Everything we know about traffic-calming is wrong - Page 4

Just zis Guy, you know? wrote:

> Velvet wrote:
>
>
>>>Er, actually ABS doesn't really affect stopping
>>>distances. It allows you to steer while braking.
>
>
>>Not convinced by this :-)
>
>
> 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!
>
> 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.
>

I think we're kindof in agreement here. My point was that
people aren't all that likely to be braking as well as ABS
would if you apply it properly - people (myself included)
either tend to overbrake (and skid if no abs) or underbrake
(abs or no, they'll not stop as fast as if they overbraked
with abs).

I've braked on ice with ABS - it was interesting and I'm
glad I did it gently. Stopped car from sliding but took a
VERY long time to stop the car. On the other hand, braked
once on snow and had to do a very abs-like recovery of it to
stop in time (downhill on snow toward T junction).

I know if I tromp on my brakes then I'll stop quicker than
if I brake with no ABS, because I tend to the underbrake not
overbrake to avoid the skid. Ergo, for me, ABS *will* mean
I'll stop in a shorter distance.

I don't drive any closer (or further away, it has to be
said) than pre-ABS. Some of my cars have had it, some
haven't. I've only once had to tromp on the brakes and could
have done with ABS (I didn't lock the wheels so probably
underbraked, with ABS I'm much more willing to tromp very
hard since I know it'll help prevent the skid) - but given
I've never actually needed to, it's not changed the way I
drive - I don't think the ABS will save me, cos actually
I've no idea if it would in any given situation or not, and
I'm not *really* all that keen on seeking out instances when
I'll find out...
--

Velvet

Tony Raven wrote:

> Interesting piece on Radio 4 Today this morning about
> "childproof containers". There are 25,000 incidents a year
> involving children.

I thought it was BeHit who put 25000 children into
containers.

John B

On Mon, 21 Jun 2004 11:05:32 +0100, "Just zis Guy, you know?"
<outlook.bugs@microsoft.com> wrote (more or less):

>On Mon, 21 Jun 2004 10:42:13 +0100, "Grant Mason"
><news@mason.sh> wrote in message <1087810951.27481.0@nnrp-t71-
>01.news.uk.clara.net>:
>
>>> Er, actually ABS doesn't really affect stopping
>>> distances.
>
>>Yes it does. http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs/sae1999-01-
>>1287.pdf "For most stopping maneuvers, made on most test
>>surfaces, ABS-assisted panic stops were found to be
>>shorter than those made with best effort or full pedal
>>applications with the ABS disabled"
>
>Because people don't know how to brake. But the statement
>was overly simplistic, of course.
>
>ABS does not increase the power of the brakes, and does not
>increase the coefficient of friction. All it does is make
>it less likely that the driver will lock the wheels.

With abs, if one wheel is about to lock, the other three
wheels can remain braking.

To avoid one wheel locking up with non-abs brakes, all four
wheels have to stop braking.

--
Cheers, Euan Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122 Smalltalk
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On Mon, 21 Jun 2004 19:01:34 +0100, JohnB <nospam@here.com> wrote in
message <40D7227E.4646C6B8@here.com>:

>I thought it was BeHit who put 25000 children into
>containers.

Tee-hee! :-)

From the **** Happens department - BeHIT keep saying that
cycling is a leading source of death and head injury in
children, but:

- over twice as many children die from congenital
abnormalities as from cycling
- more children die of leukaemia than from cycling
- more children die following assault than a cycle crash
- more children die from asthma and other respiratory
diseases than from cycling
- over twice as many children die of brain cancer than
cycling head injuries.
- as many children die of menigitis as of cycling head
injuries.

http://www.statistics.gov.uk/STATBAS.../Spreadsheets-
/D8257.xls

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

88% of helmet statistics are made up, 65% of them at
Washington University

On Mon, 21 Jun 2004 19:32:55 +0100, Gawnsoft
<xlucid@users.sourceforge.remove.this.antispam.net> wrote in message
<9caed09s1n1fkab40ukvlbti7nutcejbue@4ax.com>:

>With abs, if one wheel is about to lock, the other three
>wheels can remain braking. To avoid one wheel locking up
>with non-abs brakes, all four wheels have to stop braking.

