Written evidence submitted by the Mayor of London and Transport for London (HEN0067)

Introduction

1               The Mayor of London and Transport for London (TfL) welcome the opportunity to provide evidence to the Transport Committee's scrutiny of the draft Heathrow Expansion National Policy Statement (HENPS). This includes the accompanying assessments published as well as ‘A strategic vision for transport to an expanded Heathrow Airport’. The Mayor and TfL will also submit a response to the government’s consultation on the HENPS.

2               The Mayor has responsibility for the economic and environmental well-being of Londoners and provides this submission in that context. TfL has responsibility for the safe, sustainable and effective operation of the (surface) transport network, recognising that also has important implications for the Mayor’s wider policy objectives.

3               Heathrow Airport plays an important role in the London and wider UK economy. Nonetheless, its expansion has significant implications for the environment, public health, transport networks and the delivery of wider government objectives.

4               Government is pressing ahead with its update of the policy framework of the original Airports National Policy Statement (ANPS), designated in 2018, to take forward a third runway. An expanded Heathrow is expected to handle up to 150 million passengers per annum (mppa)[1], a 79 per cent increase on 84 mppa today[2]. This will be based on a 58 per cent increase in aircraft movements, from 480,000[3] to 756,000[4] annually. Cargo throughput is proposed by Heathrow Airport Limited (HAL) to increase by 50 per cent[5].

Key concerns

5               The strategic case for expansion at Heathrow has not been sufficiently made. The HENPS relies heavily on the 11-year-old findings of the Airports Commission, with inadequate account taken of material changes since then, including a substantial decline in business travel, approval given for increased capacity at a number of UK airports, including some serving the capital, and the UK’s adoption of a net-zero carbon target (which now formally incorporates the UK’s share of international aviation).

6               There is a significant gap between the strategic narrative and the evidence presented. Many of the benefits underpinning the government’s argument are uncertain, only partially quantified, outside the core appraisal framework, or require complementary policies beyond airport expansion which are not assessed. Even on this basis, the government’s appraisal finds the scheme to have a negative net present value (NPV) of between -£23bn and -£63bn[6] – i.e. an overall social disbenefit to the UK.

7               The three environmental tests do not provide sufficient reassurance that an expanded Heathrow can be delivered without very serious environmental impacts. Instead of seeking to avoid environmental harm, the approach appears to be to enable more flights with the negative environmental impacts they’ll bring, while meeting environmental targets by taking advantage of environmental improvements unrelated to airport expansion, which would otherwise accrue to local communities, London and the UK.

8               London has met legal limits for air pollution almost 200 years earlier than predicted, in no small part a result of Mayoral policies such as the Ultra Low Emission Zone (ULEZ). While this represents significant progress there is still more work to do in order for London to meet the more stringent World Health Organisation (WHO) Air Quality Guidelines. The HENPS allows Heathrow expansion to take advantage of this headroom created, to substantially increase air pollution back up to legal limits across a wider area, meaning the health benefits to local communities that would have otherwise been felt will be lost. Between 2019 and 2024, in the Heathrow study area, average NO2 concentrations have been reduced by 34 per cent, and PM2.5 concentrations have been reduced by 28 per cent[7] – this progress must not be undone by the expansion.

9               The requirement to maintain noise at 2024 levels is to deny local communities the benefits of any reduction in noise that comes from technological and operational advances, as this will be used instead to enable more flights. Other proposed mitigations provide no more reassurance, with respite half of what is currently offered for the majority of those under the flightpaths, while the changes in scheduled night flights proposed, far from constituting a ban on such flights, could in practice lead to them doubling.

10          The carbon test allows Heathrow expansion to claim alignment with UK net-zero targets by allowing it to rely wholesale on decarbonisation of wider sectors, and the efforts and investments by others on which they are based. The UK has made good progress on reducing its carbon emissions but we cannot assume decarbonisation will happen in other sectors of the economy and must take active steps to understand the impacts of Heathrow expansion on our Carbon Budgets.

11          More generally, public health is a key concern, with the lack of a sufficiently robust or enforceable framework in the HENPS and without proper assessment of the cumulative impacts. Communities experience air pollution, noise, climate impacts, and construction disruption in combination, not in isolation. Those already experiencing poorer health already face compounded and mutually reinforcing harms.

12          With regard to surface access, the provision as it is today would be wholly inadequate to meet the needs of an airport with a 79 per cent increase in passenger throughput. TfL and the GLA welcome recognition of the need for a significant shift to sustainable modes – including the need for new rail connectivity – but this needs to be underpinned by clear requirements on the promoter.

13          The sustainable mode share targets proposed are weak in the case of passengers, at just 55 per cent – and none are proposed for staff and freight. We estimate that this could result in an additional 60,000 highway trips every day – equivalent to 22m extra highway trips annually. This will create intolerable strain on the highway network, worsening congestion, increasing air pollution and carbon emissions and eroding the economic benefits in the wider region.

14          Aside from the improved public transport connectivity needed to encourage the shift towards sustainable modes, additional capacity will be required to accommodate the resultant flows. Even meeting the HENPS targets for passenger trips will entail an extra 40m trips by sustainable modes annually, a 200 per cent increase on today. If sufficient mode shift could be achieved to avoid any increase in highway trips, that could rise to a 63m trip and 255 per cent increase annually on sustainable modes.

15          Given the scale and potential impacts of Heathrow expansion, it is essential that the HENPS does more than state policy ambitions: it must provide confidence that these objectives will be achieved and enforced – which it currently does not do. The HENPS relies on assessment and mitigation to be undertaken by a promoter at a future date, without providing the requisite certainty regarding delivery, monitoring and accountability.

Responses to the Committee questions

a. The extent to which the draft HENPS provides clear and coherent guidance to the Secretary of State about how to assess a proposed scheme

16          In its current form, the HENPS, does not provide a sufficiently clear or coherent framework for decision-making. Across several areas and topics, the HENPS falls short of setting out the measures which would address the adverse impacts of expansion, including environmental, surface access and public health.  In many instances, the HENPS defers management of impacts to the future Development Consent Order (DCO) process, with limited mandatory requirements and overreliance on the applicant’s assessment, proposed mitigation and self-monitoring.  Whilst this approach gives the promoter flexibility as to how a future scheme may come forward, it does not provide clarity on how an applicant might be held to account. Broad principles and recommendations do not offer the certainty that the impacts will be addressed.

17          With regard to surface access, there are inconsistencies in the text, across both the HENPS and the Strategic Vision for Transport documents. Clarification is needed on whether some of the measures, such as new southern and western rail links, are necessities, recommendations or merely options for consideration – and if they have merit on their own terms or only as a stepping stone to meeting a mode share target.

18          For the most part, the HENPS does not put in place the controls that would support clarity and coherence of what is to be delivered. This is particularly problematic for surface access because if conditions are not met, there is a risk of severe congestion with detrimental economic and environmental impacts.

b. The robustness of the government’s evidence and rationale for the need for a third runway at Heathrow Airport

19          There are substantial concerns about the evidence underpinning the need for a third runway. Foremost amongst these is the heavy reliance placed by the HENPS on the 11-year-old findings of the Airports Commission (AC) to re-make the case for a third runway at Heathrow. The AC published its findings after a lengthy process of detailed analysis and calls for evidence to answer broader questions on whether there was need for new runway capacity in the South East, what form it should take and where.

