Tested against Greater Manchester and Portland, Oregon

Introduction

Few ideas in planning sound as reasonable as the claim that plans should rest on evidence. Who would argue for planning without data, analysis or monitoring? Yet in the United Kingdom, evidence-based planning has been one of the most criticised ideas in planning scholarship of the past two decades. This article follows one line of thought from the beginning: what the evidence base is and why it matters, why UK planning literature criticised the evidence-based approach, what orientations the critics preferred, and how the argument stands when tested against two real cases, the Greater Manchester Spatial Framework in England and the Portland Metro urban growth boundary in Oregon.

The article also draws on Faludi and Waterhout’s 2006 essay introducing evidence-based planning, which treats the subject more carefully than its harsher critics. Their central point, that evidence is never self-evident and has to be argued into meaning, makes a useful bridge between the critique and the cases.

What the Evidence Base Is and Why It Matters

The evidence base is the body of data, analysis and studies on which a plan’s policies rest. In practice it includes population and household projections, housing need assessments, employment and economic forecasts, land availability studies, infrastructure capacity, transport modelling, flood and environmental assessments, viability testing and the results of public consultation. It is what turns a plan from a statement of intent into something that can be defended, tested and delivered.

Its importance can be set out in six points.

• Justification. Every policy must answer the question “why this, and why here?” Without evidence, a policy is a preference.
• Procedural soundness. In England a local plan is examined by an independent inspector, who tests whether it is “sound”: positively prepared, justified, effective and consistent with national policy. Plans have been delayed or withdrawn because the evidence on housing numbers, site selection or viability was weak or out of date.
• Defence at appeal. Decisions on planning applications are more robust when tied to documented evidence than when they rest on judgement alone.
• Delivery. Viability and infrastructure evidence show whether allocated sites can be built and whether the services they need can be funded.
• Transparency and trust. Published evidence lets communities, developers and councillors see how decisions were reached, even when they disagree with the outcome.
• Monitoring. A baseline allows the plan’s performance to be measured and a review to be triggered.

Even its supporters accept limits. Evidence is selected rather than neutral, it ages quickly, it is expensive for small authorities to produce, and it favours what can be measured over place quality and lived experience. These limits are where the criticism begins.

The Critique in UK Planning Literature

The criticism comes from several directions. Davoudi (2006), writing in the same issue of disP as Faludi and Waterhout, questioned the gap between the rhetoric and the reality of evidence-based planning. Sanderson (2002) raised similar doubts about evidence-based policy more broadly, and Flyvbjerg’s work on rationality and power supplied much of the underlying argument. Together these authors make eight main points.

• A rationalist assumption. Evidence-based planning descends from the rational comprehensive model: gather data, analyse it, and the right policy follows. Critics reply that planning problems involve competing values and interests, so evidence cannot settle them alone.
• Evidence is selected and used politically. Flyvbjerg argued that power shapes which knowledge counts. In practice evidence is often assembled after the preferred policy has been chosen, a pattern sometimes described as policy-based evidence rather than evidence-based policy.
• Forecasts treated as facts. Much planning evidence is projection of population, households, jobs or prices. Projections rest on assumptions and are often wrong, yet they harden into targets. Housing numbers are the clearest example.
• Privileging the measurable. Quantitative evidence gains weight over experiential, local and tacit knowledge. Communicative theorists such as Healey and Innes argue that this narrows what counts as legitimate knowledge.
• A procedural burden. The soundness regime pushed councils to produce large volumes of studies to survive examination. The result is a defensive evidence base, costly and slow, which favours well-resourced parties.
• A contest of experts. Because soundness depends on evidence, every party commissions its own studies, and examinations become battles between consultants.
• A weak link to outcomes. Plans with extensive evidence still fail to deliver housing or infrastructure when the barriers are financial, political or about land ownership.
• Conceptual confusion. The phrase comes from medicine, where interventions can be tested under controlled conditions. Places are unique, so some authors prefer “evidence-informed” planning.

