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TAG Unit 3.17:Detailed Guidance on Social and Distributional Impacts of Transport Interventions

April 2011

pdf icon Unit 3.17 (Adobe Acrobat - 244KB)

1. Social and Distributional Impacts
   1.1 Introduction
2. The Appraisal of Social and Distributional Impacts
   2.1 Introduction
   2.2 Step 0: SDIs and ensuring proportionate approaches to appraisal
   2.3 Step 1: Confirmation of areas impacted by the proposed intervention
   2.4 Step 2: Identification of social groups in the affected area
   2.5 Step 3: Approach to screening for SDIs
   2.6 Step 4: Core appraisal and SDI analysis for each indicator
   2.7 Step 5: Collation of SDI analysis into matrix of social and distributional impacts
3. Further Information
4. References
5. Document Provenance

1. Social and Distributional Impacts

1.1 Introduction

1.1.1 This Transport Analysis Guidance (TAG) Unit provides detailed guidance on measuring the impacts of transport interventions on different groups of people. It complements and builds on Level 2 guidance for the Technical Manager in TAG Unit 2.13.

1.1.2 This Unit represents the current state of knowledge, which is a rapidly developing area and we are likely to learn from further evidence and outcomes from the continued implementation of transport interventions. This unit will be revised and updated as further information becomes available or in the light of any comments received in the application of this unit. This Unit has been updated following testing and following comments received during consultation.

Purpose and Scope of this TAG Unit

1.1.3 This TAG Unit provides detailed technical guidance on the approach to the assessment of social and distributional impacts (SDIs) of transport interventions, and complements the summary guidance provided in TAG Unit 2.13.

1.1.4 This TAG Unit excludes road pricing interventions. The social and distributional impacts of road pricing interventions should be addressed using TAG Unit 3.12.4.

2. The appraisal of social and distributional impacts

2.1 Introduction

2.1.1 This section describes the approach to be undertaken for the full (detailed) appraisal of social and distributional impacts (SDIs) using the eight impacts described in TAG Unit 2.13. An overview of the process is presented in Figure 1.

2.1.2 It should be noted that there is a degree of iteration in the process; this is because the initial tasks prior to full appraisal are important in focussing on whether appraisal is required and at what level. The initial decisions concerning whether or not appraisal is required for any impacts should be revisited as better information becomes available. While an impact may be screened out in the initial screening, that decision should be reconsidered before the final impacts for appraisal are defined.

2.1.3 While Figure 1 applies to all appraisal, the final screening (Step 3) will determine whether a full appraisal is required or whether a more proportionate and generally more qualitative appraisal process can be used. Practice is still developing and it is not possible to set out definitive requirements for the more qualitative approach.

Figure 1 - Overview of the SDI appraisal process

Figure 1 - Overview of the SDI appraisal process

2.1.4 Prior to undertaking the actual SDI appraisal, there are a set of steps that the SDI analyst (For the purposes of this guidance the role of an SDI analyst is assumed, but other arrangements may be appropriate. See TAG Unit 2.13 for further discussion.) should undertake, which are:

Step 0	Initial screening: consideration of whether the nature of the proposal will increase potential for SDIs (positive or negative).	Identification of likely SDI impacts that will require further SDI screening. Justification required for any decision not to pursue individual indicators further.
Step 1	Confirm the areas impacted by intervention.	There is a need to select spatial levels appropriate to each impact.
Step 2	Identify social groups in areas affected by the intervention.	This will involve research to build a detailed profile of each area.
Step 3	Full screening.	This will include a check on the initial screening.

2.1.5 As noted above, the full screening should confirm or amend the findings of the initial screening as better information on the areas and social groups likely to be affected improves. In parallel with these initial steps the option(s) for intervention will also be developed, and the final screening should bring together both a more developed specification for the intervention and a better understanding of its likely SDIs.

2.1.6 Following the first four steps the following will be undertaken within the full appraisal:

Step 4: Core appraisal process, for each of the impacts to generate technical data for use in the SDI analysis, with the SDI analysis undertaken as an integral part of this work; and
Step 5: Collation of SDI analysis into a matrix of social and distributional impacts and summarising this data in the Appraisal Summary Table.

2.1.7 Steps 0, 1, 2 and 3 are described in detail in this TAG Unit while an outline is provided for Steps 4 and 5. If the screening process in Step 3 identifies that an impact should be subject to detailed SDI analysis, Step 4 directs the SDI analyst to specific TAG units for the detailed technical analysis. The SDI analyst should consider this guidance in the context of the proposed intervention and the impacts for which a full appraisal is to be undertaken, and then develop a specification for each appraisal. The specification should indicate the detailed approach to be undertaken, the availability and quality of data sources, the use of transport model(s) and any primary research that will be required.

2.1.8 Where Step 3 identifies that a more proportionate / qualitative appraisal is more appropriate, the SDI analyst should provide a specification for such an appraisal.

2.1.9 The SDI appraisal specification, whether for a full or more qualitative appraisal, should be included in the Appraisal Specification Report (or similar) where one is being prepared - see TAG Unit 2.1.2, Option Development, for more details on this. The Appraisal Specification Report, including the SDI appraisal specification, should be agreed with the Department (or equivalent) prior to commencing the detailed appraisal. The Department may suggest additional research and/or analysis and provide technical advice on aspects of the appraisal.

2.1.10 Step 5 within this TAG Unit provides the guidance on the collation of the individual impacts for each indicator into the Matrix of Social and Distributional Impacts.

2.1.11 The steps in the appraisal process are described below.

2.2 Step 0: Initial screening

2.2.1 The identification of potential SDIs is important in determining the efficiency of the overall appraisal process. The SDI analyst should give consideration to the following points:

Consider if the option being considered might have negative or positive impacts on specific groups of people, including children, older people, disabled people, Black and Minority Ethnic (BME) communities, people without access to a car and people on low incomes;
Consider whether all of the expected negative impacts can be eliminated through some form of amendment to or redesign of the initial option;
Where there are positive impacts and where negative impacts cannot be eliminated, consider whether impacts are sufficiently minor and socially and / or spatially dispersed such that a detailed SDI appraisal is disproportionate to the potential impacts;
Where impacts are either significant or concentrated, a full screening (Steps 1 to 3) of those impacts should be undertaken.

2.2.2 A structured approach should be followed in the initial consideration of potential social and distributional impacts. Figure 2 illustrates the process for the planning and appraisal of interventions where there are no social and / or distributional objectives within the local objectives for intervention - that is, for interventions where social or distributional impacts would be potential consequences of, rather than part of the rationale for, the interventions under consideration.

2.2.3 In some cases the local transport objectives (for the area specifically defined for consideration) will include an explicit reference to tackling transport problems that are faced by different groups of people and which give rise to inequalities such as poor air quality in particular residential areas, and/or lack of access to opportunities, for example to employment, health care, training or other services.