20          The HENPS relies on the AC analysis to confirm the selection of the Heathrow Northwest Runway scheme without revisiting the process that the AC undertook and any supplementary analysis appears to be focused on revalidating expansion at Heathrow with insufficient thought given to the wider capacity need and whether Heathrow remains the most suitable location. This is a particular issue given key factors which have changed in the interim, which are set out in answer to question j.

21          While economic benefits are identified, the evidence provided by government does not provide an unequivocal economic case for expansion. The government’s earlier public case drew heavily on economic growth claims, including Frontier Economics analysis cited by the Chancellor in January 2025[8] suggesting that a third runway could increase potential GDP by 0.43% by 2050[9]. The recent Department for Transport (DfT) appraisal presents a more cautious picture, with DfT commissioned analysis reported as finding that expansion would add up to only 0.05% to GDP in 2056[10] – an almost 90% reduction from the previous Frontier Economics’ figure. Further, this appraisal by government also indicates a negative Net Present Value (NPV) – which could undermine growth. 

22          The appraisal framework used is arguably insufficient to demonstrate the benefits discussed in the strategic case. The HENPS would benefit from greater clarity regarding the sectors, markets and economic mechanisms expected to underpin the growth case, including how enhanced connectivity is expected to support productivity, trade, tourism, investment and wider economic growth across the UK. 

23          There is also limited evidence to suggest that economic benefits achieved from expansion are truly additional and not merely redistributed from other regions and airports. Growth benefits appear to be contingent on complementary policies and significant transport investment, which are not fully assessed in the HENPS appraisal and could further affect value for money.

24          The scope and underpinning analysis of the HENPS needs to more clearly distinguish between strategic aviation need, quantified economic benefit, and the practical conditions required to realise that benefit.

c. Whether it is appropriate for Heathrow expansion to be designated as Critical National Growth Infrastructure

25          The GLA and TfL do not believe that it is appropriate for Heathrow expansion to be designated as Critical National Growth Infrastructure (CGNI).

26          The government appears to make the argument for Heathrow’s designation as CGNI on the economic case given Heathrow’s role as the UK’s only hub airport, its importance for international connectivity, trade, freight and tourism, and the government’s view that additional capacity could support economic growth, resilience and more than 60,000 jobs.

27          A key implication of the CNGI designation would be that if legal requirements are met and mitigations are applied – including the requirements of the Habitats Regulation Assessment – then any residual impacts would be considered to be outweighed by the urgent need for the infrastructure in support of growth – i.e. the CNGI will be a proxy for consent.

28          The CNGI framework closely follows the Critical National Priority (CNP) designation that the government gave low carbon infrastructure in the then draft Energy NPS EN-1[11] when it was published for consultation in 2023. The policy and legal basis of CNP was clear and followed from major pieces of legislation such as the Climate Change Act 2008 and the Carbon Budgets.

29          By contrast, the reasoning behind the CNGI designation for Heathrow expansion is unclear. Paragraph 4.16 of the HENPS explains that the CNGI label is appropriate because the Heathrow expansion is “critical to national growth”. , This has not been demonstrated and the government’s own analysis assessed a 0.05% Gross Domestic Product uplift in 2056[12]. The CNGI designation is therefore unjustified on the grounds put forward in the HENPS.

30          Additionally, the CNGI framework sets lower environmental standards for the Heathrow expansion promoter than the CNP designation. The Overarching National Policy Statement for energy (EN-1) provides that applicants for CNP “should demonstrate that all residual impacts are those that cannot be avoided, reduced or mitigated”[13]. The accompanying footnote 79 also states: “As set out in Section 4.6 of this NPS, developers should seek opportunities to contribute to and enhance the natural environmental by providing net gains for biodiversity, and the wider environment where possible”.

31          The omission of this text from the CNGI designation is concerning and, as a minimum, should be added to the HENPS. The effect of this difference with the CNP wording is that promoter of Heathrow expansion does not need to provide as robust a justification for residual impacts.

32          The HENPS states that the exceptional circumstances that may outweigh the CNGI presumption “include where residual impacts remain which present an unacceptable risk to, or unacceptable interference with human health, public safety, defence, irreplaceable habitats or flood risk”[14]. Without the additional wording in the CNP designation mentioned above, the Heathrow expansion scheme may result in residual impacts that could have been avoided, reduced or mitigated – but so long as they do not meet the very high bar of presenting an unacceptable risk or unacceptable interference then these impacts will be permitted and no justification from the applicant will be required. This is not a fair deal for communities affected by the expansion. 

33          The Appraisal of Sustainability (AoS) makes it clear that the government seeks to use the CNGI designation to prioritise purported socio-economic benefits above the environmental impacts of the expansion scheme. It assesses the overall effect of CNGI as “mixed” despite the potential for major adverse effects on biodiversity, natural resources, landscape and communities[15]. The AoS assumes that all of these effects are balanced by the potential for economic growth, employment, productivity and international connectivity. This is flawed reasoning as socio-economic benefits do not negate the need to avoid environmental impacts.

d. How effectively and robustly the draft HENPS sets out the assumptions and requirements of the government’s ‘four tests’ for expansion, on:

» Economic growth across the country

34          The HENPS establishes that expansion must deliver a credible and meaningful contribution to UK wide economic growth, supported by a clear plan for how benefits will be realised. There is a considerable disconnect, however, between the transformational economic outcomes described in the strategic case and the impacts quantified through the DfT’s supporting appraisal. Heathrow expansion is presented as a nationally significant growth intervention capable of generating transformational economic benefits, yet the quantified wider economic impacts are relatively modest and many of the benefits relied upon by the strategic case are also either highly uncertain, only partially quantified, dependent on displacement assumptions, or deferred to future promoter-led growth strategies.

35          The HENPS states that expansion could generate £29.2bn–£42.4bn of benefits and contribute up to 0.05% to UK GDP. However, the appraisal concludes a negative Net Present Value and acknowledges that important impacts, including trade, tourism and wider distributional effects, are not fully captured. This raises questions as to whether the evidence presented adequately supports the scale of economic transformation described. The HENPS also provides limited evidence on the mechanisms through which growth will be realised in practice and the conditions required for those benefits to occur. Many of the claimed benefits also appear contingent on complementary policies and significant surface transport investment, which are not fully assessed within the appraisal and could further affect value for money. Claims relating to economic additionality, productivity impacts, international hub displacement, the distribution of benefits across the UK and the transport infrastructure required to support expansion warrant further scrutiny.

36          The HENPS requires promoters to prepare an evidence-based growth strategy[16], yet many key elements of the growth case are deferred to future promoter-led work rather than being evidenced within the HENPS itself. The HENPS needs to demonstrate how enhanced connectivity is expected to support productivity, trade, tourism, investment and wider economic growth, and on the extent to which these benefits represent genuinely additional economic activity rather than redistribution between airports, regions or sectors. Further scrutiny is also required of employment impacts, including their composition, quality, additionality and the sensitivity of the economic case to airport charges and cost pass-through assumptions.

37          The HENPS should provide greater clarity on the nature and distribution of economic benefits arising from Heathrow expansion. This should include evidence on how benefits accrue across London, the South East and the wider UK, while recognising that growth and investment in London can generate significant national economic benefits through productivity, trade, business investment and international competitiveness. The appraisal should also consider Heathrow expansion alongside alternative infrastructure investments that may better support London's and the UK’s long-term growth priorities. The London Growth Plan identifies a range of strategic infrastructure investments that are priorities for the Mayor and are critical to supporting long-term growth, many of which remain unfunded. Some infrastructure associated with Heathrow expansion, for example surface access links, are key but unfunded – and if public sector investment is required, the opportunity cost of directing funding away from these strategic priorities should be explicitly considered.

