Infrastructure Strategy: strategic environmental assessment

5. Assessment of Reasonable Alternatives

5.1. Assessing Reasonable Alternatives through the SEA

5.1.1. The assessment of ‘reasonable alternatives’ is a key element of the SEA process to meet the requirements of the 2005 Act.

5.1.2. The 2005 Act is not prescriptive as to what constitutes a reasonable alternative, stating only that “The report shall identify, describe and evaluate the likely significant effects on the environment of implementing (a) the plan or programme; and (b) reasonable alternatives to the plan or programme”.

5.1.3. An important component of the SEA process to date has been the assessment of reasonable alternatives for the Infrastructure Strategy. In this regard the assessments presented in this Environmental Report consider a range of approaches as reasonable alternatives, with a view to exploring the actions with particular potential for significant environmental effects. These assessments are designed to inform plan makers and stakeholders of the relative sustainability merits of alternative approaches the proposals could take on various elements associated with the proposals.

5.2. Defining Reasonable Alternatives

5.2.1. In developing reasonable alternatives for the SEA, a central consideration has been with respect to the key choices being made relating to the Infrastructure Strategy.

5.2.2. The Infrastructure Strategy as consulted on sets out proposals (and asks consultation questions) on the following areas:

• Role of the Infrastructure Strategy
• Infrastructure Governance Principles
• Infrastructure Themes and Enablers
• Place-Based Approach
• Private Infrastructure Investment

5.2.3. To support the consideration of which alternatives to assess through the SEA process, discussions were undertaken between the Infrastructure Strategy team and the SEA team on the key alternative approaches that could be taken with regards to the five areas set out above. The outcome of the discussions was a series of options which could be assessed as reasonable alternatives.

5.2.4. The following sections present a discussion of the reasonable alternatives considered for each of the areas set out above. These include the alternatives chosen for assessment through the SEA, and the reasons why certain alternatives were not considered.

5.2.5. Each set of alternatives are then assessed against the SEA Framework developed during scoping.

5.3. Reasonable Alternatives Considered

Role of the Infrastructure Strategy

Alternatives Based on the Definition of Infrastructure

5.3.1. How infrastructure is defined for the purposes of the Infrastructure Strategy is an important consideration. In this respect the Infrastructure Commission for Scotland recommended that Scotland’s natural infrastructure should be incorporated within the definition of infrastructure as part of a broad remit which includes transport, energy, telecoms, water, waste, flood defences, housing, education, health, justice and culture.

5.3.2. Given the clear direction provided by the Infrastructure Commission, it is viewed that it is not appropriate to consider alternative definitions for infrastructure through the SEA process.

Alternatives Based on Timescales and Sequencing

5.3.3. The timescales of the Infrastructure Strategy are an important consideration. The current Infrastructure Strategy has a timescale of five years; the new Infrastructure Strategy seeks to adopt a more strategic approach to infrastructure planning and delivery and extends this to 10 years.

5.3.4. To explore this further, the following two options can be considered through the SEA process to help understand the relevant merits of a shorter and longer-term approach:

• Option T1: Continue with a shorter-term (5 years) timescale for the Infrastructure Strategy.
• Option T2: Implement a longer-term (10 years) timescale for the Infrastructure Strategy.

Infrastructure Governance Principles

Alternatives Based on Applying the Investment Hierarchy

5.3.5. In 2020, the Infrastructure Commission for Scotland recommended that the most is made of existing assets and a presumption in favour of enhancing, re-purposing, or maintaining existing infrastructure over developing options for new infrastructure is introduced. This approach was taken forward by the current Infrastructure Investment Plan.

5.3.6. The new Infrastructure Strategy (the replacement for the Infrastructure Investment Plan) has the potential to take an alternative approach which places an additional focus on new infrastructure. In this respect the following three options can be considered through the SEA process to consider different approaches:

• Option IH1: Initiate a strengthened “maintain and enhance first” model (requiring demonstrable exhaustion of all maintain/repurpose options before considering new build).
• Option IH2: Take a balanced approach to infrastructure delivery which seeks to maintain/repurpose first in principle but allows more flexibility.
• Option IH3: Initiate a greater emphasis on delivering ‘new build’ strategic assets.

Infrastructure Themes and Enablers

Alternatives Based on Level of Environmental Ambition

5.3.7. The Infrastructure Strategy is framed around the three proposed ‘enablers’ of Public Assets, Place-Making and Private Investment. In the context of these enablers, there is the potential to consider different levels of environmental ambition for the Infrastructure Strategy.

5.3.8. Three alternatives can be considered, as follows:

• Option E1: Seek the highest level of environmental protection through the Infrastructure Strategy.
• Option E2: Initiate a minimal compliance approach through the Infrastructure Strategy.
• Option E3: Delver a balanced environmental ambition approach through the Infrastructure Strategy.

Place-Based Approach

Alternatives Based on the Role of a Place-Based Approach

5.3.9. The Infrastructure Strategy seeks to deliver a place-based approach, directly driven by an understanding of the overall assets and needs of different locations, and specific priorities.

5.3.10. Underneath this overall approach, a number of alternatives can be explored relating to the extent to which infrastructure delivery is led by national or local prioritisation.

5.3.11. In this respect the following alternatives can be explored through the SEA process:

• Option PB1: Initiate a strong place-partnership model for infrastructure.
• Option PB2: Deliver a nationally led prioritisation approach for infrastructure.
• Option PB3: Deliver a locally determined approach to infrastructure.

Private Infrastructure Investment

5.3.12. In terms of the role of private infrastructure investment, there are no reasonable alternatives that should be considered for this element of the Infrastructure Strategy. This is given that private infrastructure investment will be a vital funding mechanism for achieving the objectives of the Infrastructure Strategy.

