England and Wales High Court (Administrative Court) Decisions

IN THE HIGH COURT OF JUSTICE
KING'S BENCH DIVISION
PLANNING COURT
SITTING IN LEEDS

		17th May 2024

FORDHAM J:

Introduction

1. This case is about the legal adequacy of reasons given by a planning inspector, when addressing the fitness for purpose of a transport model used in evaluating the soundness of a local plan. The claim is for statutory review, pursuant to s.113 of the Planning and Compulsory Purchase Act 2004. The target for challenge is the decision of the Defendant ("the Council") on 22 March 2023, adopting the Calderdale Local Plan (the "Local Plan"). The Claimant ("the Forum") asks me to quash the Local Plan pursuant to s.113(7) of the 2004 Act. That jurisdiction engages conventional public law principles (Cherwell Development Watch Alliance v Cherwell DC [2021] EWHC 2190 (Admin) at §20). The legal adequacy of the inspector's reasons on fitness for purpose of the transport model is the sole ground on which permission for statutory review has been granted, by DHCJ Ridge on 25 August 2023. I am grateful to all Counsel for their focused submissions.
2. The Council is the local planning authority. It was required to prepare the Local Plan, pursuant to s.19 of the 2004 Act. The Local Plan set out a strategic framework for growth in the borough. It included site allocations and policies relating to development. The site allocations included new housing allocations within the Brighouse area, with some 5,550 homes and 32.79ha of net developable land for new employment development. There were strategic allocations for both the Thornhills Garden Suburb (indicative capacity 1,998 houses) and the Woodhouse Garden Suburb (indicative capacity 1,257 houses). Both of these were major extensions to the town of Brighouse, on the southern and eastern edges of the town, on land currently in the Green Belt.
3. On 11 January 2019 the Council submitted the Local Plan to the Interested Party (the "Secretary of State") for independent examination pursuant to s.20 of the 2004 Act. The independent examination was conducted by the planning inspector Katie Child ("the Inspector"). The Forum, a designated neighbourhood forum pursuant to s.61F of the Town and Country Planning Act 1990, participated. There were several hearings, between June 2019 and January 2022. The Inspector produced a 113-page report, dated 26 January 2023. She reported that, subject to a number of main modifications, the Local Plan provided an appropriate basis for the planning of the Borough. The Council's adoption of the modified Local Plan followed. By Googling "Calderdale local plan", any interested reader wanting more background or detail can find a "local plan examination library" with a wealth of documentation, including key materials to which I will be referring. For that reason, I will give some paragraph numbers as I go along.

The Strategic Model

4. The transport model which is at the heart of this case is called the Calderdale Strategic Transport Model (also known as the CSTM). I will call it the Strategic Model. It had first been developed in 2008. It was updated in 2014 and again in 2016. Before we go any further into this rather technical case, with its own lexicon, I am going to describe some basics.

"Observed" and "Modelled"

5. Authorities who make decisions about policies and developments will often need a picture about traffic. You can have an "observed" picture. That means someone or something has tracked real-world vehicles on a stretch of road, or on a journey between two places. You can take different times of day: like a morning peak hour (called "peak AM"), or an afternoon peak hour (called "peak PM"), or an off-peak hour in between. You can take a stretch of road between two junctions. That is called a "link". The volume of vehicles on a road is called "traffic flow" and at a link is called "link flow". A journey between two places is called "journey time". You can also have a "modelled" picture. That means a computer is giving you its picture. It could be a modelled picture of a present reality. Or it could be a modelled picture of a changed position. What would the traffic flow and journey times be like if we allowed a particular development? What would the traffic flow and journey times be like if we made a particular road improvement? That can only be observed when it has happened. But it can be modelled to help inform our decisions. For the Local Plan in this case, the Strategic Model was used to assess the implications that site allocations would have on the road network and inform policies in the Local Plan, testing proposed allocations against the modelled picture, to examine whether the existing highway network could take the additional traffic and assist in identifying what additional highways infrastructure upgrades would be required.
6. There is a dual relationship between observed information and the model. (1) A model has to be designed and calibrated. It can be tweaked, by being redesigned and recalibrated. To make the design reliable you need to input real-world information. So, observed traffic flow (at calibration links) and observed journey time go into the design or redesign. (2) A model also has to be tested and validated. To check the model is reliable you can compare what picture it gives you with your real-world information, including traffic flow information which may be from your calibration links or other "validation links". A model can have a "base year". That means the model is a representation of base year traffic conditions. The Strategic Model has a base year of 2014.

