speed limits: do they work? (of course not)

speed limits: do they work? (of course not)

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Discussion

vonhosen

40,249 posts

218 months

Friday 14th August 2015
quotequote all
Skyline33 said:
vonhosen said:
What is your source/authority for that?
Really! try google you'll find hits from the dft, and the majority of state traffic depts from the U.S.
Yes really!
Just provide a link please showing it is to show the maximum safe speed in optimal conditions. UK would be best as that's where we are talking about.

It shows the maximum 'permitted' speed in optimal conditions but it's never defined the maximum 'safe' speed in optimal conditions.


Edited by vonhosen on Friday 14th August 23:42

Skyline33

32 posts

192 months

Saturday 15th August 2015
quotequote all
vonhosen said:
Yes really!
Just provide a link please showing it is to show the maximum safe speed in optimal conditions. UK would be best as that's where we are talking about.

It shows the maximum 'permitted' speed in optimal conditions but it's never defined the maximum 'safe' speed in optimal conditions.


Edited by vonhosen on Friday 14th August 23:42
As limits used to be set using the 85th percentile concept which is acknowledged through out the world as the MAXIMUM SAFE speed in optimum conditions. Therefore by definition limits used to be set at the maximum SAFE level. This method was quietly changed to the mean speed which results in speed limits set at around the 50th percentile, therefor penalising and needlessly criminalising 50% of otherwise safe drivers.

My statement is correct.

vonhosen

40,249 posts

218 months

Saturday 15th August 2015
quotequote all
Skyline33 said:
vonhosen said:
Yes really!
Just provide a link please showing it is to show the maximum safe speed in optimal conditions. UK would be best as that's where we are talking about.

It shows the maximum 'permitted' speed in optimal conditions but it's never defined the maximum 'safe' speed in optimal conditions.


Edited by vonhosen on Friday 14th August 23:42
As limits used to be set using the 85th percentile concept which is acknowledged through out the world as the MAXIMUM SAFE speed in optimum conditions. Therefore by definition limits used to be set at the maximum SAFE level. This method was quietly changed to the mean speed which results in speed limits set at around the 50th percentile, therefor penalising and needlessly criminalising 50% of otherwise safe drivers.



My statement is correct.
That doesn't give you 'the' maximum safe speed in optimal conditions.

The 85th percentile does no such thing. You attribute incorrect meanings/relationships to the 85th percentile.

To find the 'true' 85th percentile anyway you'd need to have no speed limit in the first place. There are limits in place before an 85th percentile is measured, so you don't get a true reading (of what people would potentially choose unhindered) because the limit will be influencing speed choice.

Even then the 85th percentile doesn't tell you the maximum safe speed in optimal conditions (the maximum being an extreme), because it doesn't take all the variables into consideration. It can be possible for an individual driver to safely drive above the 85th percentile in certain circumstances. One limit will never fit all variables so can't be described as the maximum safe speed in optimal conditions.

Saying limits should be/are/or were set at the 85th percentile is entirely different to equating the 85th percentile with showing the maximum safe speed in optimal conditions. The limit weren't set exactly at the 85th percentile either & it was never gained by measuring speed solely in optimal conditions. The limit wouldn't be set exactly at any 85th percentile, it would be rounded, or are you saying that it would just happen to be measured & found to exactly equate to all those 30, 40, 50, 60, etc limits by some chance?
The 85th percentile would never be (say for instance) 48.9 & the limit set at 50 having used it?


I notice you didn't provide a link.


Edited by vonhosen on Saturday 15th August 02:03

g3org3y

20,639 posts

192 months

Saturday 15th August 2015
quotequote all
Skyline33 said:
We do need speed limits, but they have to be credible. We need to acknowledge that the most important skill in safe driving is hazard perception, concentration and driving to the conditions and the answer is education. The usual suspects will come back with the usual drivel - drivers can't be trusted, one speeding lunatic means they're all speeding lunatics. Of course the winner in the complete utter horse st awards - without speed limits they'd just drive everywhere as fast as possible!
Indeed. The apparent random (and widespread) nature by which roads in London have been made 20mph zones blow any credibility they had out the water. Completely inappropriate in almost every location. No-one obeys them (unless over Tower Bridge's average speed section) and all they do is reduce respect for all other limits.

