TfL Vision Zero: Lower Speed Limits

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Re: TfL Vision Zero: Lower Speed Limits

Post by WHBM » Tue Sep 14, 2021 23:42

Notable that today's multi-fatal high speed accident in Paddington, where the car ploughed into buildings, destroying these, was in a new 20mph section ...

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Re: TfL Vision Zero: Lower Speed Limits

Post by Bryn666 » Wed Sep 15, 2021 00:30

Have you actually got causation for that incident or are you just trying to score a gotcha?
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Re: TfL Vision Zero: Lower Speed Limits

Post by FosseWay » Wed Sep 15, 2021 08:43

thatapanydude wrote:
Fri Sep 10, 2021 13:20
My views on this is that the A13 is the least concerning as you have the parallel A1203 which is much better to use to Canary Wharf, however section 6.1 96) of the DfT Speed Limit Guidance doc suggests that 20 mph limits should only be introduced where speeds are at 24mph or less, I would guess that the A13 especially does not fit into this case - usually when Blackwall, Rotherhithe and Tower Bridge are working well its a 30mph straight run. Moreover, why hasn't 30mph average speed cameras been used if speed is the problem or localised 20mph school limits at "St Mary & St Michael Catholic Primary School". This part of the A13 unlike the A11 is mostly free of urban shopping areas of high pedestrian footfall and ought to be kept at 30mph!
I have to wonder: What's the point of prioritising speed limit changes on roads where the traffic already does the desired speed (more or less)? Surely the roads most deserving of 20 limits are those where 20 is desirable but where traffic currently goes faster than that.

What constitutes "desirable" is open to discussion, of course, and I do get the feeling that sometimes speed limits are lowered either as a way in themselves of discouraging motor vehicles without considering the consequences for users who we don't want to discourage (bus passengers, for example), or without consideration of the responsibility of *all* road users not to behave like idiots on the roads. But as a general principle, we should surely be setting speed limits, and ideally designing roads so that people do the desired speed without a load of signage and enforcement, based on all road users' needs and not solely on how fast the average driver goes on a road that is deceptively wide/straight/etc. See Bryn's comments about the 85th percentile here.
Micro The Maniac wrote:While I absolutely support lower limits on residential roads, IMHO this is going to far. And quite simply, a 20 limit on an A-road should never be appropriate - if there is justification for the road being 20, it should not be an A road.
I agree with this. It all comes back to deciding what the priority use for a given stretch of road is. On residential estate roads and on motorways, the answer to this is obvious, though only recently have we started to acknowledge that priority users on residential roads are actually the people living there, walking, playing and cycling around. But in between there is a grey area where we tend to be a bit one-sided in our thinking. At one end of the problem are the rural routes that have been upgraded to D2 online without sensible alternative provision for cyclists - drivers are the priority and everyone else can go hang. At the other are long stretches of 20 limit on roads that are through routes for general traffic, which seem to be imposed because we are unwilling/unable to insist that all road users fulfil their side of the road safety bargain. We need to be a bit more flexible, and that may mean sometimes accepting that on a given route allowing people to drive (or get the bus) at a reasonable speed for the kind of journey they're making and for the distance they're covering on that road is actually more important than pandering to pedestrians who want to treat an A road as if it's the same as the cul-de-sac they live on.
Bryn666 wrote:With buses it's not about top speed but average speed, so lower speed limits are not necessarily a concern - waiting to get back out at bus stops is what increases journey time hence the removal of many lay-bys in favour of inline stops.
Yes and no. There's no question that buses being stopped more than necessary disproportionately affects journey times. I've mentioned before that I can cycle from home to the ferry terminal (20 km) faster than the bus takes, even though the bus does 90 on the main road, which is also a more direct route than the disused railway I cycle on. While I don't hang around on a bike, I don't manage that kind of speed :shock: . So the difference lies in the last third (distance-wise) of the journey, where the bus is affected by a lot of traffic lights and other reasons to stop that aren't relevant to passengers, over and above the need to stop at bus stops. I average about 25-27 km/h on my bike over that 20 km route. Given that the bus does 90 (or even sits on its limiter at 100) on the main road, it must average considerably less than 25 km/h in town for me to be able to catch it up. So a general speed limit there of 30 km/h (20 mph, give or take) wouldn't make much difference - hence you're right, at least in large cities.

