Search found 322 matches

by swansonj
25 Oct 2011, 9:24pm
Forum: On the road
Topic: Targeted red light jumping
Replies: 43
Views: 4029

Re: Targeted red light jumping

I'm someone who does not RLJ in general. But there is one very narrow circumstance where, in your terminology, I TRLJ. On my commute, there is light-controlled fast roundabout. My approach to it has two lanes and it is ambiguous about the lane discipline; some cars use the left lane to go round the roundabout, some cars use the right line and exit from the first exit. So whichever lane you choose as a cyclist going past the first exit round the roundabout, you run the risk of being clipped by a car crossing your path. My solution is to wait for a red light, filter to the front of the stationary cars, then when I see the light for crossing traffic turning from green to amber, sprint hell for leather so I'm safely past the first exit before any of the cars in the same queue as me can get near enough to hit me.

That is, as I say, a very narrow circumstance, but it is one where I do think RLJ-ing in the sense of anticipating the green is safer.
by swansonj
25 Oct 2011, 7:42am
Forum: CTC Charity Debate
Topic: CTC Charity Application Rejected
Replies: 78
Views: 176213

Re: CTC Charity Application Rejected

Still nothing about this on the CTC website that I can find. Am I being paranoid, or could this absence of communication be interpreted as yet more evidence of the contempt the CTC powers that be feel for the members?
by swansonj
24 Oct 2011, 1:37pm
Forum: Bikes & Bits – Technical section
Topic: SwissStop brake pads
Replies: 16
Views: 3729

Re: SwissStop brake pads

Can I resurrect this thread to ask a slightly more general question: what brake pads are the best for minimising rim wear? I clearly want good stopping performance, but given a choice beyond that, I'd rather have softer pads where the pads wear out more quickly than harder pads where the rims wear out.
by swansonj
21 Oct 2011, 12:03pm
Forum: Bikes & Bits – Technical section
Topic: Variation in wheel circumference.
Replies: 104
Views: 8310

Re: Variation in wheel circumference.

Well, I take the point that the main things is cycling from A to B, and the distance that represents is secondary. Nonetheless, for all sorts of reasons, I'd like my cyclometer to be as accurate as possible about that distance. Seems to me I need a "measured mile". An accurately known distance along a road. I would then cycle along it, complete with my normal amount of front-wheel wiggle, my normal amount of front-tyre-compression on braking, my normal weight, etc, and adjust the circumference setting to make it come out correct for this measured mile. Then the cyclometer reading would already allow for these factors and would tell me a close approximation to the actual A to B distance on future trips.

I suppose GPS is the other way - I did a ride the other week where my cyclometer said a tad over 61 and someone with a GPS tracked it as 60. So maybe I should reduce my circumference setting accordingly - except that CJ explained how GPS under-reads because it takes chords not arcs. So it would have to be a straight line route for the GPS to be trusted to calibrate the cyclometer.
by swansonj
16 Oct 2011, 2:19pm
Forum: On the road
Topic: How often do you actually get a puncture?
Replies: 61
Views: 10164

Re: How often do you actually get a puncture?

swansonj wrote:Large club rides should provide a good sample. Simon should have exact statistics from some of the Friday Night rides to the coast. On the Brighton ride in May this year, there were, from memory, 140 riders doing 70 miles. There seemed to be a lot of punctures on the night, but if it was ten punctures, that is in fact only one every 1000 miles.


This weekend's FNRTTC to Brighton had, according to the official Tail End Charlie tally, 9 punctures. At 100 rider (near enough) doing 62 miles that's one per 690 miles. Mind you, three of those punctures were apparently on the same tyre. And one was on a (recumbent trike) - perhaps that ought to count as only 2/3 the mileage for comparison purposes.
by swansonj
9 Oct 2011, 6:57am
Forum: Does anyone know … ?
Topic: Statistical Probabilities....
Replies: 70
Views: 5411

Re: Statistical Probabilities....

