Approach to Detailed Appraisal
Overview of Detailed Appraisal
The purpose of this chapter is to outline the approach to Detailed Appraisal for the A96 Corridor Review, including packaging of options along with the tools and techniques employed to support the assessment of options at this stage.
The Detailed Appraisal considered all options that progressed from the Preliminary Appraisal. At this stage, multimodal ‘packages’ were developed using an ‘area-based’ approach to group options together to enhance characteristics in locations with a similar nature throughout the A96 corridor. Section 5.2 provides further details of the option packaging process.
As noted previously in Section 4.2 the Scottish Government’s current plan is to fully dual the A96 route between Inverness and Aberdeen. As such, alongside the packages that have been developed, the option for A96 Full Dualling has also been assessed as part of the Detailed Appraisal.
The appraisal at this stage has involved complementing and/or in some instances replacing the qualitative appraisal adopted at the Preliminary Appraisal stage, with quantitative appraisal as far as possible. In doing so, it should be recognised that the transport appraisal is at an early stage of development and interventions are defined at a relatively high-level such that detailed quantification of certain impacts is not always possible. Tools used for quantification within the context of the A96 Corridor Review include, but are not limited to, the use of the National Public Transport Accessibility Tool (NaPTAT), the World Health Organisation’s Health Equity Assessment Tool (HEAT) and transport and economic modelling through use of TMfS18 and the A96 Corridor Route Assignment Model (A96CRAM).
The Detailed Appraisal stage considers the appraisal of options in more detail against:
- TPOs
- STAG criteria (Environment; Climate Change; Health, Safety and Wellbeing; Economy; and Equality and Accessibility)
- Deliverability criteria (Feasibility, Affordability and Public Acceptability)
- Cost to Government
- Risk and uncertainty.
In parallel to the transport appraisal, a series of SIAs have also been undertaken (see Section 5.7) to further inform the Detailed Appraisal.
The Detailed Appraisal evaluates each package under the future ‘With Policy’ and ‘Without Policy’ transport behaviour scenarios as explained in the Preliminary Appraisal methodology (see Section 3.3), with further information on the development of these scenarios contained in Appendix A.
As with the Preliminary Appraisal, the seven-point scoring scale defined in Table 3.1 has been used to assess the performance of each package and the A96 Full Dualling against the TPOs, STAG criteria and SIAs. Established Policy Objectives are again scored through the bespoke PAF developed for the A96 Corridor Review, with further details on this scoring criteria provided in Section 3.6.
The following sections describe the key assessment criteria for Detailed Appraisal, as well as the approach taken in the A96 Corridor Review to provide quantitative data where appropriate, throughout this stage of the appraisal process.
Option Packaging
From the Preliminary Appraisal, 13 options were progressed to the Detailed Appraisal stage. In recognition that the retained options covered a range of transport modes and therefore would provide a greater net benefit if combined as a package rather than as standalone options, four multimodal packages were originally developed using an ‘area-based’ approach. These packages were developed to group options that would work in combination to meet the TPOs and thus address the identified problems and opportunities for the corridor. The area-based approach was adopted to develop multimodal packages to suit the varying needs of local communities and businesses along the transport corridor, and ensured no areas were unduly prioritised over others.
As the appraisal progressed, a fifth package was developed and added to the appraisal process. This package comprises all of the options that progressed from the Preliminary Appraisal to create an ‘all in’ package across the corridor.
The Detailed Appraisal at this stage appraised these five packages rather than individual options. The five packages that were appraised at this stage are:
- Package 1 – relating to those towns along the A96 that contain an option to bypass as brought forward from the Preliminary Appraisal, specifically Forres, Elgin, Keith and Inverurie. This also includes Nairn as it is to be bypassed as part of the separate A96 Dualling Inverness to Nairn (including Nairn Bypass) scheme that has ministerial consent. In addition, this package focuses on delivering networks of high-quality active travel routes and placemaking improvements within the bypassed settlements. Public transport interventions are also included, targeted at delivering faster and more reliable journey times as well as improving the overall passenger experience. As part of the public transport interventions, the rail network would see linespeed, passenger and freight capacity improvements delivered for the Aberdeen and Inverness rail line. This package also includes the provision of alternative refuelling infrastructure and facilities throughout the A96 corridor, seeking to encourage a shift from internal combustion engine (ICE) vehicles.