On the other hand, on longer rural routes, buses tend to go through the middle of villages and small towns so that they can pick up and drop passengers there, while cars will use the bypass if there is one. This presents a loss in time to begin with, but one that can't really be mitigated without reducing the number of bus stops. But it will get even worse if the bus is limited to 20 mph throughout that stretch. Once again, we're back to the question of which mode should be most prioritised on a given route, and to what extent users of other modes need to accept that.

And as to buses pulling out of bus stops - here, as a driver (or cyclist if you're on the road) you have a duty to let buses out of stops on any road with a limit of 50 km/h or lower. You will fail your driving test if you don't let a bus out in this circumstance, and theoretically, if there were any police around, you could get pulled over for it.
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Re: TfL Vision Zero: Lower Speed Limits

Post by Chris5156 » Wed Sep 15, 2021 15:54

WHBM wrote:
Tue Sep 14, 2021 23:42
Notable that today's multi-fatal high speed accident in Paddington, where the car ploughed into buildings, destroying these, was in a new 20mph section ...
If it had still been a 30 limit, would the result have been different? And if not… what is your point?

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Re: TfL Vision Zero: Lower Speed Limits

Post by Herned » Wed Sep 15, 2021 16:16

WHBM wrote:
Tue Sep 14, 2021 23:42
Notable that today's multi-fatal high speed accident in Paddington, where the car ploughed into buildings, destroying these, was in a new 20mph section ...
It is notable, if they had been obeying the speed limit they would almost certainly still be alive

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Re: TfL Vision Zero: Lower Speed Limits

Post by Chris Bertram » Wed Sep 15, 2021 16:32

Herned wrote:
Wed Sep 15, 2021 16:16
WHBM wrote:
Tue Sep 14, 2021 23:42
Notable that today's multi-fatal high speed accident in Paddington, where the car ploughed into buildings, destroying these, was in a new 20mph section ...
It is notable, if they had been obeying the speed limit they would almost certainly still be alive
They could easily have survived under a 30 limit, had they been minded to obey that. But we're talking about Darwin Award candidates here, to whom speed limits are but roadside decoration.
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Re: TfL Vision Zero: Lower Speed Limits

Post by WHBM » Wed Sep 15, 2021 17:04

Chris5156 wrote:
Wed Sep 15, 2021 15:54
If it had still been a 30 limit, would the result have been different? And if not… what is your point?
Come on, guys, we are meant to be professional highways engineers here. The point is that TfL have this "Vision Zero", of zero fatalities, where one of their principal stated methods is reducing the limits from 30 to 20, as here. And yet despite this we have road users for whom 20, 30, or any other limit is beyond their understanding, and indulge in high speed driving ending up like this. And so we still have such fatalities regardless of the limit - which is not how TfL play it.

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Re: TfL Vision Zero: Lower Speed Limits

Post by Bryn666 » Wed Sep 15, 2021 17:28

WHBM wrote:
Wed Sep 15, 2021 17:04
Chris5156 wrote:
Wed Sep 15, 2021 15:54
If it had still been a 30 limit, would the result have been different? And if not… what is your point?
Come on, guys, we are meant to be professional highways engineers here. The point is that TfL have this "Vision Zero", of zero fatalities, where one of their principal stated methods is reducing the limits from 30 to 20, as here. And yet despite this we have road users for whom 20, 30, or any other limit is beyond their understanding, and indulge in high speed driving ending up like this. And so we still have such fatalities regardless of the limit - which is not how TfL play it.
You have completely misunderstood Vision Zero, then, the goal is that the road design causes zero fatalities - it cannot and should not cover for reckless criminality; only taking these threats off the road in the first place through stricter traffic policing, which people on SABRE oppose, will do that.
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Re: TfL Vision Zero: Lower Speed Limits

