Just zis Guy, you know? wrote:

Velvet wrote:


Q. Does ABS reduce stopping distances?


A. Yes, in braking situations where the wheels on a non-ABS equipped
vehicle would lock up, ABS will generally provide shorter controlled
stopping distance. The amount of improvement in stopping distance
depends on many factors, including the road surface, severity of
braking, initial vehicle speed, etc. On some surfaces, such as gravel
roads, braking distances can be longer, but you will still have the
control benefits of ABS. The important capability of ABS is control.
ABS provides improved vehicle steerability and stability when braking.


In other words, yes and no, but for practical purposes no, unless the wheels
would be locking up. Which they generally don't. And, as stated, "the
important capability of ABS is control."


Interesting that you made no comment on the second snippet I posted,
which came from the designers of the ABS system themselves...

Given the amount of people who know skidding = longer stopping
distances, they almost certainly will attempt to err on the side of not
inducing a skid, thus they will be braking less effectively than if they
had ABS and knew it would stop the skid.

I also uncovered some very interesting studies which showed that brkae
assist (something different to ABS) stops the problem of a driver
lifting the braking force to start the foetal curl reaction - again,
tends to indicate that in amny situations the car will not be travelling
at the point of skidding, and that again, would would take longer to
stop than if it *is* on the point, and has ABS, and they are, therefore,
engaged. Brake assist, in case you're unfamiliar, is where the car
takes over and KEEPS the pressure on the brakes even if the driver lifts
it off. Obviously, tends to be used in conjunction with ABS. WHich
tends to suggest that ABS is misused by quite a few people who've never
tried it to feel what it is like through a pedal, or who default (quite
dangerously) to pumping the brakes even though they have an ABS equipped
car.

The solution to the dirver confusion would seem to be to either fit all
cars or no cars with ABS, thus in the instant where you have to decide
if you tromp or pump, you get it right, and given the benefits of ABS on
mixed-surfaces/low grip etc, I think ABS on all is the way to go.

And it still stops me in a shorter distance on dry roads. And I'm sure
I'm not the only one who'll err the less-pressure side of the line in
that situation to avoid the skid. Which means that ABS does stop you
quicker, in that situation. If you've got excellent braking control
then granted it's probably not going to make a lot of difference, but
lets face it, how many people have - should we be devoting our sunday
afternoons to go do emergency stops repeatedly on the public roads, once
a month, just so we can claim we can stop in the same distance with a
non-abs car as we can with an abs one?

I think not.

--


Velvet

schreef ...

It is simplistic, of course; the reality is that given perfect braking
technique a driver can stop at least as quickly in a non-ABS car; ABS makes
no difference to the grip of the tyres or the power of the brakes.


A really
expert driver can theoretically stop shorter in a non-ABS car, because ABS
senses wheel slip, while a really expert driver won't allow that to happen.
In practice few drivers have perfect braking technique, but as previously
posted, on a dry road it is close to impossible to get the ABS even to cut
in on my car - it grips too well. So, ABS prevents some skids due to poor
braking technique, and allows steering while braking with less risk of loss
of control, but it doesn't really improve the braking performance of the
car.

It's also a mistake to rely on it in ice or on gravel. If all wheels lock,
the ABS thinks you've stopped and cuts out. Don't try this at home!

Yes, I know that one (in a demonstration situation). Funny :-/

So, it's important not to think (or to allow people to think) "ABS stops you
quicker", because (a) technically it doesn't and (b) relying on that for
safety margin is a Very Bad Idea.

Agreed.

--
Regards,
Marten

Velvet wrote:

Interesting that you made no comment on the second snippet I posted,
which came from the designers of the ABS system themselves...
Given the amount of people who know skidding = longer stopping
distances, they almost certainly will attempt to err on the side of
not inducing a skid, thus they will be braking less effectively than
if they had ABS and knew it would stop the skid.

So few people get anywhere near the limiting braking performance of their
cars that I don't see that being much of an issue.