- Package 2 – relating to other settlements along the A96 where a bypass is not considered, namely Lhanbryde, Mosstodloch, Fochabers, Huntly, Kintore and Blackburn. This package focuses on delivering networks of high-quality active travel routes and placemaking improvements and public transport interventions, targeted at delivering faster and more reliable journey times. As part of the public transport interventions, the rail network would see linespeed, passenger and freight capacity improvements delivered for the Aberdeen and Inverness rail line. This package also includes the provision of alternative refuelling infrastructure and facilities throughout the A96 corridor, seeking to encourage a shift from ICE vehicles. Targeted road safety improvements, to address both real and perceived safety concerns on the A96 Trunk Road are also included.
- Package 3 – relating to more rural sections between settlements. This package seeks to address both real and perceived safety concerns on the A96 Trunk Road through targeted road safety improvements, while delivering public transport interventions, targeted at faster and more reliable journey times. As part of the public transport interventions, the rail network would see linespeed, passenger and freight capacity improvements delivered for the Aberdeen and Inverness rail line. This package also aims to deliver networks of high-quality active travel routes between settlements along the A96 corridor. This package also includes the provision of alternative refuelling infrastructure and facilities throughout the A96 corridor, seeking to encourage a shift from ICE vehicles.
- Package 4 – relating to longer distance components that may not be fully captured in the above three packages, including end-to-end movements. This package would provide high-quality active travel routes linking settlements along the A96 corridor while delivering public transport interventions targeted at delivering faster and more reliable journey times. As part of the public transport interventions, the rail network would see linespeed, passenger and freight capacity improvements delivered for the Aberdeen and Inverness rail line. This package also includes the provision of alternative refuelling infrastructure and facilities throughout the A96 corridor, seeking to encourage a shift from ICE vehicles. The package would also deliver targeted safety improvements aiming to address both real and perceived safety concerns on the A96 Trunk Road.
- Package 5 – comprising all options brought forward from the Preliminary Appraisal. The multimodal package would provide bypasses of Forres, Elgin, Keith and Inverurie, with targeted road safety improvements delivered elsewhere along the A96 Trunk Road. The package would deliver networks of high-quality active travel routes within and between settlements along the A96 corridor. Public transport improvements would be included to enhance the accessibility and quality of interchange facilities and bus priority measures to provide quicker and more reliable journeys, along with linespeed, passenger and freight capacity improvements for the Aberdeen to Inverness rail line. This package also includes the provision of alternative refuelling infrastructure and facilities throughout the A96 corridor and investment in a DRT and MaaS pilot study.
Although each package was appraised individually, where appropriate and relevant, a number of individual options are included in more than one package. The options included within each package are shown in Table 5.1.
For the Detailed Appraisal the majority of options were considered as ‘corridor-wide’. As four of the packages would cover different settlements, for appraisal purposes the Active Communities option would apply to the following locations:
- In Package 1 Active Communities are only considered within the bypassed communities of Forres, Elgin, Keith, Inverurie and Nairn [bypassed as part of the separate A96 Dualling Inverness to Nairn (including Nairn Bypass) scheme that has ministerial consent].
- In Package 2 Active Communities are only considered within the settlements and along the A96 Trunk Road sections related to Package 2, specifically Lhanbryde, Mosstodloch, Fochabers, Huntly, Kintore and Blackburn.
- In Packages 4 and 5 Active Communities are considered in the settlements of Nairn [bypassed as part of the separate A96 Dualling Inverness to Nairn (including Nairn Bypass) scheme that has ministerial consent], Forres, Elgin, Lhanbryde, Mosstodloch, Fochabers, Keith, Huntly, Inverurie, Kintore and Blackburn.