38          Greater evidence and sensitivity testing is required in relation to displacement assumptions. The economic case relies in part on Heathrow capturing demand that might otherwise be accommodated by competing domestic and international hubs, while the environmental case is also sensitive to the extent to which expansion generates new demand rather than redistributes existing demand. Further evidence should therefore be provided on the role of transfer passengers, the effects of post-pandemic changes in business travel and working patterns, and whether assumptions inherited from the AC remain valid given changes in aviation markets, travel behaviour and wider economic conditions since 2015.

39          The economic growth test also gives insufficient consideration to the transport infrastructure required to support expansion. The appraisal does not fully assess the capacity, resilience, costs and wider impacts of the surface transport interventions likely to be required. Without this analysis, there remains a significant risk that economic benefits are overstated and associated transport impacts and mitigation costs understated. Given the scale of surface transport investment likely to be required, the scheme's value for money may reduce further once these costs are fully incorporated into the appraisal.

» Air quality

40          The GLA and TfL have concerns regarding the effectiveness and robustness of the air quality test as set out in the HENPS. While the test establishes a framework for assessing compliance with legal air quality obligations, it places significant reliance on future assumptions, future mitigation and future monitoring, while providing limited assurance that existing air quality improvements will be protected or that corrective action would be taken should forecast outcomes fail to materialise.

41          The air quality test remains focused on demonstrating legal compliance rather than delivering ongoing improvements in air quality and public health outcomes. London has significantly improved its air quality through the Mayor of London’s policy interventions such as Ultra Low Emissions Zone (ULEZ), for example reducing deaths associated with air pollution in the city by around 40 per cent between 2019 and 2024. Indeed, in the Heathrow study area, average NO2 concentrations have reduced by 34 per cent, and PM2.5 concentrations have reduced by 28 per cent[17]. It is essential that Heathrow expansion does not counteract or slow the benefits from continually improving air quality.

42          Moreover, in line with the best available scientific evidence, the Mayor recognises that there is no safe level of air pollution, and that even low concentrations are associated with adverse health impacts across the population. Reflecting this, the Mayor has committed to meeting the WHO Air Quality Guidelines as soon as possible. As a critical milestone on this pathway, the Mayor has set a target for London to achieve the WHO interim target for fine particulate matter (PM₂.₅) of 10 µg/m³ annual average by 2030, while continuing to drive down air pollution further to reach the final WHO guideline levels at the earliest achievable opportunity.

43          This commitment underpins the Mayor’s long‑term approach to air quality, placing health protection—particularly for children and the most vulnerable—at the centre of policy and investment decisions. Poor air quality is the largest environmental risk to public health in the UK, as long-term exposure to air pollution can cause chronic conditions such as cardiovascular and respiratory diseases, as well as lung cancer, leading to reduced life expectancy.

44          The HENPS explicitly states that deterioration in air quality is not, in itself, a reason to refuse development consent. Given the significant progress made across London through investment in cleaner vehicle fleets, electrification and wider air quality policies, however, the objective should be to ensure expansion does not reverse those gains, rather than using them as an opportunity to increase pollution around the airport.

45          The HENPS proceeds on the basis that Heathrow expansion is capable of meeting the government’s air quality test. However, this relies on a number of future assumptions, including substantial mode shift to public transport, continued reductions in vehicle emissions, wider fleet electrification and the successful delivery of surface access interventions. While these assumptions may be reasonable individually, the overall air quality case depends on several interrelated factors that are not fully within Heathrow's direct control. It is unclear how robust the conclusions would remain if those assumptions are not realised.

46          The robustness of the test is further weakened by the extent to which elements of the evidence base remain dependent on future assessment and modelling. PM2.5 impacts were not quantified in the AC assessment or the 2018 ANPS and, while preliminary analysis suggests expansion is unlikely to cause new exceedances, further detailed modelling is still required. Similarly, while the HENPS recognises ultrafine particles (UFPs) as an emerging issue, it does not establish clear intervention thresholds, corrective actions or enforcement mechanisms should monitoring identify impacts greater than those anticipated.

47          The air quality test is also focused predominantly on human health and statutory compliance. Comparatively little attention is given to ecological air quality impacts, including nitrogen deposition, acidification and impacts on sensitive habitats and designated wildlife sites. Given the presence of internationally and nationally designated sites within the wider Heathrow area, stronger consideration should be given to these environmental pathways.

48          Overall the air quality test is not sufficiently robust in its current form. Greater certainty is required regarding the delivery of key assumptions, the implementation of mitigation measures, the resilience of the air quality case under alternative scenarios, and the mechanisms available to ensure forecast air quality outcomes are achieved in practice. The HENPS should place greater emphasis on protecting existing air quality gains and supporting continued improvement over time, rather than solely avoiding breaches of legal limits.

» Noise

49          The noise test in the HENPS requires that Heathrow expansion avoids significant adverse impacts on health and quality of life by limiting, and where reasonably possible reducing, overall aircraft noise relative to a 2024 baseline. The HENPS assumes that future reductions in aircraft noise arising from technological and operational improvements can be used primarily to accommodate increased airport activity whilst maintaining levels of community exposure broadly similar to today. Given the serious impact that current noise levels around Heathrow have on public health outcomes, preventing deterioration is not an adequate policy objective. The benefits of quieter aircraft and other technological improvements should be shared, used to reduce overall noise exposure and improve health outcomes for affected communities, rather than solely creating capacity for additional growth.

50          The health impacts of Heathrow noise are substantial and well evidenced. Previous research around Heathrow found that residents in areas exposed to the highest levels of aircraft noise experienced a 24 per cent higher risk of stroke hospital admissions and a 21 per cent higher risk of coronary heart disease admissions compared with those in the least exposed areas[18]. Further Heathrow-specific research has linked aircraft noise, particularly during evening and early morning periods, to increased cardiovascular hospital admissions.

51          Children are particularly affected. government-commissioned evidence has identified links between aircraft noise and reduced reading ability, memory and learning outcomes. Studies around Heathrow found that a 5dB increase in aircraft noise was associated with a delay in reading age equivalent to a number of months. [19]

52          The Appraisal of Sustainability (AoS) reinforces these concerns. It identifies major adverse effects at a strategic level, reflecting the large population affected, the persistence of high baseline noise exposure and the redistribution of impacts to communities not currently affected. While fleet modernisation and quieter aircraft may reduce overall noise exposure relative to a 2024 baseline, the AoS confirms that, without expansion capturing those noise benefits, the future two-runway scenario would have a lower noise exposure. The AoS further acknowledges that mitigation measures have limited ability to eliminate adverse effects, even where policy tests can technically be met.

53          The AoS also identifies major adverse effects from both construction and operational noise. During construction, significant impacts are expected from heavy plant, construction traffic and night-time works, while the proposed mitigation measures appear limited relative to the scale and duration of the programme.

54          Against this backdrop, the HENPS does not provide sufficient evidence or detail to demonstrate how noise impacts would be addressed in practice. While a range of mitigation measures are identified, there is limited information regarding their effectiveness, deliverability and enforceability.

» Climate change mitigation

55          Climate change is an important element of the government’s four tests for Heathrow expansion. Without stronger evidence, safeguards and delivery mechanisms, the HENPS does not provide sufficient confidence that Heathrow expansion can be delivered consistently with the UK's carbon budgets and wider climate commitments.