But like I say, if you want to carry on pushing the fiction that ABS is
there to make you stop quicker, think carefully about the possible
repercussions. It is a commonly held view, and it is responsible for risk
compensation behaviour which means that overall what advantage there is is
consumed as a performance benefit. As ever.

The solution to the dirver confusion would seem to be to either fit
all cars or no cars with ABS, thus in the instant where you have to
decide if you tromp or pump, you get it right, and given the benefits
of ABS on mixed-surfaces/low grip etc, I think ABS on all is the way
to go.

I think the EU is already onto that one.

And it still stops me in a shorter distance on dry roads.

Lucky you. Not having managed to get the ABS to even cut in on a dry road,
it doesn't do that for me.

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

Gawnsoft wrote:

In other words, yes and no, but for practical purposes no, unless
the wheels would be locking up. Which they generally don't.

You don't drive in the wet much, do you Guy?

I don't drive much at all these days. And I don't generally drive close
enough to the car in front that I need to brake sharply in the wet or in the
dry.

And, as stated, "the
important capability of ABS is control."

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

On Tue, 22 Jun 2004 09:21:13 +0100, "Just zis Guy, you know?"
wrote (more or less):

Velvet wrote:

Q. Does ABS reduce stopping distances?

A. Yes, in braking situations where the wheels on a non-ABS equipped
vehicle would lock up, ABS will generally provide shorter controlled
stopping distance. The amount of improvement in stopping distance
depends on many factors, including the road surface, severity of
braking, initial vehicle speed, etc. On some surfaces, such as gravel
roads, braking distances can be longer, but you will still have the
control benefits of ABS. The important capability of ABS is control.
ABS provides improved vehicle steerability and stability when braking.

In other words, yes and no, but for practical purposes no, unless the wheels
would be locking up. Which they generally don't.

You don't drive in the wet much, do you Guy?

And, as stated, "the
important capability of ABS is control."

--
Cheers,
Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk) http://html.dnsalias.net/gawnsoft/smalltalk

Just zis Guy, you know? wrote:

Velvet wrote:


Interesting that you made no comment on the second snippet I posted,
which came from the designers of the ABS system themselves...
Given the amount of people who know skidding = longer stopping
distances, they almost certainly will attempt to err on the side of
not inducing a skid, thus they will be braking less effectively than
if they had ABS and knew it would stop the skid.


So few people get anywhere near the limiting braking performance of their
cars that I don't see that being much of an issue.

But like I say, if you want to carry on pushing the fiction that ABS is
there to make you stop quicker, think carefully about the possible
repercussions. It is a commonly held view, and it is responsible for risk
compensation behaviour which means that overall what advantage there is is
consumed as a performance benefit. As ever.

I'm not pushing the fiction. You very carefully say 'its not there to
stop you quicker', I say in a given circumstance it will. We aren't
talking about the same thing, and I know it, and I think you know it too.

I'm not generalising, I'm pointing out a specific instance where having
ABS fitted - WHETHER THEY CUT IN OR NOT - will lead to stopping faster.
That is NOT pushing the fiction that ABS is there to make you stop faster.

Whether I compensate for that or not I can't say for sure - whereas you
seem to know so much about my driving that you can say catagorically
that I would. Odd that, really.

I dislike generalisations, and the 'ABS wont make you stop faster' is
just such a generalisation. It's become abundantly clear you're only
interested in the generalisation though.

I'll continue to prefer a car with ABS. Cos at the end of the day, at
some point in the estimated 35,000 miles I'll do over the coming year
(all things being equal) I *might* just be in a situation where either
they, or my enthusiasm for applying brakes without worrying about the
potential for a skid, will stop me in time when a car without would not.

*I'd* rather have something that increases the safety. If you don't mind.



The solution to the dirver confusion would seem to be to either fit
all cars or no cars with ABS, thus in the instant where you have to
decide if you tromp or pump, you get it right, and given the benefits
of ABS on mixed-surfaces/low grip etc, I think ABS on all is the way
to go.