5.4. Assessment Findings

Introduction

5.4.1. The narratives below present assessment findings in relation to the reasonable alternatives introduced under section 5.3. These are organised by the nine SEA topics. The overview below provides a summary of the assessment findings.

5.4.2. For each SEA topic, a commentary on the likely effects is presented. Options are also ranked numerically reflecting their relative sustainability performance. In addition, whether the option is likely to lead to significant adverse or beneficial effects is highlighted.

Assessment Assumptions

5.4.3. The assessment of reasonable alternatives has been undertaken using a precautionary approach, particularly in relation to the uncertainty around the location and scale of future interventions that may result from the overarching approaches taken forward by the Infrastructure Strategy. Where appropriate, the assessment assumes the application of standard good practice construction and environmental management measures (e.g. noise barriers, dust suppression, pollution prevention, and ecological timing of works), which are typically embedded in project delivery. This approach ensures a proportionate and realistic assessment of likely effects, while recognising that more detailed mitigation and enhancement measures will be developed at later stages, including through any projects which are subsequently taken forward as a result of the Infrastructure Strategy.

Reasonable Alternatives Set 1: Timescales and Sequencing

Option T1: Continue with a shorter-term (5 years) timescale for the Infrastructure Strategy.

Option T2: Implement a longer-term (10 years) timescale for the Infrastructure Strategy

Air Quality

5.4.4. Impacts to air quality from infrastructure development are likely to relate primarily to transport infrastructure (particularly roads) and to infrastructure that generates travel demand (e.g. educational facilities). The Strategy’s emphasis on decarbonising transport and strengthening place‑based planning aligned with National Planning Framework 4 (NPF4) (including active travel and infrastructure‑first principles) should cumulatively support opportunities for lower‑emission travel and associated air quality improvements. Delivered schemes such as the A77 Maybole Bypass have demonstrated local air quality benefits.

5.4.5. It is expected that infrastructure development would continue whether the Infrastructure Strategy plans for a 5- or 10- year period (with the presumption that strategy updates would be more frequent under a five-year plan scenario), but there are notable merits to longer-term planning (Option T2).

5.4.6. Firstly, within the current fiscal context (including rising construction costs and a real‑terms reduction in the capital block grant) longer‑lead‑in climate resilient infrastructure may be more challenging to prioritise within a shorter five‑year window. The Strategy notes that around two‑thirds of the capital budget could be required simply to maintain and renew existing assets, limiting headroom for new infrastructure that could contribute to air quality improvements. A 10‑year timeframe offers greater flexibility to programme larger schemes such as rail electrification.

5.4.7. Secondly, urban areas (where most growth is expected) have more complex transport pressures and existing air quality issues. While spatial decisions are guided by NPF4 rather than this Strategy, longer‑term planning could enable more comprehensive solutions to congestion and emissions in these growth areas. Similarly, remote rural and island communities, where delivery costs are higher and populations more dispersed, may benefit from the greater planning certainty offered by a 10‑year horizon.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Significant effects are not anticipated from either option.

Biodiversity, Flora and Fauna

5.4.8. The Strategy is the first to place natural infrastructure on an equal footing with economic and social infrastructure, ensuring natural assets are embedded in long‑term planning and informed by the 30‑year Needs Assessment. This presents opportunities to support biodiversity through nature‑based solutions (NbS), green and blue infrastructure (GBI), and improved ecological resilience. Longer‑term planning (Option T2) is likely to provide greater clarity and investment confidence, particularly given the private‑capital role envisaged for natural‑capital markets.

5.4.9. Planning over a longer timescale is expected to be more beneficial in attracting private investment by providing more clarity and security for investments. Additionally, most land in Scotland is held privately so achieving biodiversity targets will require complex co-working across levels of government and private landowners, which could slow delivery. The longer (10-year) timescale (Option T2) is therefore more likely to effectively capture such projects.

5.4.10. The integrated planning over a longer timescale could also allow for more consideration of the potential impacts of economic and social infrastructure development on biodiversity and potentially identify any interlinked betterment opportunities more clearly.

5.4.11. Additionally, the Strategy is likely to recognise the natural infrastructure needs and assets associated with (and more concentrated within) the more rural highlands and islands, opening up more investment avenues in these areas. A longer timescale (Option T2) is likely to provide more headroom for such improvements which will ultimately be competing with the development needs of identified growth areas.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Significant effects are not anticipated from either option.

Climatic Factors

5.4.12. The Strategy is likely to benefit climate change on two primary fronts - both mitigating greenhouse gas emissions to reach net zero and building resilience against the physical impacts of climate change.

5.4.13. Accelerating the transition to net zero is one of the three core outcomes, highlighting actions such as decarbonising transport, sustainable building and materials use, and renewable energy development. Furthermore, the Strategy identifies a presumption in favour of maintaining and repurposing existing assets rather than building new ones, thereby avoiding the high carbon footprint associated with new construction. While it is assumed that this would remain a core outcome under a 5- or 10-year strategy, it is considered likely that more opportunities and investment streams could be unlocked with a longer timescale (Option T2) and the greater planning security it provides.

5.4.14. The timescale aspect could be notably more critical when considering the types of projects and proposals that are likely to be considered under either scenario. A shorter-term strategy will naturally be focused on immediate needs rather than longer-term aspirations, and it is these longer-term aspirations that link so critically to both climate mitigation and resilience. Projects, particularly those aimed at net zero, like rail electrification, generally have long lead-in times and require a longer delivery timescale accordingly. Similarly, peatland restoration projects need the security associated with longer-term planning to leverage the private investment required. Additionally, immediate needs are likely to be focused within the urban growth areas (to accommodate the planned growth), with less targeted action at the highlands and islands in a shorter timeframe.

