Carbon Account for Transport

Carbon Account for Transport No. 8: 2016 Edition

Carbon Account for Transport

Chapter 3: Future emissions impact of transport interventions

3.1 Background

This chapter lists transport interventions, whether devolved or reserved to the UK/EU, which are firm commitments and are expected to have a direct and significant impact on Scottish transport emissions in the future. The interventions are separated between infrastructure projects, and fiscal and regulatory measures. The emissions impact estimates used here are sourced from the available project or policy documents, and have been rounded to the nearest kilo-tonne of carbon-dioxide equivalent (ktCO2e) where appropriate.

This chapter also outlines the general methodological approach or background documents used to estimate the impact of infrastructure projects and fiscal/regulatory policies. As independently commissioned projects, the precise estimation methodology of each infrastructure project may differ significantly depending upon the type of intervention and the modelling approach adopted. Second, emissions estimates are frequently assessed in isolation, and therefore will not necessarily include the full interactions between measures, or take account of the impact of any future measures on the project. Finally, for many interventions there are likely to be a number of localised impacts which may not be captured or presented consistently between infrastructure appraisals. Where possible, the impacts presented are the net emissions impact at a Scottish level.

With such methodological variation, the emissions impact from each infrastructure project and related timescales are intended as an informative guide to the direction of change and an order of magnitude only. The basis of each fiscal estimate is not known beyond what is presented in the accompanying document(s). As a result the comparison, addition or netting off of emissions estimates between interventions or against the GHGI data is not statistically valid and may lead to incorrect conclusions being drawn.

3.2 Infrastructure projects

Undertaken by Transport Scotland and announced by The Minister for Transport, Infrastructure and Climate Change in December 2008, the Strategic Transport Projects Review (STPR) sets out investment priorities for the next twenty years and provides the basis on which Ministers can make informed decisions about future transport spending. The nature of this publication means that while some projects are now underway and others completed, many will be undertaken at a future date and thus as yet lack a designated timetable and a formal appraisal process. Individual projects from within STPR likely to have a significant emission impact will be included in the CAT commentary as and when they become committed schemes.

Methodology for measuring environmental impacts

Estimates of the environmental impacts from each infrastructure project are cited from the latest available project documents. In most cases this will be the emissions estimate contained in the project specific environmental statement. More recently announced projects will have no estimate because the formal appraisal process has not yet been undertaken. For reference, links to the project home page on Transport Scotland's website are also provided where they are available.

STAG recommends that greenhouse gas emissions from road traffic are calculated according to the methodology in the Design Manual for Roads and Bridges[19] (DMRB). First introduced in 1992 in England and Wales, and subsequently in the rest of the UK, it continues to provide a comprehensive manual system which accommodates current standards, advice notes and other published documents relating to trunk road works.

For emissions associated with the running of diesel and electric trains, STAG recommends the use of the Rail Emission Model Final Report[20] produced for the Strategic Rail Authority. This is available on the Department for Transport website, and provides estimated emission factors and detailed data for individual diesel and electric train types.

There are no similar established guidelines for producing carbon estimates for other travel modes. Should such a need arise, the methodology used would be tailored specifically to the individual projects concerned. Similarly, when considering the predicted emissions impacts of infrastructure projects, the modelling procedures used can differ significantly between projects, particularly in how they account for secondary impacts such as land-use changes.


M8, M74 and M73 Motorway Improvements Project

Following award of the contract to Scottish Roads Partnership (SRP) in February 2014, the M8, M73 and M74 Motorway Improvements Project is underway, and scheduled to open in Spring 2017. This project encompasses three individual sub-projects: M8 Baillieston to Newhouse, M74 Raith Interchange, and M8 M73 M74 Network Improvements.

SRP anticipate that the project will create in excess of 1,000 jobs in Scotland, with the motorway improvements project expected to reduce the journey time for the 100,000 vehicles that use the busiest sections of the M8 each day.

It is predicted that the scheme will lead to a reduction of more than 100 accidents per year, and more freely flowing traffic on strategic routes will reduce emissions associated with queuing traffic. This will also improve air quality and health.