2.2.4 Where such objectives are stated, a full SDI appraisal (Steps 1 to 5) should be undertaken with regard to those impacts that align with the objectives. For example, if a road through a residential area has a bad safety record and an objective is to reduce the incidence of accidents especially to children and older residents, a full appraisal of safety impacts is essential. In such cases the approach set out in Figure 2 should be applied to those impacts which are not aligned with the objectives. In the above example, there may be no air quality objective but the approach shown in Figure 2 should used to appraise air quality impact and all other social and distributional impacts of the options which are developed to address the safety objective.

Figure 2 - Steps in the screening process

Figure 2 - Steps in the screening process

2.2.5 Table 1 below is intended to assist in identifying possible SDIs and how these might arise: this is necessarily general and uses examples to illustrate sources of impacts. The SDI analyst should develop this to align with specific issues and potential interventions. It is important to note that, in many cases, there may be little or no analysis of the impacts of the intervention at this stage in the study. The SDI analyst is expected to carry out a qualitative assessment, based on his professional judgement and that of the technical specialists responsible for undertaking assessment of noise, air quality, safety, security, severance, accessibility, personal affordability and user benefits. The initial screening is provisional: as better information becomes available, it should be revisited to confirm which SDIs are in-scope for subsequent appraisal.

2.2.6 A full and detailed appraisal is typically time and resource intensive, and undertaking such an appraisal in all cases where there are positive or negative impacts would not be proportionate with the potential scale and severity of the impacts, or the levels of uncertainty regarding the potential for adverse outcomes. The test to be applied for full appraisal in the case of each impact individually is whether the expected impact (positive or negative) is either significant in extent or concentrated in terms of the people groups or the spatial areas affected, or both?

2.2.7 Where the likely impact is significant and/or concentrated, the default will be a full screening (Steps 1 to 3) against that impact. The opposite outcome is that the expected impacts will be both marginal in extent and dispersed among people groups or spatially. In the latter instance a full justification of the decision not to proceed to Step 1 should be prepared.

Table 1 - Identification of potential SDIs where the SDI does not form an objective for any intervention

Impact	Potential for SDIs	Social and/or Distributional Issues
User Benefits	In the majority of cases there are user benefits associated with a transport intervention but these are generally net outcomes. Within the net outcome, some people may experience disbenefits for example through longer journey times or lower public transport service frequencies.	Because user benefits are net, there is a need to consider the distribution of user benefits. For example, a highway scheme might improve journey times for through traffic but increase bus, car and cycling journey times for local people travelling to work etc. If those experiencing longer times are in vulnerable social groups this would be an adverse social impact. Potentially adverse distributional / social outcomes need to be considered alongside the aggregate benefits of the transport intervention.
Noise	Any intervention that increases traffic levels and speeds or reduces physical gaps between people and traffic will give rise to noise impacts within a localised area.	While there are threshold levels below which changes in noise levels can normally be ignored, children are especially affected by noise levels. Where these are above and near threshold changes in noise levels, the scale and significance of impacts should be established for each vulnerable group identified, including children.
Air Quality	Any intervention that increases traffic levels (especially HGVs) and increases the amount of slow-moving traffic or reduces physical gaps between people and traffic may give rise to impacts on air quality.	-
Accidents	Any intervention that increases traffic levels and speeds or reduces physical separation between people and traffic can give rise to increases in accidents within a localised area.	Identify potential impacts of options on accident risk, including ensuring that no significant accident risk is introduced to different groups of people, particularly children, older people and people living in areas of deprivation.
Security	Some interventions may introduce perceived or real security risks that affect transport choices by different groups of people, particularly young people, women, older people and people with disabilities. Where choices are constrained by concerns regarding security, and especially where those affected do not have access to a car, access to certain places or travel at desired times may be denied to members of these groups.	Potential security issues may be identified at an early stage and in many cases a design solution may reduce or eliminate impacts. Where it is not possible to eliminate impacts the scale and significance of impacts should be established for each vulnerable group.
Severance	Severance is often an unintended consequence of a measure intended to address other problems, and typically it most affects those without access to a car, children, older people and people with disabilities.	Severance issues may be identified at an early stage and in many cases a design solution may reduce or eliminate severance impacts. Where it is not possible to eliminate impacts the scale and significance of impacts should be established for each vulnerable group.
Accessibility	Options will often have differentiated impacts on accessibility as experienced by different groups of people, including young people, older people, disabled people, Black and Minority Ethnic (BME) communities and carers. This reflects a range of social and distributional factors, including differences in travel needs and places of residence.	Accessibility issues may be identified at an early stage and in many cases a design solution may reduce or eliminate accessibility impacts. Where it is not possible to eliminate impacts the scale and significance of impacts should be established for each vulnerable group.
Personal Affordability	Some options may have a direct impact on financial costs borne by users of the transport system, including potential impacts from changes in parking charges or public transport fares. Such impacts are likely to be more severe for people with limited financial resources, particularly young people and low-income households. Lack of transport choices will generally exacerbate affordability issues by limiting scope to use an alternative mode for a particular journey.	Affordability issues may be identified at an early stage and it may be possible to provide alternative travel opportunities which will eliminate or alleviate problems. However, where fiscal measures are applied to achieve other transport objectives lower income groups will often face disproportionate increases in transport costs relative to incomes and also more limited travel choices. Potentially adverse distributional outcomes need to be considered alongside the aggregate benefits of schemes such as fiscal measures to reduce congestion.

2.3 Step 1: Confirmation of areas impacted by the proposed intervention

The initial screening process is intended to identify potential SDIs: these will be positive impacts, for which appraisal information will be required, and negative impacts where it is not possible to eliminate these through design and mitigation measures.

2.3.1 For the initial screening, a broad understanding of the areas on which the transport intervention is likely to have an impact will already exist: this information is fundamental to the identification of transport problems and the development of local objectives which underpin the whole appraisal process. Step 1 is required to investigate the spatial impacts of the proposed intervention in more detail in the context of information on both its transport impacts and external impacts such as noise and air quality. For each SDI that has been deemed in-scope for appraisal it is necessary to confirm the overall geographic area that will be impacted by the transport intervention and to consider which specific areas are relevant to the SDI under consideration.

2.3.2 The impact area will vary according to the impact under consideration. The largest area will normally be that covered by a model or will be the relevant travel to work area (TTWA). The latter is likely to be an important consideration in accessibility to employment.

2.3.3 In the case of a new quality bus corridor, the road safety impacts might be limited to the road corridor itself, while accessibility impacts could cover a wide area comprising the routes of the bus services operating along the corridor. Some impacts tend to be more localised and noise and air quality impacts affect only those areas where there are human receptors; therefore while there may be areas with no housing on a route within a TTWA, these are not likely to be relevant with regard to air quality and noise.

2.3.4 The section below sets out in detail the criteria to be used in the identification of the impact area for each of the relevant impacts under consideration. As with the screening analysis, robust evidence is required to support a decision to define an impact area or areas for each impact.

User Benefits

2.3.5 The impact area will be defined as the area in which the transport intervention will result in changes in the costs of travel (including both time-based costs and financial costs) for users of the transport network. In most cases, this should be the area represented by the transport model. In some cases, the transport model being used will have a much wider area of coverage than the transport intervention itself and the likely area in which user costs change. The SDI analyst should therefore undertake tests to establish the area impacted by changes in user costs.