I think the EU is already onto that one.


And it still stops me in a shorter distance on dry roads.


Lucky you. Not having managed to get the ABS to even cut in on a dry road,
it doesn't do that for me.


I've explained it doesn't HAVE to cut in on a dry road to reduce my
stopping distance, please see above and try to understand, I'm
explaining it as clearly as I can!


--


Velvet

Velvet wrote:

You very carefully say 'its not there to
stop you quicker', I say in a given circumstance it will. We aren't
talking about the same thing, and I know it, and I think you know it
too.

Possibly. I guess it's like the difference between "my helmet saved my
life" and "helmets save lives".

I dislike generalisations, and the 'ABS wont make you stop faster' is
just such a generalisation. It's become abundantly clear you're only
interested in the generalisation though.

I am indeed. The generalisation is what people will be thinking about as
they consume the safety benefit of ABS as a performance benefit. "I can
stop quicker thanks to ABS" therefore "I don't need to leave as much space".

I'll continue to prefer a car with ABS. [...]
*I'd* rather have something that increases the safety. If you don't
mind.

I am extremely unlikely ever to buy another car without ABS. I do not
dispute that it improves my safety should an emergency situation is reached,
by allowing control under braking and by compensating for my indifferent
braking technique. Overall, the evidence is that I will subconsciously undo
that safety benefit by worse driving, but that's risk compensation for you.

Lucky you. Not having managed to get the ABS to even cut in on a
dry road, it doesn't do that for me.

I've explained it doesn't HAVE to cut in on a dry road to reduce my
stopping distance, please see above and try to understand, I'm
explaining it as clearly as I can!

Yes, you've given an example of compensating behaviour. I don't dispute it.
But it hasn't changed the capabiliites of the car, which is my point.

Like the two old women exchanging words across the Shambles, we are arguing
from different premises.

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

Just zis Guy, you know? wrote:

Gawnsoft wrote:


In other words, yes and no, but for practical purposes no, unless
the wheels would be locking up. Which they generally don't.


You don't drive in the wet much, do you Guy?


I don't drive much at all these days. And I don't generally drive close
enough to the car in front that I need to brake sharply in the wet or in the
dry.


And, as stated, "the
important capability of ABS is control."



It's not just about driving too close to the car in front, there's
always the idiot that swerves into your path as an oncoming, or the one
that pulls out right in front from the side junction *despite* the fact
that you saw him look at (or was it *through* you)...

A whole host of other circumstances where stopping sharply can be
necessary and not always (or even often) predicted in advance.

At the end of the day if ABS adds to safety in some situations and
doesn't detract from it in others (risk compensation excluded) then it's
worth it.

If we go down the road of saying risk compensation nullifies the safety
aspects, then that has to be applied to absolutely everything else.

Builders shouldn't wear hard hats, cos, obviously, they'll take less
care than if they do. That'll save lots of lives, oh yes.

Oh, and we'd better not let climbers wear ropes/harnesses either, cos
they might not be so careful about not falling off if they have them.

And come to think of it, why bother having training and procedures in
place before you handle toxic waste - cos the risk of contamination is
obviously greater if you bother with those measures, right?

Going back to the traffic calming though - if you can put in place (or
remove) measures that make people *think* more about the situation
rather than putting their faith in the fact that the lines on the road
mean they must be able to fit their vehicle down it regardless - AND
that can be proven to result in a safer environment all around, then
it's worth doing.

You're taught (or at least I was) that roads with centre lines are at
least x wide. Roads without centre lines are invariably narrow, and
signify the fact that two vehicles may (though almost always may not) be
able to pass safely, and that reduction in speed is almost certainly
going to be necessary in that situation.

It's not a reaction to the lack of lines, it's having learnt what the
lines and lack of signify.

