Harringay Traffic Study - Initial Findings Published

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Permalink Reply by James Whyte on July 10, 2016 at 20:42

I'd back it - you can get a refund if you use a local business, charge more for Wightman, and less for Green Lanes. Seven Sisters and the A10 can handle traffic from the north, and all in the Wood Green & Green Lanes CPZ get a pass. 

None of the residents in the Gardens want to change, Wightman residents want change, and everyone in the middle has witnessed the current fiasco. 

Or we just red route Wightman freeing up those pavements bwahaha. (just flaming, not real!)

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Permalink Reply by Hugh on July 10, 2016 at 21:09

Green Lanes is a TfL road. So the option may be more complex there. It's certainly viable for Wightman though. As I've said before, the downside of this approach is that it might well be the thin end of the wedge and, if it were to be successful we'd see it creep in all over London. (After certain confessions, isn't the NHS about £350M short? Perhaps London road pricing could fill the NHS funding gap............)

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Permalink Reply by AndrewAW1 on July 10, 2016 at 22:11

I don't think it is a TFL road. They may have some input because it has a bus lane but it's not part of the TFL road network.

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Permalink Reply by Dick Harris on July 13, 2016 at 14:59

I have tried to read this document on my holiday smart phone and have found it too difficult to make a detailed analysis and critique. However, on the basis of my lengthy experience of reading and preparing other such documents I would offer the following remarks which mostly concern the proper handling, interpretation and presentation of statistical data.

1. In para 2.4 there is a reference to the population shrinking in 1991 before resuming it's growth. This seems highly improbable. Has the author considered the fall-out from the poll tax which allegedly led to widespread avoidance of registration and subsequent failure to complete census forms?

2. In paras 2.5 to 2.7 much is made of the "LTDS" a survey of 8000 people in the evening tire London area within the M25. It is not clearly stated exactly what use is made of this information but it looks rather as though the habits of these 8000 are taken as representative of the inhabitants of our area. I would say this would be preposterous but whatever the use that is made I would expect strong caveats to be expressed here as a to the statistical validity of doing so.

3. In para 3.34 we all wait with great interest better measurement of how much of the traffic on ladder streets (including Wightman Road) is simply passing through. The report as drafted so far does not seem to be interested in the answer to this question but I live in hope that a reasonable estimate will be possible.

4. Para 3.45 introduces TfL's North London Highway Assignment Model which is, I am told, a computer programme. The report cautions (in a way that ought also appear in relation to the LTDS referred to above) that this model is strategic in nature and not suitable for details. However the following paragraphs appear to do exactly that.

Quite aside from this observation, I should like to know how the computer programme knows where traffic is coming from and going to. It is this that we need to be told. No one these days is likely to be persuaded by magic words like computer or model. If the truth is that there is no reliable data available as to origin and destination - then this should be stated clearly.

The results of the camera survey may well turn out to be the only concrete data and it should be scrutinised and analysed very carefully. It will not say anything however about where a car entering the area came from nor where a car leaving the area is going to.

5. Finally, I agree with implication of an earlier responder that the conclusions should considered alongside the bald statistic that there are only so many vehicles kept in the study area. Even if the entire population of local vehicles made one trip and back each day it would explain very little of the movements on our residential streets.
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I apologise in advance to the authors of the report if I have missed some key points. Clearly the
thing is an interim report and I suppose this means that everything in it is liable change when the more complete survey data becomes available. I would urge the authors to ensure that the statistical inferences they intend to report and rely on are approved a professional statistician.

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Permalink Reply by John McMullan on July 13, 2016 at 15:28

I'm not saying that this is how they know where the vehicles are coming from and going to, but given the tools that they have (loads of traffic counters) this is how I would do it:

1. Encircle the area to be surveyed with these traffic counters, label them in and out.
2. Put some more traffic counters at strategic spots inside, the aim being to determine flow along desire lines.
3. Distribute the ins and the outs across your network according to what you saw go through the desire line counters.

The trick is having a LOT of traffic counters and timestamping the data collected properly.

The two counters on Wightman Rd, as has been pointed out, were combined to show "complete journeys" where in fact looking at the counters on the rung roads of the ladder it was apparent that there were many more partial journeys along Wightman Rd. I'm sure there are other problems but that's data interpretation, not collection.

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Permalink Reply by Dick Harris on July 15, 2016 at 9:18

None of the data collected within the study area or at its borders tells you that a car started in Enfield (for example) and was going to Hackney yet figures saying this appear in the interim report and have been remarked as though they are true. Nothing of the sort should appear in a report like this if the author can't support it. It is not enough to say that TfL uses the same model.

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