56          Since the ANPS was designated in 2018, the policy context has changed significantly. The UK has adopted a legally binding Net Zero target, and the Climate Change Committee (CCC) has identified aviation as one of the most difficult sectors to decarbonise and one of the largest sources of residual UK greenhouse gas emissions by around 2040. More recently, the UK share of international aviation has been formally included within Net Zero targets.

57          The HENPS states that:

• “The Secretary of State for Energy Security and Net Zero is responsible for assessing on a cross-economy basis whether the UK has sufficient policies and proposals overall to meet the UK carbon budgets.”
• “The increase in carbon emissions... must not be so significant that it would have a material impact on the UK's legally binding carbon budgets”

58          Taken together, this appears to enable an expanded Heathrow to align with Net Zero targets by relying wholesale on decarbonisation of other sectors to provide the headroom to expand. The HENPS does not make it clear what is considered to be a “material impact” and given the presumption of approval for CNGI, the definition of material impact is likely to afford little weight to concerns about emissions.

59          The CCC's pathway to Net Zero requires substantial emissions reductions across homes, buildings, surface transport and industry, while aviation is expected to remain a significant residual-emitting sector. If aviation emissions remain higher for longer because of airport expansion, deeper emissions reductions will be required from other sectors, or greater reliance placed on carbon removals, in order to remain within the UK's carbon budgets.

60          This raises important questions of fairness and equity. The central question is not whether Heathrow expansion can fit within the UK's carbon budgets, but who bears the burden of achieving the emissions reductions required to make that possible. Households, businesses, local authorities and communities are already being asked to undertake significant and often costly changes to support the transition to Net Zero. Any assessment of climate compatibility should therefore consider the distributional consequences of increasing emissions in one sector while requiring deeper reductions from others. Particular consideration should be given to lower-income and working households, which typically have less capacity to absorb the costs associated with decarbonisation.

61          The HENPS relies heavily on future emissions reductions from Sustainable Aviation Fuel (SAF), improved aircraft efficiency, engineered carbon removals and, ultimately, zero-emission aircraft. While these technologies and measures are likely to play an important role, there remains considerable uncertainty regarding their scale, pace and affordability. The CCC has highlighted risks associated with both SAF deployment and the delivery of carbon removals, raising important questions about the extent to which they can be relied upon to offset emissions growth associated with expansion.

62          The government’s Sustainable Aviation Fuel Mandate[20] sets a target of 10% of total jet fuel demand to be SAF by 2030, which will increase to 22% in 2040 - but any further increase is dependant on greater certainty regarding SAF supply.

63          The Appraisal of Sustainability (AoS) acknowledges the challenge of future emissions reductions, stating that:

• “While improvements in emissions intensity from technological, operational and policy developments are taken into account, the appraisal assumes that these improvements would also occur in a ‘no-expansion’ scenario and would not fully offset the increase in absolute emissions associated with the additional activity enabled by the draft HENPS.”

64          This is a significant finding: even after accounting for anticipated technological and operational improvements, Heathrow expansion would still result in higher overall emissions than a scenario without expansion. Indeed, the AoS identifies “major adverse effects on climate change mitigation”.

e. How adequate the information published alongside the draft HENPS is, including its accuracy, comprehensiveness and methodology, and how effectively evidence and data have been reflected in the draft HENPS, including on cumulative impacts

65          This paper highlights particular areas where there are issues with the adequacy of the evidence and data presented in the HENPS; these are discussed in our responses to the following questions:

• Question b: Our response sets out how the HENPS relies too heavily on the findings of the Airports Commission to re-make the case for a third runway at Heathrow.
• Question d a) economic benefits: Our response explains how the evidence presented on economic impacts and benefits is insufficient.
• Question d d) carbon: The evidence presented on future emissions from sustainable aviation fuel, improved aircraft efficiency and zero-emission aircraft is not robust enough. Furthermore, full consideration is not given to the cumulative impacts from all sectors related to expansion, including construction and surface access. Evidence should be provided that assesses against alternative scenarios.
• Question h: The information available is insufficient to allow a full understanding.

66          The HENPS considers each impact domain separately and does not entail a cumulative health impact assessment.

67          The evidence and data to underpin the approach to surface access – including the proposed passenger sustainable mode share targets – has not been presented. The exception is the data for the origins of Heathrow passengers, displayed in Figures 1 and 2 of the ‘Strategic vision for transport’ document.

f. How robust are the methodology and data used for any forecasts or assumptions about the future underlying the analysis presented in support of the HENPS, and whether the range and use of scenarios in the document are appropriate

68          The information presented with regards to aviation forecasts is partial and does not allow a comprehensive understanding of the demand context and likely response. More extensive use of sensitivities to reflect different economic and aviation market scenarios would have been helpful to reflect the considerable uncertainties.

g. How comprehensive and realistic the requirements are in terms of environmental mitigation, supporting measures for communities who will be affected by expansion, and surface access to the airport

69          The environmental mitigation, community support measures or surface access proposals set out in the draft HENPS are not sufficiently robust or demonstrably realistic. Across noise, air quality and carbon, government has placed significant emphasis on expansion meeting specified tests, however they provide insufficient reassurance that an expanded Heathrow can be delivered without a very serious increase in impacts for each of these. While it will always be a challenge to address the environmental impacts associated with a 58 per cent increase in flights, it is disappointing that, in practice, the HENPS criteria will allow for a significant increase in emissions. The concerns about these tests are set out in answer to question d, above.

70          Though the HENPS identifies a wide range of potential environmental, community and surface access mitigation measures, many are expressed as aspirations, future commitments, or requirements for further assessment rather than firm, funded and deliverable interventions. The government’s own appraisal acknowledges significant adverse effects across several environmental topics, including air quality, noise, biodiversity, climate change and impacts on local communities. These impacts, in addition to the weak public transport mode share targets which will result in severe congestion, present a risk that government’s desired economic benefits from the scheme will fail to materialise.

71          The proposed mitigation package does not provide adequate certainty that these adverse effects can be avoided or reduced to acceptable levels, particularly given the scale of expansion proposed. Similarly, the measures intended to support affected communities rely heavily on future engagement, compensation and management plans, with limited evidence that they will fully address the long-term impacts of displacement, severance, loss of community assets, health effects and reduced quality of life.

Air quality

72          While the HENPS identifies a wide range of mitigation measures relating to surface access and airport operations, the policy generally requires only that such measures have been considered. This provides limited assurance regarding which measures will ultimately be implemented, how they will be secured, or what action would be taken if mitigation proves ineffective. In practice, this risks development proceeding without certainty that the necessary mitigation will be in place to prevent adverse effects from arising in the first instance. Reliance on unspecified future interventions does not provide sufficient confidence that impacts can be successfully managed, as mitigation measures that are not embedded within development proposals, secured through clear commitments, or supported by delivery mechanisms have little realistic prospect of being implemented in practice. As a result, there is no certainty, and limited probability, that the anticipated mitigation outcomes will be achieved. Effective mitigation should therefore be designed into proposals from the outset, particularly in relation to surface access and freight, rather than being treated as a potential future response once harm has already occurred.