2.3.6 Modelled areas typically incorporate external zones to represent movements into and out of the study area. While a transport intervention might model benefits for movements to and from these zones, these should be minor relative to those conferred upon internal movements, otherwise an inappropriate model has been used for the appraisal. The SDI analysis does not need to consider in detail the impacts on residents of the external zones.

Noise

2.3.7 The impact area should be defined through the noise analysis, which should be undertaken in accordance with the requirements of The Noise Sub-Objective (TAG Unit 3.3.2). The impact area should include the alignments of new transport corridors, both road and rail, together with a suitable area on either side of the corridor, which should be agreed with the noise analyst. The impact area should also include existing transport corridors with significant changes in noise (>1dBA) or significant changes in traffic flow, speed or HGV content, if noise levels have not yet been established.

Air Quality

2.3.8 The impact area should be defined through the air quality analysis, which should be undertaken in accordance with the requirements of The Air Quality Sub-Objective (TAG Unit 3.3.3). The impact area should include the alignments of new transport corridors (generally road), together with a suitable area on either side of the corridor, which should be agreed with the air quality analyst. The impact area should also include existing road corridors with significant changes in emissions (of nitrogen dioxide and particulate matter) or significant changes in traffic flow, speed or HGV content, if levels of emissions have not yet been established.

Accidents

2.3.9 The impact area should be defined through the accidents analysis, which should be undertaken in accordance with the requirements of The Accidents Sub-Objective (TAG Unit 3.4.1).

2.3.10 For the purposes of interventions on the rail network, the primary interest is likely to be accidents occurring at rail stations. Attention should therefore be focused on the rail station itself; accidents on the road network outside the station should be addressed separately.

2.3.11 For interventions on the road network, including new or improved roads, walking and cycling interventions and road-based public transport, the impact area should include any locations with physical changes in road alignment or where links on the road network will experience significant changes in traffic flows and / or speeds (>10%). The impact area should also include a defined band, which should be agreed with the safety analyst, to capture the potential impacts on pedestrians living in the area who need to cross the road.

2.3.12 In the case of interventions that result in changes in the numbers of pedestrians, cyclists and motorcyclists using the network (including walking and cycling interventions), the impact area should include those links on the network on which increased numbers of these groups are forecast.

Personal Security

2.3.13 The impact area should be defined through the security analysis, which should be undertaken in accordance with the requirements of The Security Sub-Objective (TAG Unit 3.4.2).

2.3.14 In the case of public transport interventions, the impact area will include the specific locations where specific improvements are being made to personal security, together with the catchment area for walking to the facility, which should be agreed with the security analyst.

2.3.15 It is likely that roadside facilities on the road network will be used by a range of users from a very wide catchment area. In this case, it is not appropriate to attempt to identify an impact area.

Severance

2.3.16 The impact area should be defined through the severance analysis, which should be undertaken in accordance with the requirements of The Severance Sub-Objective (TAG Unit 3.6.2).

2.3.17 For the purposes of interventions on the road network, including new or improved roads, walking and cycling interventions and road-based public transport, the impact area should include any locations with physical changes in road alignment or where links on the road network will experience significant changes in traffic flows and / or speeds (>10%). The impact area should also include a defined band on either side of the road, which should be agreed with the severance analyst, to capture the potential impacts on pedestrians who need to cross the road.

2.3.18 For rail interventions (including new light or heavy rail lines), the impact area should include the alignment of the corridor and a band on either side of the line (to be agreed with the severance analyst) to capture the potential impacts on pedestrians making movements on foot within the corridor.

Accessibility

2.3.19 The impact area should be defined through the accessibility analysis, which should be undertaken in accordance with the process described below.

2.3.20 For all types of transport intervention, this should take account of the following:

Identification of public transport corridors affected by a transport intervention; and
Identification of key destinations served by these public transport corridors.

Identification of public transport corridors

2.3.21 The public transport corridors likely to be affected by the transport intervention need to be identified. For example, in the case of bus interventions; this will need to include the bus corridor itself and any other bus routes that use the bus corridor. New railway stations should include the station's wider catchment area and, in the case of highway interventions, bus services using existing roads being altered should be considered.

Identification of key destinations

2.3.22 Consideration of the key destinations served by the public transport corridors identified above could include town centres, major employment areas, hospitals, centres of higher and further education and secondary schools. Section 3 of The Accessibility Sub-Objective (TAG Unit 3.6.3) sets out a list of potential destinations that should be considered.

2.3.23 The SDI analyst should make reference to existing evidence and policy documents in identifying these key destinations, including the Accessibility Strategy within the Local Transport Plan. Previous accessibility audits may have been undertaken for the local area and it is therefore appropriate to contact the Accessibility Planning officer for the local authority to be certain of any existing evidence.

2.3.24 Consideration should also be given to the potential impacts of an intervention on access to key destinations outside the immediate area of interest, for example within an adjacent local authority area. This will require liaison with the relevant local authority or transport authority to obtain appropriate data.

2.3.25 The identification of destinations should also take into account the destinations that people actually need to reach. The SDI analyst should not assume that people wish (or indeed are able) to travel to their nearest facility. Understanding the local accessibility priorities and problems will be a key element of the appraisal.

Affordability

2.3.26 The impact area should be the same as that considered for user benefits analysis, i.e. the area where passengers' cost of travel (in both time and monetary terms) is changing as a result of the intervention.

Conclusion to Step 1: Determining the Overall Affected Area

2.3.27 The information gathered on each impact area should be collated to identify the overall 'affected area' for the intervention. This is the area with the widest geographical coverage as defined by the analyses for the in-scope indicators. Normally this will be the TTWA or the modelled area if that is larger than the TTWA. Where the modelled area is smaller than the TTWA, consideration must be given to whether all of the required impacts can be appraised adequately at the lower spatial level. This will depend on the in-scope impacts, but it will normally be the case that if user benefits, accessibility and affordability are to be appraised, a larger geographic area, and typically a TTWA, would be required.

2.3.28 The process of identifying the 'affected area' should be documented for the purposes of the appraisal audit trail for the intervention, particularly as the intervention evolves and appraisals for the SDIs are reviewed in future appraisal work.

2.4 Step 2: Identification of social groups in the affected area

2.4.1 The second step should also be undertaken for the impacts that were identified at the initial screening. This step requires the analysis of the socio-economic, social and demographic characteristics of

The transport users that will experience changes in travel generalised costs resulting from the intervention
The people living in those areas identified as likely to be affected by the intervention.

2.4.2 This analysis is a common element for the appraisal of all eight SDI impacts and should provide a common dataset underpinning all of the subsequent SDI analyses.

Analysing the characteristics of transport users

2.4.3 The analysis of the characteristics of the transport users should be based on good practice in the segmentation of travel demand, as described in Modelling (TAG Unit 3.1). This will be particularly important in the subsequent analysis of the User Benefits and Personal Affordability SDIs. Further guidance on this issue can be found in Transport User Benefit Computation (TAG Unit 3.5.3) and The Personal Affordability Sub-Objective (TAG Unit 3.6.4).