M74 Raith Interchange

  • Document: Environmental Statement (2007), Mouchel Fairhurst JV
  • Anticipated construction completion: 2017
  • Estimated emissions impact: +10ktCO2e p.a. from 2017; +10ktCO2e p.a. from 2020

The scheme is aligned with the M8 Baillieston to Newhouse works and the Associated Network Improvements. These are vital links in the trunk road network of Central Scotland and serve substantial existing developments as well as some of the most significant future development sites in Scotland.

Severe traffic problems exist at Raith Junction due to the interaction of heavy turning volumes from the A725 and the M74 at the signalised roundabout. This scheme aims to relieve traffic congestion at the junction creating free-flow conditions on the A725.

M8 M73 M74 Network Improvements

  • Document: Environmental Statement, 2008 (Mouchel Fairhurst JV)
  • Anticipated construction completion: 2017
  • Estimated emissions impact: +2ktCO2e p.a. by 2020

This scheme comprises capacity improvements on sections of the M73, M74 and M8 adjacent to Baillieston and Maryville interchanges as a result of changes to east-west traffic patterns following completion of the M74 and once improvements to the M8 are in place.

M8 Baillieston to Newhouse

  • Document: Environmental Statement (2007), Mouchel Fairhurst JV
  • Anticipated construction completion: 2017
  • Estimated emissions impact: +30ktCO2e p.a. from 2017; +30ktCO2e p.a. from 2020

This project is to upgrade the existing A8 between Baillieston and Newhouse to dual three-lane motorway standard equivalent.

The DMRB was used to calculate the change in greenhouse gas emissions, therefore the assessment has included all traffic on the entire modelled network, in addition to links that were explicitly included in the local assessment. The increase in emissions is due to an increase in predicted traffic levels.

A90 Aberdeen Western Peripheral Route (AWPR) and A90 Balmedie-Tipperty

  • AWPR Document: Assessment of Effects of Updated Traffic Model submitted for PLI (2008), which updates previous source of 2007 Environmental Statement, Jacobs
  • Balmedie - Tipperty Document: Environmental Statement (2007), Grontmij / Natural Capital
  • The A90 Aberdeen Western Peripheral Route and the A90 Balmedie to Tipperty projects were combined into a single scheme prior to being tendered.
  • Anticipated construction completion: Construction of the scheme commenced in February 2015 following award of the contract to Aberdeen Roads Limited. The first section of the AWPR/B-T works to open to traffic included the Craibstone and Dyce Junctions in August 2016. This section was brought forward following requests from stakeholders and subsequent discussions with the contractor. The Balmedie to Tipperty section is scheduled to open by Spring 2017 with the remainder of the AWPR/B-T expected to open to traffic in winter 2017.
  • Estimated emissions impact for AWPR: +8ktCO2e p.a. from 2012; +10ktCO2e p.a. from 2027. For Balmedie- Tipperty : +2ktCO2e p.a. from 2010 (assumed opening year in environmental statement)

A peripheral route around Aberdeen will reduce the high volumes of traffic using the A90 in the centre of Aberdeen, and reduce the traffic congestion that the city experiences as a result of the volume of traffic using the A90 and its associated radial roads. The overall increase in the number of road vehicles, however, is expected to lead to an increase in carbon dioxide emissions.

The AWPR will provide substantial benefits across the whole of the North East of Scotland and will provide a boost to the economy; increase business and tourism opportunities; improve safety; cut congestion as well as increasing opportunities for improvements in public transport facilities.

This proposed dualling of the A90 between Balmedie and Tipperty will provide continuous dual carriageway between Aberdeen and Ellon, which will remove the bottleneck caused by the existing single carriageway. The local community has been pressing for this upgrade for a number of years. The increase in emissions through Balmedie -Tipperty is mainly due to the increase in the road sections that make up the total road network assessed.

