Highwaycode and pedals question

In message <[email hidden]>

Just zis Guy said:

On 23 Nov 2005 18:04:47 GMT, Alistair Gunn <[email hidden]>
said in <[email hidden]>:

Quoted message said:

... but maybe you'd like the answer the question I actually asked? You
claimed "pedal reflectors always add to road safety at night", what I
want to know is why you believe that pedal reflectors which can't be seen
add to road safety at night?

Or indeed why this purported benefit does not apply to older bicycles.

And what about tourists bringing their bikes from countries without a
requirement for pedal reflectors. Are they illegal?

Quoted message said:

Guy

--
Gwyn

in message <[email hidden]>, Gwyn Oakley

(') said:

In message <[email hidden]>

Just zis Guy said:

On 23 Nov 2005 18:04:47 GMT, Alistair Gunn <[email hidden]>
said in <[email hidden]>:

Quoted message said:

... but maybe you'd like the answer the question I actually asked?
You claimed "pedal reflectors always add to road safety at night",
what I want to know is why you believe that pedal reflectors which
can't be seen add to road safety at night?

Or indeed why this purported benefit does not apply to older bicycles.

And what about tourists bringing their bikes from countries without a
requirement for pedal reflectors. Are they illegal?

That's a thought. With this EC Common Market thingamywhatsit, surely any
fiets bought legally in the Netherlands for use on a Netherlandish road
(and similarly any velo bought in la belle France for use on a French
road) must be legal to use in the UK?

In which case Roos is all right, IIRC, because she imported her Fiero
herself...

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; We don't just borrow words; on occasion, English has pursued other
;; languages down alleyways to beat them unconscious and riffle their
;; pockets for new vocabulary -- James D. Nicoll

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Wed, 23 Nov 2005 13:59:53 -0000, "Clive George"
<[email hidden]> said in
<[email hidden]>:

Quoted message said:

You haven't answered the question. Try again.

No, he answered a different question,

How does he know what I answered?

Quoted message said:

which was: prove, in as few words as possible, that MattB's position is
absurd.
Because if it was as crucial as he makes out, there would have been no
exemption for
older cycles,

Which, of course is fallacy. I'm sure he must know that construction
regulations are rarely, if ever, applied retrospectively. I can quite
legally, on the public road, drive a car with no stop lamps, no speedometer,
no flashing direction indicators and no rear fog lamps, if if was build
before the requirement for these was introduced.

However, most owners of such cars would accept that, in the interests of
safety, such items should be fitted retrospectively.

--
Matt B

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Wed, 23 Nov 2005 11:40:59 +0000, Peter Clinch
<[email hidden]> said in <[email hidden]>:

Quoted message said:

Quoted message said:

They are at odds in that pedal reflectors always add to road safety at
night

Not if they can't be seen they don't. *Duh*.

And obviously not if you ride a bicycle made before October 1985 -
they make no safety difference at all to these, according to TrollB's
test.

Rules aren't applied retrospectively. There is nothing to stop a resposible
owner fitting such items though.

If you bought an old car would you defy sense and not have stop lamps
"because you didn't have to"?

--
Matt B

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On 23 Nov 2005 18:04:47 GMT, Alistair Gunn <[email hidden]>
said in <[email hidden]>:

Quoted message said:

... but maybe you'd like the answer the question I actually asked? You
claimed "pedal reflectors always add to road safety at night", what I
want to know is why you believe that pedal reflectors which can't be seen
add to road safety at night?

Or indeed why this purported benefit does not apply to older bicycles.

In what way doesn't the safety benefit apply to older bikes - surely you're
not suggesting that safety benefits only accrue from the strict appliance,
to the letter, of an appropriate regulation?

It would often seem that way from what I've read of your contributions to
this ng. In fact, not only do you require a law to persuade you to behave
in a more safety conscience fashion, but you need a law and a rigorous
enforcement regime! Even then you'd apparently look for loopholes to avoid
complying. Do you consider yourself to be a responsible road user?

--
Matt B

Mike Causer said:

Alan Braggins said:

Quoted message said:

Do Cateye LD500 rear lights count as reflectors as well

Google claims the reflector is BS approved.

The LD500 front & rear lights sitting on the table in front of me are
both marked BS6102/2. The packaging for the LD-500-R says "Reflector
meets C.P.S.C. and BS standard."