Analysing the characteristics of people living in the affected area

2.4.4 The analysis of the characteristics of people in the area affected by the intervention should be based on a process of mapping of a range of social characteristics at a suitably disaggregate level for the 'affected area' that was identified in Step 1 above.

2.4.5 The table below sets out the groups of people / datasets that should be identified in the analysis, based on the indicators that have been scoped for SDI analysis.

Table 2 - Scope of Socio-Demographic Analyses for SD Impacts (Step 2)

Dataset / social group ('X' indicates analysis required for each impact)	User Benefits	Noise	Air Quality	Accidents	Security	Severance	Access- ibility	Afford- ability
Income Distribution (see below)	X	X	X				X	X
Children: proportion of population aged <16		X	X	X	X	X	X
Young adults: proportion of population aged 16-25				X			X
Older people: proportion of population aged 70+				X	X	X	X
Proportion of population with a disability					X	X	X
Proportion of population of Black and Minority Ethnic (BME) origin							X
Proportion of households without access to a car						X	X
Carers: proportion of households with dependent children							X

2.4.6 For example, if the only in-scope SDI impact is User Benefits, it is necessary only to prepare mapping of the distribution of different income groups in the affected area. If accidents have been identified as being an in-scope impact, it is necessary to prepare mapping of the proportions of children, young adults and older people within the affected area.

2.4.7 It is also possible that for the promoter's own purposes there may be an interest in examining all of the impacts in terms of how they are distributed across people in different household income groups. This would mean considering the impacts of all eight impacts in Table 1 against income distribution, which would involve gathering available information on income distribution and then looking at all the impacts and how they are distributed.

Datasets for analysis of socio-demographic characteristics

2.4.8 Table 3 below describes sources of data that are available to calculate the proportions of people in different social groups across the affected area.

2.4.9 It is recognised that these datasets are largely historic, covering the period between the date of the last census (2001) and the present day. The appraisal of schemes will relate to future years, and will generally use forecasts of volumes of trips and travel conditions for one or more future defined years. In most cases, however, there will not be forecasts of the demographic profile of the area for the future year. In such cases, the data described below should be used as the best available estimate of the demographic profile of the area. However, if forecasts have been produced for the demographic profiles of the area, these should be considered by the SDI analyst.

2.4.10 The SDI analyst should also consider if development and regeneration activity is likely to change the future demographic profile of the area. If so, these changes should be taken into account in the analyses within this step; this is likely to require consideration of the time profiles of changes in the population as well as transport changes. For example, the SDIs may have to be presented for specific years, so that if a land use development would increase the number of older people in an area in 2016, separate analyses may be required for the before and after periods in order to present adequate information to decision makers.

Table 3 - Datasets for demographic analysis (Step 2)

Data	Source	Availability
Age	Census 2001. Mid-year population estimates published by the Office of National Statistics (ONS) available at lower layer super output area (LSOA) level and ward level.	Free data available to download from the National Statistics website www.statistics.gov.uk.
Gender	Census 2001. Local Labour Force/Annual Population Survey available at District level from Nomis. Also mid-year population estimates published by ONS at LSOA and ward level.	Free data available to download from the National Statistics website. Free data available from the National Statistics official labour market statistics website www.nomisweb.co.uk.
Disability	Census 2001. Family Resources Survey. Benefits data (Department for Work and Pensions, DWP). Longitudinal Survey of Disability.	Census data is provided as free download from the National Statistics website along with benefits.
Ethnicity	Census 2001. Local Labour force/Annual Population Survey published by Nomis at District level.	Free data available to download from the National Statistics website.
Faith	Census 2001.	Free data available to download from the National Statistics website.
Household Tenure	Census 2001.	Free data available to download from the National Statistics website.
Household Income (Refer to discussion below)	CACI Paycheck (commercially available). Nomis Labour Force Survey 2009. Wealth and assets survey. Family and Resources Survey.	Most detailed datasets are co-ordinated by private sector companies and therefore a licence is required at a cost. Earnings and not Household income available from Annual Survey of Household Earnings via Nomis at Local Authority level.
Economic Activity	Census 2001. Labour Force Survey 2009. Annual Population Survey at District level published by Nomis.	Free data available to download from the National Statistics website.
Car Ownership	Census 2001.	Free data available to download from the National Statistics website.
Deprivation	Index of Multiple Deprivation (IMD) 2007. English Indices of Deprivation (ID) 2007.	Free data available to download from the National Statistics website and from the Department for Communities and Local Government (CLG) website.
Household structure (marital status/ cohabiting/ divorced/ lone parent etc)	Census 2001.	Free data available to download from the National Statistics website.
Households with dependent children	Census 2001.	Free data available to download from the National Statistics website.
Educational Qualifications	Census 2001. IMD 2007 (Education Domain). School & College achievement & attainment tables.	Free data available to download from the National Statistics website. Department for Children, Schools and Families (DCSF): GCSE and GNVQ qualifications available from Annual Population Survey (APS) /Labour Force Survey (LFS) via Nomis at District level.
Benefit Claimants	DWP (Nomis) 2009. DWP data.	Available from Nomis website free of charge. DWP website.
Urban / rural character or population density	Rural Urban Classification 2004 (Department for the Environment, Food and Rural Affairs, Defra). Census 2001 (Population density).	Free data available to download from the National Statistics website.

2.4.11 Mapping should take place at a disaggregate level to fully capture the impacts at an appropriate level of detail. In general, this should be at Output Area or Super Output Area level.(Output Areas and Super Output Areas are geographical definitions used for mapping of social characteristics. These cover different scales: for example Lower Super Output Areas typically have a resident population of around 1,500.) It should be noted that Output Areas can be diverse, and do not have a uniform distribution of different groups of people. Care should therefore be taken in the interpretation of data used in the analyses.

2.4.12 This list of datasets is not exhaustive and other local datasets can be used to develop a more detailed understanding of the specific local issues within the overall affected area.

The specific challenge of measuring income distribution

2.4.13 In certain cases, it is appropriate to consider the distribution of household income in SDI analysis. There are, however, a number of challenges in identifying a dataset that is suitable for use.

2.4.14 The Office for National Statistics (ONS) publishes annual time series data on Gross Disposable Household Income (GDHI) at a Government Region (Nomenclature of Units for Territorial Statistics, level 1 - NUTS1) level. GDHI is the money that individuals have available for spending and saving, and can be considered an accurate reflection of the funds available to households and individuals for spending and saving (and hence their ability to afford to use transport services). However, this data is not available at the fine level of spatial detail needed for SDI analysis. Whilst the data can be disaggregated to NUTS 3 level (County or Unitary council areas), this does not provide adequate data at the 'finer grain' needed for detailed transport analysis.

2.4.15 At present, information on household incomes at a small area level is through commercially available data. This is not, however, freely available, and payment is required for the data. The Department does not wish to insist that this data is used in all cases: it is for the promoter to use judgement on whether this could be useful for analysis.