WSP's "Validation" Reports

7. In June 2015 and October 2016, "Validation Reports" were produced for the Council by its appointed consultants WSP Parsons Brinckerhoff ("WSP"). These explain that WSP had been commissioned by the Local Authority to update and extend the Strategic Model. The Validation Reports express positive conclusions about the suitability and fitness for purpose of the "validated" Strategic Model. Within them was analysis, including as to traffic flow and journey times. As to traffic flow, tables were produced which gathered together information from comparing modelled traffic flow with observed traffic flow, involving calibration links and validation links. The 2015 Validation Report explains the 2014 Base Year as "determined by the Road Side Interview traffic data commissioned for this study which was collected in June 2014 and supplemented by additional junction and link surveys from April and October 2014". This is a reference to real-world observed pictures from during 2014.

Green and Blue

8. To bring "calibration link flows" and "validation link flows" to life for me, Ms Hall showed me Appendix F of the 2015 Validation Report. In that table there are 2014 calibration link flows shown in green, and validation link flows shown in blue. So, for example, there was morning peak observed vehicle flow on 8 April 2014 for the A629 (Skircoat Road/Free School Lane Junction) as a "calibration" link (green). On the same day, 8 April 2014, there was morning peak observed vehicle flow for the A629 (Skircoat Road/Heath Road Junction) as a "validation" link (blue).

DfT Criteria and the GEH Statistic

9. The Department for Transport produces criteria for validation of a model. These are set out in something called WebTAG. That means the DfT's web based Transport Analysis Guidance. WebTAG provides detailed guidance on the appraisal of transport projects and wider advice on scoping and carrying out transport studies. It is a requirement for all projects/studies that require government approval. Part of WebTAG is about what you do when looking at link flow, comparing observed and modelled flows. You calculate a value for the difference between observed and modelled flows by using a statistic named after Geoffrey Edwards Havers. It is called the GEH Statistic. It is a complicated mathematical formula. There is an "acceptability guideline" which is that the GEH Statistic for individual links is under 5 for more than 85% of links.
10. The DfT's Transport Analysis Guidance (May 2018) says this about the DfT criteria (at §§3.5.1 to 3.5.3, emphasis in the original):

Modelling Standards. 3.5.1 Guidance in the Practitioner tier of TAG describes best practice in model development. As part of producing an appropriate analytical tool, it is important that models are based on up-to-date evidence and are demonstrated to produce realistic results when tested. Without this assurance, results from a model may not be sufficiently robust to be used to adequately assess impacts of a potential intervention. 3.5.2 Obtaining this assurance is done via model validation. This ensures that sufficiently accurate traffic and passenger flows are reproduced on the transport network in the model base year and that the model responds appropriately to changes in costs when used to forecast i.e. that changes in behaviour (demand) are realistic. TAG contains suggested benchmark criteria in order to test this realism. However, the key concern of the analyst is to ensure that the model is fit for the purpose to which it is being applied and that there is appropriate evidence to support the conclusion that it is. 3.5.3 The achievement of the validation acceptability guidelines described in TAG does not guarantee that a model is 'fit for purpose' and, likewise, a failure to meet the specified validation standards does not mean that a model is not 'fit for purpose'. A model which meets the specified validation standards may not be fit for particular purposes and, conversely, a model which fails to meet to some degree the validation standards may be usable for certain applications. The test of fitness for purpose of a model is: can robust conclusions be drawn from the model outputs?

TTHC's Critiques

11. The Forum enlisted consultants TTHC who challenged the fitness for purpose of the Model, especially in a 2017 Transport Representation (September 2017); a 2019 Transport Representation (June 2019); and a 2022 Transport Position Statement (June 2022). There was also a 2021 Solicitors' Letter (24 May 2021), and reliance was placed on a 2018 WYCA Report on capital spending and project approvals for the West Yorkshire and York Investment Committee of the West Yorkshire Combined Authority (11 October 2018).