Smiler.

11,752 posts

231 months

Saturday 15th August 2015
quotequote all
Skyline33 said:
We do need speed limits, but they have to be credible. We need to acknowledge that the most important skill in safe driving is hazard perception, concentration and driving to the conditions and the answer is education. The usual suspects will come back with the usual drivel - drivers can't be trusted, one speeding lunatic means they're all speeding lunatics. Of course the winner in the complete utter horse st awards - without speed limits they'd just drive everywhere as fast as possible!
This will probably come across as condescending but it's not meant to be........

Your reply is firmly from the centre of "the thought-out world of PH rationale".

Just because you have (admirably) developed your ability to drive based upon perception of hazards & concentration on the job in hand, doesn't mean the greater proportion of the unwashed masses either do, or wish to do the same.

There are also a few holes in your assumptions, namely that hazard perception is not infallible & in many cases, one doesn't realise that a hazard has materialised until it's too late. I'd suggest that a reduction of velocity is the obvious counter to such an event.


Anecdotal I know but the majority of vehicles that use the main routes though our village exceed the 30 speed limit. Government stats would suggest the figure to be at 47%




A couple of questions for you:

Do you think that built-up residential areas are right to have 30 (and in some cases 20) limits & should be rigorously enforced?

Do you maintain 20 & 30 limits whenever you drive in them?

Skyline33

32 posts

192 months

Saturday 15th August 2015
quotequote all
vonhosen said:
That doesn't give you 'the' maximum safe speed in optimal conditions.

The 85th percentile does no such thing. You attribute incorrect meanings/relationships to the 85th percentile.

To find the 'true' 85th percentile anyway you'd need to have no speed limit in the first place. There are limits in place before an 85th percentile is measured, so you don't get a true reading (of what people would potentially choose unhindered) because the limit will be influencing speed choice.

Even then the 85th percentile doesn't tell you the maximum safe speed in optimal conditions (the maximum being an extreme), because it doesn't take all the variables into consideration. It can be possible for an individual driver to safely drive above the 85th percentile in certain circumstances. One limit will never fit all variables so can't be described as the maximum safe speed in optimal conditions.

Saying limits should be/are/or were set at the 85th percentile is entirely different to equating the 85th percentile with showing the maximum safe speed in optimal conditions. The limit weren't set exactly at the 85th percentile either & it was never gained by measuring speed solely in optimal conditions. The limit wouldn't be set exactly at any 85th percentile, it would be rounded, or are you saying that it would just happen to be measured & found to exactly equate to all those 30, 40, 50, 60, etc limits by some chance?
The 85th percentile would never be (say for instance) 48.9 & the limit set at 50 having used it?


I notice you didn't provide a link.


Edited by vonhosen on Saturday 15th August 02:03
I haven't provided a link because the objections you are making don't warrant it. The 85th percentile is widely documented and used in practice throughout the world for decades. The process indeed is once the 85th percentile I'd established in free flowing traffic conditions. The figure is rounded up to the nearest 10mph.

Skyline33

32 posts

192 months

Saturday 15th August 2015
quotequote all
Smiler. said:
This will probably come across as condescending but it's not meant to be........

Your reply is firmly from the centre of "the thought-out world of PH rationale".

Just because you have (admirably) developed your ability to drive based upon perception of hazards & concentration on the job in hand, doesn't mean the greater proportion of the unwashed masses either do, or wish to do the same.

There are also a few holes in your assumptions, namely that hazard perception is not infallible & in many cases, one doesn't realise that a hazard has materialised until it's too late. I'd suggest that a reduction of velocity is the obvious counter to such an event.


Anecdotal I know but the majority of vehicles that use the main routes though our village exceed the 30 speed limit. Government stats would suggest the figure to be at 47%




A couple of questions for you:

Do you think that built-up residential areas are right to have 30 (and in some cases 20) limits & should be rigorously enforced?

Do you maintain 20 & 30 limits whenever you drive in them?
Without wishing to be argumentative, you unfortunately do come across as condescending. Who are the "great unwashed"?

