A27 Chichester Bypass Mitigation Supplementary Planning Document - August 2023

SECTION 1 Introduction and Overview

1.1 Introduction

1.1.1 This note provides a transport response to the Chichester District Council (CDC) Planning Obligations
and Affordable Housing (July 2016) Supplementary Planning Document (SPD) and associated A27 Chichester Bypass Mitigation (August 2023).

1.1.2 It has been prepared on behalf of Henry Adams LLP in respect to the promotion of land interests in the Chichester District (Land at Maudlin Farm, Westhampnett – Site A10), and focusses on whether the proposed approach to contributions, and the methodology used to calculate its value, is appropriate.

1.2 Overview

1.2.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

1.2.2 However, there are some significant concerns with the approach taken within the SPD to calculate the
contributions, and the approach does not accord with CIL Reg 122 tests used to govern financial contributions – the contributions sought would not be ‘directly related to development’ nor ‘fairly and reasonably related in scale’. The following points are of particular note:

• The modelling evidence base upon which the infrastructure is based does not make appropriate allowance for changes in travel behaviour nor seeks to mitigate impacts through sustainable travel initiatives – thus, the extent of the mitigation may not represent a cost-effective means of mitigating the impacts of development.

• A 535 dwelling per annum (dpa) ‘cap’ artificially inflates the contribution value per dwelling – the infrastructure identified by the Transport Study accompanying the Local Plan is capable of accommodating a greater quantum of development.

• No allowance is made for any potential funding grants – improvement of the A27 has been identified historically as a priority location in the Road Investment Strategy (RIS).

• The SPD penalises development coming forward towards the end of the plan period.

• The relationship between number of bedrooms and trip generation is not linear.

SECTION 2 Transport Evidence Base

2.1 Overview

2.1.1 Land at Maudlin Farm in Westhampnett has been identified in the Chichester Local Plan (2021 – 2029):
Proposed Submission under Policy A10, which allocates the land for the development of:

• 265 dwellings, including 4 serviced self/custom build plots.
• Specialist accommodation for older persons, to include a component of care or support.
• Provision of on-site public open space and play area.
• 3 gypsy and traveller pitches

2.1.2 A review has been undertaken of the Reg 19 consultation on the 2021 – 2039 Proposed Submission
version of the Chichester Local Plan and, in particular, the Transport Study supporting this work upon which the proposed SPD is based. There is considerable disconnect between the proposed mitigation strategy and the objectives of the National Planning Policy Framework and contemporary guidance on how development should be mitigated. For example:

• The transport strategy places little emphasis on the role that sustainable travel has to play in mitigating the traffic impacts of development. This includes the impact of behavioural change arising post-pandemic; the delivery of large strategic sites with the ability to accommodate
trips within the development site through the provision of internal services and facilities; andthe potential for strategic scale sustainable travel improvements being delivered alongside planned development.

• A blanket ‘predict and provide’ is taken to trip derivation, with trip generation forecasts significantly greater than that used in other authorities across the West Sussex area – by comparison, the Mid Sussex District Council study recognises the opportunity for sustainable travel behaviours and incorporates a ‘Decide and Provide’ methodology into the assessment. This consequence of this rigid approach to assessment is that it significantly overestimates the likely traffic impact of planned development, by potentially as much as traffic equivalent to that of an additional 1,900 dwellings.

Modelling scenarios tested whether the proposed package of local plan mitigation could cater for a greater quantum of development, with the outputs indicating that a 700dpa strategy could be accommodated. Potentially, an even greater quantum of development beyond 700 dpa could also be accommodated but this remains untested. Capping the number of dwelling means that the proposed mitigation strategy goes beyond mitigating the impacts of
development and provided capacity in excess of that required to accommodate development.

2.2 Outcomes

2.2.1 As a consequence of the deficiencies in the modelling base, an unnecessarily large burden is being
placed upon planned development – the proposed mitigation can accommodate a much greater rate
of growth. An increase in the level of planned development would enable the cost per dwelling to be reduced accordingly, and the direct mitigation of development impacts only, as opposed to the provision of additional capacity beyond that required, would reduce the infrastructure costs placed upon planned development.

2.2.2 In addition to this, a greater emphasis on mitigating the impacts of development using means of encouraging sustainable travel may result in a more cost-effective approach to managing the impacts of development. This would enable greater investment in other infrastructure (both transport and nontransport) improvements.

