Change in speed restriction on Sydenham HIll 30m/h to 20m/h

[_HB]

It's quite simple, really. If you hit someone at 30 you will kill them. If you hit them at 20, you won't. 20 mph is more than enough in towns and cities.

Given the enormous toll taken on life and limb in this city by motor vehicles, blanket reductions in speed limits (that's LIMIT, not TARGET), is the very, very least a responsible public body can do.

But, the sentiment above is mostly, sadly correct. These limits will not be respected or enforced. And the cognitive dissonance continues...

[Tim Lund]

Once the penalty notices start to flood in, they'll realise the limit has changed.

https://www.youtube.com/watch?v=sb_4_C2U7e8


Ker-ching - £££££'s

What is the issue with levying taxes on anti-social behaviour, if that is not too gentle a word for defying the law to drive at potentially lethal speeds in cities?

BTW, should this be in the café?

[JRobinson]

I think 20 is too slow!
I drive a focus, nothing fancy, a 1.6. Am I expected to drive in third gear without using the accelerator? Constantly braking?

You could try driving in second gear - it's designed for slower speeds, and you wouldn't need to brake as much, just taking your foot off the accelerator slows you down a lot quicker than braking does (from 20mph in 2nd gear)

Surely, the roads could be made wider in many places, but it is always the pavement or massive verge which is improved.

in some places roads could be made wider, but this encourages speeding, and dangerous overtaking - surely the wide roads should be made narrower, and the pavement wider (or segregated cycle lanes put in), so that traffic naturally slows down.

Modern cars are designed for an economical gear ratio to engine speed.

Correct

The road is designed without the car in mind.

There are some people in my office, called transport planners, and highways engineers, who would disagree with you there... in fact I think the vast majority would tell you that roads are designed specifically with the car in mind, and not the pedestrian, cyclist, motorbike, bus, lorry, HGV, etc, etc.

Maybe we should just go back to cobblestones and wooden wheels. We can all drive at 20 and still road deaths would not decrease, more and more vehicles on over crowded roads every day adds to the problem

yes, lets all go back to the dark ages, or mediaeval times, with highway robbery, and a life expectancy of 40 ish.
maybe just get rid of all wheels - what good have wheels ever been to us anyway? without wheels there'd be no road deaths at all!

.

[GemStone]

Hello there JRobinson, many thanks for pulling me up on almost everything I said. I trust you had a splendid Christmas and are still in a cheery festive mood - or perhaps not

I think 20 is too slow!
I drive a focus, nothing fancy, a 1.6. Am I expected to drive in third gear without using the accelerator? Constantly braking?

You could try driving in second gear - it's designed for slower speeds, and you wouldn't need to brake as much, just taking your foot off the accelerator slows you down a lot quicker than braking does (from 20mph in 2nd gear)

(1) - Not very economical 2nd gear though is it? The engine would be far happier doing 2500 rpm in 3rd, rather than 3500 rpm in 2nd. Please refer to quote 3

Surely, the roads could be made wider in many places, but it is always the pavement or massive verge which is improved.

in some places roads could be made wider, but this encourages speeding, and dangerous overtaking - surely the wide roads should be made narrower, and the pavement wider (or segregated cycle lanes put in), so that traffic naturally slows down.

(2) - & becomes congested, more Co2 polluting the atmosphere and higher consumption of fuel.

Modern cars are designed for an economical gear ratio to engine speed.

Correct (3) - Thanks, (Qu1. 'economical')

The road is designed without the car in mind.

There are some people in my office, called transport planners, and highways engineers, who would disagree with you there... in fact I think the vast majority would tell you that roads are designed specifically with the car in mind, and not the pedestrian, cyclist, motorbike, bus, lorry, HGV, etc, etc.

(4) - An obviously biased opinion then if the people in your office are so-called transport planners, and highways engineers. Naturally they'd disagree. They are the kind of idiots who have caused the problems. I suppose your highly talented office colleagues are responsible for traffic calming speed humps, width restriction slaloms and bits of jutting out kerbs, I wonder, do they also repair pot holes too?

Maybe we should just go back to cobblestones and wooden wheels. We can all drive at 20 and still road deaths would not decrease, more and more vehicles on over crowded roads every day adds to the problem

yes, lets all go back to the dark ages, or mediaeval times, with highway robbery, and a life expectancy of 40 ish.
maybe just get rid of all wheels - what good have wheels ever been to us anyway? without wheels there'd be no road deaths at all!

(5) - Nah, I'm sure even a sleigh would cause at least some road death injury.
But hey, what a great idea, I like it, getting rid of wheels and going back to the dark ages and not living longer than 40.

......But from your answers, you have at least 30 years to go until you reach that fine old age

.