WSP's Responses

12. I have referred already to WSP's 2015 Validation Report and 2016 Validation Report. There was also a 2016 Technical Note (Technical Note 1, June 2016). In light of what was being said by TTHC, WSP also produced a 2018 Technical Note review of the transport evidence base (Technical Note 10, 24 May 2018); and a 2021 Technical Note response to the Forum (2 June 2021).

Law

13. This is the legal position about suitability of the Local Plan and fitness for purpose of the Strategic Model: (1) A prescribed purpose of the independent examination was to determine whether the Local Plan was sound (2004 Act s.20(5)(b)). (2) The Inspector was statutorily obliged to recommend that the Local Plan be adopted if, having carried out the independent examination, she considered it reasonable to conclude that the Local Plan was sound (s.20(7)(b)(i)). (3) The assessment of soundness involves a planning judgment (Cherwell §20). (4) The Inspector was statutorily obliged to give reasons for that decision (s.20(7)). (5) In preparing the Local Plan, a local authority is statutorily required to have regard to national policies and advice in guidance issued by the Secretary of State (2014 Act ss.13, 17(6) and 19(2)(a)). (6) Under the National Planning Policy Framework (NPPF) §182 (Cherwell §§19-20), a Local Plan is sound if it is:

Positively prepared – the plan should be prepared based on a strategy which seeks to meet objectively assessed development and infrastructure requirements, including unmet requirements from neighbouring authorities where it is reasonable to do so and consistent with achieving sustainable development. Justified – the plan should be the most appropriate strategy, when considered against the reasonable alternatives, based on proportionate evidence. Effective – the plan should be deliverable over its period and based on effective joint working on cross-boundary strategic priorities. Consistent with national policy – the plan should enable the delivery of sustainable development in accordance with the policies in the Framework.

(7) Under NPPF §158 a local authority should ensure that the Local Plan is based on adequate, up-to-date and relevant evidence about the economic, social and environmental characteristics and prospects of the area. (8) Under Government Planning Policy Guidance (PPG) on Transport Evidence Bases in Plan Making and Decision Taking (13 March 2015): (i) establishing a robust transport evidence base for Local Plans is important to support their preparation facilitate their approval (§1); (ii) WebTAG "principles", "objectives" and "methods" should be adopted in the transport assessment of a Local Plan, ensuring proposed land allocation impact is considered with a comparative analysis of transport effects, albeit that for most Local Plan assessments the full methodology recommended by WebTAG will not be appropriate but may provide some useful guidance, whereas in assessments involving major new transport infrastructure WebTAG methods should be employed (§10). (9) The Transport Analysis Guidance (May 2018) identifies (at §3.5.3) as the test of fitness for purpose of a model, whether robust conclusions can be drawn from the model outputs (§10 above).

14. This is the legal position about legal adequacy of the Inspector's reasons: (1) The Inspector was statutorily obliged to give reasons (s.20(7)). (2) The requisite standard is to give clear, adequate and intelligible reasons, which make plain how the principal important controversial issues were resolved, which can be briefly stated, with the degree of particularity required depending entirely on the issues falling for decision, which explain to the parties and the wider readership of the report why, in the exercise of her planning judgment, the inspector concluded as she did (CPRE Surrey v Secretary of State for Housing Communities and Local Government [2019] EWCA Civ 1826 at §§72, 74, 77). (3) An inspector's reasons do not have to set out the representations which have been put forward, or summarise the relevant evidence – with which participants in the process are familiar – but only need to set out the main parts of her assessment and the essential planning judgments in it (CPRE Surrey §76; Cherwell §25). The report is addressed to an informed audience and it is not necessary to refer to every material consideration or item of evidence (Cherwell §§25, 114).

