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UK cyclists kill or maim two people a week



 
 
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  #21  
Old October 13th 17, 11:55 PM posted to uk.rec.cycling
TMS320
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Posts: 3,875
Default UK cyclists kill or maim two people a week

On 13/10/17 14:04, Nick wrote:

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


Thanks for that.
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  #22  
Old October 14th 17, 03:08 PM posted to uk.rec.cycling
Simon Jester
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Posts: 2,727
Default UK cyclists kill or maim two people a week

On Friday, October 13, 2017 at 2:04:43 PM UTC+1, Nick wrote:
On 13/10/2017 00:28, TMS320 wrote:
On 12/10/17 22:11, Peter Parry wrote:
On Thu, 12 Oct 2017 01:07:40 +0100, TMS320 wrote:

On 11/10/17 12:28, Peter Parry wrote:
On Wed, 11 Oct 2017 10:20:28 +0100, TMS320 wrote:

On 11/10/17 09:35, Peter Parry wrote:
On Tue, 10 Oct 2017 12:06:02 -0700 (PDT), Simon Jester

Do these figure take into account that the majority of car miles
are on trunk roads where there are few, if any, pedestrians? Whilst
bicycles spend most of their time in urban environments.

If not then they are worthless.

They do. On urban roads Pushbikes seriously injure 26 pedestrians
per billion km and kill 0.5, cars seriously injure 10 and kill 0.7..

So you love to push this.

"Push"?Â* One mention of DfT statistics is pushing them?

Yes. You have brought this up several times before. It is obvious you
think it is meaningful.

It is clearly meaningful as it is the data used by the government to
make decisions.

I asked you why you think pedestrian casualties per vehicle-distance is
meaningful. Don't evade the question.

Of course it is.


That doesn't answer the question.


You won't get an answer. He won't even attempt an answer because he
knows he isn't clever enough.

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


So what metric should we use?
Passanger miles don't count because there is only one driver per vehicle.
  #23  
Old October 14th 17, 08:43 PM posted to uk.rec.cycling
Nick[_4_]
external usenet poster
 
Posts: 1,323
Default UK cyclists kill or maim two people a week

On 14/10/2017 15:08, Simon Jester wrote:

I asked you why you think pedestrian casualties per vehicle-distance is
meaningful. Don't evade the question.

Of course it is.

That doesn't answer the question.


You won't get an answer. He won't even attempt an answer because he
knows he isn't clever enough.

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


So what metric should we use?
Passanger miles don't count because there is only one driver per vehicle.


A suitable metric depends on the question being asked. There is no
general purpose correct metric that is useful for every question.

You might just as well ask if I want to buy something from a shop, how
much should I pay?

Presumably Peter wanted to suggest that the statistics showed that
cyclists posed as great a risk to pedestrians as motorists but this
almost certainly isn't true, either in absolute terms or in terms of per
utility unit for any sensible utility unit I can think of.

On usenet it is frightening to so how many people misunderstand basic
scientific/mathematical/statistical arguments. Cycle helmets, cycle
paths, global warming, vaccines. Even people who should know better
quote stupid ******** as if it means something.
  #24  
Old October 14th 17, 08:43 PM posted to uk.rec.cycling
TMS320
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Posts: 3,875
Default UK cyclists kill or maim two people a week

On 14/10/17 15:08, Simon Jester wrote:
On Friday, October 13, 2017 at 2:04:43 PM UTC+1, Nick wrote:
On 13/10/2017 00:28, TMS320 wrote:
On 12/10/17 22:11, Peter Parry wrote:
On Thu, 12 Oct 2017 01:07:40 +0100, TMS320 wrote:

On 11/10/17 12:28, Peter Parry wrote:
On Wed, 11 Oct 2017 10:20:28 +0100, TMS320 wrote:

On 11/10/17 09:35, Peter Parry wrote:
On Tue, 10 Oct 2017 12:06:02 -0700 (PDT), Simon Jester

Do these figure take into account that the majority of car miles
are on trunk roads where there are few, if any, pedestrians? Whilst
bicycles spend most of their time in urban environments.

If not then they are worthless.

They do. On urban roads Pushbikes seriously injure 26 pedestrians
per billion km and kill 0.5, cars seriously injure 10 and kill 0.7.

So you love to push this.

"Push"?Â* One mention of DfT statistics is pushing them?

Yes. You have brought this up several times before. It is obvious you
think it is meaningful.

It is clearly meaningful as it is the data used by the government to
make decisions.

I asked you why you think pedestrian casualties per vehicle-distance is
meaningful. Don't evade the question.