2.2.3 It is apparent that the contributions identified in the SPD would not satisfy the following CIL Reg 122 tests:

• Fairly and reasonably related in scale and kind to the development – the scale of the contribution far exceeds what is necessary of the planned development. The burden created by the artificial capping of growth and by requiring mitigation that extends beyond mitigation
of development traffic could be reduced by a more cost-effective approach to the mitigation strategy or by spreading the cost of the improvements across a greater quantum of development.
• Not directly related to the development – the SPD requires funding of mitigation that goes above and beyond direct mitigation of the traffic impacts of planned development.

SECTION 3 SPD Methodology

3.1 Number of Dwellings

3.1.1 The emerging CDC Local Plan (2021 – 2039) has placed a development cap on providing a total of 9,630 homes across an 18-year period, equating to 535 homes per year.

3.1.2 Of these, approximately 6,000 are committed, having an extant planning permission or a ‘resolution to grant’. There are now only 3,551 homes left before the development cap is reached.

3.1.3 The remaining unfunded £27m for the two proposed junction improvement schemes has been divided by the remaining number of homes (3,551) to calculate a per-dwelling contribution. At a ‘per dwelling’ ratio, this equates to £7,600 approximately per dwelling. There are no known mechanisms within existing consents to secure ‘top up’ contributions, and thus any committed developments have a much lower level of burden placed upon them. It is reasonable to assume that committed development will
not have provided additional contributions towards other mitigation required to mitigate the impacts of planned growth, and thus planned development that has yet to come forward will be required to pay full contributions towards these aspects as well as the uplifted A27 contributions.

3.1.4 The result of this is that there will be a disproportionate impact on development at the ‘tail end’ of the plan period, which is required to make up a significant proportion of the cost of the infrastructure required to mitigate the entirety of the planned growth, of which some two thirds is already permitted.

3.1.5 Therefore, it is not in keeping with the ‘fairly and reasonable related in scale and kind”, as required by
CIL Reg 122, as the remaining development is expected to mitigate the impact of development that has already obtained consent. Similarly, it also fails to adhere to the ‘necessary to make the development acceptable in planning terms’ – the level of the contribution is actually necessary to make already permitted development acceptable in planning terms, not the development to which it will be applied.

3.2 Ratios

3.2.1 CDC acknowledges the outcomes of the viability testing and recognises that dwellings do not all have
the same impact on the A27. Paragraph 4.19 of the A27 Chichester Bypass Mitigation (August 2023)SPD states:

‘Smaller dwellings generally have fewer occupants who drive and own a car and therefore have a generally smaller impact than is the case with larger dwellings where the larger number of occupants would, on average, own and drive more cars.'

3.2.2 Using guidance on the future mix of dwellings within the district contained within the latest Housing and Economic Development Needs Assessment (HEDNA), CDC has employed a scaled approach when considering the range of dwelling sizes that may come forward. This equates to a contribution rate of £3,049.16 per bedroom (£7,623 / 2.5) which would provide the following contribution scale:

• 1 bedroom - £3,049
• 2 bedroom - £6,098
• 3 bedroom - £9,147
• 4+ bedroom - £12,197

3.2.3 The number of trips generated by a dwelling does not have a linear relationship to the number of bedrooms it comprises (i.e. a four bedroom dwelling will not result in double the number of trips compared to a two-bedroom dwelling). Larger family homes are typically occupied by families where the children are not of driving age or have access to their own vehicle. However, in using a linear
relationship, the methodology in the SPD assumes that a family of 5 that includes three school age children will generate four times the number of vehicular movements than a professional couple living in a 1-bedroom property.

3.2.4 The TRICS database has been filtered to calculate a generic trip rate based upon surveys comprising
of just two-bedroom dwellings and filtered again for just four-bedroom dwelling surveys, shown in
Table 4.1 [within attachment].

3.2.5 The TRICS assessment identifies that a four-bedroom dwelling will generate an additional daily vehicle
trip rate of 0.174 per dwelling compared to a two-bedroom dwelling. This represents an increase of just 5%, and not double as outlined by CDC, demonstrating that factoring the level of A27 contributions on a per bedroom basis does not result in a contribution that would be ‘directly related to the development’ nor ‘fairly and reasonably related in scale and kind’.

3.3 Additional Funding

3.3.1 Even though the proposed improvement package goes beyond the mitigation of development impacts and addresses existing issues / introduces additional network capacity, the SPD makes no indication that further alternative means of funding the improvements will be sought and introduces no mechanism to reduce the level of contribution sought from development should further funding awards be made.