Hurrah! Then the fixer /is/ legal. No longer need I fear incarceration in
Belmarsh or extradition to the US for being a terrorist. For I have done
nothing wrong, and thus have nothing to f (cont. the Daily Mail)

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Official: Living in a wardrobe can be injurious to one's health
<URL:http://www.timesonline.co.uk/article/0,,11069-1567961,00.html>

Simon Brooke said:

in message <[email hidden]>, Gwyn Oakley

(') said:

In message <[email hidden]>

Just zis Guy said:

On 23 Nov 2005 18:04:47 GMT, Alistair Gunn <[email hidden]>
said in <[email hidden]>:

> ... but maybe you'd like the answer the question I actually asked?
> You claimed "pedal reflectors always add to road safety at night",
> what I want to know is why you believe that pedal reflectors which
> can't be seen add to road safety at night?

Or indeed why this purported benefit does not apply to older
bicycles.

And what about tourists bringing their bikes from countries without
a requirement for pedal reflectors. Are they illegal?

That's a thought. With this EC Common Market thingamywhatsit, surely
any fiets bought legally in the Netherlands for use on a
Netherlandish road (and similarly any velo bought in la belle France
for use on a French road) must be legal to use in the UK?

In which case Roos is all right, IIRC, because she imported her Fiero
herself...

One might also argue that if one assembled one's "bicycle" from a bare frame
and box of bits instead of buying it fully-assembled, it's not actually a
bicycle but rather a collection of bike parts flying in very close formation
;-)

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Barley, barley, barley, world cruise. You never see a farmer on a bike.

Dave Larrington said:

One might also argue that if one assembled one's "bicycle" from a bare frame
and box of bits instead of buying it fully-assembled, it's not actually a
bicycle but rather a collection of bike parts flying in very close formation

P: Nice bike, is that a Mercian?
C: No, its a Shackleton 531.

...d

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B said:

Quoted message said:

> Probably not as soon as he would have seen the pedal reflectors.

Thus indicating a lack of knowledge on the laws of physics.. Ever heard
of the inverse square law?

It's no to do with the intensity, but to do with the fact that the pedals
are moving, that makes the reflected light from them more conspicuous.
The
effect is similar to that of flashing amber lights, like those used to
make
tractors and other slow vehicles more conspicuous.

BTW the inverse square law also applies to the powered lights on a bike
;-)

Very good. Now, as your follow up to show you understand how the
inverse square law applies.

Even though, As I've already mentioned, the intensity is not the only factor
influencing the conspicuity, the fact that it is moving is also important.

Quoted message said:

A car light produces 100 units of light per unit area at a distance of
1 m. A bicycle rear light 1 unit.
Taht should be about the right ratio for a 100W car headlamp to a 1W
cycle lamp.
At which distances will the cycle light be brighter than the reflected
light of the headlamps assuming the reflector is 100% efficient.?

Is this a trick question?

I'm no physicist, but I'm game for a laugh... The ratio of intensities is
100(2d)**2/d**2, as the distance that the reflected light has travelled is
twice that of the cycle lamp? Which is a constant 25:1? The reflected
light will always appear to be 25 times the intensity of the cycle lamp
light?

Quoted message said:

How much brighter will the cycle light be than the reflector at 50m?

0.04 times?

I can't help thinking I've made a fool of myself here, but, hey - who cares
;-)

Please enlighten (NPI) me David, you seemed so convinced I was barking up
the wrong tree :-)

--
Matt B

Matt B said:

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B said:

>> Probably not as soon as he would have seen the pedal reflectors.
>
> Thus indicating a lack of knowledge on the laws of physics.. Ever heard
> of the inverse square law?

It's no to do with the intensity, but to do with the fact that the pedals
are moving, that makes the reflected light from them more conspicuous.
The
effect is similar to that of flashing amber lights, like those used to
make
tractors and other slow vehicles more conspicuous.

BTW the inverse square law also applies to the powered lights on a bike
;-)

Very good. Now, as your follow up to show you understand how the
inverse square law applies.

Even though, As I've already mentioned, the intensity is not the only factor
influencing the conspicuity, the fact that it is moving is also important.

Quoted message said:

A car light produces 100 units of light per unit area at a distance of
1 m. A bicycle rear light 1 unit.
Taht should be about the right ratio for a 100W car headlamp to a 1W
cycle lamp.
At which distances will the cycle light be brighter than the reflected
light of the headlamps assuming the reflector is 100% efficient.?

Is this a trick question?

I'm no physicist, but I'm game for a laugh... The ratio of intensities is
100(2d)**2/d**2, as the distance that the reflected light has travelled is
twice that of the cycle lamp? Which is a constant 25:1? The reflected
light will always appear to be 25 times the intensity of the cycle lamp
light?

