for your new limit point.

Any feedback would be greatly received. Thanks in advance Luckynumber72.

1) The limit point (on a 2 way road) is the furthest piece of uninterrupted road surface you can see on your side of the road.

2) It is the point you have to be able to stop by at all times.

3) Initially on approach it will appear that the limit point is static. If you are a long way off you may continue accelerating towards it, but there will come a point where you will realise you are going to have to start losing speed in order to comply with 2) & you will lift off the throttle to start losing that speed smoothly.

4) It will then start creeping, but at this stage you are still moving quicker than it & need to continue losing speed.

5) It then becomes matched, that is to say it moves at the same speed as you. At this point you should just go with it with throttle to match it's pace.

6) It will then start to open, that is move away from you. The danger at this point is that you start to increase acceleration after it & it suddenly closes rapidly (a double apex) & you are too fast towards it. So at this stage just keep the prior pace (throttle) & pause (from adding more) while you confirm it is actually opening up.

7) When you've confirmed it is opening up, you can gradually apply further acceleration smoothly as you also smoothly allow/take steering off.

Edited by vonhosen on Sunday 11th January 20:51

[S. Gonzales Esq.]

For the uninitiated, the Limit Point (or Limit Point of Vision) is the furthest point you can see of clear and unthreatened road surface. It's usually defined as where the kerbs appear to meet in the distance, but that definition doesn't take into account the fact that on a left hand bend you can see further along the other side of the road.

In crude terms, the distance to the Limit Point dictates your speed, and the rate at which the Limit Point is moving relative to you dictates your rate of acceleration (or deceleration). As an extreme example, think about a double-decker bus stopped round the next bend. The faster you're going, the harder you'll need to brake.

However - when practicing Limit Point Analysis, don't forget that it doesn't exist in a vacuum. It's possible to get so wrapped up in watching the Limit Point that you don't notice the wet surface or a glimpse of that stationary bus through the trees. Good observation always comes first.

Bah - just beaten to it by Von. His is a better explanation too.

Edited by S. Gonzales Esq. on Sunday 11th January 20:55

[7db]

I find it's helpful to sometime think of the point from which the nearest surprise can come (this might be laterally), which is often the limit point, and always guides speed.

[waremark]

vonhosen said:

5) It then becomes matched, that is to say it moves at the same speed as you. At this point you should just go with it with throttle to match it's pace.[/footnote]

I am fully aware that this is the classic Roadcraft explanation, but I find it much easier to understand:

'As you turn into the bend, providing the bend does not tighten, and providing you have slowed enough to be able to stop in the distance you can see to be clear, apply enough gas to maintain a constant speed (note that if you do not apply gas the effect of turning will slow your vehicle).'

[deeps]

Surely all this sort of talk just over-complicates simple matters? Like here, being able to stop in the distance you can see to be clear.

I suppose if you're driving ability is going to be tested, then you need to be able to verbally communicate why you're doing what you're doing, but apart from that it's common sense isn't it?

I've never had any basic or advanced driving lessons, but all the stuff I read on this forum is basically what I've always practiced anyway, because it's common sense.

[deeps]

S. Gonzales Esq. said:

However - when practicing Limit Point Analysis, don't forget that it doesn't exist in a vacuum. It's possible to get so wrapped up in watching the Limit Point that you don't notice the wet surface or a glimpse of that stationary bus through the trees. Good observation always comes first.

Well said.

[WhoseGeneration]

deeps said:

but all the stuff I read on this forum is basically what I've always practiced anyway, because it's common sense.

Well, it would appear many drivers out there don't exhibit your "common sense".
Now, why might that be?

[Pugsey]

deeps said:

Surely all this sort of talk just over-complicates simple matters? Like here, being able to stop in the distance you can see to be clear.

I suppose if you're driving ability is going to be tested, then you need to be able to verbally communicate why you're doing what you're doing, but apart from that it's common sense isn't it?

Hurray for COMMON SENSE! I agree 100%. Frankly I'd much rather meet an 'aware' driver coming the other way down one of my my local lanes than some self righteous string backed gloves and cloth cap wearing anorak with loads of 'how too' books in his glove compartment driving along squinting into the distance for that blxxdy Limit Point - oblivious to anything else. If you REALLY need to read pages and pages on this subject you shouldn't be driving a car frankly. Yes, maybe useful for verbalising what you're doing - or sounding like you know what you're doing - but that's about it really.

Edited by Pugsey on Monday 12th January 12:56

[S. Gonzales Esq.]

Here's a question - which is better:

A driver who thinks they know it all because they've done a short course and have a badge on their car,

or

A driver who is so sure they know it all already that there can't be any point in thinking more about their driving technique?

Different sides of the same coin I'd say, and both unhelpful attitudes.

[Pugsey]

S. Gonzales Esq. said:

Here's a question - which is better:

A driver who thinks they know it all because they've done a short course and have a badge on their car,

or

A driver who is so sure they know it all already that there can't be any point in thinking more about their driving technique?

Different sides of the same coin I'd say, and both unhelpful attitudes.

Fortunately neither seem to appear on here very often. There is another type of course - the one who thinks merely noting and commenting on others shortcomings makes him the better driver....................