[_HB]

^^^^



I may have already cited cognitive dissonance on this thread

[14BradfordRoad]

Once the penalty notices start to flood in, they'll realise the limit has changed.

https://www.youtube.com/watch?v=sb_4_C2U7e8


Ker-ching - £££££'s

What is the issue with levying taxes on anti-social behaviour, if that is not too gentle a word for defying the law to drive at potentially lethal speeds in cities?

Tim, it's just a bit of humour. No offense intended.
Let's not encourage more cognitive dissonance.

BTW, should this be in the café?

Thanks mate, I'll have a coffee with no sugar.

[JRobinson]

@Gemstone - I assumed you were on a wind up, so replied in kind.

obviously not!

Happy New Year!

[JRobinson]

(1) - Not very economical 2nd gear though is it? The engine would be far happier doing 2500 rpm in 3rd, rather than 3500 rpm in 2nd. Please refer to quote 3

- If you're after economy - try leaving the car at home for any journey less than 5 miles. walk, cycle, or take public transport. much more economical, and you don't need to worry about speed limits.

(2) - & becomes congested, more Co2 polluting the atmosphere and higher consumption of fuel.

- actual difference in levels of congestion between 20 and 30 mph limits is quite small, but there is evidence to suggest that lower limits give less congestion (counterintuitively) - consider a motorway, there can be congestion if everyone is trying to go at 70 mph, however with automatic speed limit signs, when traffic builds up, the speed limit is reduced to 60 (or 50 or 40), and the cars bunch up less, and the amount of 'congestion' is reduced - traffic is free flowing (but slower), rather than stationary in places. Same with 20/30 limits - with a 20 limit traffic takes longer to get to junctions that cause stopping, so congestion is reduced, cars are spread out more along the available space.

(4) - An obviously biased opinion then if the people in your office are so-called transport planners, and highways engineers. Naturally they'd disagree. They are the kind of idiots who have caused the problems. I suppose your highly talented office colleagues are responsible for traffic calming speed humps, width restriction slaloms and bits of jutting out kerbs, I wonder, do they also repair pot holes too?

is any informed opinion unbiased?
they're not 'so-called' - that is their job titles, and what they actually do. for a living. with qualifications, training, etc. I'll tell them that you think they're idiots, but they probably already know that some people (those who know nothing about traffic flow, or traffic management) think they're idiots. They do do all of those things listed. They don't do the pot hole repairs themselves, there are contractors for that, but yes it's that same department. The Design and Engineering team do the designs for new road layourts, improvements etc. The Highways maintenance team deal with repairs, maintenance, etc.

... and not living longer than 40.
......But from your answers, you have at least 30 years to go until you reach that fine old age.

I guess that makes us about the same age then

[stuart]

JRobinson, I agree with you on most points but I will take you up on one: reducing speed reduces congestion.

This is true at high speed. It is why on the M25 at peak times they reduce the speed limit from 70 to 50mph. That is the sweet point for maximum traffic flow. Its a complicated mathematical thing but traffic flow v speed is n shaped peaking around 50mph. That's practical on motorways, impractical in Sydenham. Traffic flow decreases if you go very fast or very slow. Its counter-intuitive but well proven.

That's something traffic engineers know but have been called worse than idiots by people who don't understand why they do it.

I do need to take GemStone up on the claim that our roads are not designed for motor vehicles. I think you should take a long hard look at some road developments around us. Who else would you say the Bell Green gyratory was designed for?

Anoher example was the consultation for Sydenham Road. The needs expressed by pedestrians and others was over ruled by the traffic engineers as they were under instruction to 'maximise traffic flow'. Arup were the consultants and we were treated to nice little simulations which showed how people got in the way of cars (which they do). So maximising car flow required them to impede other road users. That's why our zebra crossing disappeared. They were also instructed to maximise on-street parking.

They did their job as best they could. Car drivers may consider the achieved result in minimising their time in Sydenham Road hasn't been too successful but they can't argue that the impeding other users wasn't a great success! (with the one great exception of pedestrians crossing Newlands Park).

I don't blame the engineers. It was those that laid down their criteria who should take full responsibility.

Getting back to 20mph. The reason why Southwark are pushing ahead is probably based on this ground breaking paper: http://www.bmj.com/content/320/7243/1160. It's claim based on evidence from roads in London was that the reduction in speed (if enforced by passive means) led to a reduction in KSIs of around 40% - more for the most vulnerable road users (kids). If this is true - and I am not aware of any equally researched paper debunking it - then it is the single most effective way a council can act to reduce road casualties.

So well done Southwark. Shame on Lewisham.