The Inspector's Paragraph 127

15. Three things are, rightly, common ground. First, that the fitness for purpose of the Strategic Model was a principal controversial issue which the Inspector needed to resolve, giving legally adequate reasons for the view which she reached. Secondly, that the Inspector's reasons on the point were at paragraph 127 of her report. Thirdly, that in that paragraph "conclusions of WSP" were "ultimately adopted" and so the Inspector "adopted the Council's case" in relation to "the robustness of the [Strategic Model]" (as it is put in Mr Robson's skeleton argument).
16. Here is the Inspector's Paragraph 127. I have edited this so that labels are the same as in this Judgment. And I am inserting square bracketed numbers for ease of cross-referencing:

127. [i] The Strategic Model was used to assess the likely cumulative effect of the Local Plan's proposals on the highway network and to identify key interventions. [ii] The Strategic Model primarily uses 2014 as a base year and is due to be replaced by an updated multi-modal transport model. [iii] However, the Council's review of the validation levels of the Strategic Model against DfT criteria indicate[s] that it remains appropriate for strategic planning purposes. [iv] In addition, evidence of observed trends in traffic flows in Calderdale do not show significant changes between 2014 and 2019. [v] Furthermore, the Strategic Model uses data collected over long periods of time and in this respect I consider it provides a representative picture. [vi] Taking account of all evidence before me I am satisfied that the Strategic Model does not significantly underestimate traffic levels in Brighouse and is robust and proportionate for preparation of the Local Plan. [vii] Further detailed transport assessment work relating to specific sites will be required as part of the planning application process.

17. It is no function of the Court to write or rewrite reasons. But I do need to look at them and say what I see. I will start with what is on the face of §127, before we get to any question of reference-points and then criticisms.

On the Face of Paragraph 127

18. The Inspector started with a recognition of the function of the Strategic Model in preparation of the Local Plan [i]. She ended with a recognition that specific planning applications would have site-specific transport assessment work [vii]. She recognised a question-mark about 2014, outdatedness and planned replacement [ii]. She recognised a validation review [iii], traffic flow observations comparing 2014 and 2019 [iii], and data collection virtues [v]. She referenced all the evidence, and expressed her conclusions [vi]: first, regarding Brighouse (no significant underestimation of traffic levels); and then generally (robust and proportionate for preparation of the Local Plan).
19. In Lord Bingham's memorably pithy terms, I do not consider that the decision of the Inspector leaves room for genuine as opposed to forensic doubt as to what she has decided and why, this being resolved on a straightforward and down-to-earth reading of the Report, without excessive legalism or exegetical sophistication. This is from his judgment as Sir Thomas Bingham MR in Clarke Homes Ltd v Environment Secretary (1993) 66 P & CR 263 at 271-272, cited in South Bucks DC v Porter [2004] UKHL 33 [2004] 1 WLR 1953 at §33 and R (CPRE Kent) v Dover DC [2017] UKSC 79 [2018] 1 WLR 108 at §36. Without exegetical sophistication, or excessive exegetical sophistication, means without an overlay of elaborate interpretative explanation.

Reference-Points

20. The reasons were not being given in a vacuum. They were given in a setting of transparency as to published submissions and evidence, and with an informed audience. Avoiding exegetical sophistication, I can ask what reference-points I can see for the Inspector's reasons. All of this comes from the published record, fully familiar to the parties and published for the world to see. None of it constitutes my overlay or puts words into the Inspector's mouth. Here are the reference-points:

i) The model primarily uses 2014 as a base year and is due to be replaced by an updated multi-modal transport model. This is at [ii]. One criticism being made of the Strategic Model was that it represents a base year of 2014 (with some elements being from the original version in 2008), and as such was now beyond its useful life. This criticism was recorded in the 2021 Technical Note at p.2. Linked to this, a criticism was being made that the Strategic Model was further discredited as it had been identified, in an approval for funding, as subject to replacement by a multi-modal model. This criticism was recorded in the 2021 Technical Note at p.1. This approval for funding was the decision accepting the recommendation in the 2018 WYCA Report. The Forum's position was that this approval for funding confirmed the unsuitability of the Strategic Model, recorded in the 2022 Transport Position Statement at §1.5. It is clear that the Inspector considered that these raised relevant question marks, which needed an answer.