The toolkit and its critics

A second set of criticisms concerns the toolkit itself: spatial monitoring, evaluation studies, indicators and best practice. Indicators measure what is easy to measure, and best practice assumes that a solution which worked in one place can be moved to another, ignoring local politics and land markets. Critics described the whole approach as a revival of rational planning. The model of survey, analysis, forecast, plan and monitor was heavily criticised in the 1970s, notably through Lindblom’s incrementalism and later communicative theory, yet it returned with better data and GIS but without answers to the old objections. It also looked back further still, to the survey-before-plan tradition of Patrick Geddes.

Critics added that the approach was too concerned with knowing how to plan. Method and technique crowd out the question of what planning is for and for whom, so a plan can be procedurally perfect and silent on values. The New Labour slogan that policy should be framed less by the ideas of the past than by what works was read as pragmatism over ideology, but critics pointed out that deciding what works requires a prior judgement about the goal, which is a value choice. Finally, under New Public Management, evidence served accountability. Targets, indicators and audit allowed central government to steer local authorities and judge them by outputs such as completions and decision speed. Evidence became a tool of control as much as of understanding.

Why the Critics Took This Position, and What They Proposed

Several factors explain the UK critique. Many of its authors, among them Healey, Davoudi, Allmendinger, Tewdwr-Jones and Hillier, came out of the 1970s and 1980s turn against rational planning and had already argued that planning is a social and political process. The political context mattered too: the language arrived with New Labour’s modernisation agenda and the 2004 reforms that introduced the soundness test. Their view of knowledge held that planning knowledge is partly technical but also experiential, local and value-laden. And following Flyvbjerg and Foucault, they asked who defines the evidence, who commissions it and whose interests it serves.

There was no single alternative. Several orientations competed:

• Communicative and collaborative planning (Healey, Innes, Forester): planning as deliberation among stakeholders, with knowledge produced through dialogue as well as data.
• Phronetic, power-aware planning (Flyvbjerg): practical judgement and values, asking who gains and who loses.
• Agonistic planning (Mouffe-inspired work by Hillier, Gunder and others): conflict cannot be removed by consensus or evidence, so planning should make disagreement visible and legitimate.
• Strategic spatial planning (Healey, Albrechts): vision, place-making and selective long-term strategy, with evidence in support rather than leading.
• Evidence-informed planning (Davoudi): the moderate position, keeping evidence as one input into open, accountable judgement.

What unites these is that they place values, politics and judgement at the centre and treat evidence as a servant of that process. The alternatives were criticised in turn. Communicative planning was accused of naivety about power and of producing consensus that favours the already powerful, and agonistic planning of offering little practical guidance. Developers and central government argued that without a strong evidence base, plans become arbitrary and hard to challenge.

A More Balanced Reading: Faludi and Waterhout

It would be a mistake to treat the whole literature as hostile. Faludi and Waterhout (2006) helped introduce evidence-based planning, and their essay is better read as a careful qualification than as an attack. They draw on Kooiman, Flyvbjerg and Popper to make six arguments, which can serve as a second lens for the cases that follow.

• Evidence is argued into meaning. Its meaning is never self-evident and must be established through argument, so the evidence-based turn and the earlier communicative turn are not opposites.
• A decision-centred view. Defining a decision situation is itself the result of decisions about what counts as relevant, so facts and values cannot be strictly separated.
• The gap between evidence and action. Geddes’s “survey before plan” treated the step from knowledge to action as a creative leap. How evidence relates to decisions needs explicit attention.
• Choosing what to investigate is political. What counts as decisive evidence and how research programmes are framed are matters of choice, as the negotiations over the ESPON research network showed.
• Research and policy run on different clocks. Evidence is often unavailable when needed, and independent researchers face a trade-off between reliability and relevance.
• Purposes have changed. Collecting information is ancient, but evidence now works through evaluation studies, indicators and good practice, which can serve both mutual learning and the steering of partners.

The authors also reject two easy dismissals. Evidence-based planning is not simply a revival of survey before plan, and it should not be written off as technocratic. The real question is how it works in practice, which is what the two cases test.

Case One, England: The Greater Manchester Spatial Framework

The ten Greater Manchester authorities set out to prepare a joint plan, the Greater Manchester Spatial Framework, with housing need, employment land and Green Belt release at its core. A first draft appeared in 2016 and a revised version in 2019. In 2020 Stockport withdrew, and the remaining nine authorities continued with a revised plan, Places for Everyone, which was examined and adopted in 2024.