Jonty wrote:The worst case of misuse of statistics IMHO occured relatively recently when a woman was convicted of murdering her two children which she said had died from cot death.
She was convicted mainly on the evidence of an expert witness who was medicall qualified, numerate but not a statistician. The crux of his case was that the statistical probability of two cot deaths occuring in the same family were so small they could not have arisen by chance and therefore she must have killed her children.
In other words if the chances of 1 death were 1 in 100,000 the chances of two were 1 in 10,000,000,000 (100,000 squared).
Unfortunately, to say the least, his evidence was not challenged by her defence.
Where he made the mistake was in assuming that cot deaths arose by chance and were independent events; rather like the example given by Nutsey about the plane traveller carrying a bomb.
In fact research shows that they are not randomly distributed and that they are not independent events. In fact if a family has one cot death it is more likely to have a second - there is something in the medical history or practices of the family which increase "risk".
The woman was imprisoned but was eventually released after his evidence was squashed.
She never recovered and drank herself to death or committed suicide.
All because her defence team were statistically innumerate and were unaware of the fact and did not seek advice from a member of the Royal Statistical Society.
jonty


What you say (that two cot deaths in the same family are not independent events) is correct, but misses the bigger error made by Sir Roy Meadow, the expert in question. He calculated (wrongly as it happened) the probability of two deaths in one particular family, given that they were cot deaths. He should have calculated the probability that two deaths were cot deaths, given that two deaths occurred in the same family. Given that two unexplained deaths occur in the same family, the main alternatives are cot deaths or murder. Both are, taken in isolation, unlikely (obviously so, given that two deaths in the same family are unlikely, any cause that produces that unlikely event is also inevitably going to be unlikely). The question is, which is more unlikely. It turns out that, given that two deaths have occurred, cot death is MORE likely than murder. This error (calculating the probability of effect given cause, then presenting it as if it is the probability of cause given effect) is well known and called "the prosecutor's fallacy".

Sally Clark's conviction was not overturned because Roy Meadow's evidence was discredited, it was overturned because of failure to disclose bacteriological evidence at the original trial (at her first, failed, appeal, the court said the statistical evidence would have been unimportant, an example of the legal profession closing ranks if ever there was one). But Roy Meadow's evidence was indeed discredited, he was struck off the medical register as a result, then reinstated by the court of appeal who ruled that he had made an error but not sufficiently serious to merit being struck off.
by swansonj
2 Oct 2011, 8:26am
Forum: On the road
Topic: Cyclists in dark clothing
Replies: 96
Views: 8115

Re: Cyclists in dark clothing

eileithyia wrote:So from my own experiences, wearing bright colours or not makes not a jot of difference!


Sorry, but that's bad logic. Your experience shows that wearing bright colours is not infallible, but it (at least what you have reported) tells you nothing about whether wearing bright clothing alters the frequency of not being noticed by motorists.

The argument "motorists won't spot you whatever you wear so it doesn't matter if you are visible or not", expressed with varying degrees of explicitness several times on these forums, is similarly illogical.
by swansonj
1 Oct 2011, 1:41pm
Forum: Bikes & Bits – Technical section
Topic: Eureka!!
Replies: 19
Views: 1468

Re: Eureka!!

I fitted some a few weeks ago in preparation for winter. I accept that there is only a small set of circumstances where they would actually be useful (though surely it's more than just the sideways-on-at-a-sideroad situation discussed upthread, I would have thought plenty of roundabouts and other junctions involve motorists impinging on you at oblique angles, not to mention them overtaking you). But they present no safety risk (unlike rigid plastic spoke reflectors), the weight is negligible, and the cost small - so on any rational cost-benefit calculation, it seemed to me it only takes a small benefit to make them worth it.
by swansonj
24 Sep 2011, 7:48am
Forum: On the road
Topic: Mobile phone clampdown on drivers
Replies: 30
Views: 2419

Re: Mobile phone clampdown on drivers

Tonyf33 wrote: ... but having a conversation with a person be it in the car or via phone without removing ones hands from the steering wheel isn't a problem for me, however I'd like those that can't drive safely whilst doing so to be weeded out & removed from the roads forwith.


