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2 hours ago, Rockets said:

150 20mph zones implemented between 1989 and 2013

None of these would have been on the A205 - by that date - or on any of the real cross-London through routes - but clearly on residential and non-through routes (with some 'rat runs' excepted - inadvertent through-routes) from which diversion or slowing of traffic would always have been beneficial. Or precisely the sort of road which I have argued a 20mph limit was entirely appropriate. And where I would have expected there to be a significant impact on pedestrian casualties.

Well most of the time there are road works via  one conpany or another which causes jams all over the place . Not little  ones buy huge  c ones when eg doing works near South Circular or somewhere along Barry Road, Peckham Rye, Lordship Lane etc so one would be lucky to get up to 3/5 miles let alone higher! Same in the city..

But, yup have done a speed awareness course and did register the impact a mile or to above speed limit does to an individual.

Admire anyone who rides a bike in London period - doesn’t matter which borrow.. White vans, lorries, buses, cars, etc .. certainly not for me - rather walk….

 

@Rockets TfL included a cost/benefit analysis showing positive returns in their Strategic Business case for what’s called the ‘Lowering Speed Limits programme’. I believe the benefit / cost ratio was 7.63:1.

There’s plenty of post implementation monitoring data and analysis also.

But does it matter? I’ve never once seen you honestly engage with a piece of road safety data or research. We all know the standard pattern. You lazily state something as true providing no evidence at all and when the data is signposted, you’ll just ignore nearly all of it, to cherry pick anything that tenuously aligns with what you want to believe.

And again, the 20mph limit wasn't designed as a money saving measure, but as an investment in road safety. It’s been extremely successful, saving many lives.

If you want to argue that it’s a poor investment, then it’s really up to you to firstly explain how much you think it is worth spending to save a life, show your ‘alternative’ cost benefit calculation, and then explain what a better, more cost effective intervention would be. 

I have never heard you do anything but argue against every proven road safety measure that’s been implemented in London- so genuinely interested if you have anything constructive to add?

Edited by Earl Aelfheah
On 25/10/2025 at 08:31, Earl Aelfheah said:

TfL included a cost/benefit analysis showing positive returns in their Strategic Business case for what’s called the ‘Lowering Speed Limits programme’. I believe the benefit / cost ratio was 7.63:1.

Do you have the link?

On 25/10/2025 at 08:31, Earl Aelfheah said:

There’s plenty of post implementation monitoring data and analysis also.

Always be deeply suspicious of infographics that have not link to the source. I am not sure how TFL can get away with the source data quote: *This infographic uses statistics from research into 20mph limits and 20mph zones by TfL, DfT, independent academics, city councils and transport consultancies

That wouldn't pass the legal bar the company I work for sources on infographics.....and when you start following the links on the last page of the infographics you realise the claims are headline claims are tenuous at least.....

On 25/10/2025 at 08:31, Earl Aelfheah said:

If you want to argue that it’s a poor investment, then it’s really up to you to firstly explain how much you think it is worth spending to save a life, show your ‘alternative’ cost benefit calculation, and then explain what a better, more cost effective intervention would be. 

@Earl Aelfheah you and I actually agreed that the 20mph limit on the A205 didn't seem to be the most pragmatic approach and I am not arguing it's poor investment just whether TFL or the Mayor's office did the same type of economic analysis that the Welsh government did as there will be an economic impact of slowing traffic - regardless of whether TFL claims that there are "negligible" impacts on journey times - it would be interesting to see what "negligible" actually means as that infographic seems heavy on propaganda and light on the detail.  Very much an infographic aimed at those who love a headline stat but don't bother to look at the data behind it....

 

21 hours ago, Rockets said:

Always be deeply suspicious of infographics that have not link to the source

It has all the raw data in CSV format if you look

21 hours ago, Rockets said:

as there will be an economic impact of slowing traffic

Is there? What is it? What do you think the economic cost of 20mph limit is in London? Tfl suggests it has a positive benefit/cost ratio, although again, it is not intended to be money saving measure, but a road safety intervention.

