ADUK Archive

Please correct me on this as I am a AD newbie, but as far as I am aware the limit point is at the opposite edge of the road i.e. on a LH it is defined by the RH verge, RH bend the LH verge i.e. if you're looking at the limit point you may be able to see a hedgehog in the gutter but there could easily be a car, truck, lorry, combine harvester or horse at that distance ahead but you won't actually see it. The road is NOT necessarily clear to the limit point and the tighter the bend the worse the discrepancy.

I admit that I haven't read all of this thread, but I'm torn between two thoughts.

Either this is a search for a rule when all that is on offer is a guide. Or that the stated rule is really only a qualifying sub clause on the actual golden rule that hasn't been agreed on yet.

Which is that it depends...

The Golden Rule is surely "If you're going to drive, don't do it shite"

triquet wrote:Please correct me on this as I am a AD newbie, but as far as I am aware the limit point is at the opposite edge of the road i.e. on a LH it is defined by the RH verge, RH bend the LH verge i.e. if you're looking at the limit point you may be able to see a hedgehog in the gutter but there could easily be a car, truck, lorry, combine harvester or horse at that distance ahead but you won't actually see it. The road is NOT necessarily clear to the limit point and the tighter the bend the worse the discrepancy.

I agree with you for LH bends which is why for these I do not take the limit point as the opposite edge of the road. I don't think there is the same issue for RH bends.

For my likeing (even after taking into consideration the different view the driver has from mine in the passenger seat) I often feel that for LH bends many drivers go too quickly and it feels to me that their speed selection was based on the limit point on the opposite side of the road and not the nearside, which in my view is the true limit of tarmac available to stop within.

triquet wrote:... but there could easily be a car, truck, lorry, combine harvester or horse at that distance ahead but you won't actually see it. The road is NOT necessarily clear to the limit point and the tighter the bend the worse the discrepancy.

Could you clarify this, please.

Why would you not see the car, etc, etc?

"The road is NOT necessarily clear to the limit point". But, surely, the limit point is defined by the word "clear". If it's not clear... it's not the limit point.

Or, am I missing the point!

Usually the limit point is a fact of geometry - the furthest point on the road you can see. It's dominant in hazard assessment technique where the nearest hazard is the bend.

It's tempting to use an alternative definition - my particular favourite - "the nearest place a surprise can come from".

This makes the Golden Rule:-

Always drive so that you can stop before the nearest place a surprise can come from.

I assume that satisfies those who think the language was clumsy or unclear in the original version. I prefer the original for its emphasis on observation and thought.

7db wrote:Usually the limit point is a fact of geometry - the furthest point on the road you can see. It's dominant in hazard assessment technique where the nearest hazard is the bend.

It's tempting to use an alternative definition - my particular favourite - "the nearest place a surprise can come from".

This makes the Golden Rule:-

Always drive so that you can stop before the nearest place a surprise can come from.

I assume that satisfies those who think the language was clumsy or unclear in the original version. I prefer the original for its emphasis on observation and thought.

That'll do nicely. The point I was trying to make is that the "nearest point" is actually somewhere beyond the geometrical limit point as there can be stuff on the road just out of sight.

A couple of thoughts.

First, I am wary of referring to any "Golden rule" in driving. The phrasing may be taken by some to mean that if they follow the rule they will never have an accident. In relation to the stopping distance "golden rule" discussed in this thread, that is clearly incorrect. The "rule" only works if the hazard that appears in front of you on your side of the road is stationary. If it is moving towards you (e.g. it is a car overtaking on a blind bend), you are probably stuffed.

I mention this because it is another example of why I dislike any reference to "rules" in driving (and I am discriminating here between a rule and a law). No amount of rule following will reduce accident risk to zero. And as 7db has implied, slavish adherence to rules can stop people thinking.

Second, I think all this wordsmithing misses a larger point. I wonder how many drivers have any idea how to brake maximally? I bet it is a small proportion. I know of some drivers whose first reaction on feeling a pulsing brake pedal (ABS) is to jump off the brakes (they've told me!). Very few drivers will have practiced the technique of using the brakes to stop the car in the shortest possible distance, particularly on a bend. How does one factor in that variable (i.e. of driver skill) into the "Golden rule"?

I'd much prefer we get drivers to think about this stuff; to think dynamically about road situations, taking into account all available observations and select a speed that provides some safety margin to allow for the unexpected (which I appreciate will be a personal judgement and can in no way guarantee safety). So rather than trying to define the perfect set of words to tell an associate, I'd rather we asked them questions that made them figure it out for themselves.