[Pugsey]

waremark said:

vonhosen said:

5) It then becomes matched, that is to say it moves at the same speed as you. At this point you should just go with it with throttle to match it's pace.[/footnote]

I am fully aware that this is the classic Roadcraft explanation, but I find it much easier to understand:

'As you turn into the bend, providing the bend does not tighten, and providing you have slowed enough to be able to stop in the distance you can see to be clear, apply enough gas to maintain a constant speed (note that if you do not apply gas the effect of turning will slow your vehicle).'

Yep. Natural and (should be) instinctive. The need to analyse beyond that and go consciously looking for landmarks, 'limit points' etc. (which should be happening subconsciously anyway) would, to me, suggest little 'feel' for driving and the process of trying to follow this method may well distract from other danger areas that warrant attention. IMHO.

[S. Gonzales Esq.]

Pugsey said:

... looking for landmarks, 'limit points' etc. (which should be happening subconsciously anyway)...

I'd approach it a little differently and say that Limit Point Analysis can be a helpful way to start working on cornering technique.

If you relate the above quote to the theory of the Four Stages of Competence then you're expecting people to reach the fourth stage without passing through the third.

[GreenV8S]

In my view the limit point technique is not about determining the distance you can see to be clear.

The latter I think is intuitive and I would expect everyone to do it without thinking.

The limit point technique is IMO not about this. It is a way of telling how the curvature of the road is changing out towards the limit of your vision, well before you can see the road well enough for the curve to be visually obvious. I doubt that many people do this intuitively, but once you've done it you will probably get a 'eureka' moment as you realize how much more earlier you can tell the shape of the road.

I also don't like the simple rules of thumb about how you should vary your speed based on the movement of the limit point. I think that is over simplistic to the point of being downright misleading.

[S. Gonzales Esq.]

I think we can agree that simple rules don't do a very good job of explaining complex situations. Limit Point Analysis can give early information about the course of a bend and lead to better, smoother progress. However, for someone just starting down the advanced road it is also a good way to help with selecting appropriate speeds for bends.

When I get a new IAM associate their thinking is often 'how fast can I go around this without falling off'. LPA sorts out the technique first, then we add the progress back later.


Back to the OP for a moment: did you say both RoSPA and IAM? Masochist or badge collector?

[Pugsey]

S. Gonzales Esq. said:

Pugsey said:

... looking for landmarks, 'limit points' etc. (which should be happening subconsciously anyway)...

I'd approach it a little differently and say that Limit Point Analysis can be a helpful way to start working on cornering technique.

If you relate the above quote to the theory of the Four Stages of Competence then you're expecting people to reach the fourth stage without passing through the third.

Not at all. Or to turn it around are you REALLY saying that no-one can reach your 'stage four' - for our purposes we'll call stage four being able to corner with a very high degree of skill ('skill' encompassing safety, speed, awareness, smoothness etc., etc.) without having read about Limit Points? It's perfectly possible to reach level four/a very high level of driving skill WITHOUT having been physically taught about the Limit Point. As others on here have said, a great deal of this is common senese and many good drivers - on analysing themselves (which we should all be doing regularly) - will find that they are already using these techniques having developed them over time subconsciously. Lets face it someone, somewhere, had to be the first person to verbalise/write down the Limit Point theory (or any other theory for that matter) - why should he/she be the only one to have worked it out for themselves?

I am NOT saying that Advanced Driving Instruction is a bad idea, merely that some may slot in MUCH further along the learning curve than others, having achieved a high level already through a combination of natural ability (some would call it common sense) and self awareness.

[S. Gonzales Esq.]

Pugsey said:

... It's perfectly possible to reach level four/a very high level of driving skill WITHOUT having been physically taught about the Limit Point.

...some may slot in MUCH further along the learning curve than others, having achieved a high level already through a combination of natural ability (some would call it common sense) and self awareness.

That's fair enough. I was assuming that the OP isn't a driver with many years of experience - my thinking was that Limit Point Analysis could short-cut the need for decades of practice.

My limited experience with IAM associates suggests that even the more experienced ones aren't always blessed with lots of natural ability and self-awareness.

[Pugsey]

S. Gonzales Esq. said:

Pugsey said:

... It's perfectly possible to reach level four/a very high level of driving skill WITHOUT having been physically taught about the Limit Point.

...some may slot in MUCH further along the learning curve than others, having achieved a high level already through a combination of natural ability (some would call it common sense) and self awareness.

That's fair enough. I was assuming that the OP isn't a driver with many years of experience - my thinking was that Limit Point Analysis could short-cut the need for decades of practice.

My limited experience with IAM associates suggests that even the more experienced ones aren't always blessed with lots of natural ability and self-awareness.

First point accepted and taken matey - I'm an old fart and tend to forget how long it took me to reach my current God like abilities!

Second point. Oh SO, SO, true!!

[vonhosen]

GreenV8S said:

In my view the limit point technique is not about determining the distance you can see to be clear.

The latter I think is intuitive and I would expect everyone to do it without thinking.

In my experience I haven't come across many who intuitively get it right in relation to stopping distance needed. People mostly tend to over estimate the amount of room they need at lower speeds & under estimate it at higher speeds.

Edited by vonhosen on Monday 12th January 17:42