Noise

73          The HENPS stipulates mitigation in the form of “adequate, predictable respite” through runway alternation. However, for the majority of those under the flightpaths in the vicinity of Heathrow, respite would be half of what is currently offered: approximately 25 per cent of the traffic day, compared with 50 per cent today. This is a function of an expanded Heathrow having an odd number of runways, meaning one runway would generally operate in mixed mode, handling both take-offs and landings during the same period. Notwithstanding the changes to respite, thousands will be overflown by aircraft noise for the first time.

74          Similarly, a scheduled night flight ban, specified as 6½ hours within the night-time period (11pm–7am), is proposed as a key mitigation measure. In practice, however, it could still allow a doubling of night flights compared with today. A voluntary agreement already means there are no scheduled flights during most of the night. The proposed ban would lengthen the restricted period by around an hour, but, if no additional restrictions applied, it could still allow more than 150 flights between 05:30 and the end of the night period at 07:00. The effectiveness of any night flight restriction should therefore be judged by the reduction in sleep disturbance and associated health impacts that it delivers, rather than the duration of the restricted period itself.

Figure 1: Comparison of current and proposed night noise regimes at Heathrow

75          The noise assessment should rely on a broader range of metrics, incorporating both averaged and single-event measures, alongside indicators of overflight frequency, respite and night-time disturbance. Cumulative impacts should also be considered, including those arising from operations at other London airports.

76          There are further concerns regarding the assumptions underpinning future noise modelling. Assessments are likely to be based on indicative flightpaths which may differ substantially from actual operations once airspace design is finalised. Also, new navigation technologies allow much more precise routings to be followed, but these must be used in a way that ensures the distribution of noise impacts is fair and equitable – rather than disproportionately concentrating the noise on a smaller number of people.

77          Community compensation measures, including noise insulation, are welcome, but their effectiveness will depend on the extent to which they reflect actual exposure and are accessible to affected households. To secure meaningful uptake, schemes must address affordability barriers, including circumstances where only partial contributions are available or where residents are restricted to a single approved supplier. Recent heatwaves also highlight the limitations of an approach to noise mitigation which requires windows to stay closed.

78          Overall, the HENPS places significant emphasis on assessment, monitoring and mitigation processes, while providing less clarity on the outcomes that expansion must deliver for communities and public health. The focus of the noise test should therefore shift from demonstrating procedural compliance towards achieving measurable improvements in outcomes for communities.

79          Given the extensive evidence of health and quality-of-life impacts associated with aircraft noise, the HENPS should be framed around delivering progressive reductions in community noise exposure and associated harm over time, supported by clear monitoring, reporting and accountability arrangements, together with effective enforcement mechanisms where outcomes are not being achieved. The effectiveness of the test should ultimately be judged by the health and quality-of-life outcomes experienced by communities, rather than by compliance with operational or procedural requirements alone.

Carbon

80          The HENPS gives insufficient attention to the cumulative climate impacts of expansion. Additional greenhouse gas emissions would arise not only from increased aviation activity, but also from airport operations, construction activity and surface access journeys. TfL's indicative assessment estimates that expansion in line with the HENPS targets could generate approximately 60,000 additional highway trips per day, yet the HENPS provides limited assurance as to how these additional emissions would be accommodated within national carbon budgets.

81          The Mayor and TfL continue to make substantial investments to decarbonise London's transport system, including the electrification of the bus fleet, the provision of additional capacity through new rolling stock and signalling, and the procurement of renewable electricity for the London Underground. It is therefore disappointing that the HENPS appears to downplay the relevance of local action, stating:

• “Aviation emissions are a matter for national-level decision making, and planning authorities are not required to consider local carbon budgets over national aviation policy.”

82          The section of the HENPS relating to surface access emissions recognises the importance of measures such as carbon-based parking charges and strategies to reduce emissions from road freight. TfL welcomes this acknowledgement. However, the draft HENPS provides limited detail on how such measures would be implemented, monitored or enforced, or whether they would be sufficient to deliver the emissions reductions required in practice.

83          We also note that the HENPS does not propose any new climate mitigation measures specifically associated with expansion. Instead, it relies largely on existing or anticipated measures—such as SAF, engineered carbon removals and zero-emission aircraft—that depend on future technological developments and policy delivery at national and international levels. Given the significant uncertainty that remains around aviation decarbonisation pathways, the draft HENPS places considerable reliance on outcomes that have yet to be demonstrated at the scale required.

84          Overall, the HENPS should place substantially greater emphasis on demonstrating climate compatibility in practice. This should include:

• Explicit assessment against Carbon Budgets 6 and 7;
• Full consideration of cumulative emissions impacts, including aviation, construction, airport operations and surface access;
• Greater clarity regarding the assumptions underpinning aviation decarbonisation pathways;
• Assessment of the carbon impacts of Heathrow expansion against alternative scenarios for increasing UK aviation capacity;
• A transparent framework for monitoring, managing and, where necessary, constraining Heathrow's emissions over time; and
• Clear evidence that expansion can be accommodated within the UK's pathway to Net Zero without imposing disproportionate burdens on other sectors or households.

Surface access

85          The vision for sustainable access to an expanded Heathrow is welcome – but this is not matched by the sustainable mode share targets in the HENPS, which fall considerably short of securing no increase in highway trips, required to address its impacts. These targets appear similar to those in the previous ANPS – but are less ambitious, given that the baseline has since increased., The targets exclude staff trips – in contrast to the previous ANPS – and freight.

86          The HENPS states that the applicant should set out plans to manage any additional traffic created from passengers, staff, freight and ancillary functions[21], while it requires demonstration that significant impacts “can be cost effectively mitigated to an acceptable degree”[22]. Neither provides certainty that the surface access impacts will be effectively addressed.

87          TfL’s initial analysis suggests that achieving the targets in the HENPS could still result in an additional 60,000 airport-related highway trips every day compared to today – equating to around 22m additional trips highway annually. This would place an intolerable strain on the highway network, both local and strategic roads including the M25 quadrant which is the busiest section in the country. This will impact both air pollution and carbon emissions while the worsening congestion will also erode economic benefits of the scheme.

88          This will also place a very significant burden on sustainable transport modes. If no increase in highway traffic is to be secured, this could see sustainable modes handling an additional 63m trips annually – a 255 per cent increase on today. Even to achieve the less ambitious HENPS targets, TfL estimate that could entail an extra 40m trips annually, a 200 per cent increase on today.

89          If no increase in highway traffic is to be achieved, this will require a very significant shift to sustainable modes, with the connectivity to attract passengers and staff and the capacity to accommodate the resultant flows.

90          Rail will need to play a key role however, the HENPS does not highlight the need to make best use of existing services, in particular the Elizabeth line and Piccadilly line. The first phase of the Piccadilly Line Upgrade (PLU1) underway and is set to deliver new trains with 10 per cent extra capacity. Securing an increased frequency will require the currently unfunded second phase (PLU2) which entails a major signalling upgrade and the rolling stock to take advantage of that.

91          The new trains to increase Elizabeth line frequencies to Heathrow – by at least 2 tph (trains per hour) – are funded and TfL aims to deliver the additional service in 2028 subject to timetable planning and regulatory approvals.

92          It is also worth noting the role of the Heathrow Express, whose track access rights for the Great Western Main Line come up for renewal in 2028. With its patronage increasingly being squeezed by the Elizabeth line’s superior customer proposition, consideration should be given to how to optimise to make the most effective use of the limited capacity available.