Are you suggesting that it's an ineffective road safety measure, or that it's an effective one that's too expensive? If it's the latter, what's your evidence for this and what are you suggesting would be a better investment in road safety for the cost you're identifying?

Edited by Earl Aelfheah

You put a monetary value on death and serious injury, based on the costs to the health service and social care, and loss of economic activity.  And other factors such as impact on family and friends?

This report is a bit techy

https://assets.publishing.service.gov.uk/media/5b20bbe240f0b634c24e6265/process-evaluation-of-the-safer-roads-fund-phase-1.pdf

From an earlier life I thought an early death was valued at costing a £million plus.  But AI is out of touch with work I did many years ago.

On 23/10/2025 at 10:29, Rockets said:

Do you have a link to that?

That ^^ from the previous page asking about links to studies on 20mph and effect on journey times...

https://www.ciht.org.uk/news/20mph-speed-limits-mean-more-reliable-journeys/

CIHT is Chartered Institute of HIghways and Transportation. Click on the link above and read the report then there are other links taking you to who they are, what they do etc. 

Your critical point of failure in this argument is assuming that a 30mph limit means people drive at a steady and consistent 30. No-one, in the entire history of the universe, has ever driven along the South Circular at a consistent 30mph. You might get up to 30 (or even 40, although naturally no-one on here has ever exceeded the speed limit at all) but then you'll get to lights, traffic, junctions, a herd of irresponsible cyclists who think they own the road, a badly parked lorry, the front of a school at 3pm.. It is impossible to do a steady 30, you just arrive at the next pinch point or congestion fractionally sooner.

As the report shows, if you smooth the flow out by doing lower speeds, more cars can fit onto the same amount of road, there's less gas / brake / gas / brake that causes so much variance in speed and less wear and tear on your car and the road. And less vibration going through the road means fewer burst water mains too.

Your journey time *might* be fractionally slower at 20mph (although this is highly dependent on how far you're going and on what roads at what time of day) but the variance in journey time (the difference between the slowest journey and the fastest) is less so it's more consistent. And consistency / reliability of journey time is a bigger factor for most people than actual time taken.

  • Agree 2
5 hours ago, Earl Aelfheah said:

It has all the raw data in CSV format if you look

Err, some of those links are tenuous at best and read more like a "we think someone once said this so therefore it must be true". Click the link on the 20mph does not increase journey times one.......;-)

 

5 hours ago, Earl Aelfheah said:

Is there? What is it? What do you think the economic cost of 20mph limit is in London? Tfl suggests it has a positive benefit/cost ratio, although again, it is not intended to be money saving measure, but a road safety intervention.

This is why I am asking if anyone has seen that analysis as the Welsh did it and came up with a figure.

5 hours ago, Earl Aelfheah said:

Are you suggesting that it's an ineffective road safety measure, or that it's an effective one that's too expensive?

No, you and I were both saying that imposing 20mph on the A205 seemed a little bit of overkill - or have you changed your position now?

@exdulwicher Yes exactly, it is likely that in built up areas traffic can flow more freely at 20mph, due to reduced braking distances (enabling drivers to leave a smaller gap to the vehicle in front) and increased junction capacity (as drivers are able to pull into slower traffic more easily).

1 hour ago, Rockets said:
6 hours ago, Earl Aelfheah said:

Is there? What is it? What do you think the economic cost of 20mph limit is in London? Tfl suggests it has a positive benefit/cost ratio, although again, it is not intended to be money saving measure, but a road safety intervention.

This is why I am asking if anyone has seen that analysis as the Welsh did it and came up with a figure.

So you're starting with the statement that there is an economic cost to 20mph in London and then asking if anyone has evidence to prove it? Yes, that follows your usual pattern, but perhaps you can see the problem?

Edited by Earl Aelfheah
53 minutes ago, Earl Aelfheah said:

So you're starting with the statement that there is an economic cost to 20mph in London and then asking if anyone has evidence to prove it? Yes, that follows your usual pattern, but perhaps you can see the problem?