Post by Graham » Wed Sep 15, 2021 17:38

Chris5156 wrote:
Wed Sep 15, 2021 15:54
WHBM wrote:
Tue Sep 14, 2021 23:42
Notable that today's multi-fatal high speed accident in Paddington, where the car ploughed into buildings, destroying these, was in a new 20mph section ...
If it had still been a 30 limit, would the result have been different? And if not… what is your point?
WHBM's point is crystal clear.

It is futile and counterproductive to argue that reducing speed limits from 30mph to 20mph across the board will, by itself, make urban roads safer - the available evidence simply does not support this argument. The argument needs to shift to make the real point - which is that reducing speeds in urban areas is essential in order to change the way that urban roads - and the wider urban area - is used. This is a key point of change management. You cannot change people's attitudes and beliefs by lying to them and/or insulting them.

To be fair, though, I have been encouraged by the tone of some of the recent debates on SABRE. Even some of the engineers who post here seem to have realised that this issue is all about change management, and there are far fewer references to eejits and numpties than there used to be.

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Re: TfL Vision Zero: Lower Speed Limits

Post by WHBM » Wed Sep 15, 2021 22:31

Bryn666 wrote:
Wed Sep 15, 2021 17:28
You have completely misunderstood Vision Zero, then, the goal is that the road design causes zero fatalities - it cannot and should not cover for reckless criminality; only taking these threats off the road in the first place through stricter traffic policing, which people on SABRE oppose, will do that.
The TfL Vision Zero is here

https://tfl.gov.uk/corporate/safety-and ... for-london

Stricter traffic policing ? The A1020 Royal Docks Road alongside London City Airport has been plagued with late night noisy racing since Lockdown started, audible to all residents up to a mile or more away from the overtuned drag strippers. Every weekend night. It's a TfL road, where absolutely nothing has been done about it and they race with impunity despite, apparently, umpteen local complaints to their council, TfL, the Met, etc.

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Re: TfL Vision Zero: Lower Speed Limits

Post by Chris5156 » Wed Sep 15, 2021 23:09

WHBM wrote:
Wed Sep 15, 2021 17:04
Chris5156 wrote:
Wed Sep 15, 2021 15:54
If it had still been a 30 limit, would the result have been different? And if not… what is your point?
Come on, guys, we are meant to be professional highways engineers here. The point is that TfL have this "Vision Zero", of zero fatalities, where one of their principal stated methods is reducing the limits from 30 to 20, as here. And yet despite this we have road users for whom 20, 30, or any other limit is beyond their understanding, and indulge in high speed driving ending up like this. And so we still have such fatalities regardless of the limit - which is not how TfL play it.
FWIW I’m not a highway engineer.

Surely the point of reducing a road to 20mph is to reduce the likelihood of fatalities, which will in turn reduce the overall number of casualties. Reducing the limit will prevent some types of accident. But it won’t prevent this type, and I’m not sure anyone, at TfL or anywhere else, is claiming that it would.

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Re: TfL Vision Zero: Lower Speed Limits

Post by Roadiecambs » Wed Sep 15, 2021 23:19

That's true, but the name is "vision zero", which whether they mean it or not implies that the vision is one in which there are zero road fatalities.

Hyberbole aside (on both sides of the argument), it is a question of whether the widespread adoption of 20mph limits is an effective and cost effective measure of achieving this, when weighed up against the other possible interventions. That will depend on the degree to which (a) fatalities are caused by people driving between 20 and 30 mph (the idiots driving 80mph don't care what the limit is) and (b) assuming (a) is true, the degree to which it will be enforced. I remain to be convinced, but I think that's where the nub of the argument is. There are of course other side benefits (e.g. to pedestrians, cyclists etc of a less "threatening" speed limit), but if the aim is of zero deaths that is against how the intervention should be judged...

