Forum topic: Will low-traffic neighbourhoods reduce net pollution?

I'm merely making different assumptions to you in the modelling. You assume no one driving over 2km will amend their journey - I seen enough evidence of vehicle numbers expanding/contracting in line with road capacity over the years to believe that a proportion of drivers will not make the same journeys given a more 'difficult' route. Someone with more time than me will need to analyse the detail of what you say but in the interim, some good news here on Railton Road LTN where traffic numbers have fallen for both 'intra' and peripheral roads https://love.lambeth.gov.uk/new-independent-analysis-shows-traffic-levels-cut-by-a-over-a-quarter-in-railton-area/?
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Karl. Again thanks for a broad view response with which to debate. It’s true I am coming at this predominantly with a view to urban pollution and it is interesting that you say that HMG and The Mayor are not funding this with the primary objective of air quality. But if the net effect of the changes worsen pollution can this even legally go ahead ? “Improve air quality” is mentioned in the paragraph you quote from the London Plan suggesting it is at least a secondary objective. Suggesting encouraging physical activity but in dirtier air seems contraindicative.
You say “The point here is the focus on benefit of investment changes to people rather than where it has long been – drivers.” But surely for many years investment in London’s transport has financially been hugely in favour of public transport (as I agree it should be) Crossrail alone probably would cover the whole road budget and most of the non maintenance spend on roads has been geared to buses and cyclists.
I agree pollution isn’t only just localised but you will know from existing data and future modelling that NO2 and NOx have reduced greatly in the last 10 years, and will continue to do so, not due to local traffic schemes but because each generation of diesel engine over the last 15 years has become cleaner and cleaner plus a certain contribution from the central London ULEZ. However it is the local undispersed queuesmog that is likely to be the killer and the most disadvantageous to those with asthma and respiratory diseases. You know the ones that can’t walk far or cycle. It is already affecting people on the perimeter roads of the Fox Lane LTN. I can put you in touch with one if you like.
I note “the leading expert on air quality bypasses LTNs and goes straight for behavioural change”. Does he/she actually support LTNs in this regard ? The reason I ask is behavioural change and education would go a long way to achieve the various objectives, but this should be encouraged, coersed, nudged. As soon as people feel forced or given no alternative, this is what divides a community. I’m going a bit off piste here but I think it’s relevant. My own case is I own a relatively old diesel car that I need for my work. I’m a decorator so I have to carry ladders, tools and various equipment around which I couldn’t manage on the tube or buses. In any case my normal commute would be to places where I would have to go into town and out again and probably near double my commute time. This would be true for a lot of car drive commuters who are being forced off the road. I am going to have to scrap my vehicle because of the expansion of the ULEZ scheme. It’s been the most reliable vehicle I’ve ever owned and would certainly have lasted me another 3 or 4 years. However, despite the carbon cost of scrapping one vehicle and buying another, I can see that I am doing something which might be adversely and unnecessarily impacting other people’s lives in the pollution I am causing. I see the reasoning so I am persuaded. But whether I walk more, cycle or go to the gym is my decision. I don’t want to be forced into it by people unnecessarily closing roads around me. I don’t want other people evangelically imposing their lifestyles on mine. Besides, I don’t look good in lycra.
Adrian. You seem to be accepting the maths of the disappearing short journeys leading to more pollution and proposing without evidence that the possible disappearance of longer journeys will take up the slack and lead ultimately to a reduction in pollution. We know that generally the longer the journey the more necessary it is and will less likely be walkable or ultimately cyclable. Very often there isn’t a public transport alternative, at least not without a large time factor contribution like my own example above. However part of the stated intention of the LTN schemes are to encourage the removal of the short journeys that can be walked or cycled. This is what I am saying cannot work without the detrimental effects discussed previously.
Re Lambeth council, they seem to be falling into the same (convenient) trap as the Walthamstow Village scheme did.
From their own monitoring strategy document https://www.lambeth.gov.uk/sites/default/files/projects_attachements/Transport%20monitoring%20strategy%20FINAL.pdf we read “Our monitoring will also identify potential dis-benefits of the LTN schemes, these may include: • Increased traffic on boundary roads • Increased traffic in neighbouring residential areas”. Further on we read “Data will be collected inside LTN areas as well as on the immediate boundary roads that surround an LTN area for the 3 assessment stages described above” ie no measurement of data further afield. So how are they measuring increased traffic in neighbouring residential areas ?
They haven’t produced the actual report or data yet so we will have to see if they have also removed the possibility of traffic being counted on the perimeter road before turning into the LTN (pre trial). Let’s say a car were counted on the perimeter before turning into the LTN and then counted on two or three roads within the LTN. During the trial their counts would disappear from within the LTN and assuming they stayed on the perimeter road they would only be counted here. But they were counted here before so they are not counted as extra traffic. But traffic has disappeared from within the LTN. Traffic evaporation. But what car has actually disappeared ? The same car has done a probably longer journey in probably more congestion causing more pollution and has statistically disappeared.
By not measuring beyond the perimeter roads they are also counting cars that did go through the LTN, that now take a wider detour (causing more road time and pollution) as also having evaporated.
In addition cars that were on the perimeter roads that never even went into the LTN in the first place may also now be taking a wider berth to avoid congestion and so are now not counted on the perimeter roads. More false evaporation.
I now repeat what I said in my previous post. If the LTN schemes introduced in Waltham Forest between 2015 and 2018 cause a rise in traffic miles driven by cars of 11.9% over this period, far higher than its neighbouring boroughs (TRA 8902) how is this consistent with 16% net evaporation ? You have not addressed this. This also counter claims your position that those taking longer journeys are persuaded to find alternative transport options.
The strange thing is LTNs are being ridden out across London based on data like this which is at best unproven and at worst just plain wrong. It seems to be driven by pressure groups who either believe this data and feel they are doing something beneficial (I hope this is the case) or sophists who have a separate agenda who just want to live in a quiet clean little area of one of the biggest commercial cities in the world and don’t give a second thought to the rest of the community.
And since you brought up the Railton Road scheme, here is a table from http://content.tfl.gov.uk/travel-in-london-report-13.pdf page 215 figure 8.18 regarding peoples opinion of the scheme