Table 5.1: Option Packaging Summary
Transport Planning Objectives
Each package, as well as the option for A96 Full Dualling (Hardmuir to Craibstone), was assessed against the A96 Corridor Review TPOs using the seven-point scoring scale outlined above in Table 3.1. For the Detailed Appraisal, and to provide quantitative outputs to inform the scoring, the performance of the packages was measured using the appropriate tools to demonstrate how well they are likely to meet the A96 Corridor Review TPOs. The tools used included outputs from NaPTAT, HEAT, TMfS18 and the A96 Corridor Route Assignment Model (A96CRAM), along with Transport User Benefit Analysis (TUBA).
Scottish Transport Appraisal Guidance Criteria
Environment
The Environment assessment considered the performance of the packages using both quantitative and qualitative inputs relevant to the respective sub-criteria shown in Table 5.2.
| Environment Topics | Approach to Detailed Appraisal |
|---|---|
|
Noise and vibration |
Qualitative assessment considering potential increases or decreases in noise levels arising from the delivery of each package. Quantification of noise impacts has not been feasible at this stage due to the lack of detailed design work undertaken for measures to determine the effect on specific sensitive receptors. |
|
Physical fitness |
A high-level qualitative assessment of the impact of the delivery of each package on physical fitness through estimating the changes in the levels of walking and cycling. |
|
Biodiversity and habitats |
Qualitative appraisal of biodiversity, by identifying the presence of designated sites in the study area – Special Areas of Conservation (SAC), Special Protection Areas (SPA), National Nature Reserves (NNR) and Sites of Special Scientific Interest (SSSI) – and identifying the potential for significant effects on these sites or the species they support. |
|
Water quality, drainage and flood defence |
A qualitative assessment of the sensitivity of the water environment within the study area. |
|
Geology |
Identification of sites of particular geological importance (designated sites) or significant mineral reserves and a qualitative assessment of the degree to how each package may affect such sites. |
|
Agricultural soils |
Identification of the relevant grades of agricultural land in the study area with a qualitative assessment of the likely scale of land take. |
|
Local air quality – particulates (PM 2.5 ) and nitrogen oxides (NO x ) |
Estimation of the total emissions likely to be generated in the study area on a zonal basis, related to the magnitude of changes in emissions and where these changes occur. Changes in speed by mode by model zone/study area (as defined in the transport model). Changes in vehicle kilometres travelled. |
|
Global air quality – carbon dioxide (CO 2 ) |
Identification of roads that would trigger the traffic change criteria within DMRB LA 105 (https://www.standardsforhighways.co.uk/tses/attachments/10191621-07df-44a3-892e-c1d5c7a28d90?inline=true ), referred to as the affected road network. |
|
Landscape |
A qualitative assessment of both the landscape character and quality, noting any specific designations. |
|
Visual amenity |
A subjective, qualitative assessment, drawing upon desk studies and map exercises to identify key receptors and their views, which could potentially be affected by each package, and the sensitivity of receptors. |
|
Cultural heritage |
Identification of the relevant heritage designations in the study area and a qualitative assessment of the likely impact of each package on the importance and integrity of cultural heritage resources and their setting. |
Although the appraisal against selected environment sub-criteria is by its nature qualitative, and where a quantitative assessment is not possible or feasible, the assessment is more detailed at the Detailed Appraisal Stage and considers the impact of the packages.
Climate Change
In line with the approach taken during the Preliminary Appraisal, the assessment has considered the performance of the packages against the three Climate Change sub-criteria: GHG Emissions, Vulnerability to the Effects of Climate Change and Potential to Adapt to the Effects of Climate Change.
A quantitative approach has been adopted for the assessment of GHG emissions to provide the anticipated change through construction and in operation over a 60-year appraisal period. The calculation of monetised benefits of the potential change in CO 2 emissions for each package was also considered.