Of course it is.

That doesn't answer the question.


You won't get an answer. He won't even attempt an answer because he
knows he isn't clever enough.

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


So what metric should we use?
Passanger miles don't count because there is only one driver per vehicle.


Passenger miles isn't too bad - even if there is a passenger variation
from 1 to 5; at least they're actually inside the vehicles that are
doing the miles. (I expect Simpson's paradox would find a strange result
between 1 occupant, 5 occupants and average occupancy - whatever that
average is.)

I just canot fathom out why there is supposed to be a link between
pedestrians and vehicle miles.
  #25  
Old October 14th 17, 11:21 PM posted to uk.rec.cycling
Simon Jester
external usenet poster
 
Posts: 2,727
Default UK cyclists kill or maim two people a week

On Saturday, October 14, 2017 at 8:43:52 PM UTC+1, Nick wrote:
On 14/10/2017 15:08, Simon Jester wrote:

I asked you why you think pedestrian casualties per vehicle-distance is
meaningful. Don't evade the question.

Of course it is.

That doesn't answer the question.

You won't get an answer. He won't even attempt an answer because he
knows he isn't clever enough.

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


So what metric should we use?
Passanger miles don't count because there is only one driver per vehicle.


A suitable metric depends on the question being asked. There is no
general purpose correct metric that is useful for every question.


The question becomes what question do we ask?


You might just as well ask if I want to buy something from a shop, how
much should I pay?

Presumably Peter wanted to suggest that the statistics showed that
cyclists posed as great a risk to pedestrians as motorists but this
almost certainly isn't true, either in absolute terms or in terms of per
utility unit for any sensible utility unit I can think of.


Seen it all before. Hugh Davies and Steve Firth come to mind.


On usenet it is frightening to so how many people misunderstand basic
scientific/mathematical/statistical arguments. Cycle helmets, cycle
paths, global warming, vaccines. Even people who should know better
quote stupid ******** as if it means something.


You are more likely to be killed by a blue car than a green car.


  #26  
Old October 14th 17, 11:26 PM posted to uk.rec.cycling
Simon Jester
external usenet poster
 
Posts: 2,727
Default UK cyclists kill or maim two people a week

On Saturday, October 14, 2017 at 8:43:56 PM UTC+1, TMS320 wrote:
On 14/10/17 15:08, Simon Jester wrote:
On Friday, October 13, 2017 at 2:04:43 PM UTC+1, Nick wrote:
On 13/10/2017 00:28, TMS320 wrote:
On 12/10/17 22:11, Peter Parry wrote:
On Thu, 12 Oct 2017 01:07:40 +0100, TMS320 wrote:

On 11/10/17 12:28, Peter Parry wrote:
On Wed, 11 Oct 2017 10:20:28 +0100, TMS320 wrote:

On 11/10/17 09:35, Peter Parry wrote:
On Tue, 10 Oct 2017 12:06:02 -0700 (PDT), Simon Jester

Do these figure take into account that the majority of car miles
are on trunk roads where there are few, if any, pedestrians? Whilst
bicycles spend most of their time in urban environments.

If not then they are worthless.

They do. On urban roads Pushbikes seriously injure 26 pedestrians
per billion km and kill 0.5, cars seriously injure 10 and kill 0..7.

So you love to push this.

"Push"?Â* One mention of DfT statistics is pushing them?

Yes. You have brought this up several times before. It is obvious you
think it is meaningful.

It is clearly meaningful as it is the data used by the government to
make decisions.

I asked you why you think pedestrian casualties per vehicle-distance is
meaningful. Don't evade the question.

Of course it is.

That doesn't answer the question.

You won't get an answer. He won't even attempt an answer because he
knows he isn't clever enough.

FWIW the effect you are talking about with respect urban/non urban trips
is called Simpson's Paradox.

https://en.wikipedia.org/wiki/Simpson%27s_paradox


So what metric should we use?
Passanger miles don't count because there is only one driver per vehicle.


Passenger miles isn't too bad - even if there is a passenger variation
from 1 to 5; at least they're actually inside the vehicles that are
doing the miles. (I expect Simpson's paradox would find a strange result
between 1 occupant, 5 occupants and average occupancy - whatever that
average is.)


If I drive my car on a given mile of road on my own I pose 5x as much danger to other road users than if I drive the same mile with 4 passengers, that is what passenger miles tells us.

