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#121
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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/] |
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#122
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Invisible Cyclists in Solstice Dark
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 |
#123
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Invisible Cyclists in Solstice Dark
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. |
#124
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Invisible Cyclists in Solstice Dark or "Is black white?"
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 |
#125
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Invisible Cyclists in Solstice Dark or "Is black white?"
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 |
#126
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Invisible Cyclists in Solstice Dark or "Is black white?"
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 |
#127
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Invisible Cyclists in Solstice Dark or "Is black white?"
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 |
#128
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Invisible Cyclists in Solstice Dark or "Is black white?"
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/ |
#129
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Invisible Cyclists in Solstice Dark
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 |
#130
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Invisible Cyclists in Solstice Dark
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 |
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