Forth Replacement Crossing

The Forth Replacement Crossing (FRC) is a major road infrastructure project being delivered by Transport Scotland. The project was driven by uncertainty over the future viability of the existing Forth Road Bridge, and is designed to safeguard this vital connection in Scotland's transport network. It comprises a new cable-stayed bridge across the Firth of Forth (the Queensferry Crossing), to the west of the existing Forth Road Bridge, and associated new and improved road infrastructure to the north and south of the bridge. The scheme will retain the existing Forth Road Bridge as a public transport corridor for use by buses, taxis and other specified users and for continued use by pedestrians and cyclists. The Queensferry Crossing will be used by all other traffic including private cars and heavy goods vehicles. Emergency vehicles will be able to use either bridge.

The FRC was identified as a key strategic investment project in Scotland's national transport network in the Strategic Transport Projects Review (STPR) undertaken by Transport Scotland in December 2008, and the National Planning Framework (NPF2) published by the Scottish Government in June 2009. There are eight specific transport planning objectives for the FRC which have underpinned the work on the project. These are to:

  • maintain cross-Forth transport links for all modes to at least the level of service offered in 2006
  • connect to the strategic transport network to aid optimisation of the network as a whole
  • improve the reliability of journey times for all modes
  • increase travel choices and improve integration across modes to encourage modal shift of people and goods
  • improve accessibility and social inclusion
  • minimise the impacts of maintenance on the effective operation of the transport network
  • support sustainable development and economic growth
  • minimise the impact on people, and the natural and cultural heritage of the Forth area.

Construction commenced in 2011 and the FRC will open in 2017.

Dualling of A9

  • Document: Environmental Statement: not yet available
  • Anticipated construction completion: 2025
  • Estimated emissions impact: not yet available

This programme will address issues of driver frustration on the A9 caused by the limited guaranteed overtaking opportunities that current exist, resulting in improved connections between Perth and Inverness. Options for the proposed dual carriageway are currently being developed but it is likely that it will largely comprise on-line widening due to the environmental and physical constraints in the corridor.

It is too early to say how CO2e emissions may change as a result of the scheme. Design development work is now underway and the emerging findings are that the dualling will increase emissions as a consequence of changes to vehicle speeds. Quantification of that impact across the programme is not yet available and a number of route options are still being assessed. Quantification will take place as part of the preparation of the Environmental Statements for the component projects.

Dualling of A96

Document: Environmental Statement: not yet available

  • Anticipated construction completion: 2030
  • Estimated emissions impact: not yet available

This programme will address issues of driver frustration on the A96 caused by the limited availability of overtaking opportunities. It will also address issues of community severance by introducing bypasses to communities along the route. Both objectives will serve to improve connectivity between Inverness and Aberdeen. Baseline information and constraints mapping collated to support future option development for the proposed dual carriageway. Route option development and assessment on the Hardmuir to Fochabers section underway with a preferred option for Inverness to Nairn (including Nairn Bypass) announced in October 2014.

Given the likelihood of extended lengths of dual carriageway to provide bypasses it is likely that CO2e emissions will increase as a result of the scheme. However further work will be undertaken during the design development to understand changes to vehicle speeds and their consequences for emissions before and after the scheme is in place.


Edinburgh-Glasgow (Rail) Improvements Programme

  • Document: Edinburgh Glasgow Improvement Programme (EGIP) Appraisal and Analysis Model (2013), Transport Scotland.
  • Anticipated construction completion: In phases through to 2028.
Embodied emissions (construction):
Total impact (2013 – 2028) (ktCO2e)
Phase 1 +112
Phase 1 + 2 +123
Operational emissions [21]:
Average annual impact from 2017 (ktCO2e)
Phase 1 -28[22]
Phase 1 + 2 -33
Total impact (ktCO2e) By 2025 By 2050 By 2078
Phase 1 -237 -956 -1760
Phase 1 + 2 -262 -1095 -2028

This intervention was identified early in the Strategic Transport Projects Review (STPR) and brought forward in a study that considered improvements to the capacity, frequency and journey time of rail services between Edinburgh and Glasgow.