ii) However, the Council's review of the validation levels of the Strategic Model against DfT criteria indicate[s] that it remains appropriate for strategic planning purposes. This is at [iii]. It was in response to the recorded criticisms (including those at §20i above). WSP explained that the Strategic Model had been "validated against the criteria set by DfT for model validation across the model area which covers the Calderdale district"; that WSP had "reviewed the validation levels of the model and this was reported in Technical Note 10, showing that overall there was no particular issue in the Brighouse area for validation against journey times or traffic volumes" (2021 Technical Note at p.7). What was "reported in" Technical Note 10 under "Model review" – which had been "concluded from Sections 2 to 4" of that document – was that the "Strategic Model is a robust tool for the assessment of the local plan based on the validation results, comparison to Kirklees model and previous usage" (2018 Technical Note p.16). It is clear that the Inspector considered that she could rely on the indicated strategic appropriateness from this review of validation levels.

iii) In addition, evidence of observed trends in traffic flows in Calderdale do not show significant changes between 2014 and 2019. This is at [iv]. In response to the recorded criticisms (including those at §20i above), WSP explained that the Council "regularly count traffic on roads around the district"; that "the trends between 2014 (or the closest year observed) and 2019 (the latest year pre-pandemic) have been examined to understand if there have been any significant changes that would indicate that the model is under-representing the level of traffic as is claimed", and that the "conclusion" which "this note has demonstrated" was that "there has been little change in traffic flows between the base year of the [Strategic Model] and 2019" (2021 Technical Note pp. 2 and 7). It is clear that the Inspector considered that she could rely on this evidence of observed trends in traffic flows.

iv) Furthermore, the Strategic Model uses data collected over long periods of time and in this respect I consider it provides a representative picture. This is at [v]. In response to the recorded criticisms, WSP explained that: for journey times "the data used for the model was extracted from Trafficmaster GPS data from a sample of vehicles over an entire month of weekdays", in "June 2014 as this is a neutral time for traffic", and as "representative of average conditions for the year"; and for traffic flows the automatic traffic counter surveys had been "carried out for at least two weeks to give more representative observations" (2021 Technical Note p.6). This was describing the data used for the Validation Reports. It was responding to TTHC's observed journey time and traffic flow data, in the 2017 Transport Representation, based on "2 journey time runs per peak period for each day" and traffic flows in "one week in September" (2021 Technical Note p.6). It is clear that the Inspector considered that she could rely on the Strategic Model observed data collection as representative.

v) Taking account of all evidence before me I am satisfied that the Strategic Model does not significantly underestimate traffic levels in Brighouse and is robust and proportionate for preparation of the Local Plan. This is at [vi]. As everyone agrees, the evidence that was before the Inspector included from the Forum, the contents of the 2017 Transport Representation; the 2019 Transport Representation and the 2022 Transport Position Statement, as well as the contents of the 2021 Solicitors' Letter and the 2018 WYCA Report. It also included, from the Council, the contents of the 2015 Validation Report, the 2016 Validation Report, the 2016 Technical Note, the 2018 Technical Note and the 2021 Technical Note. TTHC's position was that the Strategic Model was a model which "substantially underestimates the levels of congestion in and around Brighouse and which WYCA agrees is a model no longer fit for purpose" (2022 Transport Position Statement §1.12). The latter point was another reference to the 2018 WYCA Report. WSP's position was the review of validation levels reported in the 2018 Technical Note showed that "overall there was no particular issue in the Brighouse area for validation against journey times or traffic volumes"; that "validation of the model is of an acceptable level for a Strategic Model and that there is no inherent weakness in the Brighouse area"; and that "the modelling methodology is robust and proportionate for the task of providing input to the Local Plan decision making process" (2021 Technical Note p.7). It is clear that the Inspector did not accept TTHC's criticism that the Strategic Model substantially (significantly) underestimated traffic levels in Brighouse; and she was satisfied that WSP had shown that the Strategic Model was robust and proportionate for preparation of the Local Plan.

21. In my judgment, it was clear – and especially to an informed audience – what the Inspector was referencing, and why, when she gave her reasons at Report §127. She was not in law obliged to include references to the documents or quotations from them. I have done so, to show how the reasons fit with key points which had been advanced, and how there is no mystery and would have been no mystery to the informed audience who received the Report.