5.4.15. Despite this, significant beneficial effects are considered likely to emerge under either option, given the focus on a ‘place-based’ approach that creates connected development and active travel opportunities. Additionally, the focus on incorporating NbS, building natural capital markets, and investing in primary adaption needs such as physical flood defences, will benefit climate change resilience in the longer-term.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Positive significant effects are anticipated through both options.

Cultural Heritage

5.4.16. The Strategy presents an overarching approach to infrastructure development in Scotland that seeks to influence investment decisions. It does not propose a specific list or pipeline of projects. On this basis, the Strategy is considered unlikely to significantly impact the historic environment. Key impacts are likely to emerge and be considered at the project scale, through the project pipeline, which is expected to be delivered separately from this Strategy through spending reviews and annual budget processes.

5.4.17. Whilst indirect (and uncertain) links can be drawn around ‘place-making’ principles, town centre regeneration, and the prioritisation of existing assets in the investment hierarchy, these links are unlikely to be significantly affected by the different timescales under consideration in the options.

Summary: With no meaningful differences to draw between the options, they are considered to rank broadly on par with each other. Significant effects are not anticipated from either option.

Landscape and Geodiversity

5.4.18. Whilst the Strategy does not propose a pipeline of specific projects (which have the potential to affect landscapes), there are a few links that merit discussion. Predominantly, beneficial effects are associated with the introduction of natural infrastructure, elevated to the same strategic level as social and economic infrastructure. This is expected to provide a greater focus on geodiversity and landscape improvements (such as peatland restoration and green infrastructure development), across the varying geographies of the borders, urban areas, highlands and islands.

5.4.19. An important factor to note in this respect, with regards to timescales, is the Strategy’s emphasis on limited headroom for projects above the maintenance and renewal requirements. This means that projects that have longer lead-in times or development costs are less likely to be captured by a shorter timescale (Option T1).

5.4.20. The focus on prioritising existing assets and minimising the creation of new assets (as part of an investment hierarchy), alongside the NPF4 focus on compact growth, could ultimately support the minimisation of landscape effects, by reducing development sprawl, and development in previously undeveloped areas of Scotland. Though it is noted that these effects are likely to be held constant across both options.

5.4.21. Recognising the status of private landownership across Scotland, along with the need to leverage private investment, a long-term strategy under Option T2 is considered likely to lead to greater benefits that a short-term strategy under Option T1.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Significant effects are not anticipated from either option.

Material Assets

5.4.22. The Strategy prioritises maintaining, reusing and repurposing existing infrastructure, helping to reduce demand for primary extraction of construction minerals and supporting circular-economy objectives. It is considered likely that this approach would be maintained under either a short or long timescale for the Strategy, so no significant differences are drawn between the options.

5.4.23. Despite this, it is recognised that a long-term strategy provides more headroom for longer-term projects that are also more likely to extend the targeted growth areas. To some extent, this could result in more projects that generate waste. On this basis, Option T1 is marginally preferred to Option T2.

Summary: Overall, Option T1 ranks more favourably that Option T2 with respect to this SEA topic. Significant effects are not anticipated from either option.

Population and Human Health

5.4.24. The Strategy is ultimately designed to improve the infrastructure provisions for Scottish communities. This includes healthcare services and facilities, active travel routes, natural infrastructure, and ensuring equitable access. The Strategy is notably likely to benefit communities whether planned under a 5-year (Option T1) or 10-year (Option T2) timescale, and significant beneficial effects could be expected. Despite this, there are merits associated with a longer-term strategy (Option T2) which make this option rank more favourably in relation to this theme. These include:

• The closer alignment to the 30-year Needs Assessment, integrating a longer-term focus on community needs;
• The greater headroom provided to enable a focus that extends the immediate growth areas, and benefits more communities across Scotland, in line with the proposed ‘whole Scotland approach;’
• Greater security in longer-term plans making investments more attractive and unlocking more funding streams to benefit infrastructure development; and
• More confidence in unlocking longer-term projects with longer lead-in times.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Positive significant effects are anticipated through both options

Soil

5.4.25. The Strategy benefits soil resources through the integration of natural infrastructure, elevated to the same strategic level as social and economic infrastructure. For instance, the Strategy identifies that peatland forms a vital component of Scotland’s natural infrastructure and by leveraging the Peatland Code, the strategy aims to attract private investment for restoration projects. This directly improves soil health. Recognising the need to attract private investment in such projects, a longer-term timescale (Option T2) is considered likely to provide greater security in making investment choices than the shorter timescale considered under Option T1.

5.4.26. The approach to prioritise existing assets and minimise the creation of new assets (as part of an investment hierarchy) is also likely to indirectly benefit soil resources, with less soil disturbance and contamination effects. The beneficial effects associated with this are likely to be achieved under both options, however, as this approach is less affected by timescales.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Significant effects are not anticipated from either option.

Water

5.4.27. The Strategy views water management through the dual lenses of service delivery (via Scottish Water) and climate resilience (via flood protection and nature-based solutions). Beneficial effects are considered likely in relation to water resources and water quality as a result of the Strategy’s investment hierarchy, primary adaptation projects, and integration of natural infrastructure elevated to the same strategic level as social and economic infrastructure. This means that more investments and improvements can be expected in relation to wetlands, sustainable drainage systems, and urban water corridors, and more NbS are likely to be promoted. While such moderate beneficial effects can be expected under both options, the greater headroom and security provided for longer-term projects and investment under a longer planning timescale make Option T2 rank more preferably than Option T1.

Summary: Overall, Option T2 ranks more favourably that Option T1 with respect to this SEA topic. Significant effects are not anticipated from either option

Reasonable Alternatives Set 2: Investment Hierarchy

Option IH1: Initiate a strengthened “maintain and enhance first” model (requiring demonstrable exhaustion of all maintain/repurpose options before considering new build).

Option IH2: Take a balanced approach to infrastructure delivery which seeks to maintain/repurpose first in principle but allows more flexibility.