Quoted message said:

How much brighter will the cycle light be than the reflector at 50m?

0.04 times?

I can't help thinking I've made a fool of myself here, but, hey - who cares
;-)

Please enlighten (NPI) me David, you seemed so convinced I was barking up
the wrong tree :-)

You can treat both as point sources. It is the intensity of the source
that varies.

As both reflector and light are the same distance away they light
coming from them falls of at exactly the same rate, so at 1m, 100W
light is reflected (100% efficciency) by the reflector, and 1W is given
out by the light.

At 10m, the amount of light falling on the reflector is 100/d**2 or 1W
so the amount of light the reflector can 'produce' is 1W, the same as
the bike light.

At 20m the effective power of the reflector is 0.25W, the light still
produces 1W.
At 50m the effective power of the reflector is 0.04W, the light still
produces 1W.

There are obvious simplifications here, but the principle is
essentially correct.

...d

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B said:

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B wrote:
> >> Probably not as soon as he would have seen the pedal reflectors.
> >
> > Thus indicating a lack of knowledge on the laws of physics.. Ever
> > heard
> > of the inverse square law?
>
> It's no to do with the intensity, but to do with the fact that the
> pedals
> are moving, that makes the reflected light from them more conspicuous.
> The
> effect is similar to that of flashing amber lights, like those used to
> make
> tractors and other slow vehicles more conspicuous.
>
> BTW the inverse square law also applies to the powered lights on a
> bike
> ;-)

Very good. Now, as your follow up to show you understand how the
inverse square law applies.

Even though, As I've already mentioned, the intensity is not the only
factor
influencing the conspicuity, the fact that it is moving is also
important.

Quoted message said:

A car light produces 100 units of light per unit area at a distance of
1 m. A bicycle rear light 1 unit.
Taht should be about the right ratio for a 100W car headlamp to a 1W
cycle lamp.
At which distances will the cycle light be brighter than the reflected
light of the headlamps assuming the reflector is 100% efficient.?

Is this a trick question?

I'm no physicist, but I'm game for a laugh... The ratio of intensities
is
100(2d)**2/d**2, as the distance that the reflected light has travelled
is
twice that of the cycle lamp? Which is a constant 25:1? The reflected
light will always appear to be 25 times the intensity of the cycle lamp
light?

Quoted message said:

How much brighter will the cycle light be than the reflector at 50m?

0.04 times?

I can't help thinking I've made a fool of myself here, but, hey - who
cares
;-)

Please enlighten (NPI) me David, you seemed so convinced I was barking up
the wrong tree :-)

You can treat both as point sources. It is the intensity of the source
that varies.

As both reflector and light are the same distance away they light
coming from them falls of at exactly the same rate, so at 1m, 100W
light is reflected (100% efficciency) by the reflector, and 1W is given
out by the light.

At 10m, the amount of light falling on the reflector is 100/d**2 or 1W
so the amount of light the reflector can 'produce' is 1W, the same as
the bike light.

At 20m the effective power of the reflector is 0.25W, the light still
produces 1W.
At 50m the effective power of the reflector is 0.04W, the light still
produces 1W.

There are obvious simplifications here, but the principle is
essentially correct.

Thanks for that - very interesting. I am still struggling to see the flaw
in my solution though :-(

Isn't it a mistake though to assume that the car headlamp is a point source?
The "inverse square law" assumes that the light is "disappearing" in all
directions. In a car headlamp "all" of the light emitted in the wrong
direction is collected by the reflector, or the lens, and projected forward.
The result is that "all" of the light from the bulb is concentrated into a
focussed beam. I think your example only holds true for a naked headlamp
bulb with no reflector, and we can imagine how weak that would appear at
50m.

I know from experience that pedal reflectors are very conspicuous indeed,
and that the 0.04W theory is simply not what we see in reality, and, as you
said yourself in a previous discussion "On the scale of scientific
integrity, empirical observation trumps hypothetical extrapolation hands
down." ;-)

--
Matt B

"Matt B" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Sorry officer, but if brakes _were_ fitted to my car they would have no
effect because of the clever free-wheel mechanism I have fitted to reduce
fuel consumption downhill".

An illegal design does not exempt one from the law.

--

Design can not be illegal.

Use of such may be.

jtaylor said:

Design can not be illegal.

Swastikas in Germany are.

R.