3.3.2 National Highways has included the A27 Chichester By-pass in their current RIS 3 funding review. It is
acknowledged that there is no certainty at this time for inclusion of any scheme within the RIS3. However, funding was previously identified (c. £100m) towards improvement of the Chichester Bypass, which was subsequently lost as consensus could not be reached between the local authorities as to the preferred approach. Having previously been recognised as a location where intervention is
necessary, it is not unreasonable to assume that a funding award will be made.

3.3.3 Similarly, the SPD focusses solely on residential development, and it is unclear as to whether similar
contributions will be sought from other use classes which have the potential to increase usage of the A27. Clarity should be provided in respect to the level of contribution that may be sought from other floor space, to ensure fair and equitable mitigation of impacts consistent with the requires of CIL Reg 122.

SECTION 4 Conclusion

4.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

4.2 However, the SPD fails to provide an appropriate mechanism for contributions to be secured in accordance with the CIL Reg 122 requirements, particularly those of ‘relatedness’ and ‘proportionality’.

4.3 To ensure that this can be achieved, the following recommendations are made:

1 Further modelling of traffic impacts should be undertaken through the Transport Study, allowing for ‘Decide and Provide’ principles to trip forecasting, a greater emphasis on sustainable travel and for changes in travel behaviour following the pandemic – some means
of sustainable mitigation are commented upon briefly within the Study, but it fails to build upon this.

2 Reconsider the mitigation strategy, to allow for infrastructure only that is necessary to mitigate the impacts of development and more cost effective means of mitigating the impacts of development, in line with the requirements of CIL Reg 122 and paragraphs 57 and 111 of the National Planning Policy Framework.

3 The artificial 535 dpa cap places an undue burden on planned development at the ‘tail end’ of the plan. The cap should be lifted and a greater quantum of development, of at least 700 dpa, be permitted.

4 Consider alternative means of deriving financial contributions that reflect the impact of development, recognising that there is not a linear relationship between the size of a dwelling and its trip generating properties.

5 Encourage, and make allowance for, the award of further funding streams to assist with delivery of the project. Provide clarity as to the level of contribution that may be sought from use classes other than residential.

SECTION 1 Introduction and Overview

1.1 Introduction

1.1.1 This note provides a transport response to the Chichester District Council (CDC) Planning Obligations
and Affordable Housing (July 2016) Supplementary Planning Document (SPD) and associated A27 Chichester Bypass Mitigation (August 2023).

1.1.2 It has been prepared on behalf of Henry Adams LLP in respect to the promotion of land interests in the Chichester District (Land at Maudlin Farm, Westhampnett – Site A10), and focusses on whether the proposed approach to contributions, and the methodology used to calculate its value, is appropriate.

1.2 Overview

1.2.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

1.2.2 However, there are some significant concerns with the approach taken within the SPD to calculate the
contributions, and the approach does not accord with CIL Reg 122 tests used to govern financial contributions – the contributions sought would not be ‘directly related to development’ nor ‘fairly and reasonably related in scale’. The following points are of particular note:

• The modelling evidence base upon which the infrastructure is based does not make appropriate allowance for changes in travel behaviour nor seeks to mitigate impacts through sustainable travel initiatives – thus, the extent of the mitigation may not represent a cost-effective means of mitigating the impacts of development.

• A 535 dwelling per annum (dpa) ‘cap’ artificially inflates the contribution value per dwelling – the infrastructure identified by the Transport Study accompanying the Local Plan is capable of accommodating a greater quantum of development.

• No allowance is made for any potential funding grants – improvement of the A27 has been identified historically as a priority location in the Road Investment Strategy (RIS).

• The SPD penalises development coming forward towards the end of the plan period.

• The relationship between number of bedrooms and trip generation is not linear.

SECTION 2 Transport Evidence Base

2.1 Overview

2.1.1 Land at Maudlin Farm in Westhampnett has been identified in the Chichester Local Plan (2021 – 2029):
Proposed Submission under Policy A10, which allocates the land for the development of:

• 265 dwellings, including 4 serviced self/custom build plots.
• Specialist accommodation for older persons, to include a component of care or support.
• Provision of on-site public open space and play area.
• 3 gypsy and traveller pitches

2.1.2 A review has been undertaken of the Reg 19 consultation on the 2021 – 2039 Proposed Submission
version of the Chichester Local Plan and, in particular, the Transport Study supporting this work upon which the proposed SPD is based. There is considerable disconnect between the proposed mitigation strategy and the objectives of the National Planning Policy Framework and contemporary guidance on how development should be mitigated. For example:

• The transport strategy places little emphasis on the role that sustainable travel has to play in mitigating the traffic impacts of development. This includes the impact of behavioural change arising post-pandemic; the delivery of large strategic sites with the ability to accommodate
trips within the development site through the provision of internal services and facilities; andthe potential for strategic scale sustainable travel improvements being delivered alongside planned development.