The case is useful because the evidence base was central and openly contested. The housing target depended on official population and household projections and on the government’s standard method for calculating housing need. When projections and the method changed, the numbers moved, and with them the argument about how much Green Belt to release. Proponents said release was needed for growth. Objectors answered that brownfield capacity and lower projections made it unnecessary. The same evidence supported opposite conclusions. Table 1 shows points from discussion for this case study

Table 1 – points from discussion for this case study

Through the Faludi and Waterhout lens, the case shows evidence being argued into meaning, since the decisive question was which projection and which method to accept. It shows research and policy running on different clocks, because new projections arrived while the plan was still in preparation. The withdrawal of one authority shows the limit of the approach most plainly: a disagreement about values could not be resolved by more technical work. The case also bears on devolution. A city region with a joint plan still operated inside national rules on how need is calculated, which reflects the central steering the critics described.

The procedural burden is visible as well. A plan that began in 2014 reached adoption only in 2024, a decade in which the evidence had to be refreshed, defended and re-examined. Supporters of the process would say that this scrutiny protected communities from poorly justified Green Belt release. Critics would answer that the time and cost favoured those able to fund consultants, and that homes and infrastructure waited while the evidence was argued over.

Case Two, United States: Portland Metro and the Urban Growth Boundary

Oregon’s statewide planning system, created in the 1970s, requires urban areas to maintain a 20-year supply of land for housing and employment. In the Portland region, the elected regional authority Metro prepares an Urban Growth Report every few years, with population and employment forecasts and an inventory of buildable land. It then decides whether to expand the urban growth boundary or to accommodate growth by building at higher densities inside it. Metro also maintains regional indicators and draws on smart growth and transit-oriented development models that other cities have copied.

This is among the most systematic examples of evidence-based land planning in the western world. It is also a strong contrast with Manchester, because the process sits within a stronger regional and state framework, so evidence is used where authority is real rather than where local authorities are steered from above. Table 2 shows points of discussion for this case study

Table 2 – points of discussion for this case study

In Faludi and Waterhout’s terms, the Portland system makes the political choice about evidence unusually visible. The boundary itself is a value decision, and the forecast, the land inventory and the assumptions about future density are all arguments about what the future should be. The design also shows the independence trade-off: a regional body with its own analytical capacity can produce credible forecasts, but those forecasts are still produced by the institution that will act on them.

The Portland case also tests the idea of best practice. Planners elsewhere have borrowed the growth boundary and the indicators, but the system works because of conditions that cannot be copied easily: a state law that obliges every city to plan, a regional government elected by the people it governs, and a political culture that accepts containment. Where those conditions are missing, the techniques travel and the results do not, which is exactly the transferability problem the UK critics identified.

What the Two Cases Show Together

Four conclusions follow from placing the cases side by side.

• In both, evidence structured the argument but did not settle the decision.
• In both, the key evidence was a forecast, and the real dispute was about assumptions.
• The governance structure changes the political weight of evidence. In England it worked as an instrument of central steering over weak local authorities and an unfinished city-region. In Oregon it operates within a rule-based regional system with genuine powers.
• Both support the evidence-informed position: evidence is necessary, but legitimacy comes from open political judgement.

These points matter for the wider debate. The UK critics were right that evidence cannot settle questions of value, but the cases suggest that the remedy is not to abandon evidence. In Manchester, the planning process improved when the political choices were made openly and the evidence was used to test them. In Portland, the system is credible because its value position is stated in law and the evidence is used to implement it. In both, the quality of the plan depended less on the volume of evidence than on how honestly the argument around it was conducted.

Is Planning, Then, a Political Activity?

The argument so far invites a strong conclusion: that in the UK, planning is a political activity, and that it rejects rationalism and management. That conclusion is partly right, but it needs careful wording.

What is accurate is that a major strand of UK planning theory treats planning as inherently political. Healey, Flyvbjerg, Hillier and others argue that planning always involves choices about values, interests and power, and that no technical method removes them. The evidence-based, rationalist and managerial approach was criticised because it presented political choices as technical findings. Both cases support this reading, since in each the decisive questions, how much Green Belt to release and where to draw the growth boundary, were questions of value.

