LTN Discussion

[Bic Basher]

So I decided to cycle through the village and East Dulwich Road at lunchtime. The queue to get into EDG from Dulwich Village was long and as mentioned by our EDG residents, the road is very busy in both directions which gets worse the closer you get to LL.

Yet the main part of the village where the shops are has a bus gate in operation during the peaks and a very quiet Court Lane/Calton Avenue which is supposed to be bike heaven.

[CPR Dave]

New Crowd Fund appeal has been posted requesting contributions to pay for Dulwich Square Xmas Tree!!!!!! Appeared on the Peckham 'Next Door'site

 

These people are unbelievable. Imagine being so utterly shameless and entitled as this.

[heartblock]

Something that might annoy you even more is the ATC (traffic counters) you see on ED Grove and Croxted Rd, that are used by most councils - the ones with the double pneumatic tubes........................ cannot register a vehicle that travels less than 10 kilometres per hour. So the slow moving traffic, polluting both roads is undercounted..... hence the magic disappearing traffic on ED Grove, despite us seeing traffic and the dodgy numbers.

This ‘evaporating’ traffic we can all see and hear and smell is not counted if idling below 10km per hour.

Ta da.........well done Southwark

[heartblock]

Explanation from the company that makes the pneumatic tube ACT as used by Southwark.

The equipment, which relies on two rubber tubes strung across the road, is recommended to only be used in FREE FLOWING traffic. When you introduce congestion, and vehicles stop with their wheels between or bridging the tubes, or they do not travel over the tubes fast enough, the vehicles are simply not counted. Preparing a report with a 10km filter from this raw data increases the number of vehicles not counted. 🤔

[borderpaul]

EX Dulwicher said: "So for a CPZ, the purpose is to temporarily limit the parking supply to prevent the residential areas around schools and stations in particular from turning into Piccadilly Circus for 2hrs every morning and evening".

 

 

We are seeing both LTNs and CPZs being put in for the same reasons. They both have the same effect to remove traffic and parking from a residential area but those in CPZs have to pay for the privilege while those in LTNs have been given a privilege for free. It seems fair to have an LTN charge for this privilege proportional to property values such as the council tax bands.

[Rockets]

Explanation from the company that makes the pneumatic tube ACT as used by Southwark.

The equipment, which relies on two rubber tubes strung across the road, is recommended to only be used in FREE FLOWING traffic. When you introduce congestion, and vehicles stop with their wheels between or bridging the tubes, or they do not travel over the tubes fast enough, the vehicles are simply not counted. Preparing a report with a 10km filter from this raw data increases the number of vehicles not counted. 🤔

 

Heartblock - where did this come from? I remember in tbe early days the council moved the counter from the junction of Lordship Lane and Court Lane down to the junction of Melford and Lordship Lane where it has remained for over a year. I always suspected this was to manipulate the count. Didn't Ex- claim the under 10kmh issue wasn't correct.

[first mate]

Words fail. This is disgraceful. They really do not care about pollution or the truth. So, traffic count data that has been used to support the notion that car use has gone down since introduction of LTNs, is a massive lie.

I hope those in the habit of posting 'your daily reminder' notes about data showing traffic evaporation, wake up and smell the coffee.

[heartblock]

Well LTNs are here to stay despite the terrible burden of extra pollution and traffic for us less entitled residents but best to contact the company that manufactures these ATCs, in short in stop – start congestion, the machine software needs four pulses (in a short period of time) to be able to group these together and call it a car (or lorry etc.) so if a vehicle stops between the strips or bridging the strips’ the pulses made by this vehicle are not grouped together and the pulses are ignored going either into a random hits bin or an unidentified vehicle bin, neither of which are counted in a report.

Also Enfield court case -

[Rockets]

Wow - this confirms my suspicions on why they moved the Lordship Lane monitoring to closer to Melford Road - I wondered why the site located originally near Court Lane moved to Melford after a few months. I wonder if Southwark was seeing data they didn't like so made the switch. I presume Southwark use the same system as Enfield?

Has anyone plotted where each of the monitoring sites are located as it seems that any near choke points or junctions won't be giving accurate readings.

I know Ex-, as an industry insider, suggested the slow moving vehicles over monitoring wasn't an issue when challenged with it many moons ago so I wonder if they have any comment in light of the Enfield disclosure or what the circumstances of that one are that means the same thing isn't happening here. Does this mean that all monitoring data from choke points needs to be reset?

[exdulwicher]

I know Ex-, as an industry insider, suggested the slow moving vehicles over monitoring wasn't an issue when challenged with it many moons ago so I wonder if they have any comment in light of the Enfield disclosure or what the circumstances of that one are that means the same thing isn't happening here. Does this mean that all monitoring data from choke points needs to be reset?

 

I didn't say it wasn't a problem, just that any errors tend to average out since a vehicle is not stationary on the tubes for long. Worst case you get a week of slightly duff data and just change the location. Generally they work out at about 90+% accurate.