7db wrote:Usually the limit point is a fact of geometry - the furthest point on the road you can see. It's dominant in hazard assessment technique where the nearest hazard is the bend.

It's tempting to use an alternative definition - my particular favourite - "the nearest place a surprise can come from".

This makes the Golden Rule:-

Always drive so that you can stop before the nearest place a surprise can come from.

I assume that satisfies those who think the language was clumsy or unclear in the original version. I prefer the original for its emphasis on observation and thought.

The nearest place a surprise can come from is only a limit point (by definition) when it 'limits' your view of the tarmac ahead. Similarly a fixed hazard is only the limit point whilst it remains part of the 'border' of the limit point. There are plenty of hazards we should reduce our speed for (or maybe stop for) that don't limit our view of the tarmac ahead.

A side road might be part of the limit point (and the nearest place a surprise can from) but it ceases to be a limit point once we have an unobstructed view of the tarmac beyond it. It then remains only a hazard that will form part of our judgement of our speed and driving plan.

Granted if a moving hazard appears (one that obscures your view or obstructs your path) then it creates a new limit point but you can't always guarantee that it will be at a distance you can stop (or slow sufficiently slow for) as it is beyond your absolute control i.e.you can only reduce your speed and/or adjust your position to limit the chance and severity of any collision!

A limit point is by definition a place on the road you can always be guaranteed to stop for (if your speed is correctly adjusted). That can only logically be the tarmac that is currently clear (not what may or may not be). Again, I repeat, that this does not mean I am suggesting that you shouldn't make further allowances for possible or definite hazards.

I've resisted so far, but ...

I would submit that the limit point is a geometric certainty, that shouldn't be messed with. It's a guide to driving bends, that is useful in the absence of other hazards. The wording of the "golden rule" (note the quotation marks) does not include anything about the limit point.

Hazard density varies with type of road, and there are always hazards both seen and unseen. It's our duty to be aware of the potential hazards and modify our speed so that we can always stop for both kinds. Observing potential or developing hazards in the foreground is one source, imagining or using experience or observation links to predict currently invisible ones is another.

So 7db's wording is very apt, albeit a "surprise" may turn out to be something you used your skill to preduct - e.g. the tractor round the corner that's producing all the hedge cuttings you've been driving through for the last half a mile, etc.

7db wrote:It's tempting to use an alternative definition - my particular favourite - "the nearest place a surprise can come from".

This makes the Golden Rule:-

Always drive so that you can stop before the nearest place a surprise can come from.

I assume that satisfies those who think the language was clumsy or unclear in the original version. I prefer the original for its emphasis on observation and thought.

That is not possible. Other than braking to a stop before every hazard, how can you always be certain that you can stop?!

Stopping for the limit point is only achievable because it is based on a known fact that you will have to keep slowing to keep your stopping distance until the limit point moves away. Any other 'surprise' would be exactly that; something you could ever be certain of stopping for even if you had reduced your speed considerably to reduce the risk and severity of a collision.

I believe what you are in fact saying is;

1. Always drive so that you can stop in the distance you can see to be clear.
2. Where there are additional hazards reduce your speed further to reduce the risk of a collision.

Statement 1 is an objective rule and statement 2 is a subjective addition that is subservient to statement 1.
If we combine them into the same statement the objective nature of rule 1 is lost.

In fact what the golden rule logically means (with the clumsy addition) is that a driver should allow a stopping distance for a length of road that may be obstructed at any time as the driver closes in or may remain clear! How is this possible?! Only if the driver plans to stop completely and is a mind reader!

Illogical and not in fact what is meant! I am not in disagreement with the underlying principles just the incorrect use of the English language to explain it.

Horse wrote:http://roadarbloggers.wordpress.com/2011/03/18/corners-and-cornering/

Exactly. On a LH bend the true limit point is the LH side (which you can't see).

triquet wrote:

Horse wrote:http://roadarbloggers.wordpress.com/2011/03/18/corners-and-cornering/

Exactly. On a LH bend the true limit point is the LH side (which you can't see).

AKA 'The Surprise Horizon' in Mind Driving.

triquet wrote:as far as I am aware the limit point is at the opposite edge of the road i.e. on a LH it is defined by the RH verge, RH bend the LH verge

I think you might consider theorising less - go out and look at a bend from a stationary point, see where the limit point lies, note what can be seen, try to work out what useful information may be gleaned, and how it might best be used while driving. If one bend isn't enough, repeat with other bends until you can draw some useful conclusions.