The Edinburgh Glasgow Improvement Programme is expected to result in a significant reduction of carbon emissions through the electrification of approximately 260 km of single track and the move from diesel to electric trains.
The change in CO2e emissions has been calculated in line with guidance from the Department for Energy and Climate Change. Previous estimates derived from the Network Modelling Framework (NMF) have been revised to account for reduced fuel consumption/increased fuel efficiency estimates for class 170 diesel trains (reducing EGIP operational emission savings) and the latest changes to WebTag parameter values that have increased the calculated displaced car emissions (increasing EGIP operational emission savings).

Once the project is fully completed (phase 1 + 2) by 2028, the projected long term annual reduction of road emissions is approximately 3ktCO2e.

The programme achieves emissions reductions and also transfers emissions from non-traded (e.g. car emissions) sectors to traded sectors (e.g. electricity generation).

If both electricity emissions and those from embodied carbon are included, the total net impact of EGIP (phase 1 + 2) is -1529 ktCO2e by 2078. Of this total, -1847 ktCO2e arises from diesel savings from trains removed from the rail network, +376 from the new electric trains added to the rail network and -181 ktCO2e from cars removed from the road network. Table 5 demonstrates further breakdown of the expected emissions impact across the different sectors.

Table 5: Change in emissions as a result of EGIP, by sector (ktCO2e)
Budget Period Operational Embodied**
Non-transport sector*
  Phase 1 Phase 1 +2 Phase 1 Phase 1 + 2 Phase 1 Phase 1 + 2
2013 - 2017 -17 -19 +12 +12 +92 +92
2018 - 2022 -133 -146 +90 +90 +20 +20
2023 onwards -1610 -1863 +240 +274 0 +11
Total -1760 -2028 +342 +376 +112 +123

* Electricity production and distribution sector
** Primarily manufacturing and construction

Aberdeen to Inverness

  • Document: Not yet available
  • Environmental Statement: not yet available
  • Anticipated construction completion: In phases through to 2030
  • Estimated emissions impact: not yet available

This project will deliver significant journey time improvements and greater connectivity for both passenger and freight services operating on the Aberdeen to Inverness rail corridor. It is too early to say how CO2e emissions may change as a result of the improvement project. Further work will be undertaken during the design development to understand the impact the increased frequency and additional services will have on emissions following their introduction.

Highland Mainline

  • Document: Not yet available
  • Environmental Statement: not yet available
  • Anticipated construction completion: In phases through to 2025
  • Estimated emissions impact: not yet available

This project will deliver significant journey time improvements and greater connectivity for both passenger and freight services operating between Inverness and the Central belt. It is too early to say how CO2e emissions may change as a result of the improvement project. Further work will be undertaken during the design development to understand the impact the increased frequency and additional services will have on emissions following their introduction.

Shotts Electrification

  • Document: Not yet available
  • Environmental Statement: not yet available
  • Anticipated construction completion: By end of March 2019
  • Estimated emissions impact: not yet available

Route clearance work is currently being undertaken in advance of the award of contract for the actual electrification works. The route is currently served by diesel multiple units (DMU). When construction works have been completed, a new fleet of electric multiple units (EMU) will be deployed. The route will also benefit from a reduction in journey times. The environmental and emissions impacts are not yet available.

Table 6: Estimated net emissions impact of individual transport infrastructure projects

Project title

Published emissions estimate

M74 Raith Interchange

+10 ktCO2e p.a. from 2020

M8 M73 and M74 Network Improvements

+2 ktCO2e p.a. by 2020

M8 Baillieston-Newhouse

+30 ktCO2e p.a. from 2020

A90 Balmedie-Tipperty

+2 ktCO2e p.a. from 2010*

A90 Aberdeen Western Peripheral Road

+10 ktCO2e p.a. from 2027

Forth Replacement Crossing

+20 ktCO2e p.a. in 2032

Edinburgh-Glasgow (Rail) Improvements Programme

-33 ktCO2e from 2017**

* This was the assumed opening date at the time of the environmental statement
** Impact from operational emissions
The emission estimates within this table are forecast changes in carbon dioxide emissions with the project compared to without the project in a given future assessment year. These estimates have been calculated using a variety of methodologies and, consequently, it is not statistically valid to aggregate the individual figures or directly compare them with one another.