Normally, any readings from those are used in conjunction with other info from (eg) Vivacity sensors, manual counts, other automated counts in the vicinity, GPS / mobile phone data and so on to allow cross-referencing.

I'd be more concerned that the council are apparently (from that short excerpt posted above) trying to "measure" pollution by pneumatic tube traffic counters since that's not measuring, that's inferring. OK, you can (to a certain extent) model it but honestly, the results are so variable you're often better off not even bothering. It's easier (and just as accurate) to say "too many cars = too much pollution". Pollution is highly dependent on external factors too like surrounding buildings, weather, type of traffic etc and it'll vary seasonally and of course "pollution" covers a huge range of issues like greenhouse gas, NOx, particulates and so on.

[exdulwicher]

This ‘evaporating’ traffic we can all see and hear and smell is not counted if idling below 10km per hour.

 

That's not technically true.

If you count traffic along (say) the South Circular via whatever means you want - sensors, manual count etc - at some point you're going to find that only 20 vehicles passed your count in 15 mins. That's kind of low so there are two conclusions.

One: it's a really quiet road, very little traffic.

Two: it was really congested and slow moving at that time.

You can therefore do a number of things to cross reference that. Look at the speed data (if available), collate counts from different times of day/week/month, video or in-person surveillance to report back on the situation, look at other info for live traffic data (Google Maps is great for this plus it has historical data and will calculate delays based on time of day to a fair degree of accuracy) and go from there.

Plus you'll have historical data from various sources and be able to cross reference. Bottom line is, it's not (or it shouldn't be) based on JUST a count, it's a range of data.

[heartblock]

The tubes in ED Grove central ( which is not in the centre of ED Grove) are placed just where traffic turns across the opposing lane to access the Health Centre… leading to stationary traffic frequently during the day. In fact the stationary turning point is on top of the tubes. ED Grove bring the magic disappearing point of traffic. Some reports suggest 1 in 20 cars are missed per day at least.

[exdulwicher]

Some reports suggest 1 in 20 cars are missed per day at least.

 

"Some reports"... Which ones? Link?

And 1 in 20 is 95% accuracy which is pretty decent. If it's always counting at 95% accuracy then it's the same baseline throughout and the figures get processed anyway to account for a few % either way.

If it's consistently missing 1 in 20, that's not the end of the world; you really don't need to count every single vehicle on every single road 24/7/365. What you're looking for is trends and patterns.

Nothing is going to give you 100% accuracy 100% of the time but you actually don't need that.

[heartblock]

Yawn o’clock… ooh the ATCs are accurate….. ooh they are not accurate but that doesn’t matter…… ooh they prove traffic has dropped in ED Grove central…..ooh EDG Central is exactly where cars stop to turn into the Health Centre but that doesn’t matter…. Ooh prove your figures even though the ATC is in the worst place for accuracy….

You know.. as I say the LTNs are here to stay despite them not actually providing any of the benefits they supposedly give so called ‘boundary rds’ or as I like to call them HTNs as provided and designed by this local council. Go do your own research and find your own links, it’s all out there. I’m bored by the ever changing rationale for these ridiculous gated, elitist roads.

[CPR Dave]

If it's missing 5% of traffic but the LTN is hailed as a success because of a 2% reduction then it is a hug problem. A 60% overestimate of the impact of the LTN

[Kathleen Olander]

One of the planter barriers has been moved to one side again outside Harold George. confusing if you are in a car as gap big enough to drive a bus through now.

What happened to the posh seating that appeared in the road almost outside Romeo Jones last year, just noticed it's disappeared?

[Rockets]

Some reports suggest 1 in 20 cars are missed per day at least.

 

"Some reports"... Which ones? Link?

And 1 in 20 is 95% accuracy which is pretty decent. If it's always counting at 95% accuracy then it's the same baseline throughout and the figures get processed anyway to account for a few % either way.

If it's consistently missing 1 in 20, that's not the end of the world; you really don't need to count every single vehicle on every single road 24/7/365. What you're looking for is trends and patterns.

Nothing is going to give you 100% accuracy 100% of the time but you actually don't need that.

 

Ex- is the issue here that if the pre-Covid monitoring locations are no longer the ones being used for the post-Covid monitoring (and are closer to choke points and junctions) then this is clearly the council trying to use their knowledge of the monitoring strip inaccuracies to influence the monitoring in their favour? I suspect this is what has happened in Enfield and all the monitoring data has been discarded by the judge thus invalidating the council's air quality assessment as it was based on misleading data.

You also say that a council would get duff data for a week or so then move the strips but the strips on Lordship Lane near Melford (which is under constant slow traffic flow for much of the day) have been there for months - what's your assessment for that - that the council are happy with inconclusive/potentially inaccurate data or something else? Surely the position the strips where they started near the junction of Court Lane would have been better for accurate number gathering?

