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My Town Cleaned the Streets Today

Old 09-10-05, 10:41 AM
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Why would you need to know "how many people have been hit from 'elsewhere' and simply walked away... in order to detrmine whether being hit from elsewhere is much more likely to KILL you while you are cycling than is being hit from behind in daylight?
In order to determine "likelihood," you need to determine the aggregate… This is typically done in the insurance business and is known as “actuary,” or the analysis, evaluation, and management of statistical information.

All your current data says is that more people do die in collisions from “elsewhere,” but it does not determine “whether being hit from elsewhere is much more likely to KILL you.”

The data to determine that is missing. You may be more likely to be hit from elsewhere, but the likelihood of dieing is indeterminate, based on the data available.
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Old 09-10-05, 11:24 AM
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Originally Posted by genec
In order to determine "likelihood," you need to determine the aggregate… This is typically done in the insurance business and is known as “actuary,” or the analysis, evaluation, and management of statistical information.
Well that's pretty vague, but, in general, I agree. Of course, the aggregate you need to determine depends on what likelihood you're looking for.

In particular, if you're looking for the likelihood of death from a given type of hit, then the aggregate data you need is all hits of that type (fatal and non-fatal), and to know how many of those hits resulted in death. As I've pointed out for too many days and too many posts now, I think you're confusing this, determing the likelihood of death given a hit, with what we need to determine to evaluate whether a cyclist is more likely to die from hit-from-behind or hit-from-elsewhere.

If you're just comparing the likelihood of hit and death from one type of hit to the likelihood of hit and death from another type of hit, which is what we're doing when we're trying to determine which type is more likely to kill a cyclist, then the non-fatal data from either type is completely irrelevant. The only aggregate you need is the total number of deaths from each.


Originally Posted by genec
All your current data says is that more people do die in collisions from “elsewhere,” but it does not determine “whether being hit from elsewhere is much more likely to KILL you [than is getting hit from behind in daylight].”
It most certainly does determine that. The way you determine relative likelihoods of two events is by comparing the incidence of those events. In the case of "killed from being hit from behind" the incidence is much lower than that for "killed from being hit from elsewhere", therefore being hit from elsewhere is much more likely to kill you than is being hit from behind. How much simpler can it be?

But even if the available data didn't determine which was more likely to kill you, how would knowing "how many people have been hit from 'elsewhere' and simply walked away", which has nothing to do with deaths, provide the necessary data for determining “whether being hit from elsewhere is much more likely to KILL you" than is getting hit from behind?

Last edited by Helmet Head; 09-10-05 at 12:27 PM.
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Old 09-10-05, 12:08 PM
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To illustrate, let's pretend all of the non-fatal data is obtainable to see how that might help determine if a cyclist is more likely to be killed from behind or elsewhere.

Assume:
  • 10,000 car-bike collisions (all types) per year.
  • 700 result in death.
  • 10 are hit-from-behind during the day, and all 10 result in death.
  • Therefore 9,990 (10,000 - 10) are hit-from-elsewhere, and 690 (700 - 10) of the 9,990 hits-from-elsewhere result in death.

Now, let's determine whether likelihood of death from hit-from-behind or hit-from-elsewhere is higher. What data do we need to look at?

According to my argument, all we need to know is:
  • Number of deaths from hit-from-behind (10).
  • Number of deaths from hit-from-elsewhere (690).

From this data alone we can conclude that a given cyclist is 69 times more likely to die from hit-from-elsewhere then from hit-from-behind. None of the data about non-fatal deaths is required to determine that a given cyclist is much more likely to die from hit-from-elsewhere than from hit-from-behind.

According to Gene, we also need to know "how many people have been hit from 'elsewhere' and simply walked away". Well, we do know this (in this hypothetical example). Of the 9,990 where the cyclist was hit-from-elsewhere, 690 resulted in death, so 9300 walked. How does that help us?