Stuart

[_HB]

Getting back to 20mph. The reason why Southwark are pushing ahead is probably based on this ground breaking paper: http://www.bmj.com/content/320/7243/1160. It's claim based on evidence from roads in London was that the reduction in speed (if enforced by passive means) led to a reduction in KSIs of around 40% - more for the most vulnerable road users (kids). If this is true - and I am not aware of any equally researched paper debunking it - then it is the single most effective way a council can act to reduce road casualties.

Stuart - Is that BMJ stat of 40% based on 20 mph zones that have been in operation? Or is it based on some other data around collisions and their effects? (Apologies, I don't see a way of reading it without signing up).

If it is the former then that is a very powerful stat given that the 40% reduction is being achieved in existing 20mph schemes the vast majority of which go unrespected and unenforced.

[stuart]

Stuart - Is that BMJ stat of 40% based on 20 mph zones that have been in operation? Or is it based on some other data around collisions and their effects? (Apologies, I don't see a way of reading it without signing up).

Yep, sadly it has now gone behind a paywall which is a great shame. it used to be freely readable. Is it worth trying to chase it down at archive.org?

The study was of roads in London that had 20 mph limits and passive enforcement. They were matched with roads with 30 mph limits without passive enforcement. They found a reduction in average speed from 27 to 17 mph. Such a speed reduction would be expected to have a very significant impact (sic). That is both the driver and the victim have much longer to spot the danger, have longer thinking time to take avoiding action. Hence collisions would be reduced and the kinetic energy of any unavoidable collision very much reduced. Isn't it the square of the impact speed? Hence a K might well become a SI and a SI a bruise or nowt.

The credibility of the paper rested on the accurate matching of the roads. I obviously can't check on that - but the power of the paper should have got well funded organisations with other agendas to check it out. I'm not aware that they found much to argue with. But if GemStone has found some contrary research evidence than I'm sure we would all like to see it.

Stuart

[JRobinson]

further a quote from a recent paper I've seen on introducing a 20mph limit on A and B roads in this (where I work) borough

Speed is a major contributory cause of road accidents. Every 1 mph reduction
in the average speed brings a 5% reduction in the number of accidents,
whereas an increase of 1 mph by the faster drivers leads to a 19% increase in
accidents. Higher speeds also lead to more severe injuries, in a collision with
a vehicle travelling at 20mph most pedestrians survive but with a vehicle
travelling at 40mph most do not. The management of vehicle speed is
therefore a key element of road casualty reduction. 20mph zones I speed
limits are a proven method of reducing vehicle speeds and casualties on
residential roads.
Since the introduction of 20mph limit on residential roads the number of traffic
accidents in 20mph zones fell by upto 50 percent and it is hoped that by
extending the scheme to major roads further reductions of approximately 10
percent can be achieved.
Portsmouth was the first local authority in the UK to introduce a 20mph speed
limit on all residential roads. In London, borough-wide 20mph limits have
already been adopted by four local authorities- Southwark,
Camden, Islington and City of London, while Lambeth, Haringey, Greenwich
and Waltham Forest have committed to 20mph limits
Whilst more evidence is needed on the long term effectiveness of default 20
mph speed limits, that which is currently available has demonstrated some
promising results. The scheme in Portsmouth has been independently
evaluated and showed that it has been associated with reduced traffic speeds
and casualty figures.

[alywin]

It's a long time since I've driven (I was living around Birkbeck at the time), but I do remember that with my 1-litre engine I had to push 30 mph just to make it up the hill of Elmers End Road around the crematorium. I don't know Sydenham Hill as a road, but presume that its name describes it accurately: can a small-engined car actually get up it safely at 20 mph?

I also remember my driving instructor telling me that optimal in-town driving in terms of reducing fuel consumption/pollution would be achieved at around 28 mph in 4th gear. I don't know how much engines have improved in the last couple of decades, but I know that hovering around the 2nd/3rd-gear border used to be pretty bad pollution-wise. If that's still the case, then while there may be a significant reduction in accidents, do the reduced death rates take into consideration increased numbers of people dying from pollution-related causes?

Ironically, back in my Birkbeck days, Bromley Council sent us round a notice telling us that our area had been identified as having a higher-than-average accident rate so we were going to be turned into a 20-mph zone and have speed reduction measures introduced. You can see where this would end up, can't you? Once our accident rate was reduced, somewhere else would be higher than average and made into another 20 mph zone. And so on and so on. Once everywhere had been reduced to 20 mph, we might well go back to having a higher-than-average accident rate, and need to be reduced to perhaps 15 mph ...

[Eagle]

Alywin

20 mph is I think about right for urban areas as long as it is properly policed , either by cameras or actual Police.

How many people abuse the current 30 mph limit and how many get punished.