Option IH3: Initiate a greater emphasis on delivering ‘new build’ strategic assets.

Air Quality

5.4.28. The investment hierarchy options influence air quality mainly through construction activity, transport emissions, and the use of existing assets. A strong “maintain and enhance first” approach (Option IH1) would limit new construction and associated short‑term emissions, but it may also restrict targeted new transport or mobility projects that could address persistent air quality issues.

5.4.29. Option IH2 offers the most balanced performance. It retains a preference for repurposing existing infrastructure (reducing unnecessary construction) while allowing new development where it supports cleaner transport systems or improved connectivity. This flexibility makes it more likely to contribute to long‑term air quality improvements.

5.4.30. Option IH3 increases the likelihood of additional construction and traffic during development phases and therefore carries a higher risk of short‑term adverse effects unless strongly aligned with modal‑shift and decarbonisation objectives.

Summary: Overall, Option IH2 ranks most favourably with respect to this SEA topic, followed by Option IH1, with Option IH3 least favourably ranking. Significant effects are not anticipated from the options.

Biodiversity, Flora, and Fauna

5.4.31. Under all three investment hierarchy options, effects on biodiversity will depend on how infrastructure is prioritised relative to land take, construction activity, and opportunities for ecological enhancement.

5.4.32. Option IH1 (a strengthened maintain‑and‑enhance‑first approach) would help minimise unnecessary land‑take, disturbance and fragmentation by directing investment toward existing assets wherever feasible. This is broadly beneficial for protecting existing habitats. However, a strict presumption against new infrastructure may constrain opportunities for proactive biodiversity enhancement where new land or new natural‑infrastructure interventions are required.

5.4.33. Option IH2 performs most favourably. It maintains a preference for reusing and repurposing existing assets, thereby avoiding avoidable ecological harm, while also allowing new development where this demonstrably supports wider outcomes (including NbS or habitat‑enhancement opportunities). This flexibility enables the Strategy to respond to local ecological priorities while retaining the core safeguard of avoiding unnecessary new build infrastructure.

5.4.34. Option IH3 (greater emphasis on new build strategic assets) may create space for more proactive ecological interventions where new natural‑infrastructure projects are part of wider development. However, it also increases the likelihood of habitat loss, fragmentation and disturbance associated with new build construction. These risks could be substantial where projects occur in sensitive areas or require significant land take. For this reason, Option IH3 is also considered to have mixed effects, combining potential positive contributions with a higher risk of adverse outcomes.

Summary: Overall, Option IH2 ranks most favourably with respect to this SEA topic, followed by Option IH1 and IH3, which are ranked equally. Positive significant effects are anticipated from Option IH2.

Climatic Factors

5.4.35. The Strategy emphasises decarbonisation, reducing embodied carbon, and improving climate resilience.

5.4.36. Option IH1 aligns well with these aims by prioritising refurbishment over new build, reducing emissions linked to materials and construction. However, a strict maintain‑first approach may limit delivery of new low‑carbon or climate adaptation infrastructure where repurposing is not feasible.

5.4.37. Option IH2 performs the most favourably of the three options. It maintains a default preference for reuse while allowing new development where essential for net zero delivery, grid reinforcement, renewable energy expansion, or adaptation projects. This flexibility supports both mitigation and resilience outcomes.

5.4.38. Option IH3 could accelerate new low‑carbon assets but brings higher embodied‑carbon impacts and greater risk of maladaptation if new assets are not well located or designed.

Summary: Overall, Option IH2 ranks most favourably with respect to this SEA topic, followed by Option IH1, with Option IH3 the least favourably ranking. Positive significant effects are anticipated from Option IH2, with potential negative significant effects possible from Option IH3.

Cultural Heritage

5.4.39. The effects in relation to the historic environment are largely uncertain in the absence of a project pipeline and specific locations or schemes. It could be assumed that a ‘maintain and enhance first’ model would limit the extent of ‘new build’ infrastructure that could affect cultural heritage assets, but it could have the counter effect of greater levels of disruption and development within historic settlements, town centres, and targeted areas of growth. It is therefore difficult to summarise meaningful differences between the options at this (high-level strategy) stage, which are ranked on par as a reflection.

Summary: It is not possible to rank the options in relation to this SEA topic. Significant effects are also uncertain.

Landscape and Geodiversity

5.4.40. The focus on a ‘maintain and enhance first’ model, when aligned with NPF4’s compact growth spatial principles, could support the minimisation of landscape effects, by reducing development sprawl, and development in previously undeveloped areas of Scotland. On this basis, Options IH1 and IH2 are considered more likely to avoid significant effects arising for landscapes as a result of infrastructure development. In contrast, Option IH3, by providing a greater emphasis on ‘new build’ strategic assets, has greater potential to deliver schemes with significant landscape implications, including through development sprawl and the loss of greenfield land and local landscape features.

Summary: Overall, Option IH1 ranks most favourably with respect to this SEA topic, followed by Option IH2, with Option IH3 the least favourably ranking. Potential negative significant effects are possible from Option IH3.

Material Assets

5.4.41. The ‘maintain and enhance first’ model is considered to lead to significant beneficial effects in relation to this theme by supporting the efficient use of existing infrastructure and encouraging reduced consumption of raw materials through reuse, refurbishment and recycling. On this basis, Option IH1 and IH2 rank significantly better than Option IH3. In contrast, significant adverse effects could be associated with the less sustainable approach of emphasising ‘new build’ assets, that would likely increase the amount of waste and use of raw materials and expand the portfolio of maintenance and renewal needs.

Summary: Overall, Option IH1 ranks most favourably with respect to this SEA topic, followed by Option IH2, with Option IH3 the least favourably ranking. Potential positive significant effects are possible from Options IH1 and IH2, with potential negative significant effects from Option IH3.