Matt B said:

Thanks for that - very interesting. I am still struggling to see the flaw
in my solution though :-(

Isn't it a mistake though to assume that the car headlamp is a point source?

No.

Quoted message said:

The "inverse square law" assumes that the light is "disappearing" in all
directions. In a car headlamp "all" of the light emitted in the wrong
direction is collected by the reflector, or the lens, and projected forward.
The result is that "all" of the light from the bulb is concentrated into a
focussed beam. I think your example only holds true for a naked headlamp
bulb with no reflector, and we can imagine how weak that would appear at
50m.

Think about it a bit more. It would also help to look at teh beam
patterns for your car headlights.
Whilst the light emission may indeed be assymetric, the intensity per
unit area will diminish in accordance with the inverse square law (or
approximating closer to the greater the distance is over the width of
the reflector.

Quoted message said:

I know from experience that pedal reflectors are very conspicuous indeed,
and that the 0.04W theory is simply not what we see in reality, and, as you
said yourself in a previous discussion "On the scale of scientific
integrity, empirical observation trumps hypothetical extrapolation hands
down." ;-)

Well, the 0.04W is an overestimate.. And you probably are noticing
cyclists with substandard (or non-existent) lights. If you have the
time, find a dark night and a long country lane with no street lights.
Do the experiment, parking a bike at the end of a long run and seeing
whether you see the rear light or the reflectors first.

...d

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B wrote:

Quoted message said:

Quoted message said:

Quoted message said:

So, in teh real world, the pedal reflectors have no actual benefit for
an otherwise legally (or comparitively well) lit cyclist.

Unless you you include conspicuity as a benefit maybe not.

You have yet to demonstrate that they aid conspicuity in any meaningful
way. Your data please? or references to studies? Your ignorant [1]
bletherings do not add up to anything without data.

There is not much, if any research that I could find into the effect of
pedal reflectors on cyclist conspicuity, as stated in this little winner
that I came across in a report about nighttime bicycle safety from The
Consumer Product Safety Commission of the United States:
"The argument is made that if motorists see a pattern of lights that clearly
indicates that it comes from a bicycle, they will less often discard the
image and will therefore more often take the appropriate action to avoid a
collision. This is the argument used for wheel reflectors and pedal
reflectors.
There has never been any experimental evidence for the hypothesis..."

There is however a study by Wagner et al titled "Conspicuity of Aids to
Navigation: II. Spatial Configurations for Flashing Lights", looking at
conspicuity issues. Here is the abstract:

"Lights used as aids to navigation are typically point sources that are
easily confused with the background clutter of lights on shore. This study
investigated the conspicuity, or how well lights of various spatial
configurations stand out from a background of lights, and serves as a basis
for the design of lighted aids to navigation. The measure of conspicuity was
the response time for an observer to find a flashing target among
backgrounds of steady lights on a CRT display. Twenty observers
participated. There were nine targets tested, each at three temporal flash
patterns and four background light densities. ANOVAS showed significant
effects of target, flash pattern, and background. Simultaneously flashing
the target elements of two horizontal bars of lights produced the greatest
conspicuity, followed by two diagonal bars and a triad of lights. Search
time increased with the density of background lights."

I know pedal reflectors don't "flash" but the effect due to their motion is
more accurately characterised as "flashing" than as "steady". They also
appear to conform to the configuration of "two horizontal bars" which were
found to produce "the greatest conspicuity".

Quoted message said:

[1] I'll withdraw that comment if you can provide appropriate data.

How awfully magnanimous you are ;-)

--
Matt B

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B said:

The "inverse square law" assumes that the light is "disappearing" in all
directions. In a car headlamp "all" of the light emitted in the wrong
direction is collected by the reflector, or the lens, and projected
forward.
The result is that "all" of the light from the bulb is concentrated into
a
focussed beam. I think your example only holds true for a naked headlamp
bulb with no reflector, and we can imagine how weak that would appear at
50m.

Think about it a bit more. It would also help to look at teh beam
patterns for your car headlights.
Whilst the light emission may indeed be assymetric, the intensity per
unit area will diminish in accordance with the inverse square law (or
approximating closer to the greater the distance is over the width of
the reflector.

Yes it will diminish. It will diminish though not by the normal 100/d**2 as
if a 100 unit point source. It will be f(100)/d**2, where f is a function
of the reflector and lens properties. If the whole sphere of light emitted
from a point source is concentrated uniformly into a cone occupying 1/10th
of the sphere 1000/d**2 will be the formula?