Or, perhaps, as people used to say:

"... but driving after having a couple of pints isn't a problem for me, however I'd like those that can't drive safely whilst doing so to be weeded out & removed from the roads forwith." :wink:
by swansonj
23 Sep 2011, 7:43am
Forum: On the road
Topic: Mobile phone clampdown on drivers
Replies: 30
Views: 2419

Re: Mobile phone clampdown on drivers

Tonyf33 wrote: Given what people are saying here that conversation is the the main culprit then we should ban talking to other passengers, ban smoking in cars, touching sat-navs, in fact ban listening to music or any other process that involves distracting our brains :roll:


There are two overlapping reasons why conversations on a mobile have worse effects on driving concentration than talking to other passengers, using satnavs and listening to music:
- we can break off from any of the others very easily if a situation arises on the road that needs more concentration. We do this all the time when listening to music in the car - how often have you been listening to a familiar track and suddenly realised you've got further through it than you'd realised because you'd momentarily switched off to concentrate on the road? And other passengers assist this by responding to road conditions themselves - they pause while you overtake, or wait for an answer while you negotiate a roundabout. Breaking off from a conversation with someone remote from your setting requires more effort.
- when we talk to somone on the phone, we project ourselves into their setting. Some fraction of our concentration is no longer on our own surroundings and environment but on theirs.
by swansonj
22 Sep 2011, 9:40pm
Forum: On the road
Topic: Mobile phone clampdown on drivers
Replies: 30
Views: 2419

Re: Mobile phone clampdown on drivers

stork wrote: You're quite right that the main danger is that a mobile phone occupies and distracts your mind, rather than your hands. Unfortunately, Government failed to understand this when they legislated, ....


Actually, I think Government understood the evidence perfectly well. The story was that there was an easy legislative route for banning hand-helds, but no easy legislative route for banning hands-free.
by swansonj
21 Sep 2011, 6:48am
Forum: On the road
Topic: How often do you actually get a puncture?
Replies: 61
Views: 10164

Re: How often do you actually get a puncture?

Previously, with Panaracer Hi-Road: about every 1000 miles
Now, with ordinary Marathon on front and Marathon Plus on rear: not for about 3000 miles

Large club rides should provide a good sample. Simon should have exact statistics from some of the Friday Night rides to the coast. On the Brighton ride in May this year, there were, from memory, 140 riders doing 70 miles. There seemed to be a lot of punctures on the night, but if it was ten punctures, that is in fact only one every 1000 miles.
by swansonj
15 Sep 2011, 9:32pm
Forum: Does anyone know … ?
Topic: Balaclava advice
Replies: 7
Views: 670

Re: Balaclava advice

I have a thin silk balaclava. I just checked it, it's unbranded ("made in China") and I can't remember where I got it. Works well for me. On a moderately cold day, pull the lower portion down under the chin: keeps ears and neck warm without misting up. On a slighly colder day, have the lower bit over the chin but under the mouth. On a very cold day, have it over the mouth as well. The only problem is, pulling it on and off tends to catch on glasses.
by swansonj
11 Sep 2011, 8:43am
Forum: On the road
Topic: Defending yourself
Replies: 35
Views: 3347

Re: Defending yourself

Cunobelin wrote:Interesting, but more extreme version on a US website....

How many of you carry a gun as part of your cycling equipment?


I've only read as far as page 5 of what apparently is a 240 page thread. However, I did come across this gem:

For me it depends on where I am riding, I'll carry my S&W ti .38. Since I sometimes ride in or on the border of the worst precient in the city, to me having it just like wearing my helmet, common sense.


If I could be bothered, I'd go over the helmets subforum and post:

For me, wearing a helmet is just like carrying my S&W ti .38, common sense