  #27  
Old October 16th 17, 10:29 PM posted to uk.rec.cycling
TMS320
external usenet poster
 
Posts: 3,875
Default UK cyclists kill or maim two people a week

On 14/10/17 23:26, Simon Jester wrote:
On Saturday, October 14, 2017 at 8:43:56 PM UTC+1, TMS320 wrote:
On 14/10/17 15:08, Simon Jester wrote:


So what metric should we use? Passanger miles don't count because
there is only one driver per vehicle.


Passenger miles isn't too bad - even if there is a passenger
variation from 1 to 5; at least they're actually inside the
vehicles that are doing the miles. (I expect Simpson's paradox
would find a strange result between 1 occupant, 5 occupants and
average occupancy - whatever that average is.)


If I drive my car on a given mile of road on my own I pose 5x as much
danger to other road users than if I drive the same mile with 4
passengers, that is what passenger miles tells us.


No. I understood your passenger miles to mean occupant casualties per
vehicle distance. If the number reduces (so long as average number of
people carried per vehicle has not reduced), it is generally considered
to be good development.

  #28  
Old October 17th 17, 02:49 PM posted to uk.rec.cycling
Peter Parry
external usenet poster
 
Posts: 1,164
Default UK cyclists kill or maim two people a week

On Mon, 16 Oct 2017 22:15:16 +0100, TMS320 wrote:

On 15/10/17 18:35, Peter Parry wrote:
On Fri, 13 Oct 2017 00:28:39 +0100, TMS320 wrote:

On 12/10/17 22:11, Peter Parry wrote:
On Thu, 12 Oct 2017 01:07:40 +0100, TMS320 wrote:



Safety (incidence rate) is the quotient of the number of
fatalities/injuries divided by the measure of exposure
(trips/miles/hours).


When the terms are make sense. Vehicle occupants per vehicle distance
does. Pedestrians per vehicle distance does not.


In a vehicle/pedestrian impact I'm not sure why you think there is a
meaningful difference if the car has a driver and three passengers
compared with a driver alone.

Whether you look at impacts per pedestrian or impact per vehicle the
result is going to be the same.

For whatever reason the DfT have chosen to use distance as the measure
of exposure. The problem of course is that no matter what you chose
if it is inadequately measured or missing altogether it forms a poor
basis for planning the future.


Government departments are not unknown to measure apples and pears and
ending up with oranges. You haven't answered the question of why you
think vehicle-distance is meaningful to pedestrians.


You have to have a common base to allow for the detection of trends.
Looking for impacts per pedestrian mile or impacts per pushbike mile
is going to produce the same result.Why they chose the measurement
they have I do not know - but it seems to be used by many road
transport investigators worldwide.

Let's try to be more specific. Let's hypothesise that a significant
proportion of pedestrians suddenly stopped walking. We don't know the
original population or the proportion but we would probably see
casualties per vehicle-distance to reduce. Does it inform us whether the
people that continued to walk are more or less safe?


As long as you have an adequate supply of targets the accident per
unit of distance is sound. If your pedestrian population is exposed to
all the threats you are trying to assess then accidents per x miles is
as valid as any other measure and better than most others.


It isn't sound when targets are unrelated.


The targets are not unrelated. The vehicles (whether cars or
pushbikes) are operating in an environment containing similar numbers
of pedestrians. The absolute numbers of accidents per unit of
distance may differ between urban and rural settings and the ratio of
accidents between pushbikes/pedestrians and cars/pedestrians may alter
between rural and urban settings but these a captured in RAS30018.

The simplest way of stopping all bicycle related accidents whether
vehicle bike or pedestrian bike is to ban bicycling. Overnight the
number drops to zero. However, accident reduction has to take into
account the benefit of the mode of transport as well as the cost.


If cycling was banned the pedestrian casualties would move across to
motor vehicles.


Not necessarily, many cycle/pedestrian accidents involve cyclist
traveling fast on the inside of a slow traffic stream and impacting
pedestrians stepping out from behind obstructions in the expectation
there will be a space there only to find the space contains a cyclist
at speed. Similarly in cities cyclists often ignore pedestrian
crossings and weave between crossing pedestrians. Pedestrians also
often ignore cyclists when crossing the road whereas they would not
risk confrontation with a car. It is by no means certain that
accidents would simply transfer from bikes to cars.

Given the death to injury ratio, we also know that cycle
related injuries are, in general, less severe.


At slow speeds it isn't necessarily so. In cities Pushbikes often
travel faster than cars and whereas cars are designed to give some
degree of pedestrian protection in an accident pushbikes are not.
Indeed some pushbikes sport potentially lethal modifications such as
aerobars, Bullhorn bars and bar ends. Cars are also quicker to stop
than bikes thus avoiding an accident altogether.