Essentially you are expressing an opinion that isn't supported by fact. The vast majority are reasonable drivers who simply want to get from A to B without incident and take care accordingly. Should we educate people to do this better? Absolutely, there are many many people whose driving record suggests that the best way of preventing accidents is through improving driving skills.

You ask the question about enforcing speed limits? What does enforcement achieve? It means drivers match their speedo to a number on a pole and if the rhetoric is to be believed we hit people at slower speeds.

What are the negatives? In poor weather conditions and high hazard density the limit is too fast for the conditions rendering enforcement pointless. Observation suffers because drivers run the risk losing their licence in a rigorously enforced limit. It does not address the issue of concentration or assessing hazard density. It doesn't teach the skill of anticipation or taking into account potential accident situations.

The answer to your question is that I judge my speed according to actual and perceived hazards and my stopping distance in the event of the unexpected.

Road safety should be about teaching and prioritising accident prevention or "not hitting people at all", trouble is there's no revenue in that though!

My question to you is hypothetical: what would happen if you or I were driving along and the speedo stopped working. Would You or I suddenly become an unsafe or dangerous driver because we can no longer match speed to a number on a poll?

robinessex

11,068 posts

182 months

Saturday 15th August 2015
quotequote all
Ok. Firstly, there is an organisation doing it's best for the motorist, it's called ABD.

http://www.abd.org.uk/
http://www.abd.org.uk/topics/speed_limits.htm
http://www.abd.org.uk/topics/speed_cameras.htm
http://www.abd.org.uk/topics/road_safety.htm

ALL PH'ers should belong to it. They have published numerous papers re speed limits, how to determine them, their implementation, inappropriate levels etc. So Mr OP, if you are really keen to 'do something', join up, and I'm sure they will be delighted with your offers of assistance.

vonhosen

40,249 posts

218 months

Saturday 15th August 2015
quotequote all
Skyline33 said:
vonhosen said:
That doesn't give you 'the' maximum safe speed in optimal conditions.

The 85th percentile does no such thing. You attribute incorrect meanings/relationships to the 85th percentile.

To find the 'true' 85th percentile anyway you'd need to have no speed limit in the first place. There are limits in place before an 85th percentile is measured, so you don't get a true reading (of what people would potentially choose unhindered) because the limit will be influencing speed choice.

Even then the 85th percentile doesn't tell you the maximum safe speed in optimal conditions (the maximum being an extreme), because it doesn't take all the variables into consideration. It can be possible for an individual driver to safely drive above the 85th percentile in certain circumstances. One limit will never fit all variables so can't be described as the maximum safe speed in optimal conditions.

Saying limits should be/are/or were set at the 85th percentile is entirely different to equating the 85th percentile with showing the maximum safe speed in optimal conditions. The limit weren't set exactly at the 85th percentile either & it was never gained by measuring speed solely in optimal conditions. The limit wouldn't be set exactly at any 85th percentile, it would be rounded, or are you saying that it would just happen to be measured & found to exactly equate to all those 30, 40, 50, 60, etc limits by some chance?
The 85th percentile would never be (say for instance) 48.9 & the limit set at 50 having used it?


I notice you didn't provide a link.


Edited by vonhosen on Saturday 15th August 02:03
I haven't provided a link because the objections you are making don't warrant it. The 85th percentile is widely documented and used in practice throughout the world for decades. The process indeed is once the 85th percentile I'd established in free flowing traffic conditions. The figure is rounded up to the nearest 10mph.
Free flowing conditions that are already subject to a speed limit!

I'm not saying the 85th percentile doesn't exist or isn't a method that was used to determine speed limits. I'm saying it doesn't equate with what you claimed it represented. That is it does not tell you what the maximum safe speed is in optimal conditions. So please provide a link that says its says what you say it does.

Not everybody travelling at a speed above the 85th percentile will be doing so dangerously, ergo the 85th percentile is not the maximum safe speed.

You appear to be preaching about something you don't understand.

So which is it now?

Are you saying that everybody who travelled 'at' the speed limit which was set using the 85th percentile was driving unsafe (after all it's rounded up & they are exceeding it)?
OR
Are you saying that everybody who exceeded that limit in optimal conditions was driving unsafe?