Population and Human Health

5.4.42. All options have potential to enhance wellbeing by strengthening infrastructure that supports services, connectivity, and access.

5.4.43. Option IH1 would prioritise improving the condition and performance of existing public‑service infrastructure (such as healthcare buildings, schools, community facilities, digital networks, and local transport infrastructure). This is likely to have beneficial effects on service reliability and resilience. However, a strict presumption against new development may constrain delivery of new facilities or upgraded networks where existing assets cannot meet changing demand, particularly in fast‑growing areas or remote communities.

5.4.44. Option IH2 performs most favourably. It maintains a strong preference for reusing and repurposing existing assets while still allowing new development where this is necessary to address unmet needs, support accessibility, or deliver wider wellbeing improvements (for example, improved active travel links, upgraded health facilities, or resilient local service models). This balance is most likely to support long‑term improvements in health outcomes and reduce inequalities. Option IH3 could improve access to services in some areas by enabling the delivery of new facilities that respond to changing demographic or spatial needs. However, this approach also introduces higher short‑term disruption from construction activity and may divert resources away from the maintenance of existing facilities, potentially affecting service quality elsewhere.

Summary: Overall, Option IH2 ranks most favourably with respect to this SEA topic, followed by Option IH1 and IH3, which are ranked equally. Positive significant effects are anticipated from all options.

Soil

5.4.45. The approach to prioritise existing assets and minimise the creation of new assets (as part of an investment hierarchy) is likely to indirectly benefit soil resources, with less soil disturbance and contamination effects. The beneficial effects associated with this are most likely to be achieved under Option IH1, followed by IH2. Conversely, Option IH3 which provides a greater emphasis on ‘new build’ assets is likely to have greater implications for soil resources in terms of disturbance and contamination, and potentially loss of productive soils.

Summary: Overall, Option IH1 ranks most favourably with respect to this SEA topic, followed by Option IH2, with Option IH3 the least favourably ranking. Potential negative significant effects are possible through Option IH3.

Water

5.4.46. Focusing on water resources, the ‘maintain and enhance first’ model is likely to benefit existing water infrastructure (including wastewater) by focusing on capacity upgrades where they are most needed. Alongside the NPF4 commitment to compact growth, benefits are associated with utilising existing infrastructure to deliver upgrades that expand capacity and address existing issues, such as leakage, at the same time. In this respect, Options IH1 and IH2 perform well. In contrast, Option IH3, which seeks to support ‘new build’ assets, could place additional strains on water resource management and lead to more costly projects that detract from the ongoing maintenance and renewal needs of existing assets.

5.4.47. Whilst few direct effects can be drawn in relation to water quality, the ‘maintain and enhance’ first model will do more to avoid new development in the vicinity of watercourses and within flood plains and will reduce the extent of new development that affects drainage (e.g. hard surfacing).

Summary: Overall, Option IH1 ranks most favourably with respect to this SEA topic, followed by Option IH2, with Option IH3 the least favourably ranking. Significant effects are not anticipated as a result of the options.

Reasonable Alternatives Set 3: Environmental Ambition

Option E1: Seek the highest level of environmental protection through the Infrastructure Strategy.

Option E2: Initiate a minimal compliance approach through the Infrastructure Strategy.

Option E3: Delver a balanced environmental ambition approach through the Infrastructure Strategy.

Air Quality

5.4.48. Option E1 would place a strong emphasis on reducing emissions from both infrastructure construction and operation, which could encourage the use of cleaner technologies, improved construction practices and low‑emission fleet requirements. The option would also support investment in sustainable transport, active travel networks and measures that target air quality improvements in areas currently experiencing higher pollution levels.

5.4.49. Option E2 would meet the required statutory standards for air quality, ensuring compliance with national regulations and minimum emissions performance thresholds. It may not, however, encourage wider adoption of enhanced or locally targeted mitigation that could further reduce exposure to air pollution.

5.4.50. Option E3 would support air quality improvements where they align with wider strategic objectives, allowing a degree of flexibility in how air quality considerations influence delivery choices. The option would therefore deliver varied outcomes depending on project location, scale and the relative priority assigned to environmental ambition in individual decisions.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Biodiversity, Flora and Fauna

5.4.51. Option E1 would prioritise avoidance of ecological impacts and promote measures that protect, restore or expand natural habitats, including integrated GBI. The option would also help maintain ecological connectivity and support Nature Network aims by encouraging NbS and improvements to the wider ecology.

5.4.52. Option E2 would comply with statutory biodiversity requirements, ensuring impacts on designated sites and protected species are managed appropriately. It may not, however, promote the broader ecological enhancements or habitat connectivity improvements that could be achieved through a higher level of ambition.

5.4.53. Option E3 would allow biodiversity protection and enhancement measures to be applied where they are compatible with other planning and investment priorities. Option E3 would therefore result in a mixed pattern of outcomes, with some projects delivering ecological benefits and others offering only baseline protection.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Climatic Factors

5.4.54. Option E1 would place strong emphasis on reducing greenhouse‑gas emissions through the use of low‑carbon materials, efficient energy systems and sustainable design practices. It would also support adaptation by encouraging resilient infrastructure, including measures that address increased flood risk, heat stress and other climate impacts identified in national and regional assessments.

5.4.55. Option E2 would ensure that legal obligations relating to climate mitigation and adaptation are met, but it may not pursue wider opportunities to exceed minimum requirements. The option may therefore miss opportunities to deliver more climate resilient or lower‑carbon infrastructure where these benefits rely on additional ambition.

5.4.56. Option E3 would encourage climate‑related improvements where these can be balanced with the Strategy’s wider economic and social objectives. It may therefore lead to varied levels of emission reduction and climate adaptation depending on the local priorities and budget constraints influencing individual projects.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Cultural Heritage

5.4.57. Option E1 may help promote higher design and environmental standards that reduce risks to the setting and character of cultural‑heritage assets. The option could also support more proactive consideration of the historic environment by encouraging early integration of heritage evidence into project planning.