Indeed. But that's only relevant in specific conditions.
I've already said it: ABS does not increase the braking
performance of the car. It does compensate in some degree
for poor technique, but even then you can fool it. Relying
on ABS to "help you stop quicker" is stupid, and allowing
people to think that's what it does is Not Smart.

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

88% of helmet statistics are made up, 65% of them at
Washington University

On Mon, 21 Jun 2004 09:43:35 GMT, "Richard J."
<rjnews@blueukder.co.yon> wrote (more or less):

>Just zis Guy, you know? wrote:
>>
>>> I don't rely on ABS to stop me quicker - I use it to
>>> even out the fact that the car in front probably has it
>>> and will stop quicker than I can if I don't have it...
>
>If you are relying on ABS to stop you, you are driving too
>close to the vehicle in front.
>
>> Er, actually ABS doesn't really affect stopping
>> distances. It allows you to steer while braking.
>
>Er, have you driven on snow with and without ABS? It
>certainly does affect stopping distance on ice or snow.

And in different ways.

On ice, it will prevent lock-up of each wheel, increasing
braking efficiency across the four wheels, decreasing
stopping distance compared to a manually-controlled wheel.

On snow, locking up the wheels can have the beneficial
effect of causing a wedge of snow to build up in front of
the locked wheel, which decreases stopping distance on snow
compared to an abs wheel.

--
Cheers, Euan Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122 Smalltalk
links (harvested from comp.lang.smalltalk)
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On Mon, 21 Jun 2004 17:57:44 GMT, Velvet <velvet@not.a.valid.domain>
wrote in message <skFBc.1998$K81.18184246@news-text.cableinet.net>:

>I think we're kindof in agreement here. My point was that
>people aren't all that likely to be braking as well as ABS
>would if you apply it properly - people (myself included)
>either tend to overbrake (and skid if no abs) or underbrake
>(abs or no, they'll not stop as fast as if they overbraked
>with abs).

Indeed. That was my point: what ABS is doing is compensating
for poor technique, not helping you "stop quicker".

>I don't drive any closer (or further away, it has to be
>said) than pre-ABS.

You think. But on average, people do. That's what risk
compensation is about. It's pretty widespread - see Tony's
comment re "childproof" containers above.

Or read Risk - it's very interesting.

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

88% of helmet statistics are made up, 65% of them at
Washington University

On Mon, 21 Jun 2004 09:43:35 GMT, "Richard J."
<rjnews@blueukder.co.yon> wrote (more or less):

>Gawnsoft wrote:
>> On Sun, 20 Jun 2004 20:08:54 GMT, "Richard J."
>> <rjnews@blueukder.co.yon> wrote (more or less):
>>
>>> Paul Dicken wrote:
>>>> Mention of Mayer Hillman reminded me of a view he
>>>> expressed in a meeting I attended. He suggested all car
>>>> bumpers should be made of glass and drivers seated on
>>>> them. His view was that standards of driving will go up
>>>> immediately.
>>>
>>> ... because people driving in a vulnerable vehicle would
>>> drive more safely?
>>
>> There is a big difference between 'more safely' and
>> 'absolutely safely'.
>>
>> People drive less safely with seatbelts than they do
>> without seatbelts == People drive more safely without
>> seatbelts than they do with seatbelts. <> people never
>> have accidents when driving without a seatbelt.
>
> Are you suggesting that we should abandon seat belts in
> order that we should drive more safely?
...
>Well, severity of accident is part of the safety equation.
>My point was that before seat belts were introduced, there
>were very many disastrous accidents because many people
>*didn't* drive safely enough to avoid being thrown through
>the windscreen.

And people drive /less/ safely than that now. It's just that
a great deal of the risk has been transferred to others.