3.3 Fiscal / regulatory measures

The current split between devolved and reserved powers means that the majority of fiscal and regulatory decisions that impact on Scottish transport emissions are taken at either the UK or EU level. However, the areas which Scottish Ministers have direct control over are still extremely important for emissions performance, particularly in respect of investment behavioural change and mode switching. These are vital component of long term emissions reductions because they involves the removal of key barriers that could affect the significant uptake of ultra-low or zero carbon vehicles by households and switching to more efficient and active modes of travel. Furthermore, The Scottish Parliament now has the power to legislate for a tax to replace the currently UK-wide Air Passenger Duty (APD) in Scotland. The new Air Departure Tax (ADT) is scheduled to come into effect from April 2018.

Published in June 2013, the Second Report on Proposals and Policies provides the most up to date and comprehensive analysis and assessment of these Scottish policies and the potential impact these measures can have on emissions out until 2027[23]. The impact of tightening EU car and van emissions standards and the Renewable Fuels Transport Obligation are also covered within the RPP's analysis.

With a narrower focus on road transport emissions, and particularly on the transition from reliance on fossil-fuelled vehicles towards plug-in cars and vans, Switched on Scotland [24] sets out the necessary steps and barriers to be overcome on the pathway to the almost complete decarbonisation of road transport. The recently published review of Switched on Scotland considers the progress made since the publication of the original document. [25] Following a period of consultation with partners across the public and private sectors, a refreshed plug-in vehicle action plan will be published by Spring 2017.

It is more difficult to ascertain the potential emissions impact in Scotland from UK and (other) EU fiscal or regulatory measures, not least because the impacts are analysed and estimated at a more aggregate level. That said, some Scottish estimates have been generated and where available these are recorded below alongside the description of the policy intervention.

The best and most readily available sources of information for the remaining aggregate UK emissions impacts include published Impact Assessments, associated documents accompanying the annual HM Treasury (HMT) Budget and Autumn Statement/Pre-Budget reports, HMRC notes and the House of Commons Library for more general topic background and briefing.

Air Passenger Duty (APD)

Key documents and analysis:

Air passenger duty (APD) is charged on all passenger flights from almost all UK airports[26]. The rate of tax varies according to passenger destination and the class of passenger travel. Between 2009 and 2014 APD was structured around four distance bands, but in 2014 it was simplified to just two bands. Flights to a country with a capital city more than 2000 miles from London are now charged at the Band B rate, a shorter capital to capital distance would fall into Band A. This change is estimated in increase annual UK emissions by 0.3 MtCO2e but is unlikely to have a material impact on Scottish emissions as very few direct flights from Scotland were affected by this simplification in banding structure.

In May 2015 children under 12 travelling in the lowest class of travel became exempt from APD, and from March 2016 children who are under the age of 16 years on the date of the flight, and in the lowest class of travel, also became exempt. Children 16 years and over, or travelling in any other class, are chargeable passengers and APD is due. For 1 April 2017 rates will increase in line with inflation.

With powers over rates of APD being devolved to Scotland a Transport Scotland publication in 2014 estimated that cutting Scottish APD by 50% could lead to an annual increase in Scottish emissions of 0.05 MtCO2e to 0.06 MtCO2e[27].

Inclusion of aviation in EU ETS

Key documents and analysis:

  • Implementation date: 2010
  • Estimated emissions impact: up to - 183 MtCO2e p.a. in 2020 across Europe relative to no cap

The Aviation Greenhouse Gas Emissions Trading Scheme Regulations 2010 came into force in the UK on 31 August 2010. The inclusion of aviation within the emissions trading system allowed the sector to take responsibility for its carbon emissions in the most cost effective way. While it is difficult to predict the exact impact of the scheme, particularly with the ongoing economic uncertainties, earlier estimates made by the Commission suggest that the aviation cap could reduce emissions in 2020 by up to 183 million tonnes CO2e.