Health, Safety and Wellbeing
At the Detailed Appraisal stage, the packages have been assessed against the five Health, Safety and Wellbeing related sub-criteria as defined in Table 5.3.
| Health, Safety and Wellbeing Sub-criteria | Description of Assessment at Detailed Appraisal Stage |
|---|---|
|
Accidents |
Consideration was given to whether each package would have any measurable impact on the number of transport related accidents and/or the severity of transport related accidents. Where measurable changes to accident numbers and/or severity have been identified, well established methodologies are adopted to quantify the road traffic accidents. A Cost and Benefit to Accidents – Light Touch (COBALT) based approach has been adopted, using the change in vehicle kilometres travelled, extracted from the transport models (post-adjustment to capture the overall modal changes). COBALT is a software package developed to forecast the monetised benefits associated with changes in the number and severity of accidents as a result of introducing a transport scheme. COBALT was used to determine any accident benefits that are anticipated from road improvements over a 60-year appraisal period. |
|
Security |
The impacts of each package on the security of those walking, wheeling and cycling, as well as public transport and car users has been considered. Also, the impact of each package on particularly vulnerable sections of the community such as children, the elderly or women travelling alone has been taken into account. The adopted approach to assess security is largely qualitative. For this sub-criterion, the Preliminary Appraisal outcomes have been revisited, with further consideration given at this stage to the effect of each package on actual and perceived health risks associated with travel. This additional consideration is in response to heightened public concern and awareness of aspects such as hygiene, air circulation and ability to socially distance. |
|
Health Outcomes |
To capture some of the benefits specific to active travel schemes, HEAT was used to quantify health benefits from increased use of walking and cycling over a 20-year appraisal period. |
|
Access to Health and Wellbeing Infrastructure |
NaPTAT was used to set out the relative changes in highway and public transport accessibility and connectivity to health centres, places of exercise (gyms, pools, etc), parks and community centres. |
|
Visual Amenity |
For this sub-criterion, the Preliminary Appraisal outcomes have been revisited. At Detailed Appraisal, the impact of each package on visual amenity is still qualitative in the absence of any robust and feasible tool to quantify results. |
The Department for Transport (DfT) Transport Analysis Guidance (TAG) Unit A1.1 Cost-Benefit Analysis ( https://www.gov.uk/government/publications/webtag-tag-unit-a1-1-cost-benefit-analysis-may-2018 ) has been used to establish appropriate appraisal periods. In general, the well-established appraisal period of 60 years is suitable for the majority of transport infrastructure schemes. This has therefore been used in the A96 Corridor Review for the majority of transport modelling and economic outputs, including for accident analysis and the calculation of GHG emissions. However, it is noted that a shorter appraisal period is more appropriate for projects that involve assets that may have a more limited lifespan, for example active travel interventions. The DfT Active Mode Appraisal Toolkit User Guide ( https://assets.publishing.service.gov.uk/media/631744188fa8f50220e60d1a/active-model-appraisal-toolkit-user-guidance.pdf ) indicates that most appraisals of cycling and walking infrastructure schemes should assume an appraisal period of 20 years. As such, when using HEAT to quantify the health benefits associated with active travel interventions, a 20-year appraisal period has been adopted for use in the A96 Corridor Review.
Economy
As in the Preliminary Appraisal, the Economy criterion comprises two sub-criteria of TEE and WEIs.
TEE benefits have been assessed using the DfT TUBA software. As STAG treats the monetised benefits from a reduction in accidents separately to the economic analysis, a separate analysis of changes in accidents has been undertaken using the transport model outputs as well as COBALT.
WEIs were monetised using data describing demand for transport and the cost of travel from the TMfS and A96CRAM, with socio-economic data drawn from the national land use model TELMoS18. WEIs outputs were also mapped using GIS software to better understand effects across the study area.
Further monetised benefits have been identified from HEAT which evaluates health benefits as a result of increases in active travel, i.e. walking and cycling. To quantify Driver Frustration benefits, a microsimulation traffic model of the A96 has been developed with benefits determined from factors including time spent travelling behind a platoon (i.e. a cluster of vehicles travelling in close proximity to one another, often due to a slower moving vehicle at the head of the platoon), the difference between the desired and actual speed, the length of the platoon and its composition in terms of cars and LGVs and the opportunity to overtake.
Equality and Accessibility
As per the Preliminary Appraisal, the Equality and Accessibility criterion comprises five sub-criteria; Public Transport Network Coverage, Active Travel Network Coverage, Comparative Access by People Group, Comparative Access by Geographic Location and Affordability.