>Overall, driving with belts is safer than it used to be,
>i.e. it kills fewer people.

Is, perhaps counter-intuitively to you, not true.

>I assume that <> means "not that"; please write in English.

To be exact, it means 'is not equal to'. But your inference
in context works perfectly well.

I'll continue to use arithmetic and logic symbols in my
posts.

--
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

On Mon, 21 Jun 2004 07:08:11 GMT, "Orienteer"
<orienteeruk@NOSPAMhotmail.com> wrote (more or less): ...
>Bit of a myth that ABS enables a vehicle to stop quicker,
>in fact it can have the opposite effect.

Only on loose surfaces like snow or gravel.

On clean dry surfaces a car with independent ABS per wheel
can stop faster than a non-abs car (which will likely skid
under extreme braking), and gains the controllability
advantage of cadence-braking without having to stop braking
all four wheels, which a non-abs car has to do to effect
cadence braking.

>It's purpose is to enable the vehicle to be steered while
>braking hard, which without ABS often results in a skid and
>loss of control.

A skid also results in longer braking distances.

--
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:
> On Mon, 21 Jun 2004 17:57:44 GMT, Velvet
> <velvet@not.a.valid.domain> wrote in message <skFBc.1998$K81.18184246@news-
> text.cableinet.net>:
>
>
>>I think we're kindof in agreement here. My point was that
>>people aren't all that likely to be braking as well as ABS
>>would if you apply it properly - people (myself included)
>>either tend to overbrake (and skid if no abs) or
>>underbrake (abs or no, they'll not stop as fast as if they
>>overbraked with abs).
>
>
> Indeed. That was my point: what ABS is doing is
> compensating for poor technique, not helping you "stop
> quicker".

Whether it compensates for my technique or not is
immaterial, in the same given circumstance, with ABS I will
stop quicker, in a shorter distance, than without ABS.

>
>
>>I don't drive any closer (or further away, it has to be
>>said) than pre-ABS.
>
>
> You think. But on average, people do. That's what risk
> compensation is about. It's pretty widespread - see Tony's
> comment re "childproof" containers above.

If I remembered I actually had ABS more than once a few
months then I might believe I drive closer/faster. But given
I don't, I doubt it has any affect. To be honest, since I've
never been in a situation where tromping the brakes has
actually activated the ABS, it seems likely that I'm not
compensating for the percieved increase in safety.

>
> Or read Risk - it's very interesting.
>
> Guy

I'm sure it's fascinating :-)

--

Velvet

On Mon, 21 Jun 2004 07:08:11 GMT,
Orienteer <orienteeruk@NOSPAMhotmail.com> wrote:
>
> Bit of a myth that ABS enables a vehicle to stop quicker,
> in fact it can have the opposite effect. It's purpose is
> to enable the vehicle to be steered while braking hard,
> which without ABS often results in a skid and loss of
> control.
>
I don't have any figures for it but I suspect that when
braking hard from high speeds (70mph+) ABS may well enable a
car to stop quicker.

Some (10+?) years ago there was an artical in SciAm about
emergency stops in cars at motorway speeds and it was
suggested that the best bet for the cars of the time might
well be to deliberately skid.

IIRC stopping distances from these sorts of speeds when
skidding were about 20% further than the perfect stop.
However, without ABS the braking is split in a fixed
percentage between back and front wheels. The weight
transfer to the front wheels can cause the rear wheels to
lock putting the car into a spin. By deliberately locking
all the wheels the car will stay pretty much in a straight
line (motorways don't tend to have enough camber to be
likely to put a skidding car into a spin.)

ABS eliminates this problem and allows maximum braking on
the front wheels.