The International Civil Aviation Organization (ICAO) agreed in 2013 to develop a global market-based mechanism to address international aviation emissions by 2016 and apply it by 2020. To allow time for the international negotiations, the EU ETS requirements were suspended for flights in 2012 to and from non-European countries. In the period 2013-2016, only emissions from flights within the EEA fell under the EU ETS. The impact of this revision on the Commission's original assessment of emissions reductions is unclear but the revision is unlikely to have any material effect on Scottish aviation emissions as the majority of flights from Scotland are within the EAA.

The ICAO agreement reached in October 2016 foresees the establishment of a Global Market-Based Measure (GMBM), which will oblige airlines to offset the growth of their CO2 emissions post-2020. To do so, airlines will buy "emission units" generated by projects reducing CO2 emissions in other sectors of the economy (e.g. renewable energies). All EU Member States will join from the start.

Fuel duty

Latest documents and analysis:

Budget 2016: fuel duty

Due to high oil prices, Budget 2011 cut the fuel duty by one penny per litre and since then all increases in fuel duty have been cancelled. Up until 2014, this cancellation has been estimated to add 0.5 MtCO2e per annum to the UK emissions total compared to where it would otherwise have been. It should be noted that this gross impact from the cancellation of the fuel duty rise does not take account of the fluctuations wholesale fuel prices and therefore pump prices had on demand and therefore emissions, or the continued freeze in duty announced since the March 2014 budget.

From 31 May 2015 the Rural Fuel Rebate allowed customers in certain rural post codes to benefit from a cut of 5 pence per litre in the fuel price. Thirteen of the seventeen named post codes eligible for this cut are in Scotland, eleven in Highland and two in Argyll and Bute. The introduction if the Rural Fuel Rebate is unlikely to lead to a noticeable increase in emissions.

Reform to vehicle excise duty

Latest documents and analysis:

Overview of Tax Legislation and Rates

  • Budget 2016 HMRC documentation
  • Estimated emissions impact of 2010 change: -0.9 MtCO2e by 2020
  • Estimated impact of 2017 proposal:- not quantified

In April 2010, the Government introduced a new first-year rate of VED. Under this system, all cars emitting up to 130 g CO2e per km paid no VED in the first year. Cars emitting over 165 g CO2e per km paid additional VED in the first year. In 2016 only cars over 150 g CO2e/km will see an increase in in VED. Together, these changes are estimated to result in a cumulative reduction in UK emissions of 0.9 MtCO2e by 2020, relative to where they would otherwise have been.

In 2017 a new VED banding system will be introduced. First year rates for newly registered cars will depend on CO2 emissions. Thereafter all but zero emitting vehicles will pay £140 with a 5 year supplement of £310 for cars costing over £40,000. This is likely to have an initially small but negative impact on the emissions outcome with all but zero rated cars in 2017 seeing an increase in VED over their existing equivalent makes and models. The reverse is true for more polluting cars as newer cars will see a reduced rate of VED.

Company car tax

Latest documents and analysis:

Overview of Tax Legislation and Rates

  • Anticipated implementation date: Ongoing
  • Estimated emissions impact: Not quantified

The UK Government's June 2010 budget set out to reform company car tax and provide incentives to purchase the lowest emitting vehicles on the market. This has been reinforced in subsequent budgets to incentivise the purchase and manufacture of ultra-low emission vehicles in the UK. The 2013 Budget set out rates for company cars emitting 75g CO2e per km or less from 2016-17 onwards and provides a commitment that in 2017-18 there will be a 3 percentage point differential between the 0-50 and 51-75 g/km CO2e bands and between the 51-75 and 76-94 g/km CO2e bands. The 2014 budget further lifted the percentage of a company car list price that would be subject to tax for cars emitting more than 75 g CO2e /km.

This policy aims to encourage the purchase of ULEVs and hence contribute to the objectives of reducing greenhouse gas emissions from road transport. However, given that the market is at an early stage of development it is not possible to precisely estimate the impact on ULEV sales or emissions savings. That said the savings are likely to be small to begin with.

Subsequent budgets have further lifted the percentage of the car list price to be taxed although the increase in the rates on the most efficient cars are higher than for the least efficient over the next few years.