2.4.16 One dataset that is freely available at the small area level is the Income Deprivation domain of the English Indices of Multiple Deprivation (IMD) 2007. Income Deprivation is one of seven domains of deprivation, and its aim is to capture the proportions of the population experiencing income deprivation in an area. Rather than an absolute measure of household income, the domain uses the rate (percentage of resident population) of means tested benefit recipients as a proxy for the number of low income households / individuals. It does not therefore reflect actual household income in a given area, nor does it cover the distribution of that income across its resident population.

2.4.17 The Income Deprivation domain is therefore an imperfect measure of income distribution. Whilst it effectively captures concentrations of low income households (within the most deprived areas) it does not identify areas of affluence. Instead, it identifies areas of relatively low deprivation, ie areas with lower proportions of low income households. It is notable that these areas could still include low income households, but they are likely to be more dispersed.

2.4.18 With the above caveats, and under the proviso that alternative disaggregate income data are not available, the IMD income domain can be used as a proxy measure for the most vulnerable groups. By calculating the absolute number of benefit recipients in a Super Output Area (SOA), and grossing this up to a bottom quintile (or alternative) using regional or national level GDHI data, a representation of the proportion of the population affected by any affordability or user benefits issues can be gained. Any processes and assumptions undertaken by the SDI analyst in deriving such datasets should be documented.

The role of Geographic Information Systems (GIS) in analysis

2.4.19 The mapping should be undertaken using Geographical Information Systems (GIS) or similar appropriate approaches, to provide detailed information on the characteristics of the people using the intervention or living in the affected area. This will be important in providing a clear picture of the different groups that could be impacted by the transport intervention.

2.4.20 The SDI analyst should examine the proportions of people within the affected area (defined in Step 1) from the potential 'vulnerable groups' in accordance with the requirements of Table 2 above.

2.4.21 In addition, the SDI analyst might wish to explore specific issues in relation to different faith communities and for people in different forms of household tenure: data sources are provided in Table 3 above.

2.4.22 The SDI analyst should then compare the proportions of people in these groups within the overall affected area with the corresponding regional average. The SDI analyst should identify any significant differences. For example, in a coastal area, are there relatively high proportions of older people compared with the regional average? In a city, are there relatively high proportions of people in BME communities?

2.4.23 This Unit does not identify specific thresholds above which differences are significant. In analysing the socio-demographic mix of the area, and in comparing with corresponding regional averages, the SDI analyst must use judgement in determining if these differences are significant.

2.4.24 The SDI analyst should then identify, using GIS, clusters within the overall affected area where there are particularly high proportions of these different groups of people. There are likely to be significant spatial variations in the proportions of households in different income groups. It is important to map these differences, which will form the subsequent analysis of the distributional impacts of the intervention. The mapping of differences by age, disability and ethnic origin will also be important in informing the analysis of the social and distributional impacts.

2.4.25 Figure 3 below provides an example of the expected mapping (at Output Area level), which shows the proportions of residents aged 70+ in the affected area. It can be seen that there are particular concentrations of older people in certain parts of the affected area.

Figure 3 - example of mapping of demographic profiles in the affected area

Figure 3 - example of mapping of demographic profiles in the affected area

2.4.26 This can be used to identify parts of the affected area in which particular attention must be given to the issues facing certain groups of people. In the example above, particular attention would be paid to the potential SDIs facing older people in the areas shown with darker shading.

2.4.27 This mapping of the demographic profiles across the overall affected area will be a crucial foundation in the SDI analysis for each SDI impact.

2.4.28 The demographic profiling within the affected area should be based on the requirements described below for the eight impacts.

2.4.29 The SDI analyst should use the guidance below to identify the proportions of the population in the key social groups of interest, compare against regional averages, and identify significant concentrations (at a detailed level) of these populations within the affected area.

User Benefits

2.4.30 The SDI analyst should use local income data where this is already available, and identify the distribution of incomes in line with the regional quintiles for each Census area or model zone within the affected area.

2.4.31 Where income segmentation is available within the transport model being used, then model zones will be the spatial unit of analysis, in preference to Super Output Areas (SOAs). In most cases, this will mean that a greater detail of analysis will be achieved, as well as using a more robust means of identifying income levels. Where income data has been acquired as a separate dataset, it should then be aggregated as closely as possible to match model zones.

Noise

2.4.32 In the case of noise, the SDI analyst should map, using GIS, variations in income deprivation, through the use of the Index of Multiple Deprivation (IMD) income domain at Super Output Area level. More detailed income data can be mapped through the use of other data, if this is available. This data will be subsequently used in the analysis of noise impacts experienced by households with different levels of income.

2.4.33 Children are particularly vulnerable to the effects of noise. The locations of schools and other facilities used by children, as sensitive receptors, should be mapped for the purposes of the noise analysis.

Air Quality

2.4.34 In the case of air quality, the SDI analyst should map, using GIS, variations in income deprivation, through the use of the Index of Multiple Deprivation (IMD) income domain at Super Output Area level. More detailed income data can be mapped through the use of other data, if this is available. This data will be subsequently used in the analysis of air quality impacts experienced by households with different levels of income.

2.4.35 There may, in addition, be places within the affected area that attract large numbers of people from different income groups. An example would be clusters of shops in a town which may be used exclusively or predominantly by low (or high) income groups, in which HGV traffic causes serious air quality problems. The SDI analyst should identify attractors that might experience changes in air quality, and consider the distribution of potential impacts across different groups in the population.

Accidents

2.4.36 There are several potential vulnerable groups in terms of accidents. The SDI analyst should analyse, using Census 2001 data, social groups living in the area that are vulnerable to accidents on the transport network, including children and older people. Consideration should also be given to any key destinations that are frequented by these vulnerable groups, such as schools or GP surgeries.

2.4.37 In addition, in the case of interventions on the road network, analysis of deprivation statistics should take place, because there is evidence that people living in more deprived areas are more vulnerable to accidents on the road network. The profile of local transport users should also be considered, including potentially vulnerable groups, for example pedestrians, cyclists and motorcyclists.

Security

2.4.38 There are certain groups that have particular concerns about their personal security. The SDI analyst should analyse, using Census 2001 data, the proportions of people within these groups living in the affected area that could be affected, in terms of personal security, by the proposed transport intervention. This should include older people, children, women and people with disabilities.

2.4.39 The SDI analyst should compare the proportions of the population in each area from these groups with the regional average, and highlight where there are significant concentrations of these groups.

Severance

2.4.40 There are certain groups that are particularly vulnerable to the effects of severance. The SDI analyst should analyse, using Census 2001 data, the proportions of people within these groups living in the affected area that could be affected, in terms of severance, by the proposed transport intervention. This should include no-car households, older people, children and people with disabilities.

2.4.41 In view of the local nature of severance effects, this analysis should take place at Output Area level. The SDI analyst should compare the proportions of the population in each area from these groups with the regional average, and highlight where there are significant concentrations of these groups.

Accessibility

2.4.42 There are certain groups that are particularly vulnerable to the effects of poor accessibility. The SDI analyst should analyse, using Census 2001 data, the proportions of people within these groups living in the affected area that could be affected, in terms of accessibility, by the proposed transport intervention. This should include no-car households, young people, older people, households with dependent children, Black and Minority Ethnic communities and people with disabilities.