Is the 85th percentile the maximum safe speed in optimum conditions?
OR
Is it the speed limit it's rounded up to the maximum safe speed in optimum conditions?


I'll give you a clue
Neither are true/correct.




Edited by vonhosen on Saturday 15th August 11:04

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
robinessex said:
Ok. Firstly, there is an organisation doing it's best for the motorist, it's called ABD.

http://www.abd.org.uk/
http://www.abd.org.uk/topics/speed_limits.htm
http://www.abd.org.uk/topics/speed_cameras.htm
http://www.abd.org.uk/topics/road_safety.htm

ALL PH'ers should belong to it. They have published numerous papers re speed limits, how to determine them, their implementation, inappropriate levels etc. So Mr OP, if you are really keen to 'do something', join up, and I'm sure they will be delighted with your offers of assistance.
Excellent post. Thank you.

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
anonymous said:
[redacted]
I think if you are trying to detract from that post and desire to be understood it will be helpful if you explain your reasoning, possibly without religious references, though it is of course entirely up to you if you want to offer any foundation for what you have to say - unless it's no more than how you feel in which case enough said.

Skyline33

32 posts

192 months

Saturday 15th August 2015
quotequote all
vonhosen said:
Free flowing conditions that are already subject to a speed limit!

I'm not saying the 85th percentile doesn't exist or isn't a method that was used to determine speed limits. I'm saying it doesn't equate with what you claimed it represented. That is it does not tell you what the maximum safe speed is in optimal conditions. So please provide a link that says its says what you say it does.

Not everybody travelling at a speed above the 85th percentile will be doing so dangerously, ergo the 85th percentile is not the maximum safe speed.

You appear to be preaching about something you don't understand.

So which is it now?

Are you saying that everybody who travelled 'at' the speed limit which was set using the 85th percentile was driving unsafe (after all it's rounded up & they are exceeding it)?
OR
Are you saying that everybody who exceeded that limit in optimal conditions was driving unsafe?


Is the 85th percentile the maximum safe speed in optimum conditions?
OR
Is it the speed limit it's rounded up to the maximum safe speed in optimum conditions?


I'll give you a clue
Neither are true/correct.




Edited by vonhosen on Saturday 15th August 11:04
Which percentile would you prefer 90th? 95th? You are engaged in an argument of pointless pedantry which has no bearing or value on using the 85th percentile the best way to set speed limits.

tapereel

1,860 posts

117 months

Saturday 15th August 2015
quotequote all
Skyline33 said:
Smiler. said:
This will probably come across as condescending but it's not meant to be........

Your reply is firmly from the centre of "the thought-out world of PH rationale".

Just because you have (admirably) developed your ability to drive based upon perception of hazards & concentration on the job in hand, doesn't mean the greater proportion of the unwashed masses either do, or wish to do the same.

There are also a few holes in your assumptions, namely that hazard perception is not infallible & in many cases, one doesn't realise that a hazard has materialised until it's too late. I'd suggest that a reduction of velocity is the obvious counter to such an event.


Anecdotal I know but the majority of vehicles that use the main routes though our village exceed the 30 speed limit. Government stats would suggest the figure to be at 47%




A couple of questions for you:

Do you think that built-up residential areas are right to have 30 (and in some cases 20) limits & should be rigorously enforced?

Do you maintain 20 & 30 limits whenever you drive in them?
Without wishing to be argumentative, you unfortunately do come across as condescending. Who are the "great unwashed"?

Essentially you are expressing an opinion that isn't supported by fact. The vast majority are reasonable drivers who simply want to get from A to B without incident and take care accordingly. Should we educate people to do this better? Absolutely, there are many many people whose driving record suggests that the best way of preventing accidents is through improving driving skills.

You ask the question about enforcing speed limits? What does enforcement achieve? It means drivers match their speedo to a number on a pole and if the rhetoric is to be believed we hit people at slower speeds. What are the negatives? In poor weather conditions and high hazard density the limit is too fast for the conditions rendering enforcement pointless. Observation suffers because drivers run the risk losing their licence in a rigorously enforced limit. It does not address the issue of concentration or assessing hazard density. It doesn't teach the skill of anticipation or taking into account potential accident situations.