• A blanket ‘predict and provide’ is taken to trip derivation, with trip generation forecasts significantly greater than that used in other authorities across the West Sussex area – by comparison, the Mid Sussex District Council study recognises the opportunity for sustainable travel behaviours and incorporates a ‘Decide and Provide’ methodology into the assessment. This consequence of this rigid approach to assessment is that it significantly overestimates the likely traffic impact of planned development, by potentially as much as traffic equivalent to that of an additional 1,900 dwellings.

Modelling scenarios tested whether the proposed package of local plan mitigation could cater for a greater quantum of development, with the outputs indicating that a 700dpa strategy could be accommodated. Potentially, an even greater quantum of development beyond 700 dpa could also be accommodated but this remains untested. Capping the number of dwelling means that the proposed mitigation strategy goes beyond mitigating the impacts of
development and provided capacity in excess of that required to accommodate development.

2.2 Outcomes

2.2.1 As a consequence of the deficiencies in the modelling base, an unnecessarily large burden is being
placed upon planned development – the proposed mitigation can accommodate a much greater rate
of growth. An increase in the level of planned development would enable the cost per dwelling to be reduced accordingly, and the direct mitigation of development impacts only, as opposed to the provision of additional capacity beyond that required, would reduce the infrastructure costs placed upon planned development.

2.2.2 In addition to this, a greater emphasis on mitigating the impacts of development using means of encouraging sustainable travel may result in a more cost-effective approach to managing the impacts of development. This would enable greater investment in other infrastructure (both transport and nontransport) improvements.

2.2.3 It is apparent that the contributions identified in the SPD would not satisfy the following CIL Reg 122 tests:

• Fairly and reasonably related in scale and kind to the development – the scale of the contribution far exceeds what is necessary of the planned development. The burden created by the artificial capping of growth and by requiring mitigation that extends beyond mitigation
of development traffic could be reduced by a more cost-effective approach to the mitigation strategy or by spreading the cost of the improvements across a greater quantum of development.
• Not directly related to the development – the SPD requires funding of mitigation that goes above and beyond direct mitigation of the traffic impacts of planned development.

SECTION 3 SPD Methodology

3.1 Number of Dwellings

3.1.1 The emerging CDC Local Plan (2021 – 2039) has placed a development cap on providing a total of 9,630 homes across an 18-year period, equating to 535 homes per year.

3.1.2 Of these, approximately 6,000 are committed, having an extant planning permission or a ‘resolution to grant’. There are now only 3,551 homes left before the development cap is reached.

3.1.3 The remaining unfunded £27m for the two proposed junction improvement schemes has been divided by the remaining number of homes (3,551) to calculate a per-dwelling contribution. At a ‘per dwelling’ ratio, this equates to £7,600 approximately per dwelling. There are no known mechanisms within existing consents to secure ‘top up’ contributions, and thus any committed developments have a much lower level of burden placed upon them. It is reasonable to assume that committed development will
not have provided additional contributions towards other mitigation required to mitigate the impacts of planned growth, and thus planned development that has yet to come forward will be required to pay full contributions towards these aspects as well as the uplifted A27 contributions.

3.1.4 The result of this is that there will be a disproportionate impact on development at the ‘tail end’ of the plan period, which is required to make up a significant proportion of the cost of the infrastructure required to mitigate the entirety of the planned growth, of which some two thirds is already permitted.

3.1.5 Therefore, it is not in keeping with the ‘fairly and reasonable related in scale and kind”, as required by
CIL Reg 122, as the remaining development is expected to mitigate the impact of development that has already obtained consent. Similarly, it also fails to adhere to the ‘necessary to make the development acceptable in planning terms’ – the level of the contribution is actually necessary to make already permitted development acceptable in planning terms, not the development to which it will be applied.

3.2 Ratios

3.2.1 CDC acknowledges the outcomes of the viability testing and recognises that dwellings do not all have
the same impact on the A27. Paragraph 4.19 of the A27 Chichester Bypass Mitigation (August 2023)SPD states:

‘Smaller dwellings generally have fewer occupants who drive and own a car and therefore have a generally smaller impact than is the case with larger dwellings where the larger number of occupants would, on average, own and drive more cars.'