--
Matt B

David Martin said:

Well, the 0.04W is an overestimate.. And you probably are noticing
cyclists with substandard (or non-existent) lights. If you have the
time, find a dark night and a long country lane with no street lights.
Do the experiment, parking a bike at the end of a long run and seeing
whether you see the rear light or the reflectors first.

Driving through Poland, I saw a bike reflector that was at least as
bright (apparently, obviously) as a vehicle brake light at well over 300
yards. It was about A6 size. Sadly being i) in a hurry, and ii)
unable to speak Polish, I was unable to stop and ask the cyclist where
he got it from.

But your point is valid; most reflectors underperform compared to
lights, particularly the ultrabright LEDs. The reflector I saw must
have been highly retroreflective.

R.

Matt B said:

"David Martin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B said:

The "inverse square law" assumes that the light is "disappearing" in all
directions. In a car headlamp "all" of the light emitted in the wrong
direction is collected by the reflector, or the lens, and projected
forward.
The result is that "all" of the light from the bulb is concentrated into
a
focussed beam. I think your example only holds true for a naked headlamp
bulb with no reflector, and we can imagine how weak that would appear at
50m.

Think about it a bit more. It would also help to look at teh beam
patterns for your car headlights.
Whilst the light emission may indeed be assymetric, the intensity per
unit area will diminish in accordance with the inverse square law (or
approximating closer to the greater the distance is over the width of
the reflector.

Yes it will diminish. It will diminish though not by the normal 100/d**2 as
if a 100 unit point source. It will be f(100)/d**2, where f is a function
of the reflector and lens properties.

Actually by a function of 100/f(d)**2

Quoted message said:

If the whole sphere of light emitted
from a point source is concentrated uniformly into a cone occupying 1/10th
of the sphere 1000/d**2 will be the formula?

No. It won't.

If you take a beam from a headlight and measure the intensity at a
distance d, this will eb equivalent to a beam from a point source at an
apparent distance p.

so the ratio between teh intensity at 1 unit distance , and the
intensity at n units distance is

p**2/(p+n-1)**2

As n becomes large, p becomes negligible. You can measure this
effective distance by looking at how rapidly the beam on your lights
spreads with respect to distance. It is still obeying the inverse
square law, but from a virtual point light source, rather than the
reflector.

...d

Quoted message said:

--
Matt B

Matt B twisted the electrons to say:

Quoted message said:

"Alistair Gunn" <[email hidden]> wrote in message

Quoted message said:

what I
want to know is why you believe that pedal reflectors which can't be seen
add to road safety at night?

Of course they can't,

So why did you say that they did then?

Quoted message said:

which is why I was questioning the wisdom of using the vehicle illegally.

Hmm ... Clearly with only 2 BS-compliant rear reflectors, strips of
scotchlite on the back of the seat, and the scotchlite on HiVis of my
uniform and one BS-standard rear-light my 'bent will always be missed by
other road users, but if I magically had visible pedal reflectors then
that would make all the difference???

As the legal side of things, I'm not altogether convinced that the
emergency services bikes where I live have pedal reflectors ...
--
These opinions might not even be mine ...
Let alone connected with my employer ...

"Alistair Gunn" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Matt B twisted the electrons to say:

Quoted message said:

"Alistair Gunn" <[email hidden]> wrote in message

Quoted message said:

what I
want to know is why you believe that pedal reflectors which can't be
seen
add to road safety at night?

Of course they can't,

So why did you say that they did then?

I didn't mention the ones which can't be seen.

The safety benefit is only present if they are fitted and used in compliance
with the regulation.

Quoted message said:

Quoted message said:

which is why I was questioning the wisdom of using the vehicle illegally.

Hmm ... Clearly with only 2 BS-compliant rear reflectors, strips of
scotchlite on the back of the seat, and the scotchlite on HiVis of my
uniform and one BS-standard rear-light my 'bent will always be missed by
other road users, but if I magically had visible pedal reflectors then
that would make all the difference???

You're (deliberately?) missing the point. The law is the law. Does it say
"unless you've provided a better alternative"? I think not.

I'm not saying that I support this particular regulation, although I can see
the conspicuity benefits of a moving light (albeit reflected), but I'm
questioning the moral aspect of picking and choosing which laws we are
prepared to obey.

Quoted message said:

As the legal side of things, I'm not altogether convinced that the
emergency services bikes where I live have pedal reflectors ...

Go round and ask them if they think they are setting a good example ;-)

--
Matt B