5.4.58. Option E2 would meet statutory requirements to protect designated heritage assets and archaeological remains but may not provide additional emphasis on design quality or contextual sensitivity. It would therefore rely more heavily on project‑level assessments to manage heritage impacts effectively.

5.4.59. Option E3 would allow heritage considerations to be incorporated where these align with other policy aims or design requirements. The option may therefore lead to a range of outcomes depending on local circumstances and the degree to which environmental ambition is prioritised in each case.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Landscape and Geodiversity

5.4.60. Option E1 would provide stronger protection for valued landscapes and geodiversity features through more sensitive siting and design and by minimising unnecessary land disturbance. It may also encourage the use of NbS, which can help maintain natural landforms, reduce visual intrusion and support landscape character.

5.4.61. Option E2 would maintain compliance with statutory landscape and geodiversity protections but may offer fewer opportunities to enhance landscape quality or address cumulative effects. The option would therefore generate outcomes that depend largely on how individual projects are designed and delivered.

5.4.62. Option E3 would allow for landscape and geodiversity protection where this supports wider development aims. It may therefore lead to varied landscape outcomes across different areas, reflecting the degree to which environmental ambition is applied.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Material Assets

5.4.63. Option E1 would strongly support the efficient use of existing infrastructure and encourage reduced consumption of raw materials through reuse, refurbishment and recycling. The option would also promote circular‑economy principles, which can reduce waste generation and improve long‑term resource efficiency.

5.4.64. Option E2 would ensure compliance with minimum standards for waste management and material use but may not actively promote higher levels of efficiency or resource conservation. It would therefore rely on separate project choices or funding constraints to drive any further improvements.

5.4.65. Option E3 would allow a flexible approach to material use, supporting reuse where feasible while still allowing new materials where needed. The option would therefore lead to a varied set of outcomes depending on local project needs and how environmental ambition is applied.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Population and Human Health

5.4.66. Option E1 supports healthier environments by improving air quality, greenspace, and resilience, which can benefit physical and mental health. However, its stronger emphasis on environmental protection may limit the delivery of new infrastructure, which could reduce access to important services and constrain wider wellbeing benefits.

5.4.67. Option E2 meets statutory environmental requirements that help safeguard basic health outcomes. However, it does not actively promote wider health improvements that could arise from enhanced environmental quality or improved access to services.

5.4.68. Option E3 provides a more balanced approach by supporting both environmental improvements and the delivery of necessary infrastructure. As a result, it is more likely to strengthen access to services, greenspace, and transport while still supporting environmental conditions that benefit health.

Summary: Overall, Option E3 ranks most favourably with respect to this SEA topic, followed by Option E1, with Option E2 the least favourably ranking. Positive significant effects have the most potential to take place through Option E3.

Soil

5.4.69. Option E1 would promote stronger protection of soils by prioritising reuse of previously developed land, reducing soil sealing and avoiding unnecessary land disturbance. It may also support NbS that help restore soil structure and enhance carbon storage in soils.

5.4.70. Option E2 would meet minimum regulatory requirements relating to soil protection but may not promote additional actions to minimise soil loss or disturbance. This would therefore result in soil outcomes that vary depending on individual project siting and management.

5.4.71. Option E3 would incorporate soil‑protection measures where they align with wider development needs. The option may therefore lead to more variable soil outcomes, depending on how environmental ambition is balanced with delivery priorities.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Water

5.4.72. Option E1 would encourage higher standards of water management, supporting improved water quality, integrated drainage and enhanced flood risk mitigation. This may also promote wider use of GBI and NbS, which can help manage surface water pressures more sustainably.

5.4.73. Option E2 would maintain compliance with statutory requirements for water quality and flood risk but may not promote additional measures beyond these minimum standards. It would therefore deliver water environment outcomes that depend on project‑level practices.

5.4.74. Option E3 would support improvements to water management where these align with other strategic or local priorities. The option may lead to more variable outcomes across the Strategy, depending on the extent to which environmental ambition is applied in different areas.

Summary: Overall, Option E1 ranks most favourably with respect to this SEA topic, followed by Option E3, with Option E2 the least favourably ranking. Positive significant effects have the potential to take place through Option E1.

Reasonable Alternatives Set 4: Role of a Place-Based Approach

Option PB1: Initiate a strong place-partnership model for infrastructure.

Option PB2: Deliver a nationally led prioritisation approach for infrastructure.

Option PB3: Deliver a locally determined approach to infrastructure.

Air Quality

5.4.75. Option PB1 is likely to perform best for air quality because it aligns infrastructure investment with local transport needs, settlement patterns, and opportunities to reduce vehicle emissions. Local partners can prioritise interventions such as active travel networks, public transport improvements, and low‑emission mobility tailored to community needs. It also supports integrated planning between transport, land use, and regeneration, increasing the chance of reductions in air quality hotspots.

5.4.76. Option PB2 may deliver large‑scale transport improvements, but it risks applying uniform solutions that do not reflect local conditions, air quality issues or behaviour patterns. National prioritisation could lead to investment decisions that optimise strategic networks but overlook localised exposure, sensitive receptors, or cumulative issues in deprived communities.

5.4.77. Option PB3 provides flexibility to target local air quality issues, particularly in areas affected by congestion or poor connections. However, without national coordination or funding alignment, local authorities may struggle to deliver broader modal‑shift infrastructure, which limits its overall effectiveness.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Biodiversity, Flora and Fauna

5.4.78. Option PB1 supports coordinated delivery across local, regional, and national partners, allowing biodiversity considerations to be embedded early and consistently. Place‑based planning is well placed to integrate Nature Networks, green and blue infrastructure (GBI), and habitat enhancement opportunities at the landscape scale. Additionally, cross‑boundary ecological issues (such as species corridors or cumulative impacts) can be better managed.