93          If the requisite step-change in sustainable mode share is to be achieved, then providing direct rail access in corridors currently not served by rail from Heathrow is essential. This would include direct services from Heathrow to Waterloo via Clapham Junction, Richmond, Feltham and Staines (4 tph), to Basingstoke and Guildford via Woking (2+2 tph) and to Reading via Maidenhead and Slough (4 tph). The new rail links entailed could also enable Elizabeth line services to be extended to Staines (4 tph).

94          The GLA and TfL welcome the recognition in the HENPS that improved rail connectivity to the South and West is required to support expansion. However, these schemes should be deemed essential enabling infrastructure and delivered alongside expansion, not deferred until passenger numbers reach 130 mppa. In order to shift significant numbers of people from less sustainable modes, new rail connectivity is needed as soon as possible.

95          While the role of bus and coach is recognised in the HENPS in supporting mode shift at an expanded Heathrow Airport, this must be underpinned by steps to increase its attractiveness. As such, it is essential that bus priority measures are delivered on corridors to, from and around Heathrow (rather than focusing exclusively on the latter). It is also important to recognise the dispersed nature of the airport campus, particularly staff locations. High-quality bus interchanges will be required at the terminals and around the airport perimeter, to facilitate onward journeys – the latter likely to include Hatton Cross and Harlington Corner.

96          The HENPS needs to go further in supporting active travel, with safe, inclusive, well-connected and high quality, priority cycle infrastructure to, from and around Heathrow, as well as ensuring direct access to all the terminals and other major airport employment sites within the airport campus. The latter has taken on particular importance given HAL proposals to permanently close off the entire central terminal area to cyclists – including the enlarged Terminal 2 –which is a source of concern. There also needs to be a requirement to address the barriers which cause severance.

97          The important role of safety in enabling sustainable transport journeys is not recognised in the HENPS. An outcome of expansion should be a road network that is safer than it currently is now, for all road users, including during construction.

98          The HENPS requires the applicant to include proposals to increase cargo capacity within the airport campus, and while there are requirements to mitigate the impact of freight on congestion, road safety, noise, air quality and greenhouse gas emissions, there are no binding targets attached to these to ensure these are adopted and met by the applicant.

99          The acknowledgement of the role of demand management[23] in supporting sustainable mode shift is sensible and increasing the terminal drop-off charge and a new road access charge are both cited. The recognition of the role of a car parking strategy in this is welcome, especially given HAL’s proposals to build two of the world’s largest car parks adjacent to the M4 and M25, however what best practice looks like could be made more explicit. The HENPS should also limit the number of parking spaces to current levels. Furthermore, as passenger mode choice will be influenced by the location of airport car parking and onwards connections to the airport, these should not undermine or have priority over sustainable transport options.

100     There are concerns that the proposed southern road tunnel will only serve to increase highway trips. Even if a lane is set aside for bus and coach, the tunnel will make Terminal 2 much more accessible by highway, encourage non-sustainable trips and increase traffic on lower capacity roads to the south of Heathrow. The opportunity cost associated with such a substantial piece of infrastructure, is that investment could be deployed elsewhere to support sustainable surface access interventions. At a minimum, the HENPS should require the promoter to demonstrate such a new highway intervention would not have adverse localised impacts on congestion or emissions before it can proceed.

101     It is recognised that here will always be some, typically coming from more rural locations away from London, for whom public transport access will be difficult. Parkway locations away from Heathrow, but with fast, frequent, reliable direct access by rail or coach, could encourage people to interchange, leaving their cars behind and so reducing highway traffic around Heathrow and the M25. The HENPS could be explicit in requiring such an approach as part of the shift to sustainable modes.

102     As the transition to electric vehicles (EVs) picks up pace – in line with the government’s Zero Emission Vehicle mandate, EVs will constitute an increasing proportion of the vehicle fleet and it is essential that that EV infrastructure is provided to support the transition. The HENPS needs to ensure promoters make sufficient provision for charging of private cars, taxis, Private Hire Vehicles (PHVs), buses, coaches, vans, HGVs and airport operational vehicles, with facilities which are accessible, reliable and conveniently located.  Indeed, the HENPS should go further, by requiring all airport operational vehicles to be electric. A forward-looking approach also needs to consider provision for the land, grid capacity and energy infrastructure required.

103     Funding of surface access is a vital issue, and the HENPS requirement for promoters to set out credible plans[24] is welcome. However, the Civil Aviation Authority (CAA), as economic regulator has a key role. It supports a ‘user pays’ principle, albeit we would define that as a surface access user more broadly paying for surface access improvements, to avoid the perverse outcome that a levy on rail passengers pushed people to less sustainable modes. Concretely, that could mean hypothecation of a proportion of the terminal drop-off charge, parking charges and as well as any new highway charges introduced, to provide an ongoing funding stream for a sustainable surface access fund as well as for specific major schemes. If the CAA is not to be an obstacle to securing funding for sustainable surface access, the HENPS could play a useful role in setting out such a framework and/or identifying schemes as planning requirements.

h. How the government’s decision to select the Heathrow Northwest Runway scheme to inform the review has affected the draft HENPS and is likely to affect potential promoters

104          The decision by the government in November 2025 to endorse the Heathrow Northwest Runway scheme, as proposed by HAL, was clearly essential in underpinning the drafting of the HENPS, as a national policy statement focused on a single preferred scheme. That is notwithstanding the concerns raised above in response to question b as to whether the case for selecting that scheme has been made.

105          However, the government has yet to determine the promoter who would take forward that scheme. As things stand, alongside HAL, as owners of the airport, the Arora-led Heathrow West Limited (HWL) has also indicated it would be ready to take forward the Heathrow Northwest Runway scheme, though it has indicated that it would build the new terminal opposite Terminal 5 but leave the Terminal 2/3 works to HAL; there is also some uncertainty as to whether it would deliver the new runway itself or leave this to HAL.

106          Both HAL and HWL have announced their intentions to submit DCOs for Heathrow expansion in late 2027. As currently conceived, the DCO applications would be both competing and complementary, in that HWL would be putting forward a rival proposal but would be reliant on HAL delivering other aspects.

107          These parallel DCOs will create very considerable challenges for the Planning Inspectorate, but also for stakeholders having to resource engagement with both processes in parallel.

108          In addition, the potential division of roles raises questions as to where responsibility will lie for meeting conditions, such as mode share targets.

i. How well the draft HENPS reflects government policy on airports and aviation, and on other elements of broader a) transport, b) planning and c) climate and environment policy

a) Transport policy

109     The HENPS is directionally aligned with the government’s transport policy, but does not translate that alignment into sufficiently clear, measurable and enforceable requirements. It is welcome in recognising that Heathrow expansion must be supported by reliable, affordable, accessible and sustainable surface transport. Its guiding principles: making public transport the first choice, minimising impacts on the road network and prioritising environmental sustainability, are consistent with the government’s integrated transport agenda.

110     However, the HENPS does not yet fully reflect the ambition of Better Connected: A Strategy for Integrated Transport[25]. Better Connected sets out a vision for transport that works well for people: safe, reliable, affordable and accessible, with people at the heart of transport design and delivery. It is based on the principles of People, Place and Partnership, and seeks to create seamless journeys across local and national networks. The HENPS should therefore require Heathrow expansion to be assessed not only as an airport capacity project, but as a major intervention in the wider transport system.

111     The HENPS makes references to relevant modal policy, such as the government’s vision for buses and approach to delivery[26], but does not go far enough to set out a credible path to translate policy into delivery for the different surface access modes.