The Forum's 'Unanswered' Points

22. Again, without exegetical sophistication, here is how Mr Robson helpfully encapsulated his case on why the Report §127 failed to give legally adequate reasons (again, edited to use the same labelling as in this Judgment):

The Inspector does not grapple at all with the following points underpinning the conclusion on robustness: (1) The conclusions of WYCA that the Strategic Model will not stand up to scrutiny … (2) That the Council, through WSP, do not dispute that the Strategic Model shows lower levels of traffic than observed for validation. (3) That the Council's evidence is that the WebTAG acceptability criteria are not met. And that the additional validation put forward through comparison with neighbouring Kirklees Council is also not passed. (4) In light of failing the WebTAG acceptability criteria, how can robust conclusions still be drawn from the Strategic Model to justify the Plan and conclude it is sound.

23. I will address these in turn:

i) The conclusions of WYCA that the Transport Model will not stand up to scrutiny. This was the 2018 WYCA Report. It was part of "all evidence before me" (at [vi]). It was relied on by TTHC and the Forum as to outdatedness and multi-modal replacement, raising questions, as was recognised by the Inspector (at [ii]): see §20i above. It was alongside the "significantly underestimate" point (at [vi]), in the context of fitness for purpose: see §20v above. It was in law unnecessary for the Inspector to say more. She identified her answers to the questions which had been raised. The 2018 WYCA Report was one item of evidence. The points made about it were one strand of argument.

ii) I add this. I find it unsurprising that the Inspector did not say more. I make these observations by way of footnotes. (1) The 2018 WYCA Report did not involve any freestanding evidence base or analysis. (2) It was about a "multi-modal model" in the context of a programme incorporating multiple modes of transport – including "public transport, highway and active pedestrian and cycling modes" – rather than being about highways and vehicles (2018 WYCA Report §2.39). (3) The "issues" were about suitability to support the development and appraisal of full business cases" for 6 listed projects (§2.38). (4) Those issues raised "concerns" about whether analytical works would "stand up to scrutiny" at a public inquiry in relation to one of these projects (§2.40). (5) The Inspector was concerned with modelling for adoption of the Local Plan and specifically recognised (Report §127 at [vii]) that full detailed transport assessment work would be needed as part of any project-specific planning application. (6) In the event, even WYCA continued – at least to 2021 – to use the Strategic Model for assessing WYCA transport schemes (2021 Technical Note p.1). (7) WSP carried out a "further check" exercise using modelled flows from the unapproved "2019 base year multi-modal model", for key locations in Brighouse, which WSP said "further demonstrates" that the Strategic Model "is not underplaying traffic levels as suggested" (2021 Technical Note p.5).

iii) That the Council, through WSP, do not dispute that the Strategic Model shows lower levels of traffic than observed for validation. This too was part of "all evidence before me" (Report §127 at [vi]). It was discussed at 2021 Technical Note p.7. This was being relied on by the Forum and TTHC in points made when TTHC "reviewed the validation of the [Strategic Model] against the traffic counts recorded in 2014 and highlight that generally the model shows lower levels of traffic than observed". WSP explained that "this fact is not disputed" but went on to make the very points which the Inspector recorded (Report §127 at [iii]) about the review of the validation levels of the Strategic Model against DfT criteria indicating that it remained appropriate for strategic planning purposes. I have already summarised the reference-point material (§20ii above). TTHC was pointing to data within the Validation Reports themselves, comparing observed traffic levels against modelled traffic levels. WSP's answer was to point to the overall validation judgments, against the DfT criteria. As has been seen, the Inspector considered that she could rely on the indicated strategic appropriateness from this review of validation levels.

iv) That the Council's evidence is that the WebTAG acceptability criteria are not met. And that the additional validation put forward through comparison with neighbouring Kirklees Council is also not passed. In light of failing the WebTAG acceptability criteria, how can robust conclusions still be drawn from the Strategic Model to justify the Plan and conclude it is sound. These two points go together. This too was part of "all evidence before me" (Report §127 at [vi]). This was another point about comparing observation data with modelled data, looking at the Validation Reports themselves and WSP's review of validation of levels. The reference to comparison with Kirklees is to an exercise within the 2021 Technical Note p.1, from the 2018 Technical Note pp.4-7, which included a comparison using the GEH Statistic and comparing modelled traffic flows at 9 key routes, including "further investigation" said by WSP to show "very similar flows" and where there was a discrepancy, the Strategic Model was validating well and more accurate than the Kirklees model. As to the WebTAG acceptability criteria "not being met" – and "failing" those criteria – this was a point about link flows and the GEH Statistic. Both TTHC and WSP drilled down into this picture. It was addressed in the 2018 Technical Note at p.4 (§§2.14 and 2.15), where WSP had said

