Invisible Cyclists in Solstice Dark

In uk.rec.cycling Tony Raven wrote:
Chris Malcolm wrote:

But the populations aren't comparable. Cyclists on average are
younger and fitter and in better health, and less likely to be drunk.
What you really want to know is whether the same mile of road is
safer when walked or when cycled by *you*. These statistics have
nothing to tell you about that. It could quite easily be that for
*you* cycling is four times as risky as walking per mile.

They are also not comparable in that cyclists are generally on the road
mixed with motorised traffic while pedestrians are generally on the
pavement segregated from motorised traffic.

But your contention that population statistics are of no value in
assessing the risk to an individual are worthy of Wally.

But that wasn't my contention. My contention was that population
statistics are of no use in comparing risk factors when the
populations aren't comparable. And they're can be misleading in
assessing risk to you if you're not typical of the population. These
are the kind of things you get taught in elementary statistics
classes.

--
Chris Malcolm +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Chris Malcolm wrote:
In uk.rec.cycling Tony Raven wrote:
Chris Malcolm wrote:

But the populations aren't comparable. Cyclists on average are
younger and fitter and in better health, and less likely to be drunk.
What you really want to know is whether the same mile of road is
safer when walked or when cycled by *you*. These statistics have
nothing to tell you about that. It could quite easily be that for
*you* cycling is four times as risky as walking per mile.


But your contention that population statistics are of no value in
assessing the risk to an individual are worthy of Wally.

But that wasn't my contention. My contention was that population
statistics are of no use in comparing risk factors when the
populations aren't comparable.

Perhaps you should re-read what you wrote; you were contending that
statistics told me nothing about the risk to "me".

And they're can be misleading in
assessing risk to you if you're not typical of the population. These
are the kind of things you get taught in elementary statistics
classes.


OK so what evidence do you have that cyclists are on average younger and
fitter and in better health and less likely to be drunk than pedestrians?

Plotting the data here
http://www.hants.gov.uk/roadsafety/s...s/rawdata.html
shows a very similar age profile for pedestrian and cyclist casualties.


--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

in message , Chris Malcolm
') wrote:

But that wasn't my contention. My contention was that population
statistics are of no use in comparing risk factors when the
populations aren't comparable.

In Holland, however, or indeed Cambridge, the populations (of cyclists
and pedestrians) are extremely comparable. Anyone got figures for KSI
per billion kilometres for cyclists and pedestrians in Holland? Roos?

My personal guess is that the risk ratio will tilt even more in the
cyclists' favour - Holland is known to be a very safe place to cycle.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken, and I found when I looked that we had run out
of copper roove nails.

crabsallover wrote:

So in at least one case the cyclists reflective garment was visible
before the tail-light had been seen. Therefore in at least one case it
might have been safer for the cyclist to wear a reflective garment in
addition to the use of the tail-light.

And "if only one life can be saved"... (cont. Daily Mail)

--
Guy

wrote:

Common sense tells one that non-flashing lights
are more visible as flashing lights are switched off intermittently.

Whereas the DfT tells one the opposite: that flashing lights are around
four times more visible. Which is why I always use both, even in the
absence of any actual evidence that either increases safety.

- -
Guy

Just zis Guy, you know? wrote:
wrote:

Common sense tells one that non-flashing lights
are more visible as flashing lights are switched off intermittently.

Whereas the DfT tells one the opposite: that flashing lights are around
four times more visible.

For very good reasons that are well understood in visual perception
theory. It why emergency vehicles, tall structures and aircraft have
flashing, and not continuous, warning lights.

--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

Nigel Cliffe wrote:
And five minutes looking into human perception will reveal two
important facts:

Flashing lights are good for attracting attention, but relatively
poor for spatial positioning.
Fixed lights are relatively poor for attracting attention, but good
for spatial positioning.


Wow! Is that 'referenceable" as it is in complete accord with my subjectice
expereince as cyclist and driver, in either case working out my position
relative to a "flasher" is MUCH more difficult.

I ride with one flasher and one steady.

ie
Flash: SEE ME

Steady: THIS IS WHERE I AM

pk

Nigel Cliffe wrote:


And five minutes looking into human perception will reveal two important
facts:

Flashing lights are good for attracting attention, but relatively poor for
spatial positioning.
Fixed lights are relatively poor for attracting attention, but good for
spatial positioning.

So, if trying to be noticed, use flashing. If trying to give your position
(and thus not be hit) use fixed.


Which might be why lots of people have suggested the best lights are a
combination of fixed and flashing.

As I understand it, the idea of flashing lights being poor for spatial
positioning refers to the case where flashing lights have a relatively
long "off" state. Light is perceived, but when the observer tries to
focus on it, it's (confusingly) no longer there.

This rule of thumb doesn't seem applicable to the LED blinkies I own
and use. These are better described as "twinkling" rather than
"flashing." There is no easily perceptible "off" state, so there is no
time for the observer's brain to wonder "where is that light I saw half
a second ago?"

I think "twinkling" LEDs are fine.

- Frank Krygowski





--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Chris Malcolm wrote:

The average distance walked per pedestrian injury is certainly less
than the average distance cycled per cyclist injury, but that does
*NOT* mean that walking is more dangerous than cycling, because the
populations are significantly different. The pedestrian population
includes people too old, drunk, or ill to be cycling. In general
cyclists tend be fitter, younger, and more alert than pedestrians, so
they're less accident prone to start with.

The pedestrian population is, to a first approximation, everybody.

But your argument sounds, I'm afraid, a lot like "whatever the facts, I
hold to the view that cycling isd dangerous". Actualy I think cycling
is very safe, by lots of measures.

This is going to wreck.bikes; the Leftpondians will probably know of
Frank Krygowski, who has posted data showing that in the States cyclists
are at less risk per unit exposure than motorists.

In the end I think Bob Davis has it right: cycling is not dangerous,
it's just that cyclists are vulnerable.

--
Guy

p.k. wrote:

A distortion of statistical meaning that is trotted out here quite
regularly, sometimes innocently sometimes with deliberate intent to deceive
and confuse. to which camp do you belong?

LOL! Five points to that man!

--
Guy