Four qualifications are needed. First, the critics did not say that planning is only politics. Most accept that evidence, analysis and technical skill matter, and their claim is that planning is never only technical. Faludi and Waterhout make the same point: facts and values cannot be strictly separated, yet evidence still has to be argued over. Second, most scholars rejected the claim that rational methods can settle planning questions, not rationality as such, and even the moderate position of evidence-informed planning keeps reasoned analysis. Third, management was criticised when it steered local planning through targets and audit and reduced planning to the delivery of outputs, but coordination, delivery and monitoring are not rejected. Fourth, the critique comes mainly from the academic literature, while UK practice largely adopted the evidence-based and managerial model, because the soundness test and national policy require it.

A safer formulation therefore runs as follows. Much of the UK planning literature treats planning as an inherently political activity. It rejects the claim that rational, evidence-based and managerial methods can make planning a neutral technical exercise. At the same time, UK practice has embraced those methods, so the tension between political and technical views of planning is built into the system.

Conclusion

Evidence-based planning is important because it makes plans defensible, transparent and deliverable. The UK critique is also right that it is not neutral. It carries a rationalist theory of planning, a managerial theory of government and a claim that ideology has given way to what works. Faludi and Waterhout’s contribution is to keep both truths in view: evidence matters, and its meaning is always argued.

The Manchester and Portland cases bear this out. In both, evidence shaped the debate but values decided it, and the difference lay in the institutions around the evidence. The practical lesson is to be explicit about what counts as evidence and why, define the decision before gathering data, and keep the political choice visible instead of hiding it behind a technical finding. Evidence should serve judgement, not replace it.

Frequently Asked Questions

What is an evidence base in planning?

The evidence base is the body of data, analysis and studies that a plan’s policies rest on. It includes population and household projections, housing need, employment forecasts, land availability, infrastructure capacity, environmental assessments and viability testing. It lets a plan be justified, tested and defended.

Why is evidence-based planning important?

It makes policies justifiable, helps a local plan pass independent examination, strengthens decisions at appeal, shows whether sites can actually be delivered, and gives communities a transparent record of how decisions were reached. It also provides a baseline for monitoring the plan.

Why has evidence-based planning been criticised in the UK?

Critics argue that it revives the rational planning model and treats evidence as neutral when it is selected and framed politically. They also note that much evidence is forecasting, that it favours what can be measured, that it turns examinations into contests between consultants, and that it can serve central government steering through targets and audit.

What is the difference between evidence-based and evidence-informed planning?

Evidence-based planning implies that evidence decides the outcome. Evidence-informed planning treats evidence as one input into open, accountable judgement. Many UK planning scholars prefer the second term because planning involves values that evidence cannot settle.

What alternatives did critics propose?

Communicative and collaborative planning, phronetic and power-aware planning, agonistic planning, and strategic spatial planning. All place values, politics and judgement at the centre and treat evidence as support.

What do the Greater Manchester and Portland cases show?

In both, evidence structured the debate but did not settle the decision. The key evidence was a forecast, and the real dispute was about assumptions and values. The difference lay in governance: England used evidence for central steering, while Oregon used it within a regional system with real powers.

References

Davoudi, S. (2006) Evidence-based planning: rhetoric and reality. disP – The Planning Review, 42(165), 14–24.

Faludi, A. and Waterhout, B. (2006) Introducing evidence-based planning. disP – The Planning Review, 42(165), 4–13.

Flyvbjerg, B. (1998) Rationality and Power: Democracy in Practice. Chicago: University of Chicago Press.

Healey, P. (1997) Collaborative Planning: Shaping Places in Fragmented Societies. Basingstoke: Macmillan.

Lindblom, C. (1959) The science of “muddling through”. Public Administration Review, 19(2), 79–88.

Sanderson, I. (2002) Evaluation, policy learning and evidence-based policy making. Public Administration, 80(1), 1–22.

Greater Manchester Combined Authority, Places for Everyone and associated evidence documents; Metro (Portland), Urban Growth Reports.