Now, in order to determine the likelihood of death if you get hit from elsewhere, you do need those non-fatal numbers. That would be 690 / 9990, or .069 (6.9%). And according to our statistics, the likelihood of death if you are hit from behind is 10 / 10, or 1.0 (100%). OK, so what? The likelihood of death, if you are hit from behind, is much higher than the likelihood of death if you are hit from elsewhere. OK, but that does not tell us which type of hit is more likely to kill you.

How does this additional non-fatal data help us determine whether a given cyclist is more likely to be killed from behind or elsewhere? It doesn't at all. It tells us squat about that, because we already have all the data we need by just looking at total deaths from each type.

Does this make sense?

Do you recognize that you are more likely to die from a car collision than from a gunshot to the head? Now, if you are shot in the head the likelihood of death is very high, and the likelihood of death if you are in a car collision is significantly lower. And we do need the non-fatal statistics to determine what those likelihoods are. But in order to determine whether you are more likely to die from a car collision or from a gunshot to the head, all we have to do is look at the fatality statistics for car collisions and gunshots to the head. The number of people who die from car collisions is much higher than the number of people who die from gunshots to the head. We therefore know that you are much more likely to die from a car collision than from a car collision, and the number of people who away from gunshot woulds and car collisions is totally irrelevant to this.

Now do you understand why we only need death statistics to determine whether a cyclist is more likely to die from a hit-from-behind in daylight or a hit-from-elsewhere?

Now do you understand why we know that a cyclist is much more likely to die from a hit-from-elsewhere than from a hit-from-behind, even though we don't have the non-fatal data?

If not, please reread this post a couple of times, and really give it some thought. Until your subsequent posts indicate that you have given this serious consideration, and you actually address the points made (or finally concede, of course), I'm not going to continue.

Last edited by Helmet Head; 09-10-05 at 01:39 PM.
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Old 09-12-05, 10:15 AM
  #79  
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Originally Posted by Helmet Head
Perhaps the problem is in separating these two issues.

1) Is the following statement TRUE, or not? Being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight.

2) IF the above statement is TRUE, can it be used to support a particular lane position?
The first statement needs to be modified for me to agree with it to read:
"Being hit from elsewhere is much more likely to kill you while you are cycling the vast majority of the time to the very far right of the road, in a bike lane or on the sidewalk, than is being hit from behind in daylight."

Of course we don't know the most common place cyclists are riding when the fatality data was collected, but I assume it is where I obverve on daily basis (and have observed when traveling in many parts of the US) where 95% of cyclist ride which is primarily the sidewalk followed by curb hugging.

We have zero data on how many full lane using VC cyclists are being hit from behind.
We have zero data on how many sidewalk only cyclists are being hit from behind, but it can be deduced the number is zero.

Al
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Old 09-12-05, 10:34 AM
  #80  
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Look Helmet Head, I understand how the math works, but the bottom line is that you used the "700 death" reference to backup your statement that it is OK to move further left. Yet nothing in that data shows conclusively that moving further left out into the street is safer.

In fact, in San Diego, a recent news story pointed out that that older cyclists seem to be the ones dying.


Originally Posted by San Diego Union
Chances are most of those dying were middle-aged and male. In 1993, the average age of those killed in bike accidents was 27.8. By 2003, it had risen to nearly 36 years of age.
Now this is indeed speculation, but the odds are that these older cyclists are riding in more of a VC fashion and are not your red light running/wrong way cyclists.
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Old 09-12-05, 01:43 PM
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Gene, now you're back to issue 2. Are you saying that now that you've given it some thought, you now that being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight, and the statement is not BS or a fallacy?

Al, are you saying you disagree with the statement without modification?
The statement being... Being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight.

Do you agree that hits-from-behind-in-daylight kill far fewer cyclists than do hits-from-elsewhere (any hit other than a hit-from-behind-in-daylight)?