Now this is somewhat what you might expect. When looking at the total it is broadly fifty fifty with those living inside the scheme definitely more favourable with those outside the scheme more distinctly against. But let’s look at these figures a little more closely. Take the forth row figures that disagree with the question (in pink). I’m using these figures as they are the easiest to follow mathematically. Inside the LTN 66% disagree with the question, outside 44% disagree. Now if an equal number of people were surveyed from inside the LTN as outside,( ie the survey population sizes were the same), the total in the first column you would expect should be 55%. But it isn’t, it’s 58%. As this is nearer the 66% (inside LTN) figure what this shows is that more people were surveyed from inside the LTN than outside. Now 55% to 58% isn’t that much difference you might think but to achieve this headline total figure of 58% for every 100 people surveyed approximately 64 were inside and 36 were outside, getting close to a two to one ratio. I say approximately as the figures have all been rounded up to whole percentages so it could be 63/37 or even 65/35, but it applies to each pair of figures in the table above that add up to the total in the first column.
But the predetermined bias is even worse than this. On the previous page the methodology reads “Survey respondents were recruited to take part in an online survey through a door-to-door leaflet drop at every residence inside the defined neighbourhood, which included both the LTN itself, addresses located on boundary roads, and in an area that was in the same neighbourhood but was not directly impacted by road closures.” (My Italics) So they have lumped together both groups from outside the scheme thus giving equal weight to those people actually impacted by the scheme to those they chose who were deliberately “not directly impacted” by the scheme. Is this fair to deliberately statistically dilute the opinions of those directly affected ? Without the raw data we have no way of knowing what proportion of those outside the LTN were affected or unaffected by the scheme, yet still roughly 75% were generally against the LTN. The only justification that could be argued for including residents not directly impacted is to suggest an opinion for the borough overall in which case the figures should have been weighted with respect to those living inside an LTN (I’m guessing 5% of the borough at best) to those living outside (95%) in which case the total headline figure should be close to 75% against LTNs. This wouldn’t look good for TfL.

Sorry the inserted table is a bit blurry but you can find it on the link given

Just to be clear - no I don't accept the assumptions in your model - they are just that, assumptions. My assumptions are different. It's common knowledge that road volumes increase and decrease in line with capacity.

You seem to be drawing this debate to a conclusion. To be clear the assumptions made by me were the pro LTN best case scenario for the claims of reducing short journey traffic. Every assumption made was generously in your favour. More pollution will be produced whether these cars return to the road or not, if the traffic that remains is delayed, or caused to drive further, for just one minute. You have resorted to unsupported assumptions that a significant number of longer journeys will not take place to account for the extra pollution produced. Your evidence for this is " I seen enough evidence of vehicle numbers expanding/contracting in line with road capacity over the years". I have provided you with evidence that between 2015 and 2018 when Waltham Forest implemented several LTN schemes and closed off a significant number of roads to through traffic, Dept of Transport statistics show the borough's traffic volumes went up considerably more than its neighbouring boroughs. This is not consistent with claims of traffic evaporation or traffic expanding/contracting with road capacity as you claim.

I don’t believe I can add significantly to my earlier comments other than perhaps suggesting not getting too focused on one simple scenario of one strand of what is an immensely complex system. One risk of that route is to generate the doubt / distraction / uncertainty which can divide people and seems to be what is trying to be avoided. Spending time on the numerous informing reports, data, public hearings and such of the transport element of the London spatial strategy in particular but also that of HMG which led in the round to the current policy implementation may be useful. London’s latest transport strategy was agreed in 2018 but the overarching London Plan has been held up by the Secretary of State over housing matters for a long while. His latest two Directives have however just been answered by the GLA which should theoretically see it signed off very early in 2021. You would then have a 6 week window to challenge it legally.
All that said, with 100+ live LTN trials of this part of the UK’s / London’s strategy roll out, plus other equivalent UK experiences, there is shortly going to be more than enough experiential data to powerfully inform future iterations of transport policy.