5.4.79. Option PB2 may help ensure that national biodiversity requirements and statutory protections are applied consistently. However, a nationally led approach may not always have the level of detail needed to address local ecological sensitivities, habitat connectivity, or opportunities for enhancement. This means that smaller‑scale biodiversity issues or locally important habitats may not always be fully reflected in decision making.

5.4.80. Option PB3 can respond well to local biodiversity considerations because it allows decisions to be informed by site‑specific information. However, ecological systems often extend across local boundaries, and without wider coordination there is a risk that approaches differ between areas. This could lead to inconsistent practice, difficulties in managing cumulative effects, or gaps in habitat connectivity.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Climatic Factors

5.4.81. Option PB1 offers a coordinated way to plan for both climate mitigation and climate adaptation needs. Through joint working arrangements, this approach can help align decisions on heat, energy, transport, flood management and land use. It also allows climate resilience measures, such as coastal protection, flood‑alleviation schemes and nature‑based solutions, to be tailored to local risks and delivered in a more integrated way.

5.4.82. Option PB2 may support the delivery of large‑scale national projects that help reduce emissions, such as energy‑network upgrades or wider decarbonisation infrastructure. However, because climate impacts vary between places, a nationally led approach may be less able to respond to local adaptation needs, including more localised flooding, erosion or heat‑stress risks.

5.4.83. Option PB3 allows local areas to focus on their own climate‑related priorities, but a fully local approach may lead to gaps in strategic decarbonisation infrastructure, such as energy networks or heat systems that require wider coordination. Local authorities may also face capacity or resource constraints, which could limit their ability to plan and deliver climate mitigation measures at scale.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Cultural Heritage

5.4.84. Option PB1 supports early and coordinated use of local and national heritage information, including Historic Environment Records, conservation area work, and locally valued heritage features. Because decisions are shaped jointly, this option can reflect both local heritage character and wider policy requirements. This helps achieve more consistent outcomes across areas while still ensuring development responds to local context.

5.4.85. Option PB2 would apply national heritage protections and policy consistently. However, because it is driven mainly by national priorities, it may be less responsive to local heritage settings, townscape qualities, and the distinct character of individual places. This could mean local context is not fully reflected in decision making, even though statutory protections remain in place.

5.4.86. Option PB3 can respond effectively to local heritage considerations, including the character of streets, neighbourhoods and conservation areas. However, without national coordination, approaches may vary between areas, leading to different standards of assessment or management. This could make it harder to address cross‑boundary heritage issues in a consistent way, even though nationally designated heritage assets would still be protected.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Landscape and Geodiversity

5.4.87. Option PB1 supports coordinated work across different areas, which is helpful because landscape character, views, and geodiversity features often extend beyond local boundaries. This approach can promote consistent landscape‑led design, support alignment with National Scenic Areas objectives, and help identify and manage cumulative effects in rural, coastal or transitional landscapes.

5.4.88. Option PB2 may help deliver major strategic projects, but a national approach may be less responsive to local landscape character or detailed geodiversity considerations. As a result, some locally important landscape or geological sensitivities may not be fully reflected in decision making.

5.4.89. Option PB3 can respond well to local landscape character assessments and local views about landscape change. However, without cross‑boundary coordination, it may be more difficult to consider wider landscape settings or cumulative effects that occur between neighbouring areas, especially where shared landscapes or geological features are involved.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Material Assets

5.4.90. Option PB1 allows different organisations to plan and manage infrastructure together. This can help make better use of existing assets, reduce duplication, and support approaches that use materials more efficiently. Coordinated working can also help identify shared solutions for utilities, transport, and public services.

5.4.91. Option PB2 may help improve major national infrastructure, but it may be less able to recognise local opportunities such as shared use of facilities, reuse of materials, or coordinated maintenance between neighbouring areas.

5.4.92. Option PB3 can support local asset management, but local authorities may not always have the resources or capacity needed to plan infrastructure or material use strategically across wider areas.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Option PB2 and PB3, which ranks least favourably. Positive significant effects have the potential to take place through Option PB1.

Population and Human Health

5.4.93. Option PB1 helps align infrastructure decisions with both local needs and wider priorities. By working jointly across areas, it supports coordinated planning for healthcare access, active travel routes, greenspace, digital connectivity and other services that influence health and wellbeing. This approach can also help ensure that improvements are delivered more consistently between areas and that investment is better targeted where health inequalities are greatest.

5.4.94. Option PB2 may help deliver major national health‑related infrastructure, but it may not fully reflect the specific needs of different communities. As a result, some local patterns of health outcomes or inequality may not be addressed as effectively through a national approach alone.

5.4.95. Option PB3 can respond well to local health and wellbeing priorities, particularly where communities have specific service or accessibility needs. However, if decisions are made mainly at the local level, there may be differences in provision between areas, and some wider or cross‑boundary health‑infrastructure needs may be harder to coordinate without broader partnership working.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Soil

5.4.96. Option PB1 supports coordinated decisions about how land is used, which helps manage soil resources more consistently across different areas. This includes encouraging brownfield redevelopment, protecting high quality soils, and planning for soil‑related issues such as erosion, peat protection or land contamination. By working jointly, partners can take account of soil pressures that cross boundaries and ensure that soil‑management approaches are applied more evenly.

5.4.97. Option PB2 can help deliver major infrastructure, but national approaches may not always take full account of detailed soil conditions or local land‑quality constraints. Large projects may also require more land, meaning that soil disturbance or greenfield loss may be greater unless managed carefully.