112     In particular, the HENPS should provide stronger requirements for integrated surface access. A future scheme should demonstrate how passengers, staff and freight will access the airport through a joined-up network of rail, Underground, Elizabeth line, bus, coach, active travel and taxis/PHVs, alongside freight, servicing and construction trips. It should also address affordability, accessibility, reliability, integrated ticketing, passenger information and first- and last-mile connectivity.

b) Planning policy

113     Although the HENPS introduces a number of updated policies on land use and placemaking compared with the 2018 ANPS, it ultimately maintains a light-touch approach to spatial planning and land use issues within the mitigation and decision-making framework. Consequently, it does not set out robust policy requirements to avoid, minimise and mitigate the adverse impacts of expansion, including major adverse effects on communities, local amenity and residents' quality of life. In addition, the HENPS does not sufficiently acknowledge or account for the wider direct and indirect land use impacts and associated growth demands resulting from the expansion. There is a risk that wider growth objectives and objectively assessed development needs may not be adequately met. These issues require further consideration through the development of a robust spatial framework capable of identifying, managing and coordinating the land use, infrastructure and growth implications arising from airport expansion. 

114     As a result of the above, we are concerned with the HENPS’ alignment with broader spatial planning objectives for accommodating housing and wider growth, especially when considering the specific objectives relating to planning for good growth, and underpinning presumption in favour of sustainable development within the NPPF and the London Plan.

115     In terms of more immediate impacts within the vicinity of Heathrow, expansion requires significant land take for the expanded airport footprint. The land take implications also go beyond the red line boundary as defined by the HENPS, including safeguarding for transport network capacity, and suitability of land for other uses due to impacts of noise and public safety considerations. The significant land take and safeguarding requirements would result in loss of housing and other uses through compulsory purchase powers and limit other development outside the red line boundary, which has direct implications for London’s ability to address increased demand in housing, infrastructure, and other community services. The HENPS falls short of requiring robust measures to address the implications of significant land take as well as associated safeguarding for infrastructure and height restrictions beyond the red line boundary. For instance, the London Plan has a strong and well-established presumption of no-net loss of homes and protective policies apply across other land uses where compensatory capacity would typically be expected in instances where there is demonstrable outstanding need (for example, in relation to various forms of other economic, social and community infrastructure). Within this context, impacts of displacement and increased pressures resulting from wider population growth and the expansion itself may affect the ability to meet future needs in these areas. 

116     For example, the HENPS introduces a new standalone policy on placemaking which recognises a range of direct and indirect impacts involved which expansion at Heathrow would have on local communities in the vicinity. However, it then simply sets out that the applicant ‘should’ engage with Local Planning Authorities to demonstrate how the scheme can contribute and be integrated with wider place making and how land has been used efficiently to limit impacts and enables local authorities to deliver local needs for the area. The HENPS lacks a strategic direction on how the adverse impacts of land take on communities will be addressed. The drafting only indicates that impacts will be minimised where possible, rather than obligating a future applicant to address any shortfalls resulting from the proposals in instances where there is outstanding need. The land use section includes similar drafting in relation to engagement and impacts on land uses. Further, neither section addresses mitigation and decision-making in the event that uses are not deemed surplus to requirements, or Local Planning Authorities consider that there isn’t sufficient mitigation to address major adverse impacts on land uses and communities at pre-application stage and matters included in subsequent Local Impact Reports.

117     A further key concern is that the HENPS does not address impacts on the public transport network, traffic congestion and public health impacts associated with expansion. Heathrow expansion cannot rely on infrastructure capacity designed for the benefit of Londoners and which will already be stretched to accommodate London’s considerable population growth requirements. This could fundamentally undermine development that these schemes were intended to unlock and is likely to have implications for meeting wider growth objectives. Similarly, indirect impacts of road congestion, air quality, and noise on growth opportunities on existing and emerging land uses have not been adequately addressed, nor have the associated knock-on impacts on capacity and economic activity. 

118     Another spatial land implication of the expansion relates to pressures placed on green belt in London. The presumption in favour of protection of the green belt from inappropriate uses is established within national planning policy. Given the pressures of housing delivery and wider growth, the Mayor is also considering how best to  strategically release small amounts of green belt for development. The HENPS now states that while construction on brownfield sites can make a major contribution to sustainable development, it may not be possible for some forms of infrastructure. We have considerable concerns that indirect impacts resulting from land take for expansion will add to the pressures on the Green Belt to deliver housing and other land uses to meet the growth needs of communities. This increased need and pressures resulting from expansion have not been sufficiently accounted for in the assessment and decision-making policies of the HENPS.

119     The HENPS falls short on requiring robust scrutiny of impacts on housing capacity in London – both loss and delivery – and growth related to other land uses.  

c) Climate and environment policy

120     The draft HENPS has been updated to reflect developments in climate and environmental policy since the ANPS was designated in 2018. The document explicitly recognises the UK's Net Zero target, carbon budgets, air quality obligations, biodiversity requirements, noise and wider environmental protections. However the HENPS does not provide clarity over how those objectives will be delivered in practice. Stronger alignment would be achieved through greater emphasis on reducing pollutant exposure, protecting environmental gains, and establishing clear mechanisms to ensure that assumed emissions reductions and mitigation measures are delivered in practice.

Climate change

121     The HENPS appropriately recognises the UK's legally binding climate framework and the need for Heathrow expansion to be compatible with carbon budgets and Net Zero. However, the practical effect of the climate test is considerably weaker than the policy ambition suggests.

122     The HENPS effectively assumes that provided the UK remains within its overall carbon budgets, Heathrow expansion can proceed. This places significant reliance on emissions reductions being delivered elsewhere in the economy and provides limited assurance that aviation itself will contribute proportionately to achieving climate objectives.

123     This is particularly important given that the Climate Change Committee identifies aviation as one of the most difficult sectors to decarbonise and one of the largest residual sources of UK emissions by around 2040. The draft HENPS relies heavily on future emissions reductions from Sustainable Aviation Fuel (SAF), operational efficiencies and engineered carbon removals, despite significant uncertainty regarding their future scale and deployment.

124     Insufficient consideration is given to the fairness and equity implications of accommodating additional aviation emissions within finite national carbon budgets. The central question is not simply whether Heathrow expansion can fit within the UK's carbon budgets. As referenced in the response to question d, this approach will, in practice, mean households, businesses, local authorities and communities are being asked to bear the burden of the delivery of net zero.

Air quality

125     The HENPS reflects a number of important developments in wider government policy on air quality, including the introduction of statutory PM2.5 targets through the Environment Act 2021, the Environmental Targets (Fine Particulate Matter) (England) Regulations 2023, and increasing recognition of ultrafine particles as an emerging issue. However, there remains a disconnect between these wider policy objectives and the air quality test applied within the HENPS.

126     Recent government policy has increasingly emphasised reducing population exposure to air pollution, improving environmental quality and delivering wider public health benefits. By contrast, the HENPS is primarily focused on ensuring that Heathrow expansion does not create new breaches of legal air quality obligations or materially worsen existing exceedances. This sets a relatively low threshold and does not require expansion to contribute towards wider environmental improvement objectives or support delivery of national air quality targets. Issues with the reliance of SAF in relation to reducing not only carbon emissions but potentially PM2.5 emissions also remain where considerable uncertainty in the viability of SAF or connected Jet Zero measures remains.

127     The HENPS further gives limited consideration to ecological air quality impacts, including nitrogen deposition and impacts on designated habitats and ecological sites. This appears only partially aligned with wider government objectives relating to nature recovery, biodiversity enhancement and environmental protection.