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Re: TfL Vision Zero: Lower Speed Limits

Post by ajuk » Thu Sep 16, 2021 00:43

I think it's best to ask awkward questions like what design changes are proposed etc, do you actually understand what speed limits are for and how they work?

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Re: TfL Vision Zero: Lower Speed Limits

Post by thatapanydude » Thu Sep 16, 2021 13:37

Graham wrote:
Wed Sep 15, 2021 17:38
The argument needs to shift to make the real point - which is that reducing speeds in urban areas is essential in order to change the way that urban roads - and the wider urban area - is used. This is a key point of change management. You cannot change people's attitudes and beliefs by lying to them and/or insulting them.
While this point is true, it doesn't explain the wider point of speed limits cuts in London being blanket across the board with no real consideration on whether its appropriate.

Are places like here on the A10 proposed cut to 30mph going to promote cycling or walking instead of driving - probably no. Like is cutting the A501 to 20mph going to see everyone ditch there cars - again no because the A501 is the only decent route to travel across London.

These two examples in particular are where the needs of car drivers which make up the large proportion of traffic ( the A501 is roughly 60 to 80k aadt from memory) ought to be catered for more strongly and where higher speeds are appropriate.

Cutting the A10 to 30mph and 20mph from the A406 to Stamford Hill will push more traffic onto residential roads who were using the A10 because of higher speeds. Take myself as an example driving from Shoreditch to Wood Green, I travel now via Hackney and Clapton to the A10 rather than via Dalston because of more 30mph driving. Now with every road in this part of London becoming 20mph there is no incentive to stop me using residential rat runs which can cut time out of journeys because of no traffic lights.
A1/A1(M) >>> M1

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Re: TfL Vision Zero: Lower Speed Limits

Post by thatapanydude » Thu Sep 16, 2021 13:40

Micro The Maniac wrote:
Sun Sep 12, 2021 11:04
On Friday, I did the A24 all the way from Worthing to Clapham... again, I'll be in no hurry to do that inside the M25 again...
Again not ventured on the A24 but from a quick streetview look the 20mph and narrow roads don't look appealing for making a long journey like that. Thankfully the A3 is nearby for commuters.
A1/A1(M) >>> M1

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Re: TfL Vision Zero: Lower Speed Limits

Post by 2 Sheds » Thu Sep 16, 2021 14:24

Bryn666 wrote:
Sun Sep 12, 2021 16:00
You provide safe cycling infrastructure, places to store bikes, etc.

Something like 15% of all city land is given over to car parking. Imagine what we could do with that if we were more creative - and yes, some of that land could be multi storey or underground with human priority facilities on top like houses and shops.
I’m interested to see your source for this. Not any city I know.

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Re: TfL Vision Zero: Lower Speed Limits

Post by ajuk » Fri Sep 17, 2021 14:50

Trying to get more drivers to drive more sensible speeds is not exactly a new idea, if just setting the speed limit really low was thought to work, that would always have been the way you set them.
What I think is quite insidious is when councils drop speed limits knowing in advance of doing it that even if their most optimistic expectation for an average speed drop is met, the average speed will still be well over the speed limit, so it's non-compliance by design.

As someone may have pointed out in already in this thread, by including higher-standard and main roads in 20 schemes it may only serve to water down any effect a 20 limit might have on ordinary tight residential streets and sat-navs may no longer see those main roads as faster and send more cars down ordinary residential streets.
Last edited by ajuk on Sat Sep 18, 2021 01:58, edited 1 time in total.

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Re: TfL Vision Zero: Lower Speed Limits

Post by pjr10th » Fri Sep 17, 2021 16:09

ajuk wrote:
Fri Sep 17, 2021 14:50
Trying to get more drivers to drive more sensible speeds is not exactly a new idea, if just setting the speed limit really low was thought to work, that would always have been the way you set them.
What I think is quite insidious is when councils drop speed limits knowing in advance of doing it that even if their most optimistic expectation for an average speed drop is met, the average speed will still be well over the speed limit, so it's non-compliance by design.