For the Detailed Appraisal, the NaPTAT tool was used to inform the public transport network coverage aspect of Community Accessibility. The tool also considers distributional impacts, such as SIMD and car availability. NaPTAT presents results in the context of these identified datasets by the proportion of the resident population to reflect different demographic groups in terms of accessibility to key destinations (such as employment and healthcare) as well as average journey times.
Where active travel measures are sufficiently defined and location-specific, accessibility to local services by walking and cycling were also assessed using NaPTAT.
Additional consideration was given to the impacts of transport changes on particular societal groups through the work undertaken in progressing the EqIA, and this was used to inform the transport appraisal.
Established Policy Objectives
The bespoke PAF assessment developed for the A96 Corridor Review was used to assess the packages at Detailed Appraisal. The assessment has taken account of the packaging of options and considers their overall likely effect against policy objectives.
As with the PAF assessment undertaken at the Preliminary Appraisal stage, it should be noted that at this early stage of development options are defined at a relatively high level (i.e. with limited detail on location, engineering design or environmental mitigation), the scoring reflects the information that is available. The scoring does not therefore reflect the potential for design development and mitigation to enable policy consistency, as this is as yet unknown.
The A96 Full Dualling follows the same methodology applied to the packages and has been assessed against the same objectives.
More information on the development of the A96 Corridor Review bespoke PAF and its use in the appraisal can be found in Section 3.6.
Deliverability Criteria
The qualitative assessment regarding the deliverability criteria (Feasibility, Affordability and Public Acceptability) undertaken at Preliminary Appraisal has been revisited at the Detailed Appraisal stage. The section takes cognisance of any additional detail available and the overall impact of combining the individual options together to form the packages.
At the Detailed Appraisal stage this has included reference to the feasibility of constructing multiple options together, the updated costs for each package and the associated risks with uncertainties. Public acceptability again makes reference to supporting evidence from the findings of the public consultation survey and stakeholder engagement, as presented in the A96 Corridor Review Stakeholder & Public Engagement Consultation Report ( https://www.transport.gov.scot/publication/stakeholder-public-engagement-consultation-report-december-2022-a96-corridor-review/ ).
Statutory Impact Assessments
A review of the qualitative assessment and scoring for the SIAs has been undertaken and updated to reflect the impact of the packages. As the development of the separate SIAs has progressed additional detail has been included at Detailed Appraisal stage, along with updates to reflect the effects of the packages and the inter-relationships of individual options within them. Where possible, quantified outputs have also been produced to further develop the evidence base behind the scoring of these assessments.
Cost to Government
The Detailed Appraisal has identified the estimated capital cost range of each package, and A96 Full Dualling, and takes into account optimism bias. Monetised and non-monetised benefits of the packages and the A96 Full Dualling option are also presented as part of the Detailed Appraisal.
Risk and Uncertainty
As stated in the HM Treasury Green Book, in appraisals there is a demonstrated, systematic, tendency for project appraisers to be overly optimistic (known as optimism bias). To redress this tendency appraisers should make explicit, empirically based adjustments to the estimates of a project’s costs. As a result, it is important to identify and mitigate risks, making allowances for optimism bias.
For the purposes of the A96 Corridor Review, the ‘With Policy’ and ‘Without Policy’ transport behaviour scenarios developed as part of the scenario planning undertaken for STPR2 were used in the Detailed Appraisal of each package. These demand scenarios were developed to consider the risk associated with future uncertainties and enable the appraisal of the packages to be undertaken using a range of transport demand levels.
Reporting
ASTs have been produced for each package considered as part of the Detailed Appraisal stage, as well as for the A96 Full Dualling option. Full ASTs are provided in Appendix D with a summary of the outcomes provided in Chapter 6.
The ASTs record how each package and the A96 Full Dualling option perform under the ‘With Policy’ and ‘Without Policy’ scenarios against the relevant TPOs, STAG criteria and SIAs, along with a consideration of the Deliverability criteria.