By removing all signage and lines, I'm sure there would be a lot of
drivers who would feel too confused and intimidated to drive ever again.
This could be good, but consider that those who stick it out and
succeed in driving successfully in that sort of environment will be
those who already have a tendancy to intimidate other drivers into
giving way to them, letting them pass, and taking any other sort of
action to avoid an accident that would otherwise result.

Do you really want roads full of people driving like that? I know I
wouldn't.

--


Velvet

Velvet wrote:

It's not just about driving too close to the car in front, there's
always the idiot that swerves into your path as an oncoming, or the
one that pulls out right in front from the side junction *despite*
the fact that you saw him look at (or was it *through* you)...

Oh really, I didn't know that, only having had a driving licence for 20
years...

Different premises. What ABS is designed to do is prevent the wheels
locking, allowing you to maintain control when braking. As an aside it also
helps to ensure that hammering the brakes doesn't end up in a skid.

So, we can either say "ABS allows you to maintain control when braking",
which is useful, or we can say "ABS lets you stop quicker" which is a
dangerous oversimplification of a secondary benefit and risks causing
precisely the kind of risk copensation observed in those German taxi
drivers.

If we go down the road of saying risk compensation nullifies the
safety aspects, then that has to be applied to absolutely everything
else.

It depends on the extent of the compensatry behaviour. A key part of
minimising that is sending out the right messages about the capabilities of
the device.

You really do need to read Risk.

Going back to the traffic calming though - if you can put in place (or
remove) measures that make people *think* more about the situation
rather than putting their faith in the fact that the lines on the road
mean they must be able to fit their vehicle down it regardless - AND
that can be proven to result in a safer environment all around, then
it's worth doing.

Undoubtedly.

By removing all signage and lines, I'm sure there would be a lot of
drivers who would feel too confused and intimidated to drive ever
again. This could be good, but consider that those who stick it out
and succeed in driving successfully in that sort of environment will
be those who already have a tendancy to intimidate other drivers into
giving way to them, letting them pass, and taking any other sort of
action to avoid an accident that would otherwise result.

I wonder why, then, when this has been tried, the result has been a
reduction in speeds and a substantial reduction in crashes?

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

Just zis Guy, you know? wrote:

Velvet wrote:


It's not just about driving too close to the car in front, there's
always the idiot that swerves into your path as an oncoming, or the
one that pulls out right in front from the side junction *despite*
the fact that you saw him look at (or was it *through* you)...


Oh really, I didn't know that, only having had a driving licence for 20
years...

Different premises. What ABS is designed to do is prevent the wheels
locking, allowing you to maintain control when braking. As an aside it also
helps to ensure that hammering the brakes doesn't end up in a skid.

So, we can either say "ABS allows you to maintain control when braking",
which is useful, or we can say "ABS lets you stop quicker" which is a
dangerous oversimplification of a secondary benefit and risks causing
precisely the kind of risk copensation observed in those German taxi
drivers.


If we go down the road of saying risk compensation nullifies the
safety aspects, then that has to be applied to absolutely everything
else.


It depends on the extent of the compensatry behaviour. A key part of
minimising that is sending out the right messages about the capabilities of
the device.

You really do need to read Risk.


Going back to the traffic calming though - if you can put in place (or
remove) measures that make people *think* more about the situation
rather than putting their faith in the fact that the lines on the road
mean they must be able to fit their vehicle down it regardless - AND
that can be proven to result in a safer environment all around, then
it's worth doing.


Undoubtedly.


By removing all signage and lines, I'm sure there would be a lot of
drivers who would feel too confused and intimidated to drive ever
again. This could be good, but consider that those who stick it out
and succeed in driving successfully in that sort of environment will
be those who already have a tendancy to intimidate other drivers into
giving way to them, letting them pass, and taking any other sort of
action to avoid an accident that would otherwise result.


I wonder why, then, when this has been tried, the result has been a
reduction in speeds and a substantial reduction in crashes?



--


Velvet