If so, is it not then true, by definition, that being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight?
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Old 09-12-05, 02:18 PM
  #82  
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Originally Posted by Helmet Head
Gene, now you're back to issue 2.
Uh, could it be because you have yet to prove that the very use of the numbers supports your original premise, therefore any other logical dancing around is just that... "dancing," while not resolving the initial problem.
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Old 09-12-05, 02:19 PM
  #83  
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Originally Posted by Helmet Head
Al, are you saying you disagree with the statement without modification?
The statement being... Being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight.
Yes I disagree as there is no data to support hit rates based on the way I (and others who ride like I do) ride on the road.

Originally Posted by Helmet Head
Do you agree that hits-from-behind-in-daylight kill far fewer cyclists than do hits-from-elsewhere (any hit other than a hit-from-behind-in-daylight)?
Yes.

Originally Posted by Helmet Head
If so, is it not then true, by definition, that being hit from elsewhere is much more likely to kill you while you are cycling than is being hit from behind in daylight?
No, it is not true by definition because I do not know how the way I ride vs. the they way the average cyclist rides (with the vast majority where I live riding on sidewalks) compare as to relative hit rates.

If I rode exclussively on the sidewalk I would very much agree that I would be much more likely hit from elsewhere than hit from behind.

Al

Last edited by noisebeam; 09-12-05 at 02:32 PM.
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Old 09-12-05, 02:38 PM
  #84  
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Originally Posted by genec
Uh, could it be because you have yet to prove that the very use of the numbers supports your original premise, therefore any other logical dancing around is just that... "dancing," while not resolving the initial problem.
Are you just playing dumb, or is this for real?

If I was able to prove that the very use of the numbers supported my original premise, I would be done. So of course I have not proved it yet. Have you ever heard of breaking down a problem into subproblems?

In the process of trying to find out what the source of your disagreement was, we've isolated a more fundamental question. That's what I've been trying to focus on for over 50 posts now, and you refuse.

Are you really incapable of breaking it down in your mind, or are your just refusing to do so?

Originally Posted by noisebeam
No, it is not true by definition because I do not know how the way I ride vs. the majority of cyclist ride (with the vast majority where I live riding on sidewalks) compare as to relative hit rates.
Oh, please. Using that strict interpretation, no statistical statement derived from general group numbers saying anything about "your" probabilities could be true. Everyone knows that individual characteristics are not accounted for in such proclamations. That's implied.
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Old 09-12-05, 03:01 PM
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Originally Posted by Helmet Head
Oh, please. Using that strict interpretation, no statistical statement derived from general group numbers saying anything about "your" probabilities could be true. Everyone knows that individual characteristics are not accounted for in such proclamations. That's implied.
But the very issue at hand has to do with being hit from behind. There are clearly at least two very different modes (with some overlap between) of using a bicycle to travel - on the road and on the sidewalk. But the data groups it all together. So the data is meaningless to draw conclusions from. That is my only point and unless there is data that comes from a set of cyclists that more closely match my cycling methods it would be in error to draw conclusions as to how my lane position affects the rate of me being hit from behind vs. other direction.

For example if you had data that showed death during sleep happens to 20% of people, do you assume if you die there is a 20% of it occuring while sleeping? What if further data found (but was not available at the time, but annectodally was fairly apparent) that of those sleeping deaths 80% had heart disease, and 80% were over 50, but in both cases you are not. Does that mean that you still going about you life thinking you have a 20% that when you die it will be while sleeping, because all you had at the time was only data from the general population? (all numbers made up for example only)

Al

Last edited by noisebeam; 09-12-05 at 03:14 PM.
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Old 09-12-05, 03:03 PM
  #86  
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Originally Posted by Helmet Head
Are you really incapable of breaking it down in your mind, or are your just refusing to do so?
I am refusing to play "the straw man game" and the "follow Serge's logic game."

The latter especially, because motorists don't play by the scenerios you pose.

If the traffic rules were followed as written, then no "accidents" would ever occur.

Then again, you never did show how your "numbers" actually related to riding further to the left, so everything since my challange has just been "playing games... "
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Old 09-12-05, 03:20 PM
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Originally Posted by noisebeam
For example if you had data that showed death during sleep happens to 20% of people, do you assume you have a 20% chance of dying while sleeping?
Yes, and no.