Fuel benefit charge (FBC)

The provision of free fuel to company car drivers provides a perverse environmental incentive. The aim of the fuel benefit charge is to tax this benefit as though it were income. The figure on which the calculation is based rises each year and for cars currently stands at £22,100. The van fuel benefit charge – on which tax on free van fuel is payable – stands at £594. The Government has committed to pre-announcing the FBC multiplier one year in advance and has announced that the FBC multipliers will increase in line with inflation in 2016 and 2017.

Table 7 summarises the previous information. As with Table 6, these emissions estimates are not produced using a single, consistent methodology so are not directly comparable.

Table 7: Net emissions impact estimates of fiscal / regulatory measures

Project title

Published emissions estimate

Air passenger duty

i) -0.3MtCO2e p.a from 2015-16 (UK)

ii) +0.05 MtCO2ep.a in Scotland from 50% cut in APD

Inclusion of aviation in EU ETS

-183MtCO2e* p.a. in 2020 (Europe)

Fuel Duty

+0.5 MtCO2e p.a. by 2013 from two freezes (UK)

Negligible impact from Rural Fuel Rebate

Reform of Vehicle Excise Duty[28]

-0.9 MtCO2e total savings by 2020 (UK)

2017 proposal – impact not quantified

Company car tax

Not quantified

Fuel benefit charge

Not quantified

The emission estimates within this table are forecast increases or decreases in carbon dioxide emissions with the policy compared to without the policy in a given future assessment year. These estimates have been calculated using a variety of methodologies and, consequently, it is not statistically valid to aggregate the individual figures or directly compare them with one another.
* Estimate from before the introduction of 'Stop the Clock' – see relevant section in EU ETS above

3.4 Projected net emissions impact from Scottish projects

The Carbon Account for Transport collates information from a variety of sources and outputs with one of the key sources being the findings generated from the application of the Scottish Transport Appraisal Guidance (STAG) to transport proposals. Two key concepts in STAG are that an appraisal:

  • should be applied proportionately but comprehensively. The whole process should be used and the level of detail required will be determined by the scale of the impacts of the transport issue being addressed.
  • should not prioritise between options. Instead, it is an aid to decision makers in order to make more informed choices. STAG may provide an initial rationale for investment and it is important that the STAG outcomes are revisited as the Business Case for an intervention develops.

As such, a study undertaken using STAG is not required to provide an absolute prediction of all of the outcomes of an intervention. Instead, it provides sufficient information to understand the relative impacts between different options. The individual results cannot therefore simply be summed to produce an aggregate impact.

While these assessments provide one of the key purposes of the CAT - to improve transparency - something further is needed to monitor progress towards the NTS strategic outcome of reduced transport emissions. In 2010 a single model run of the Land-Use and Transport Integration in Scotland (LATIS) service was commissioned to estimate the net impact of all measures within the CAT that fall under the competence of the Scottish Government or other Scottish public body[29]. LATIS includes a strategic transport and land-use model covering all of Scotland and all motorised modes of transport so the use of LATIS to assess the carbon impacts of Scottish transport schemes ensures network consistency and takes full account of the potential displacement of developments between one area and another. The modelling of this set of projects over the timescale of their introductions also provides a greater understanding of the full impact that Scottish interventions are having, or are expected to have, on underlying emissions from transport. The model is not a complete assessment of the likely impact as it does not include the impacts of those measures taken at a reserved level - for example changes to fuel duty or some of the demand side measures outlined in RPP2.

The updating of the baseline data within LATIS enabled a revised set of projections to be run 'with' and 'without' the identified infrastructure projects over which Scotland has direct control. The latest available estimates from the revised projection are shown in Table 10. The table shows that the combined impact of the projects generates a small increase in overall emissions, with the long-run impact estimated at an additional 50 ktCO2e p.a. by 2027. This is equivalent to an additional 0.4% on annual transport emissions in 2027 relative to where emissions would otherwise have been.

Table 8: Projected net emissions impact of Scottish projects[30]
Year Annual Change in Emissions (ktCO2e)
2017 30
2022 50
2027 50