2.4.43 In view of the local nature of accessibility effects, this analysis should take place at Output Area level. The SDI analyst should compare the proportions of the population in each area from these groups with the regional average, and highlight where there are significant concentrations of these groups.

Affordability

2.4.44 The primary group of interest in this case is people on low incomes. To ensure consistency of analysis, the same basis for identifying the income profile of the study area used in the User Benefit analysis should also be used for Personal Affordability. As a minimum this will mean that an approximation of the resident population in the bottom regional income quintile will have been created using Index of Multiple Deprivation (IMD) income domain data for all Super Output Areas (SOAs) or model zones in the study area. The area may also be assigned to local income quintiles, or income bands defined in terms of other income measures.

Conclusion to Step 2: Building a comprehensive picture of the socio-demographic profile of the affected area

2.4.45 The guidance described above should be used to provide an in-depth picture of the socio-economic and socio-demographic profile of the affected area. The datasets generated will then be used for the technical analysis of the relevant indicators, following the identification of impacts in the screening process described in Step 3 below.

2.5 Step 3: Approach to screening for SDIs

2.5.1 This step refers to the full screening which is to be undertaken

Following analysis of information on the affected areas;
Using any additional information on the proposed intervention, including an assessment of whether it is likely that any SDIs which were considered amenable to a design solution can in reality be eliminated in this way; and
Prior to developing a specification for full or proportionate / qualitative SDI appraisal.

2.5.2 It is important to take a proportionate approach to appraisal, as the full analysis is potentially time and resource intensive. The level of analysis to be undertaken where impacts are marginal and highly dispersed should reflect the likely value of such additional information in the appraisal and in decision making. Guidance on a more proportionate approach to appraisal is provided in TAG Unit 2.1.2, Option Development.

2.5.3 The full screening is the point where the SDI analyst has to finalise decisions on which SDIs are in scope for appraisal, and whether the scale, significance and degree of spatial or socio-demographic concentration of impacts, or the levels of uncertainty regarding the potential for adverse outcomes, warrants a full appraisal or not.

2.5.4 The SDI analyst will therefore undertake a detailed screening based on the information developed in the preceding Steps and will then prepare a detailed specification for the full appraisal for each indicator where this is judged to be required.

2.5.5 A similar process applies where a more proportionate approach is deemed more appropriate; it is more difficult to be prescriptive regarding such an approach and until a body of experience on proportionate appraisal is developed, the specification and review process will involve a degree of experimentation and iteration, but overall is intended to yield resource savings without compromising the relative value of the appraisal information generated.

2.5.6 Steps 1 and 2 will have provided a detailed understanding of the 'affected area' and the socio-demographic profile in this area. At this point, the appraisal (non distributional and non-social) of the user benefits and impacts relating to noise, air quality, accidents, security, severance, accessibility and personal affordability (as appropriate) will be ongoing, and there is likely to be a more detailed understanding of the potential scale of these impacts. However, it is recognised that these analyses will still be at an early stage, so the SDI analyst must continue to rely on his professional judgement and that of the technical specialists responsible for undertaking assessment of noise, air quality, safety, security, severance, accessibility, personal affordability and user benefits.

2.5.7 At this point in the appraisal process, it is necessary to review if it is appropriate to proceed with the detailed analysis of the social and distributional impacts for the indicators identified to date. This requires the application of a screening process, which applies a series of criteria to assist the SDI analyst to determine if more detailed analysis of the SDIs should take place for each indicator. As advised, the SDI analyst will then prepare a specification for appraisal.

2.5.8 At this stage in the development of SDI appraisal, there are no hard and fast quantitative screening criteria. Rather, a degree of judgement will be required on the part of the SDI analyst. As evidence develops, more precise guidance may be possible. In general, however, consideration needs to be given to baseline conditions and whether a proposed intervention is going to make a noticeable and significant difference to, or impact upon, any group within society, and whether those impacts are systematically concentrated within particular groups or places (and especially places in which particular groups are more likely to be found), or are more widely and randomly dispersed.

2.5.9 The suggested criteria for the screening of each of the SDI indicators are described in Table 4 below. The criteria are in two parts: the first is concerned with changes in transport conditions likely to arise from an intervention, and the second outlines factors for consideration when deciding whether a full appraisal is needed or whether a more proportionate approach is warranted. Changes in transport conditions alone do not trigger an appraisal: there must also be some consideration of how these changes will work through to the individuals who make up the various groups within society.

Table 4 - Screening criteria (used in Step 3) for the eight SDI Impacts

Impact	Changes in transport conditions necessary for SDI appraisal to be considered	Additional considerations for full or proportionate appraisal
User benefits	Refer to the more detailed commentary below this table.	-
Noise	Any change in alignment of transport corridor or any links with significant changes (eg >10%) in vehicle flow, speed or %HGV content. Also note comment in Noise (TAG Unit 3.3.2).	Potential impacts on receptors; likely change in ambient noise level within buildings; numbers of receptors by social group; proximity to transport corridor. Extent to which physical impacts are concentrated; numbers and characteristics of receptors in locations where impacts are concentrated. Are significant impacts concentrated in low income areas?
Air quality	Any change in alignment of transport corridor or any links with significant changes (eg >10%) in vehicle flow, speed or %HGV content for which there are properties within 200m.	Potential impacts on receptors; likely change in air quality in / around buildings; numbers of receptors by social group; proximity to transport corridor. Extent to which physical impacts are concentrated; numbers and characteristics of receptors in locations where impacts are concentrated. Are significant negative impacts concentrated in low income areas?
Accidents	Any change in alignment of transport corridor (or road layout) that may have positive or negative safety impacts, or any links with significant changes (>5%) in vehicle flow, speed, %HGV content or any significant change (>10%) in the number of pedestrians, cyclists or motorcyclists using road network.	Base conditions / accident record and evidence on socio-demographic characteristics of accident victims; evidence of systematic bias in victim typography. Expected changes in accident levels; local presence of vulnerable road users; expected / planned changes in numbers and proportions of vulnerable users eg due to land use etc.
Security	Any change in public transport waiting/interchange facilities including pedestrian access expected to affect user perceptions of personal security.	Base conditions, evidence of use, evidence of deterrence due to security factors. Levels of use; socio-demographic characteristics of users and any victims of crime, assault etc; evidence of systematic bias in victim typography. Benchmarking with other facilities. Expected / planned changes in numbers and proportions of vulnerable users eg due to land use etc.
Severance	Introduction or removal of barriers to pedestrian movement, either through changes to road crossing provision, or through introduction of new public transport or road corridors. Any areas with significant changes (>10%) in vehicle flow, speed, %HGV content.	Base conditions, evidence of use of existing areas by pedestrians, evidence of deterrence due to traffic and any existing severance. Socio-demographic characteristics of pedestrian users. Assessment of locations of alternative services / facilities if severance takes place. Appropriate benchmarking with other areas. Expected / planned changes in numbers and proportions of pedestrians (by socio-demographic group) due to land use changes etc.
Accessibility	Changes in routings or timings of current public transport services within the study area, any changes to public transport provision, including routing, frequencies, waiting facilities (bus stops / rail stations) and rolling stock, or any indirect impacts on accessibility to services (eg demolition & re-location of a school).	Base conditions, evidence of use of public transport, evidence of deterrence due to routes / timing / frequency of existing services. Socio-demographic characteristics of public transport users. Assessment of locations of alternative services / facilities if public transport changes take place. Appropriate benchmarking with other areas. Expected / planned changes in numbers and proportions of potential public transport users (by socio-demographic group) due to land use changes etc.
Affordability	Refer to the more detailed commentary below this table.	-

2.5.10 The screening process will be undertaken by the SDI analyst, who should normally involve the technical experts responsible for each indicator and an SDI specialist (if appointed). This group should consider the evidence and determine which of the in-scope indicators should be subject to detailed or proportionate appraisal of social and distributional impacts. This group should also review decisions made at the earlier initial screening and either confirm decisions to exclude an indicator from appraisal or amend that decision by including the indicator in the appraisal process from this point forward.