But ABS doesn't have to be a good thing. The one time I have
skidded on the motorway I was very grateful for the noise.
Picture the scene - me on empty motorway, slip lane joining.
Slow lorry almost at end of slip lane that would be joining
shortly after I had passed. Another car on sliplane that
would be joining about the same time as the lorry. So I
moved from lane 1 to lane 3 in order to give both vehicles
joining room to join without having to adjust their speeds.
But the car doesn't move into lane 2 to pass the lorry but
continues into lane
3. Now I should have anticipated this but by the time I
realised he wasn't going to stay in lane 2 I was about
level with his rear door and going maybe 10mph faster. I
didn't have time for the horn but my squealing tyres
meant he only came about 2 feet into lane 3. (Skidding
from 70mph to about 45mph leaves a big cloud of smoke!)

Tim.

--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H
= J + @D/@t," and there was light.

http://tjw.hn.org/
http://www.locofungus.btinternet.co.uk/

On Mon, 21 Jun 2004 19:59:49 +0000 (UTC), Tim Woodall
<devnull@locofungus.org> wrote in message
<slrncdefhl.tsh.devnull@pauli.locofungus.org>:

>I don't have any figures for it but I suspect that when
>braking hard from high speeds (70mph+) ABS may well enable
>a car to stop quicker.

I have only ever once managed to skid a car at 70, and that
was a BX with no ABS where the same hydraulics work the
brakes and the suspension. Weight transfer makes it quite
hard to skid a car at 70.

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

88% of helmet statistics are made up, 65% of them at
Washington University

On Mon, 21 Jun 2004 19:55:05 GMT, Velvet <velvet@not.a.valid.domain>
wrote in message <t2HBc.2117$YN1.18999492@news-text.cableinet.net>:

>Whether it compensates for my technique or not is
>immaterial, in the same given circumstance, with ABS I will
>stop quicker, in a shorter distance, than without ABS.

If you want to continue believing that "ABS stops you
quicker" then be my guest. But I refuse to indemnify you
against any damage which may result.

Angels dancing on the head of a pin notwithstanding, that is
/not/ what it's designed for. Assuming that it is, will end
in tears. As the studies prove.

>If I remembered I actually had ABS more than once a few
>months then I might believe I drive closer/faster. But
>given I don't, I doubt it has any affect. To be honest,
>since I've never been in a situation where tromping the
>brakes has actually activated the ABS, it seems likely that
>I'm not compensating for the percieved increase in safety.

So you say - now...

>> read Risk - it's very interesting.

>I'm sure it's fascinating :-)

It is. Genuinely.

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

88% of helmet statistics are made up, 65% of them at
Washington University

Just zis Guy, you know? wrote:
> On Mon, 21 Jun 2004 19:55:05 GMT, Velvet
> <velvet@not.a.valid.domain> wrote in message <t2HBc.2117$YN1.18999492@news-
> text.cableinet.net>:
>
>
>>Whether it compensates for my technique or not is
>>immaterial, in the same given circumstance, with ABS
>>I will stop quicker, in a shorter distance, than
>>without ABS.
>
>
> If you want to continue believing that "ABS stops you
> quicker" then be my guest. But I refuse to indemnify you
> against any damage which may result.

Look, I've explained how ABS could stop ME quicker, you'll
note I've not said it'll stop EVERYONE quicker.

Perhaps you overlooked that subtle point?

>
> Angels dancing on the head of a pin notwithstanding, that
> is /not/ what it's designed for. Assuming that it is, will
> end in tears. As the studies prove.

If I ever have cause to test it in that sort of situation
then I'll find out, won't I, one way or t'other.

>
>
>>If I remembered I actually had ABS more than once a
>>few months then I might believe I drive closer/faster.
>>But given I don't, I doubt it has any affect. To be
>>honest, since I've never been in a situation where
>>tromping the brakes has actually activated the ABS, it
>>seems likely that I'm not compensating for the
>>percieved increase in safety.
>
>
> So you say - now...
>
>
>>>read Risk - it's very interesting.
>
>
>>I'm sure it's fascinating :-)
>
>
> It is. Genuinely.
>
> Guy

--

Velvet

Marc Brett wrote:
> Everything we know about traffic-calming is wrong

But is there a proven alternative to speed bumps, round or
flat tops, and the raised platforms our Council are fitting
at each minor road junction?