Hang on @Earl Aelfheah where do I state there is an economic impact?You're doing your twisting what was said thing again and misrepresenting what people write. May I suggest you go back and have another read.

Did I just not pose a question based on the economic assessment the Welsh government did and asked whether TFL and/or the mayor had done one as well?

23 minutes ago, Rockets said:

Hang on @Earl Aelfheah where do I state there is an economic impact?

Page 3, a post you made on Oct 23rd:

On 23/10/2025 at 10:29, Rockets said:

Because I am talking about economic impact and when talking about arterial routes like the A205 they used to flow at 30mph and traffic lights were phased to keep it moving as such.

Have you noticed how journeys are now taking longer in London - that has an economic impact.

  • Agree 1
1 hour ago, Rockets said:

Hang on @Earl Aelfheah where do I state there is an economic impact?

...

On 28/10/2025 at 12:00, Rockets said:

there will be an economic impact of slowing traffic - regardless of whether TFL claims that there are "negligible" impacts on journey times

3 hours ago, Rockets said:
8 hours ago, Earl Aelfheah said:

It has all the raw data in CSV format if you look

Err, some of those links are tenuous at best and read more like a "we think someone once said this so therefore it must be true". Click the link on the 20mph does not increase journey times one.......;-)

the CSV files contains raw data. No narrative.

1 hour ago, Rockets said:

Come on @exdulwicher that's what's called doing an @Earl Aelfheah...in the context of the discussion your usage does not stand up to any level of scrutiny! 

It's right there Rockets, you've said that slowing traffic has an economic impact. I'm assuming something something people sitting in their car for longer instead of being at their desk Doing Important Work...?

The flipside is that there's an economic impact to collisions as well.
A vehicle / pedestrian crash at 30mph is about 8x more severe (8x higher likelihood of death) than a crash at 20mph. 
https://www.brake.org.uk/get-involved/take-action/mybrake/knowledge-centre/speed/speed-and-injury

At 20mph you're less likely to crash, if you do crash the consequences are much less severe. You've seen the pics on here of cars on their roofs, cars in central reservations (usually playing them down with the inevitable "we don't know what happened!!") - what about the economic impact of clearing up all that, the delays, the impact on the NHS, the cost to insurance (and ultimately the customer)?

There's an economic impact to congestion as well. At 20mph, traffic flows more smoothly (it's right there in the CIHT report I linked to), journey times are more reliable. There's another (very in depth) report here about driving styles, pollution, journey times and so on also looking at the type of vehicle.

https://futuretransport.info/urban-traffic-research/

Towards the bottom of that page, there is a link to a computer simulation model looking at vehicle sizes, normal stop/go urban traffic and speed limits and the conclusion was that if everyone drove golf cart vehicles at 15mph, everyone would get to the destination faster based on a combination of smaller vehicles being more space-efficient (you can fit more of them through a set of green lights) with lower speed limits reducing congestion and smoothing traffic flow. 

These kind of threads are always entertaining.
20mph in a car is far too slow, inefficient, "economic impact", it's too difficult to drive at 20mph, it's not appropriate on this road blah blah.
20mph on a bike is reckless and foolhardy and hooligan and lycra lout and "what if they hit someone?!"

Standard motorcentric attitude... 

  • Agree 1

The issue with cyclists is to do with increasing incidents of inappropriate, careless/ dangerous cycling on pavements and other pedestrian priority areas. 

I have in the past suggested trying to enforce 20 mph for all cyclists more to counteract the grey area of illegal e-bikes that 'pass' as legal. Melbourne Grove LTN is now a great cut through for motorbikes and e-bike delivery drivers- would any of us want our kids playing in the streets with that going on...?

I should add that these motorbikes or illegal e-bikes often seem to drive well in excess of 20mph, but that is okay? Not only that they use both road and pedestrian areas and they can also cause serious injuries.