2.5.11 In addition to the criteria defined in the table above, the SDI analyst should refer to the detailed guidance below in relation to the triggers for undertaking SDI analysis for User Benefits and Personal Affordability.

2.5.12 A detailed overview is provided below for Personal Affordability because impacts on the affordability of travel are often unintended consequences of transport interventions, and the SDI analyst should pay particular attention to this issue.

User Benefits

2.5.13 In the majority of cases, interventions have been developed for the very purpose of generating benefits to users, and the quantification of the benefits will be central to the appraisal case for the intervention. In any situation in which the User Benefits of intervention have been quantified, a User Benefit SDI analysis should be undertaken. Specifically, this applies where:

The TUBA user benefit analysis software or an equivalent process has been used in the appraisal; and/or
A Transport Economic Efficiency (TEE) table is presented in which the value of User Benefits is non-zero.

2.5.14 In the majority of cases, User Benefits will have been quantified through the use of TUBA in conjunction with a spatially disaggregate transport model. There may, however, be cases where a User Benefit has been quantified through different approaches. The question then is: can User Benefits be mapped to either residential catchments or directly to income groups.

2.5.15 Take, for example, two interventions that improve the quality of interchange at railway stations. If one is a smaller station serving a distinct local catchment, then the User Benefits of the intervention can reasonably be assumed to be concentrated on this catchment, and it will be possible to undertake an SDI analysis by mapping to the income profile of that catchment. If the second intervention, however, involves a large station that is both the transport hub for a large urban area and a point of interchange between different train services, then its catchment cannot readily be identified. An SDI analysis in this case will not be practical and may not even be meaningful.

2.5.16 There are some cases where the nature of the intervention is such that User Benefits are not a significant or quantifiable aspect of its impacts. Safety-related interventions, for example, may have no discernable effect on travel times or costs, or any other aspect of users' travel experience, and hence will not meet either of the conditions above and are therefore exempt from User Benefits SDI analysis.

Affordability

2.5.17 This involves screening to determine whether any significant changes in user cost (i.e. financial costs to transport users) are anticipated as a result of the intervention, and thereby determine whether or not a full appraisal is required.

2.5.18 If no changes or potential changes to the charging regime can be discerned, then no further analysis is required. Where changes are identified, then the next step is to undertake analysis to determine which areas and hence which groups will be affected.

2.5.19 The following table provides a checklist of potential changes to the cost of travel that could result from a transport intervention, classified by mode. This checklist is not exhaustive, but should cover the majority of changes that are likely to occur.

Table 5 - Scope of Potential Changes in the Costs of Travel

Mode	Cost Change
Car	Car fuel and non-fuel cost
	Road user charges
	Public parking charges - management
	Other car charge/costs
Public Transport	Bus fares
	Rail fares
	Rapid transit fares
	Mode shift between public transport modes due to change in supply
	Ticket / interchange discounts
	Concessionary fares
	Other public transport charges/costs
Non-motorised Modes	Walking costs (in the vast majority of cases, nil)
Non-motorised Modes	Cycling costs

2.5.20 To undertake the checklist analysis, the SDI analyst will need to undertake a desk research exercise to establish the current pricing structure for the modes under consideration, covering the modes and aspects covered in the checklist. The SDI analyst should then make an assessment of how these are likely to change in the future, both without and with the intervention.

2.5.21 Note that the interest is focussed on the types of charge that may apply to different types of travellers, so inflationary effects, which are in any case hard to forecast, are not of interest, but effects that, for example, change the level of discount available to a particular traveller group are of interest. It is not necessarily the case that the future 'without intervention' charging regime will be 'as now,' although in the majority of cases this is likely to be the most appropriate assumption.

2.5.22 In many cases, the level of definition of the intervention may not allow an assessment to be undertaken: for example it might not be possible to state how the charging regime on a new Light Rail system will operate until a preferred bidder has been selected. In such cases, the SDI analyst is required to flag potential changes to the charging regime to highlight areas where there is a risk of change occurring, be it positive or negative in impact. For example, it may not be clear whether or not a new LRT intervention will accept concessionary passes: the issue here is that it cannot be assumed that they will, and therefore it should be noted in the appraisal that this risk exists, and that the promoter should consider whether mitigation measures should be considered.

2.5.23 As part of this step, the SDI analyst should make use of the SDI analysis of User Charge element of the Distribution of User Benefits, where this has been undertaken, to demonstrate where significant changes in PT fares, tolls or parking charges could be occurring. The output from this step should be in the form of a change in User Charge disaggregated by mode and geographic area (ideally at SOA level). Changes greater in magnitude than +/-10% should be highlighted as being significant, and these should be noted in the Worksheet as having been included in the TUBA analysis.

Conclusion to Step 3: appraisal specification

2.5.24 The final element in Step 3 is critical, especially at this stage in the development of the appraisal of social and distributional indicators. It involves first the SDI analyst and his/her team preparing a proposal for further SDI appraisal in the form of a specification or terms of reference and a methodology which will meet the terms of reference for the appraisal. A proposal is required for each indicator that is taken forward for appraisal.

2.5.25 These proposals should be included in the Appraisal Specification Report (or similar) - see TAG Unit 2.1.2, Option Development, for more details on this. The promoter's Senior Responsible Officer should submit this report to the Department (or equivalent, as appropriate) for consideration and subsequent discussion, with a view to reaching agreement regarding the appraisal to be undertaken. Where the report indicates that an SDI will not be appraised, evidence should be provided to support this position.

2.6 Step 4: Core appraisal and SDI analysis for each indicator

2.6.1 The process described in Step 4 below will only apply for the impact(s) that go forward for full appraisal following discussions with the Department (or equivalent).

2.6.2 In the case that a more qualitative approach to appraisal has been identified, the SDI analyst should develop a proportionate approach that will provide adequate information on the social and distributional impacts of each of the impacts of interest. The SDI analyst should refer to the guidance above on Step 0 for advice on the issues that should be considered in this process.

2.6.3 If potential social and distributional impacts have been identified for full appraisal following the screening process, the appraisal of these impacts should be undertaken in accordance with the requirements of the respective TAG Units: each TAG unit includes a module to describe the work required to describe the social and distributional impacts for each indicator.