It is a fact that cyclist cause more serious injuries to pedestrians
than cars per distance traveled. It is highly probable that far more
pushbike/pedestrian accidents occur than are reported. It is almost
certain that the number of injuries to pedestrians by cyclists is
grossly under reported.


You emphasise accuracy of injury reporting but make no mention of
accuracy of distance reporting.


All of the data collection concerning cycling accidents is inaccurate.
The main impact is seen in the often poor design of measures meant to
reduce pushbike casualties.
  #29  
Old October 18th 17, 09:37 AM posted to uk.rec.cycling
TMS320
external usenet poster
 
Posts: 3,875
Default UK cyclists kill or maim two people a week

On 17/10/17 14:49, Peter Parry wrote:
On Mon, 16 Oct 2017 22:15:16 +0100, TMS320 wrote:

On 15/10/17 18:35, Peter Parry wrote:
On Fri, 13 Oct 2017 00:28:39 +0100, TMS320
wrote:
On 12/10/17 22:11, Peter Parry wrote:
On Thu, 12 Oct 2017 01:07:40 +0100, TMS320
wrote:



Safety (incidence rate) is the quotient of the number of
fatalities/injuries divided by the measure of exposure
(trips/miles/hours).


When the terms are make sense. Vehicle occupants per vehicle
distance does. Pedestrians per vehicle distance does not.


In a vehicle/pedestrian impact I'm not sure why you think there is a
meaningful difference if the car has a driver and three passengers
compared with a driver alone.


I wasn't intentionally connecting vehicle occupants to pedestrian
casualties. I should have said vehicle occupant casualties per vehicle
distance. The cost/benefit of the journey goes to the occupants.

Whether you look at impacts per pedestrian or impact per vehicle the
result is going to be the same.


For whatever reason the DfT have chosen to use distance as the
measure of exposure. The problem of course is that no matter what
you chose if it is inadequately measured or missing altogether it
forms a poor basis for planning the future.


Government departments are not unknown to measure apples and pears
and ending up with oranges. You haven't answered the question of
why you think vehicle-distance is meaningful to pedestrians.


You have to have a common base to allow for the detection of trends.
Looking for impacts per pedestrian mile or impacts per pushbike mile
is going to produce the same result.Why they chose the measurement
they have I do not know - but it seems to be used by many road
transport investigators worldwide.


The French look at it by population... As I said, their figures show no
connection between casualties and vehicle distance, pedestrian or
occupant. The only feature that connects with distance travelled is that
the occupant fatal/injury ratio rises. Perhaps this suggests that trips
over longer distances mean there crashes occur at higher speeds and
there is more likelyhood of the driver falling asleep.

Let's try to be more specific. Let's hypothesise that a
significant proportion of pedestrians suddenly stopped walking.
We don't know the original population or the proportion but we
would probably see casualties per vehicle-distance to reduce.
Does it inform us whether the people that continued to walk are
more or less safe?

As long as you have an adequate supply of targets the accident
per unit of distance is sound. If your pedestrian population is
exposed to all the threats you are trying to assess then
accidents per x miles is as valid as any other measure and better
than most others.


It isn't sound when targets are unrelated.


The targets are not unrelated. The vehicles (whether cars or
pushbikes) are operating in an environment containing similar
numbers of pedestrians. The absolute numbers of accidents per unit
of distance may differ between urban and rural settings and the ratio
of accidents between pushbikes/pedestrians and cars/pedestrians may
alter between rural and urban settings but these a captured in
RAS30018.


We have to disagree.

The simplest way of stopping all bicycle related accidents
whether vehicle bike or pedestrian bike is to ban bicycling.
Overnight the number drops to zero. However, accident reduction
has to take into account the benefit of the mode of transport as
well as the cost.


If cycling was banned the pedestrian casualties would move across
to motor vehicles.


Not necessarily, many cycle/pedestrian accidents involve cyclist
traveling fast on the inside of a slow traffic stream and impacting
pedestrians stepping out from behind obstructions in the expectation
there will be a space there only to find the space contains a
cyclist at speed. Similarly in cities cyclists often ignore
pedestrian crossings and weave between crossing pedestrians.
Pedestrians also often ignore cyclists when crossing the road whereas
they would not risk confrontation with a car. It is by no means
certain that accidents would simply transfer from bikes to cars.


If cycling was banned the ex-riders would not disappear off the face of
the earth. Some would become pedestrians producing pedestrian
casualties, some would increase the number of cars, causing pedestrian
casualties.