The answer to your question is that I judge my speed according to actual and perceived hazards and my stopping distance in the event of the unexpected.

Road safety should be about teaching and prioritising accident prevention or "not hitting people at all", trouble is there's no revenue in that though!

My question to you is hypothetical: what would happen if you or I were driving along and the speedo stopped working. Would You or I suddenly become an unsafe or dangerous driver because we can no longer match speed to a number on a poll?
What evidence do you have that any kind of drivers stick to the limit because they think it is what speed they can and should drive at? I don't know anyone who does that nor have I seen any sort of study or evidence that anyone does.

Seemslike you want evidence of any view contrary to yours but won't evidence the justification for your views.

Drivers driving at the "speed on the stick" ... complete bollix IMHO.

Dammit

3,790 posts

209 months

Saturday 15th August 2015
quotequote all
robinessex said:
Ok. Firstly, there is an organisation doing it's best for the motorist, it's called ABD.

http://www.abd.org.uk/
http://www.abd.org.uk/topics/speed_limits.htm
http://www.abd.org.uk/topics/speed_cameras.htm
http://www.abd.org.uk/topics/road_safety.htm

ALL PH'ers should belong to it. They have published numerous papers re speed limits, how to determine them, their implementation, inappropriate levels etc. So Mr OP, if you are really keen to 'do something', join up, and I'm sure they will be delighted with your offers of assistance.
In the same way that UKIP are doing their best for Britain.

The ABD are, to a man, thick as a prison door with the ethics of Lord Janner.

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
tapereel said:
What evidence do you have that any kind of drivers stick to the limit because they think it is what speed they can and should drive at? I don't know anyone who does that nor have I seen any sort of study or evidence that anyone does.

Seemslike you want evidence of any view contrary to yours but won't evidence the justification for your views.

Drivers driving at the "speed on the stick" ... complete bollix IMHO.
pot calling the kettle black. Where is YOUR evidence?

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
Dammit said:
robinessex said:
Ok. Firstly, there is an organisation doing it's best for the motorist, it's called ABD.

http://www.abd.org.uk/
http://www.abd.org.uk/topics/speed_limits.htm
http://www.abd.org.uk/topics/speed_cameras.htm
http://www.abd.org.uk/topics/road_safety.htm

ALL PH'ers should belong to it. They have published numerous papers re speed limits, how to determine them, their implementation, inappropriate levels etc. So Mr OP, if you are really keen to 'do something', join up, and I'm sure they will be delighted with your offers of assistance.
In the same way that UKIP are doing their best for Britain.

The ABD are, to a man, thick as a prison door with the ethics of Lord Janner.
Interesting. Evidence please. Maybe you can persuade me.

Dammit

3,790 posts

209 months

Saturday 15th August 2015
quotequote all
No problem, here you go: http://www.abd.org.uk

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
Dammit said:
No problem, here you go: http://www.abd.org.uk
that is not evidence, that is a link to their web site.

Dammit

3,790 posts

209 months

Saturday 15th August 2015
quotequote all
anthonym said:
that is not evidence, that is a link to their web site.
If you can read, and think critically, it's all the evidence you need.

It's primary evidence - you can't get better.

So I'm afraid you are demonstrably incorrect in your assertion.

anthonym

Original Poster:

51 posts

176 months

Saturday 15th August 2015
quotequote all
anonymous said:
[redacted]
Doesn't seem to stop you making all your own replies, whether I reply or not or whether you are clear about what I mean or not, and you say not. That suggests any further reply I make to you will receive your standard detractions based on your beliefs (no evidence offered), which is to waste my time since you are not the audience to whom I write. Others here are and I clearly do not need to add anything for them. You are welcome to explain your beliefs if you want to, and I will read with interest.

If you can refrain from hostility that would be helpful, as you say passive aggressiveness is not constructive and you engage in it too, though less passive methinks. You will no doubt understand that responding to hostility without being aggressive is difficult. If I engage in anything that has any appearance of being aggressive or hostile I regret it and certainly do not have that intention.