As someone people may have pointed out in already in this thread, by including higher-standard and main roads in 20 schemes it may only serve to water down any effect a 20 limit might have on ordinary tight residential streets and sat-navs may no longer see those main roads as faster and send more cars down ordinary residential streets.
Modern sat navs are normally good enough to not bother with speed limits, but the actual speeds of the vehicles. The only way to stop motor vehicles rat running down side streets is to physically or legally prevent them from doing so. Not to mention local drivers as well.

When these speed limits are set, they should be set with a view to doing the engineering work when possible within highway authorities' funds. However, it's better to have a 20mph limit on a badly designed residential road than a 30mph limit because then at least local residents & good drivers will help to bring down speeds somewhat. If you set it at 30mph, then barely anyone will go under 30mph, provided the road is clear. If you set it at 20mph, then at least you will get some drivers doing 20mph and the police will have the powers to enforce safe speeds if they want to.

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Re: TfL Vision Zero: Lower Speed Limits

Post by ajuk » Sat Sep 18, 2021 00:36

pjr10th wrote:
Fri Sep 17, 2021 16:09
ajuk wrote:
Fri Sep 17, 2021 14:50
Trying to get more drivers to drive more sensible speeds is not exactly a new idea, if just setting the speed limit really low was thought to work, that would always have been the way you set them.
What I think is quite insidious is when councils drop speed limits knowing in advance of doing it that even if their most optimistic expectation for an average speed drop is met, the average speed will still be well over the speed limit, so it's non-compliance by design.

As someone people may have pointed out in already in this thread, by including higher-standard and main roads in 20 schemes it may only serve to water down any effect a 20 limit might have on ordinary tight residential streets and sat-navs may no longer see those main roads as faster and send more cars down ordinary residential streets.
Modern sat navs are normally good enough to not bother with speed limits, but the actual speeds of the vehicles. The only way to stop motor vehicles rat running down side streets is to physically or legally prevent them from doing so. Not to mention local drivers as well.

When these speed limits are set, they should be set with a view to doing the engineering work when possible within highway authorities' funds. However, it's better to have a 20mph limit on a badly designed residential road than a 30mph limit because then at least local residents & good drivers will help to bring down speeds somewhat. If you set it at 30mph, then barely anyone will go under 30mph, provided the road is clear. If you set it at 20mph, then at least you will get some drivers doing 20mph and the police will have the powers to enforce safe speeds if they want to.
I can only say is I've come across this in a few part of Bristol. I know SatNavs often look at average speeds, but if the limit is lower than the average speed then it goes by the limit rather than working on the assumption most people will exceed the limit.

You seem to be alluding to the hypothesis that if you set the speed limit lower than many or most drivers will only only drive X amount over or under the posted limit.
I have to admit I used to assume that to be true, but it's not by a long chalk. That claim has come to be like nails down a chalk board to me, so I wrote a blog post about it.
You may achieve a very small average speed drop of about 1mph, but it's the fastest drivers who are least likely to slow down, most likely to do harm and they're also the one properly set speed limits are more efficient at targeting.

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Re: TfL Vision Zero: Lower Speed Limits

Post by Debaser » Sat Sep 18, 2021 09:06

2 Sheds wrote:
Thu Sep 16, 2021 14:24
Bryn666 wrote:
Sun Sep 12, 2021 16:00
You provide safe cycling infrastructure, places to store bikes, etc.

Something like 15% of all city land is given over to car parking. Imagine what we could do with that if we were more creative - and yes, some of that land could be multi storey or underground with human priority facilities on top like houses and shops.
I’m interested to see your source for this. Not any city I know.
This study refers to London - 16% of its streets given over to parking. Other international studies appear to be available.

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