If I don't have the additional data, then yes - because that's all I know.

Consider the odds of picking the winning numbers in a lottery. Say it's one in 100 million.

Now say you have additional data... from your crystal ball which tells you the winning numbers in advance. Now your odds are looking much better.

The point is that for 99,999,999 combinations, the odds of winning are actually 0, and the odds for the winning number winning is 1. But when we don't know which is the winning number, we just say the odds are all the same for all the numbers... 1 in 100,000,000.
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Old 09-12-05, 03:55 PM
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Originally Posted by Helmet Head
Yes, and no.

If I don't have the additional data, then yes - because that's all I know.

Consider the odds of picking the winning numbers in a lottery. Say it's one in 100 million.

Now say you have additional data... from your crystal ball which tells you the winning numbers in advance. Now your odds are looking much better.

The point is that for 99,999,999 combinations, the odds of winning are actually 0, and the odds for the winning number winning is 1. But when we don't know which is the winning number, we just say the odds are all the same for all the numbers... 1 in 100,000,000.
But we do know that riding 'styles/behaviors' can vary widely and I do know you do agree that riding 'style/behavior' can greatly affect ones likelihood of an accident.

Your analogy above doesn't hold as we are not looking for winning numbers based on luck alone, but trends based on behavior.

Al
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Old 09-12-05, 04:25 PM
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Your argument would apply if we were trying to ascertain a fairly accurate estimate of probability.

The fact is that being hit from behind during the day is so rare, the odds of it happening to anyone, regardless of their riding style/behavior, or any realistic/reasonable factors, are negligible.

In comparison, the incidence of being hit from elsewhere is so much higher that it is obvious that anyone's odds of behing hit from elsewhere are much higher than being hit from behind.

The irony is that the better you get at defending against hits-from-elsewhere, the lower becomes the difference between the two probabilities. But the hit-from-behind possibility remains fairly constant no matter what you do, short of not getting on the bike in the first place.

Why worry about something over which you have no practical or reasonable control, and the probability of which is neglible anyway?
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Old 09-12-05, 04:44 PM
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Originally Posted by Helmet Head
The irony is that the better you get at defending against hits-from-elsewhere, the lower becomes the difference between the two probabilities.
Agreed.
Originally Posted by Helmet Head
But the hit-from-behind possibility remains fairly constant no matter what you do, short of not getting on the bike in the first place.
No, as soon as you move from the sidewalk to the road your hit from behind possibility increases from near zero to some unknown but certainly non zero value. Sidewalk riders know this which is one of the reasons they select the sidewalk (while being ingnorant of or working around the much increased hit from everywhere else scenario, while avoiding only a very small accident scenario, not a good trade off)
Originally Posted by Helmet Head
Why worry about something over which you have no practical or reasonable control, and the probability of which is neglible anyway?
I am not worried about it per se, but it needs to be better understood with data what the chance of being hit from behind is if one rides in center of lanes vs. to the right. VC proponents have no data, only thought experiments, that suggest that riding further into the lane is safer from a hit from behind perspective.

BUT - I understand you point that even if there is a slight difference in chance of being hit from rear between center of lane vs. right side of lane, that being hit from behind is rare enough so as not to be a consideration as to riding on the road or not - i.e. relative to other scenarios it should be low on the list of concerns.

Al
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Old 09-12-05, 05:36 PM
  #91  
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Last week a regular on the recumbent forum and the BROL forum was struck from behind and killed. His handle was Bnet1, and his real name was Brian Kennedy. HH may argue about the unlikely nature of this type of accident, but it does happen.

Newspaper reports:
https://www.chroniclet.com/2005_Arch...Html/Head5.html

https://news.bellinghamherald.com/ap.../509110339/1011

The first article says he was struck while riding in the lane:
Brian Kennedy, 54, was riding in the southbound lane at 4:40 p.m. toward his Webster Road home when a red Taurus driven by 21-year-old Danita Cole struck the bike and sent him 70 feet into the roadside ditch.
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