5.4.98. Option PB3 allows soil considerations to be reflected in local land use decisions, particularly where communities prioritise brownfield use or the protection of agricultural soil or peat. However, because soil functions often operate across wider landscapes, a fully local approach may lead to uneven management or different standards between neighbouring areas.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

Water

5.4.99. Option PB1 supports coordinated water‑management across catchments, recognising that drainage, flood risk and wastewater issues often extend beyond individual local authority boundaries. This approach helps integrate decisions on GBI, surface‑water management, and flood risk mitigation, and allows different organisations to plan together so that both local and cross‑boundary water‑environment needs are considered.

5.4.100. Option PB2 may help deliver major national water‑infrastructure improvements, such as large treatment works or strategic supply upgrades. However, because this approach is directed mainly by national priorities, it may be less able to respond to locally specific drainage challenges, surface‑water flooding patterns, or smaller‑scale water‑quality issues.

5.4.101. Option PB3 can respond well to local water‑management issues, such as localised drainage improvements or smaller‑scale flood risk concerns. However, because many water systems operate across catchments, locally led decision making may not fully address cross‑boundary pressures without mechanisms for wider partnership working.

Summary: Overall, Option PB1 ranks most favourably with respect to this SEA topic, followed by Options PB2 and PB3, who are ranked equally. Positive significant effects have the potential to take place through Option PB1.

5.5. Summary of Assessment Findings

Timescales and Sequencing

5.5.1. Across the SEA topics, the assessment indicates that a longer‑term 10‑year Strategy (Option T2) performs more favourably against the environmental assessment themes than a 5‑year cycle. Option T2 provides greater certainty for coordinating programmes with long lead‑in times and supports better alignment with the 30‑year Needs Assessment and the Strategy’s focus on climate resilience, natural‑infrastructure integration and place‑based planning. These features result in more favourable performance for climatic factors, biodiversity, landscape, water, soil and population and human health, where longer‑term planning horizons tend to enable more strategic, coordinated and preventative outcomes.

5.5.2. A shorter 5‑year Strategy (Option T1) still enables incremental improvements and allows more frequent review cycles, but the reduced time horizon limits sequencing of larger or more complex interventions, resulting in more modest performance across several SEA topics. While both options avoid significant adverse effects, the SEA evidence base shows that Option T2 performs more favourably across multiple environmental topics, whereas Option T1 performs relatively less favourably across themes where long‑term planning is particularly beneficial.

Investment Hierarchy

5.5.3. Across most SEA topics, a balanced application of the investment hierarchy (Option IH2) performs more favourably within the SEA evidence base. IH2 maintains a preference for maintaining and repurposing existing assets (helping limit avoidable impacts on soils, habitats, landscapes, materials and water) while still enabling new infrastructure where required to achieve wider outcomes. As a result, IH2 performs more positively for topics such as air quality, biodiversity, climatic factors, population and human health, and generally avoids the significant adverse effects.

5.5.4. Option IH1, which places greater emphasis on retaining and upgrading existing assets, performs favourably for soil, landscape, material assets and water, as reduced reliance on new build activity helps limit land‑take, disturbance and resource use. However, IH1 performs less favourably where new assets may be required to meet future infrastructure needs. In contrast, IH3 performs least favourably across the SEA topics, with potential significant adverse effects for climatic factors, landscape and geodiversity, soil and material assets due to increased construction activity and resource consumption.

Environmental Ambition

5.5.5. The assessment shows that Option E1, representing the highest level of environmental ambition, performs more favourably across all but one SEA topic. Stronger environmental safeguards support air quality, biodiversity, climatic factors, material assets, soil, and water, and help maintain high‑quality environments that contribute to long‑term health and resilience. These outcomes align with the Strategy’s strategic focus on natural‑infrastructure enhancement, climate resilience and net zero transitions.

5.5.6. Option E2 performs least favourably across all SEA topics, providing only baseline environmental protection and missing opportunities for broader environmental gain. Option E3 performs moderately, enabling environmental benefits where they align with wider priorities, but its performance is more variable than E1.

Role of a Place-Based Approach

5.5.7. The SEA assessment identifies Option PB1 as performing most favourably across all the SEA topics. PB1 supports coordinated work across local, regional and national partners, enabling infrastructure delivery that better reflects local environmental sensitivities, climate‑risk patterns, water‑catchment dynamics, landscape character, habitat connectivity and soil considerations. This coordination aligns strongly with the Strategy’s place‑based approach and helps avoid fragmented decision‑making across functional geographies.

5.5.8. Options PB2 and Option PB3 each perform similarly, but less favourably than Option PB1, across many SEA topics. Option PB2 provides consistency across the country but may under reflect localised constraints, while Option PB3 allows decisions to respond closely to local needs, but risks inconsistency across boundaries and reduced ability to manage cross‑boundary issues. Option PB2 performs slightly more favourably than Option PB3 for material assets and water, where nationally coordinated investment can better support shared infrastructure planning, resource efficiency, and catchment‑scale management.

5.6. Developing the Preferred Approach

Choice of Options Taken Forward for the Purposes of the Infrastructure Strategy

5.6.1. Drawing on the SEA assessment of reasonable alternatives the Scottish Government has adopted a preferred approach that combines the strongest performing elements from across the option sets. This includes a longer-term 10-year strategic horizon which provides greater certainty for sequencing major programmes and aligning with the 30-year Needs Assessment; a balanced application of the Infrastructure Investment Hierarchy, ensuring existing assets are optimised while enabling essential new development for net zero, resilience and inclusive growth; a high level of environmental ambition that embeds climate and nature considerations across investment decisions; and a strong place-partnership model that aligns national, regional, and local priorities.

5.6.2. Collectively, these choices form a coherent and evidence led approach that maximises long-term environmental, social, and economic outcomes while ensuring that infrastructure investment remains adaptable, fiscally responsible, and responsive to the diverse needs of Scotland’s people and places.