2.6.4 Reference should be made to the following TAG units for a description of the approach required to assess social and distributional impacts in each case.

Table 5 - Signposting to SDI appraisal in other TAG units (Step 4)

Impact	TAG Unit Name	TAG Unit No.	Section of TAG Unit
User benefit	Transport User Benefit Computation	Unit 3.5.3	Section 7 (new)
Noise	The Noise Sub-Objective	Unit 3.3.2	Section 3 (new)
Air quality	The Local Air Quality Sub-Objective	Unit 3.3.3	Section 3 (new)
Accidents	The Accidents Sub-Objective	Unit 3.4.1	Section 4 (new)
Security	The Security Sub-Objective	Unit 3.4.2	Section 3 (new)
Severance	The Severance Sub-Objective	Unit 3.6.2	Section 3 (new)
Accessibility	The Accessibility Sub-Objective	Unit 3.6.3	This new TAG unit provides a comprehensive appraisal process
Affordability	The Personal Affordability Sub-Objective	Unit 3.6.4	This new TAG unit provides a comprehensive appraisal process

2.6.5 The SDI appraisal for each of the eight impacts includes a series of core concepts, as follows:

Core analysis for the impact, which follows the requirements of the respective TAG Unit;
Application of the demographic profile data, collated in Step 2 of this TAG Unit, to analyse the proportions of people in the key social groups of interest for the impact; and
Analysis of social and distributional impacts, across the groups of interest for the impact under consideration.

2.6.6 As noted above, the Output Areas used for the analyses are often diverse, and do not have an even distribution of different groups of people. The SDI analyst should therefore take into account the limitations of the available datasets in the analyses.

2.6.7 The guidance on this process is provided in the TAG Units signposted in Table 5 above.

2.7 Step 5: Collation of SDI analysis into matrix of social and distributional impacts

2.7.1 For each of the impacts assessed during Step 4, the TAG Units provide an approach that should be followed by the SDI analyst in assigning qualitative scores for each of the social groups under consideration.

2.7.2 For each impact, and for each of the social groups under consideration, an impact score is determined, as follows:

Large beneficial / Moderate beneficial / Slight beneficial;
Neutral;
Slight adverse / Moderate adverse / Large adverse.

2.7.3 In addition, a qualitative assessment should be provided in the worksheet for each indicator to describe the key impacts in each case.

Application of the assessments into the Matrix of Social and / or Distributional Impacts

2.7.4 The scores and qualitative assessment should then be taken from the worksheet for each impact and summarised in the Matrix of Social and / or Distributional Impacts.

2.7.5 In the event that a more qualitative approach to appraisal has taken place (as discussed above), the assessment scores should also be summarised in the Matrix, although a note should be added that a more qualitative approach has been used.

2.7.6 The Worksheet should be used for compiling the matrix of social and distributional impacts. Table 6 provides an example of the completed social and distributional impacts matrix. It uses the summary scores determined for each social group from the analyses for each of the indicators (described in Step 4) and, in this case, has highlighted a series of adverse social and distributional impacts.

2.7.7 Each impact has a specific approach to determining the scale of impacts, and the impact scales should not therefore be directly compared between the indicators. However, this information can give a detailed picture of the 'winners' and 'losers' from a transport intervention, and the key issues of relevance.

2.7.8 This information, on social and/or distributional impacts, should be used as supporting information to the Appraisal Summary Table, to enable decision-makers to understand the impacts of the transport intervention on different groups of people.

2.7.9 The key findings from the matrix of social and distributional impacts should be reported in the AST. For each of user benefits, noise, air quality, accidents, security, severance, accessibility and affordability, any vulnerable groups that would be negatively affected and the associated qualitative assessment using a seven-point scale should be reported under the 'distributional' column.

2.7.10 In addition, for accessibility and affordability, the overall assessment score, determined in the technical analyses in TAG Unit 3.6.3 (for accessibility) and TAG Unit 3.6.4 (for affordability), should be reported in the 'qualitative' column of the AST.

2.7.11 Where appropriate, key points may be briefly summarised in under the 'summary of key impacts' column The emphasis should be on the provision of essential information to inform the decision-making process.

Table 6 - Example of a Matrix of Social and Distributional Impacts (Step 5)

Table 6 - Example of a Matrix of Social and Distributional Impacts (Step 5) (Adobe Acrobat - 29KB)

Key to Impacts (Table 6):

✓✓✓ = Large Ben.
✓✓ = Mod. Ben.
✓ = Slight Ben.
x = Slight Adv.
xx = Mod. Adv.
xxx = Large Adv.

Qualitative Statements:

User benefits = Greatest share of benefits is experienced by higher income groups. Whilst there are benefits in low income groups, these are relatively modest.

Noise = There are large adverse impacts on communities in which there are low incomes and low car ownership. Noise benefits are concentrated amongst higher income groups.

Air quality = There are moderate to large benefits on communities in which there are low incomes. There are adverse impacts on some middle income communities.

Accidents = There are forecast to be slight beneficial impacts (in terms of reductions in casualties) for children and young males that have been identified in the analyses, with moderate beneficial impacts for older people.

Security = There are slight benefits from the intervention to older people and moderate benefits to young people and women.

Severance = Overall, there are slight benefits from the intervention. However, because of the impacts of the intervention at location f, which is heavily used by older people and people with disabilities, and because of the additional distance that must be walked following the introduction of the pedestrian footbridge, the intervention has moderate adverse impacts on older people and people with disabilities.

Accessibility = There are slight benefits for most of the population, due to the package of improved bus frequencies, reduced journey times and better buses. The improvements to physical accessibility result in large benefits to older people and people with disabilities, making possible journeys that were previously very difficult.

Affordability = The intervention will result in premium fares being charged for the upgraded services, which will have an adverse effect on lower income households. In addition, the increase in parking charges in the town centre will have an adverse impact on low-income motorists in the town.

3. Further Information

The following documents provide information that follows on directly from the key topics covered in this Unit.

For information on:	See:	TAG Unit number:
The summary of the approach to the analysis of social and distributional impacts	Summary Guidance on Social and Distributional Impacts of Transport Interventions	Unit 2.13
Characteristics of transport users should be based upon good practice in the segmentation of travel demand (Paragraph 2.3.3)	Modelling	Unit 3.1

4. References

Highways Agency Design Manual for Roads and Bridges (DMRB)

Social Exclusion Unit (February 2003) Making the Connections: Final Report on Transport and Social Exclusion

Atkins and MVA (Forthcoming) Assessing Social and Distributional Impacts in Transport Scheme Appraisal

5. Document Provenance

This unit, originally released in January 2010, has been updated in April 2011. Major changes have been highlighted; however, a number of smaller cosmetic changes, which do not affect the main requirements of the guidance, have not been highlighted.

Technical queries and comments on this Unit should be referred to:

Integrated Transport Economic Appraisal (ITEA) Division
Department for Transport
Zone 3/04 Great Minster House
33 Horseferry Road
London SW1P 4DR
Email: itea@dft.gsi.gov.uk
Tel: 020 7944 6176
Fax: 020 7944 2198

Updated: April 2011