Rear LED light effectiveness.

I've just read the discussion on flashing rear lights, here's my comments:

I agree with those who say that chasing lights are not effective as from a
distance they look like one LED
permanently on.

Some early flashing lights seemed to spend a small fraction of the time on
(about 0.1 second per second). They gave wonderful battery life but I
thought they were not good, despite others swearing by them.

I think the flash frequency needs to be about 0.1 seconds on and off (as
modern ones seem to). Much faster and it merges into continuous, slower and
it isn't as eye-catching.

Lights usually have a wide beam, the LEDs being arranged on a slight ark.
Because of mounting problems some people put them vertically - lots of light
up and down but little to the side.

Some people don't aim the light horizontally straight backwards.

Rechargeable batteries fade very quickly so a rear light can go out
unnoticed; disposables give more warning.

Why do so many cyclists point front lights down to the ground about 2 metres
ahead? If it's to be seen by then point it forwards, if it's to see by then
point it far enough ahead to see something before you hit it (and you should
be looking well ahead not at the puddle of light 2 metres away).

www.JohnPitcock.com

Zog The Undeniable wrote:
I thought the drop in output was quite scary when I measured it (I can't
remember if the alkalines were new or not - I think they may have been
used for half an hour or so). It was a full stop on the light meter at
a measured distance from the lamp, so the output was halved. Of course,
some LEDs may be better than others at coping with rechargeables - I did
the test on the (mediocre) Cateye HL-EL200 front light.

IMHO the conclusion here is that LED lights should really be properly
regulated. If the light is inadequate with NiMH batteries it will also
become inadequate with alkaline batteries long before they're fully
discharged.

Unfortunately regulated LEDs are harder to find -- I don't know of any
regulated rear lights. I think the only reason for this is that it
allows manufactures to exaggerate power to runtime ratio.

Anthony

On Thu, 16 Mar 2006 09:44:57 GMT, Mark Thompson
pleasegivegenerously@warmmail*_turn_up_the_heat_t o_reply*.com wrote:

It's an open offer. Tell me why you think that road conditions in
China and London are comparable, leaving the personal stuff out, and
we'll take it from there.

Is it because, despite the roads in China being more dangerous, the Chinese
still trundle about 2 up on a bike and no one bats an eyelid. In the UK
with very safe roads, going 2 up on a bike makes Terry have a hernia?

Very eloquently put. Thanks.

Don't follow these links if you are of tender disposition.

[Repost]

http://www.ananova.com/images/web/277699.jpg
http://www.ananova.com/images/web/277698.jpg
http://www.ananova.com/images/web/277694.jpg
--
Let us have a moment of silence for all Americans who
are now stuck in traffic on their way to a health club
to ride a stationary bicycle. -
Congressman Earl Blumenauer (Oregon)

On Thu, 16 Mar 2006 09:53:05 +0000, Simon Brooke wrote:

Sorry if that's slightly tetchy. I do get irritated with people thinking
that the way /they/ access Usenet is the 'only' way, and that what works
on their client should work for everyone else.

.... and especially when the way they do it is the /wrong/ way.

regards, Ian SMith
--
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|o o|
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Iain

My main point is that you saw the cyclist very well even though he had no
lights.

I know that some people say that if it increases the chance of being seen
then it may save your life and would definately be worth it.

I do not subscribe to that. I think that any reduction in risk must be
weighed up against the other factors. You may say that adding a second light
has no downside. I would disagree with you. There a re a number of downsides
:-

1. As cycling becomes more popular then motorists will adjust their speed
according to the risk they perceive from cyclists. More cyclists without
lights, or low levels of lighting tend to reduce the speed of motorists,
therefore compensating for any very slight increase in reaction times.

2. By lighting up cyclists well we are enabling motorists to mnaintain high
prevailing speeds of 30mph in our communities which are very fast. Within
towns and villages 30 mph is unnatural and out of line with most of Europe.
Highly visible cyclists help justify higher speeds.

3. In countries where cycling is an accepted way of getting from a to b it
is done with the minimum of fuss. Multiple lights are "fuss". They shift the
responsibility for being seen from the driver to the cyclist.

Whilst I respect your right to put whatever lights on you wish as long as
they are in accordance with the law, I also think that it is responsible to
consider the effect that they have on motorists attitude to cyclists in
general rather than just yourself.

Equally you may challenge the weighting to attach to the above and that is
OK, but I do not think they should be dismissed out of hand.

You may say that all of this is rather academic, but then there is no
evidence that statistically lighted cyclists fare any better or worse on the
roads than unlighted cyclists.


Best regards

Rod King



Th. wrote in message
ups.com...
Rod King wrote:
Iain

Let me get this right.

From 100m away you saw the light.

How fast does one have to go in order that 100m visibility of a cyclists
rear light is not sufficient warning. If he had been a pedestrian he
would
not have had any rear light.

Far from being useless it seemed to be very effective.

Were you looking for a higher degree of visibility than was reasonable?

What would you have done if his light had been brighter?

Would you have driven any differently?

Rod
In answer to your questions. The street concerned was a well lit
urban street. At the point I overtook it was a 30mph limit although it
changed to a 50mph limit a couple of hundred metres later. I wouldn't
describe his light as being effective as I saw the cyclist (despite
dark non reflective clothing) before I saw the light.
I wasn't looking for any degree of visibility. If an unlit
pedestrian (a drunk perhaps) had been lying in the road I would have
seen him in plenty of time and taken the appropriate action.
What I would have done if his light had been brighter is I would
have seen him earlier.
I woud have driven differently by moving into the outside lane
earlier.
The vast majority of drivers will see cyclists whether lit or not
early enough to miss them. But I believe that being very visible might
save my life one night when that 1 in 100,000, or whatever, driver who
is drunk, using a mobile, with poor eyesight, or careless sees me a few
seconds earlier than he or she otherwise might.
With regard to pedestrians being seen there was a pedestrian
killed a few years ago 2 miles from where I live. He was walking along
an unlit road with no pavement and was killed by a taxi (driver sober)
who didn't see him in time. If that ped had been wearing bright
clothing he might be alive who knows. The accident as far as I'm
concerned was 100% the drivers fault but that doesn't make the ped any
less dead.
Given that it costs next to nothing (in either cash or hassle) to
be well lit I see no argument for not running at least 2 rear lights.
But it's a free country and its an individual choice. Long may it
remain so.