VALIDATION LINK FLOW PERFORMANCE. 2.14. In the AM peak the counts to the west of Elland show a number of high GEH values, otherwise the sites which do not meet the DfT criteria set out in WebTAG are very close to passing. 2.15. In the PM peak, a similar pattern is shown with most failures against the DfT criteria showing a GEH of less than 10. A few counts show higher GEH values in central Elland.

v) Again, the questions were being answered in the very points which the Inspector recorded (Report §127 at [iii]), about the review of the validation levels of the Strategic Model against DfT criteria indicating that it remained appropriate for strategic planning purposes (§20ii above). Again, TTHC was pointing to data within the Validation Reports themselves, here where the GEH Statistic was applied to various "validation links". WSP's answer was to point to the overall validation judgments, against the DfT criteria. Again, as has been seen, the Inspector considered that she could rely on the indicated strategic appropriateness from this review of validation levels.

vi) Again, I find it unsurprising that the Inspector did not say more. I make these observations by way of footnote. (1) The 2015 Validation Report had set out the picture regarding link flow calibration and validation (§6.4), applying the GEH Statistic (§6.4.2), and setting out traffic flow tables viewed against the GEH Statistic, for calibration links and validation links including in AM Peak and PM Peak (pp.37-40) and reasoned conclusions were set out as why the results were of a sufficient standard to provide confidence that the Strategic Model was replicating existing traffic conditions (§§6.7.1 to 6.7.2). (2) The 2016 Validation Report revisited that picture (§6.5), with corresponding tables (pp.39-44), and included this about whether the GEH Statistic was a litmus test (§6.5.5):

A GEH value greater than 10 indicates that closer attention is required as the match between observed and modelled flows is poor, while a GEH of less than 5 indicates a very good fit.

That report went on to make observations about the picture "when calibration and validation links are combined" (§6.5.11); about link validation falling "just outside WebTAG criteria", with "not very many links with large differences in flow" and with a "good overall fit" when calibration and validation results are combined (§6.5.31); and about a picture which shows that the model provides a satisfactory representation of existing traffic conditions (§6.7.1). (3) Those Validation Reports provided the source material on which the TTHC criticism and WSP response were based. (4) The 'litmus test' point is addressed in the DfT Transport Analysis Guidance (May 2018) at §3.5.3 (see §10 above) and in the PPG (13 March 2015) at §10 (see §13(8)(ii) above).

Conclusions

24. I have not been able to find any legal inadequacy in the Inspector's reasons, whether: (1) viewed in terms of what they say on their face (§§18-19 above); or (2) viewed in terms of the context of clear reference-points (§§20-21 above); or (3) viewed in terms of the criticisms made (§§22-23 above). Stepping back, I can test the position in these ways. First, the Forum knows what views the Inspector took and accepted and would be able to criticise her conclusion on its merits. Secondly, the Forum knows what views the Inspector took and accepted and would have been able to have mounted a legal challenge – if there were a viable legal challenge – as to the reasonableness of her conclusion that the Strategic Model was robust and proportionate for preparation of the Local Plan. The Inspector discharged her statutory obligation to give reasons. She gave clear, adequate and intelligible reasons, which make plain how she resolved the principal important controversial issue as to the fitness for purpose of the Strategic Model. She did not have to set out the representations which have been put forward, or summarise the relevant evidence, with which the participants in the process were familiar. The reasons were briefly stated, but with a legally sufficient degree of particularity in light of the issues falling for decision. The Inspector's reasons explained to the parties and the wider readership of the Report why, as a matter of evaluative judgment, she concluded as she did. I will therefore dismiss the claim for statutory review.
25. The parties were agreed that the appropriate order, in light of this judgment circulated in draft, is: (1) the claim is dismissed; (2) within 28 days of the Order, the Forum is to pay the Council's costs of contesting the claim in the sum of £10,000.