Noise

128     The government’s current aviation noise policy, set out in the 2023 Aviation Noise Policy Statement, is:

• "The impact of aviation noise must be mitigated as much as is practicable and realistic to do so, limiting, and where possible reducing, the total adverse impacts on health and quality of life from aviation noise."

129     Noise is the subject of one of the government’s four specific tests for Heathrow expansion, alongside climate change, air quality and economic growth. The noise test requires that Heathrow expansion avoids significant adverse impacts on health and quality of life by limiting, and where reasonably possible reducing, overall aircraft noise compared with 2024 baseline levels.

130     A third runway at Heathrow would substantially increase aircraft movements. Even if individual aircraft become quieter, the number of flights, the geographical spread of flight paths, and the frequency of overflights are likely to increase. The AoS indicates that expansion will increase noise exposure compared to a two-runway Heathrow.

131     The HENPS relies heavily on mitigation measures rather than measures that guarantee an overall reduction in noise impacts. The HENPS prioritises enabling growth subject to mitigation, whereas current policy places the emphasis on limiting and, where possible, reducing adverse effects.

132     The HENPS focuses primarily on compliance with noise contours, noise envelopes and operational controls, without demonstrating how expansion would affect sleep disturbance, annoyance, wellbeing and public health outcomes. It could be argued that it does not fully reflect the evolution of government policy away from purely technical noise measures and towards health-based outcomes.  To do this, HENPS should establish:

• clear noise reduction requirements;
• measurable thresholds;
• strong monitoring and enforcement mechanisms; and
• clearly state that overall noise impacts will not worsen.

Wider environment

133     The HENPS broadly reflects current environmental policy through its references to biodiversity, habitats protection and environmental assessment. However, across several environmental themes the policy framework relies heavily on future mitigation and compensation without providing sufficient confidence that environmental outcomes will be achieved.

134     The biodiversity framework is a good example. The HENPS references Biodiversity Net Gain, the mitigation hierarchy and Habitats Regulations Assessment requirements, but provides limited clarity regarding how these obligations will be delivered, monitored and enforced. Important concepts such as "reasonable alternatives", long-term ecological management and the interaction between biodiversity requirements and aviation safety remain insufficiently defined. There is also significant reliance on future compensatory measures and external strategies, creating uncertainty regarding practical deliverability.

135     The HENPS also does not provide sufficient confidence that internationally and nationally designated sites, river corridors, habitats and ecological connectivity can be adequately protected. This is particularly important given Heathrow's proximity to sensitive ecological assets and the potential impacts on designated sites, river systems and wildlife corridors.

136     More broadly, a recurring theme throughout the HENPS is that environmental improvements arising from technological change, wider public policy or community action are treated as capacity that can be utilised by expansion. Across carbon, air quality and noise, insufficient weight is given to the possibility that those improvements should also deliver better outcomes for communities and the environment.

j. To what extent the draft HENPS adequately takes into account changes in the context of airport expansion since 2018, such as, for example, current and future capacity at other airports, new legislative requirements, and developments in technology

137     There are significant deficiencies in the case for Heathrow expansion that is presented by the draft HENPS. The HENPS is clear in its heavy reliance on the findings of the Airports Commission (AC), albeit with selected updates to that analysis, which was published 11 years ago.

138     This is important as the Heathrow expansion scheme being brought forward is, to a great extent, a carbon copy of that previously put forward over a decade ago and the subject of the 2018 Airports National Policy Statement (ANPS), for which this new HENPS is an update. Nevertheless, the case made for the ANPS eight years ago cannot be taken as a given in bringing forward this updated HENPS. A great deal has changed in the intervening period, much of it pertinent to the analysis which shaped the different stages of the previous AC process, some of which are set out below:

• A number of UK airports have secured planning permission for substantial growth in the intervening decade, including Gatwick, Stansted and Luton. The HENPS indicates that they would “be full by the mid to late 2040s” but does not evidence why any extra capacity would be needed or should be provided at Heathrow. 
• There have been a number of changes in the political, economic and commercial space. Most notably amongst these is Brexit, which has impacted trade patterns as well as taking the UK out of the single European aviation market.
• Important environmental changes since the ANPS include the incorporation of the Paris climate change agreement into UK law and London meeting legal limits for NO2 pollution in 2024, almost 200 years earlier than predicted.
• With regards to surface access, the opening of the Elizabeth line constitutes the most significant change. London’s ULEZ has also been extended to the Greater London boundary –  now including all of Heathrow – and HAL has also introduced a new terminal drop-off charge.

139     Perhaps the most significant development in the intervening years – and accelerated since the pandemic – has been the decline in business travel. This is not accounted for in the HENPS. In the context of record passenger numbers, Civil Aviation Authority data[27] indicates that the proportion of travel for business through Heathrow fell by a quarter between 2019 and 2024 from 25.2 to 18.9 per cent of passenger traffic. Heathrow has a disproportionately higher share of business travel and the decline of this market segment – which also has implications for the value of its role as a hub – notably weakens the case for its selection.

k. Whether the draft reflects lessons learned from legal challenges to the 2018 Airports NPS

140          The legal challenges highlighted the critical role of the relevant environmental obligations and the HENPS would need to ensure that these are effectively met.

l. The effectiveness of the government’s consultation on the draft HENPS

141     The length of consultation period on the HENPS is broadly aligned with the previous NPS consultations such as the 2023 consultation on the National Networks NPS, although it is worth noting that the consultation period falls across a summer holiday period.

142     However, the HENPS is the first NPS to provide a policy and decision-making framework that is restricted to development exclusively at a single site and this creates unique demands. Consultees have been required to review and consider the specific potential impacts of the proposed expansion while also weighing the far-ranging policy proposals of the HENPS. As this submission has outlined, some of the data provided is inadequate and outdated. The consultation asks stakeholder to comment on an updated policy framework while continuing to rely heavily on evidence and strategic conclusions developed through the AC process more than a decade ago. Given the significant changes that have occurred since then, the consultation should provide a clearer explanation as to why the underlying strategic conclusions remain valid – or alternatively, undertake a more fundamental reassessment of the evidence base. Without such an approach, it poses a fundamental risk to the adequacy of the HENPS consultation.

143     The consultation seeks views on the acceptability of Heathrow expansion whilst leaving many of the critical mitigation measures, delivery mechanisms and supporting infrastructure proposals to be determined at a later stage. This makes it difficult for consultees to assess with confidence whether the objectives set out in the HENPS are capable of being delivered in practice.

144     The consultation takes place before several important decisions and regulatory processes that are fundamental to the deliverability of the scheme, creating uncertainty regarding how key aspects of the policy framework will operate in practice.

145     Additionally, the resourcing challenge for the HENPS consultation is obvious and it is clear that demands on consultees will continue for many years to come as the volume of information provided by the DCO applicant(s) increases. Stakeholders are being asked to respond to a range of interrelated policy initiatives and infrastructure proposals concurrently, making it important that adequate time and information are available to allow informed responses on issues of considerable complexity and national significance.

146     Unlike the AC process, which involved the comparative assessment of alternative locations and options for additional aviation capacity, the current consultation largely proceeds on the basis that Heathrow expansion remains the preferred solution. This limits stakeholder’s ability to comment on the underlying strategic choice itself and instead focuses consultation on the updated policy framework for a predetermined outcome.

July 2026

Endnotes