Here's my guess: the strips were put in near Court Lane as that is where, I suspect, the pre-Covid monitoring was done and the council saw data they didn't like so moved the strips to close to Melford - isn't it the oldest trick in the book for traffic monitoring experts and well known trick they use?

[exdulwicher]

If it's missing 5% of traffic but the LTN is hailed as a success because of a 2% reduction then it is a hug problem. A 60% overestimate of the impact of the LTN

 

Again, not really.

Let's suppose that heartblock is right and it misses 1 car in every 20 (so 95% accurate). For the sake of argument we'll assume that's consistent and it never over-reads. Again, for simplicity, we'll assume that the council are getting their data from this one counter and nothing else.

The counter reliably tells the council that an average of 9500 vehicles are going past it every day. Of course that's not the true figure, it's missing 1 in every 20 so the actual number of cars going past it is an average of 10,000/day.

Post intervention, the council, based on info from that same counter, announce there's been a 2% drop in traffic. That must mean that the counter is recording 2% less so 9310 vehicles (on average) going past it (2% less than 9500, yes?). Of course, once again, it's missing one car in every 20 so the true number of vehicles going past it is (on average) 9800. Still a 2% drop. Still the same percentage.

The counter doesn't need to be 100% accurate, it only needs to be precise* and consistent.

And in practice, this will be cross-referenced with other traffic data anyway.

*precise is not the same as accurate

 

Here's my guess: the strips were put in near Court Lane as that is where, I suspect, the pre-Covid monitoring was done and the council saw data they didn't like so moved the strips to close to Melford - isn't it the oldest trick in the book for traffic monitoring experts and well known trick they use?

 

Not really cos working with shit data doesn't benefit anyone. I fear you're attributing too much conspiracy theory capability to Southwark Council. Most councils aren't very good at conspiracy theories cos you need to be quite competent to run them...

I've not even bothered to look at which count sites are active to be honest so I have no idea if they're getting any info from there or not.

[heartblock]

At least 1 in 20 is what I said and was conveniently ignored ... but where it is positioned on EDG Central (the 'poster-boy' of the success of 'reducing' traffic on ED Grove central) it will be higher as cars slow down and stop on that exact point on EDG - do go see it for yourself.

The detail -

Where cars only shuffle forwards a couple of car lengths at a time you will not count 25 per cent of the cars (that’s one in every four), in milder congestion where cars move forwards 10 car lengths at a time you will miss five per cent of vehicles (one in every 20).

Just to throw in another euurgh point - surveyors sometimes use a filter when generating a report so it also leaves out the slowest moving traffic below a certain speed, but I cannot say if Southwark also added this extra dimension.

By the way, the research bounced around by the HTN purveyors - such as Walthamstow Mini Holland scheme - all have used the double-tube system.....

[heartblock]

And again.. not conspiracy. A mix of incompetence and careerist enterprise. If Liz Truss can become PM -then any of these individuals can float to the top.

[Rockets]

The growing weight of evidence certainly suggests that the council have been more than manipulating the narrative with less than transparent data.

Probably the recent episodes with councillors abusing TFL staff is a culmination of the stresses of the council and councillors trying to manipulate the story and finally losing control and the truth finally starting to leak out.

[CPR Dave]

Let's hope not!!!

[Rockets]

Clean Air Dulwich does seem a little confused and their posts recently make me wonder whose interests they are looking after and who is actually behind it.

Currently their two strategic goals seem to be:

1) Prevent emergency vehicle access through the Calton/DV junction by closing it to all vehicles again

2) Prevent school buses from dropping and picking up children at Alleyn's/JAGS etc.

When I see the below recent examples of their posts I do question what their motives are and whether Clean Air or Dulwich are really at the core of their concerns or whether they are just moaning for the sake of moaning - one presumes from the tweets that they are cyclosexuals (with credit to Jeremy Vine who coined the phrase petrosexuals which applies just as well to Cyclo-obsessives as well as car obsessives!)..

The way they carpet bomb and troll all of our local councillors must really become wearing for them as the content and message is all over the place and all a bit lunatic fringe.

Does anyone know who is behind it and what their aims are?

[malumbu]

Breath deeply.

Relax.

I've had a nice night out at the Ivy/Goose

Better still I've not watched the football. See my incredibly unpopular thread on the political bit of the forum.

[northernmonkey]

@Rockets —as long as I can remember there have been issues with the foundation schools coaches parking illegally and idling on Townley road. The schools always claim to be working towards a solution but nothing changes other than it seems to get worse.

The situation as it stands is really dangerous, do you genuinely think that having coaches parked on double yellows and zebra zig zags is ok? Cars driving on the wrong side of traffic islands because they can’t pass on the right side? Would you be happy letting your child cycle home along Townley Road as it is today?