Why the data doesn’t add up

In July, the Leader of the Council said he wanted us to have trust and faith in the numbers. But we still have more questions than answers…

1) The promise from the Leader of the Council

On 19 July 2021, talking to Dulwich residents about the Streetspace scheme, the Leader of the Council, Cllr Kieron Williams, said: “Clearly there are questions about a methodology and just about people being able to be clear what methodology we’re using, is it accurate, is it transparent. So we’ve done some work to present that, but we absolutely take away there’s more to do to make sure everyone’s clear on the numbers – where they come from – so that you can have trust and faith in them.

Since this promise was made, nothing further has been published – neither raw data, nor explanations of methodology, making it impossible to know whether Southwark’s overall claims are fair or misleading.

Southwark Council knows this, so why hasn’t it published what the Leader of the Council promised?

Fundamental questions that can only be answered once the raw data and methodology are published include:

(a) Which baseline data is being used, and does it seem accurate when compared to other sources?

(b) On what basis have percentage adjustments (for seasonal fluctuations, for example) been made when comparing 2019 figures with 2021 figures? Can we rely on these estimated average changes to create reasonable baselines? Does the data include adjustments for specific local changes (a growing school intake, for example), for Easter falling at a different time, or – very importantly – for Covid?

(c) What attempt has been made to understand the difference between (i) average figures and those showing what’s happening at peak times of day (e.g. at commuter and school travel times), and (ii) weekdays vs weekends?

(d) Can the changes in traffic and cycling be directly linked to the LTNs or might there be other causes? For example, the fourth Department of Transport National Travel Attitudes Study (January 2021) found that 34% of people nationally were cycling more after the pandemic than before.

(e) Is the report comparing all the different types of count (ATC, Vivacity and manual) on a truly like-for-like basis?

(f) Have all relevant boundary roads been monitored and, if so, why haven’t they all been included?

(g) What attempt has been made to understand car volume decreases and cycling increases depending on the time of year? How does September 2019 compare with September 2021? Would a different picture emerge if we were given raw data for September 2021, especially on school roads?

2) The benefits claimed

Despite this lack of published data, the key conclusions from the review are still being presented as evidence of the scheme’s success. These keys claims are:

  • Cycling is up 66% across the area; and

  • Traffic is down 10% across the area.

3) Why we are questioning these claims

a) Exaggeration: Overall, across Southwark, traffic was down 8% in June 2021 compared with June 2019. The key claim, therefore, should be that traffic is down a further 2% on top of the borough-wide decrease of 8% – a much lower figure. Added to this, some roads have been left out of Southwark’s analysis altogether. The overall figure might show an increase if boundary roads like Dulwich Common had been included.

b) Inflation: A detailed review of the interim monitoring report (published in July 2021) shows that the claim of a huge increase in cycling on Calton Avenue (an alleged 231%) was grossly overstated because Southwark Council chose to use a highly inappropriate baseline figure. The Council has not responded to the conclusions of this review, so it is assumed that the same baseline for Calton Avenue is still being used in the final monitoring report, and that other baselines may be similarly inappropriate.

c) Omission: Active travel is walking as well as cycling. Before the LTNs, 65% of short journeys in Dulwich were made on foot (according to TfL’s London Traffic Demand Survey data). What is the figure now? (Vivacity data shows only a snapshot of the number of people walking through the junction on an average weekday, but provides no comparison to pre-closure figures.)

d) Misrepresentation: One example is the Council’s claim of an increase of traffic of just 6% on Grove Lane. However, this fails to take into account the cumulative impacts of the 2019 and later 2020/21 Champion Hill trials. The true figure is a total increase of 1532, or 15.8%.

e) Inequality: Even if we accept Southwark’s figures as accurate, the averages mask the fact that there are clear winners and losers. Traffic is down 80% on Calton Avenue (a road with no schools), but up 28% on East Dulwich Grove (a road with three schools and a health centre). Similarly, bus journey times have decreased on some routes, but have increased on major routes like East Dulwich Grove and the South Circular. In an area with poor PTAL ratings, a heavy reliance on buses, and worsening bus services, this is significant.

f) Inconsistencies:

i) If traffic has, as the reports claim, gone down on both Croxted Road and Lordship Lane, why have bus journey times increased?

ii) If cycling has gone up by 66%, why do the consultation results (asking people how they travel) not reflect that dramatic increase?

4) Conclusion

Southwark’s headline figures claiming that the Dulwich Streetspace scheme is a success cannot be verified because data and methodology have not been published, even though this was promised by the Leader of Southwark Council in July 2021. Highlighted here are just a few examples of exaggeration, omission, inflation and misrepresentation that suggest the benefits claimed cannot be relied upon.

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