In regard to cars, do you really think that 20mph is going to tackle the problem of lunatic borderline criminal behaviour, as is most likely with the Norwood Fountain and the DV central reservation car incident you referred to?

Do you think 20 mph will 'solve' the rare but possible case of a driver having a cardiac arrest or similar at the wheel?

Edited by first mate
33 minutes ago, first mate said:

In regard to cars, do you really think that 20mph is going to tackle the problem of lunatic borderline criminal behaviour, as is most likely with the Norwood Fountain and the DV central reservation car incident you referred to?

Do you think 20 mph will 'solve' the rare but possible case of a driver having a cardiac arrest or similar at the wheel?

Individual crashes - unlikely. Not a lot can stop someone who's determined to drive at 50mph while drunk at 3am.
Collectively (when driving in normal traffic conditions) - yes. All it needs is one car doing 20mph and everyone else behind is forced to drive at 20.
Medical episodes - statistically, medical issues are a factor in about 7% of crashes so it's pretty rare (certainly rare enough to usually not immediately leap to that as a "well the driver could have had a medical episode!" excuse that gets trotted out here as soon as a car ends up in a wall) but if the speed limit is 20, assuming the driver is doing 20-ish at the time they have this incredible coincidence heart attack, the out of control car is going to do less damage than one doing 30mph.

58 minutes ago, exdulwicher said:

Standard motorcentric attitude... 

It seems to many of us that the reason many of these threads exist is because those in power take a very anti-motorcentric view and are not pragmatic in the way these things are rolled out. I mean even @Earl Aelfheah kind of agreed.....

1 hour ago, exdulwicher said:

It's right there Rockets, you've said that slowing traffic has an economic impact. I'm assuming something something people sitting in their car for longer instead of being at their desk Doing Important Work...?

Come on @exdulwicher you're supposed to be an expert on such things and the above comment seems to be deliberately daft - if journeys do take longer can you work out how that might have a negative economic impact (let me give you a clue - it's not about people sitting in cars driving to work......;-)) The Welsh government bothered to model it....and one wonders if TFL did too....

44 minutes ago, Earl Aelfheah said:

And of course 20mph isn’t meant to be a money saving scheme. It’s meant to make roads safer, which it does.

I don't think anyone suggested it was a money saving scheme....it probably makes a few bob mind you....

On Bicycles less than an hour ago:

2 hours ago, first mate said:

The issue with cyclists is to do with increasing incidents of inappropriate, careless/ dangerous cycling on pavements and other pedestrian priority areas. 

I have in the past suggested trying to enforce 20 mph for all cyclists

On cars less than half an hour ago:

1 hour ago, first mate said:

Those addicted to risk, with zero social conscience, do not tend to adhere to any sort of rules. Most if not all the big car crashes or incidents cited on here point to criminal behaviour that will not be changed by 20mph.

Edited by Earl Aelfheah
  • Confused 1
12 minutes ago, exdulwicher said:

assuming the driver is doing 20-ish at the time they have this incredible coincidence heart attack, the out of control car is going to do less damage than one doing 30mph.

Yes, agreed and for those rare, 7% of crashed/incidents 20mph will help mitigate damage but it will have probably have zero effect on the risk taker/criminal driver.

That was organised a couple of years ago as I participated.. was very interesting. Clearly remember two cars zipping along so fast, couldn’t even get number plate!! 

So what is the point ? Raise awareness to drivers and now it is on EDF forum, those who speed along will just slow down and no doubt let friends etc know speed  will be monitored which totally defeats the object of the exercise..-  will prob catch say 50/100 if not - total waste of time.. 

Thought object was speeders not to know where it was happening or time ie surprise element and  I am speaking from past experience.

For those not use to this sort of community event - the idea is your presence and number place recognition means that the owner of car not individual driver  who may be anyone using car will be sent a caution letter from police.

All this said, will be interested to hear just how many were caught speeding on this day and time and if my guess is right..

 

 

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