Given the death to injury ratio, we also know that cycle related
injuries are, in general, less severe.


At slow speeds it isn't necessarily so. In cities Pushbikes often
travel faster than cars and whereas cars are designed to give some
degree of pedestrian protection in an accident pushbikes are not.
Indeed some pushbikes sport potentially lethal modifications such
as aerobars, Bullhorn bars and bar ends. Cars are also quicker to
stop than bikes thus avoiding an accident altogether.


Bikes are better for going round thus avoiding an accident.

The death to injury ratio (RAS30018 Reported casualties sheet), removing
the vehicle-distance element, is the only thing that provides us with an
indication of the severity of non-fatal injuries in a collision, ie, if
a smaller proportion of injuries convert to death, there must be fewer
life threatening injuries in the mix. Where injuries are under reported
the ratio improves. You provide only speculation.

Pedestrian fatal/serious ratio:-
Urban A road Urban other
cycle - 2.38% 2.56%
mcycl - 2.86% 6.02%
car - 7.9% 3.89%
bus - 11.49% 15.5%
van - 10.00% 6.37%
hgv - 53.59% 33.3%

(The ratio for motorcycles on A roads is a curious one though.)

It is a fact that cyclist cause more serious injuries to
pedestrians than cars per distance traveled. It is highly
probable that far more pushbike/pedestrian accidents occur than
are reported. It is almost certain that the number of injuries
to pedestrians by cyclists is grossly under reported.


You emphasise accuracy of injury reporting but make no mention of
accuracy of distance reporting.


All of the data collection concerning cycling accidents is
inaccurate. The main impact is seen in the often poor design of
measures meant to reduce pushbike casualties.


There measures are more likely to be political and nothing to do with data.
  #30  
Old October 19th 17, 05:51 PM posted to uk.rec.cycling
Peter Parry
external usenet poster
 
Posts: 1,164
Default UK cyclists kill or maim two people a week

On Wed, 18 Oct 2017 09:37:51 +0100, TMS320 wrote:

On 17/10/17 14:49, Peter Parry wrote:
On Mon, 16 Oct 2017 22:15:16 +0100, TMS320 wrote:

On 15/10/17 18:35, Peter Parry wrote:
On Fri, 13 Oct 2017 00:28:39 +0100, TMS320


You have to have a common base to allow for the detection of trends.
Looking for impacts per pedestrian mile or impacts per pushbike mile
is going to produce the same result.Why they chose the measurement
they have I do not know - but it seems to be used by many road
transport investigators worldwide.


The French look at it by population... As I said, their figures show no
connection between casualties and vehicle distance, pedestrian or
occupant.


A vehicle/bike/pedestrian is exposed to the risk of an accident
whenever it is on the road. It would be surprising if the likelihood
of an event turned out to be unrelated to the exposure to the risk be
that in terms of miles traveled or hours driving/walking etc.

You can certainly use the overall measure of accidents per million
inhabitants per year to see if large scale policies are having an
overall effect and you could use the same measure for groups within
the whole - what you cannot do is use the measure of accidents per
million inhabitants to compare the relative probability of an accident
across multiple groups. The French appear to use accidents/million
population for overall figures and accidents/million km for
comparative purposes (for example comparing accidents attributed to
foreign drivers against locals). They also use accidents per hour
when looking at relative risks.

They also lament the poor quality of data collection "Accidents with
pedal cyclists who were hospitalised are very under estimated in the
national register of accidents particularly as the police and
gendarmerie are not always called to these accidents
especially if no motorist is involved."

The death to injury ratio (RAS30018 Reported casualties sheet), removing
the vehicle-distance element, is the only thing that provides us with an
indication of the severity of non-fatal injuries in a collision,


The severity of injury data for more serious injuries at is available
in hospital admission data and has certainly been included is some
studies.

if
a smaller proportion of injuries convert to death, there must be fewer
life threatening injuries in the mix.


Which has no relationship with causation.

You emphasise accuracy of injury reporting but make no mention of
accuracy of distance reporting.


All of the data collection concerning cycling accidents is
inaccurate. The main impact is seen in the often poor design of
measures meant to reduce pushbike casualties.


There measures are more likely to be political and nothing to do with data.


Politicians are not noted for their intelligence and their general
mantra is "Don't just stand there - do something" where "something"
can bear no relationship to the problem. They tend to be overly
influenced by shouty lobby groups (who are also rarely interested in
the truth, their mind is made up and they don't want to be confused by
facts). The civil servants who do make up the briefing papers would
dearly like better facts as they generally do like getting the right
answer.
 




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