3.2.2 Using guidance on the future mix of dwellings within the district contained within the latest Housing and Economic Development Needs Assessment (HEDNA), CDC has employed a scaled approach when considering the range of dwelling sizes that may come forward. This equates to a contribution rate of £3,049.16 per bedroom (£7,623 / 2.5) which would provide the following contribution scale:

• 1 bedroom - £3,049
• 2 bedroom - £6,098
• 3 bedroom - £9,147
• 4+ bedroom - £12,197

3.2.3 The number of trips generated by a dwelling does not have a linear relationship to the number of bedrooms it comprises (i.e. a four bedroom dwelling will not result in double the number of trips compared to a two-bedroom dwelling). Larger family homes are typically occupied by families where the children are not of driving age or have access to their own vehicle. However, in using a linear
relationship, the methodology in the SPD assumes that a family of 5 that includes three school age children will generate four times the number of vehicular movements than a professional couple living in a 1-bedroom property.

3.2.4 The TRICS database has been filtered to calculate a generic trip rate based upon surveys comprising
of just two-bedroom dwellings and filtered again for just four-bedroom dwelling surveys, shown in
Table 4.1 [within attachment].

3.2.5 The TRICS assessment identifies that a four-bedroom dwelling will generate an additional daily vehicle
trip rate of 0.174 per dwelling compared to a two-bedroom dwelling. This represents an increase of just 5%, and not double as outlined by CDC, demonstrating that factoring the level of A27 contributions on a per bedroom basis does not result in a contribution that would be ‘directly related to the development’ nor ‘fairly and reasonably related in scale and kind’.

3.3 Additional Funding

3.3.1 Even though the proposed improvement package goes beyond the mitigation of development impacts and addresses existing issues / introduces additional network capacity, the SPD makes no indication that further alternative means of funding the improvements will be sought and introduces no mechanism to reduce the level of contribution sought from development should further funding awards be made.

3.3.2 National Highways has included the A27 Chichester By-pass in their current RIS 3 funding review. It is
acknowledged that there is no certainty at this time for inclusion of any scheme within the RIS3. However, funding was previously identified (c. £100m) towards improvement of the Chichester Bypass, which was subsequently lost as consensus could not be reached between the local authorities as to the preferred approach. Having previously been recognised as a location where intervention is
necessary, it is not unreasonable to assume that a funding award will be made.

3.3.3 Similarly, the SPD focusses solely on residential development, and it is unclear as to whether similar
contributions will be sought from other use classes which have the potential to increase usage of the A27. Clarity should be provided in respect to the level of contribution that may be sought from other floor space, to ensure fair and equitable mitigation of impacts consistent with the requires of CIL Reg 122.

SECTION 4 Conclusion

4.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

4.2 However, the SPD fails to provide an appropriate mechanism for contributions to be secured in accordance with the CIL Reg 122 requirements, particularly those of ‘relatedness’ and ‘proportionality’.

4.3 To ensure that this can be achieved, the following recommendations are made:

1 Further modelling of traffic impacts should be undertaken through the Transport Study, allowing for ‘Decide and Provide’ principles to trip forecasting, a greater emphasis on sustainable travel and for changes in travel behaviour following the pandemic – some means
of sustainable mitigation are commented upon briefly within the Study, but it fails to build upon this.

2 Reconsider the mitigation strategy, to allow for infrastructure only that is necessary to mitigate the impacts of development and more cost effective means of mitigating the impacts of development, in line with the requirements of CIL Reg 122 and paragraphs 57 and 111 of the National Planning Policy Framework.

3 The artificial 535 dpa cap places an undue burden on planned development at the ‘tail end’ of the plan. The cap should be lifted and a greater quantum of development, of at least 700 dpa, be permitted.

4 Consider alternative means of deriving financial contributions that reflect the impact of development, recognising that there is not a linear relationship between the size of a dwelling and its trip generating properties.

5 Encourage, and make allowance for, the award of further funding streams to assist with delivery of the project. Provide clarity as to the level of contribution that may be sought from use classes other than residential.

SECTION 1 Introduction and Overview

1.1 Introduction

1.1.1 This note provides a transport response to the Chichester District Council (CDC) Planning Obligations
and Affordable Housing (July 2016) Supplementary Planning Document (SPD) and associated A27 Chichester Bypass Mitigation (August 2023).

1.1.2 It has been prepared on behalf of Henry Adams LLP in respect to the promotion of land interests in the Chichester District (Land at Maudlin Farm, Westhampnett – Site A10), and focusses on whether the proposed approach to contributions, and the methodology used to calculate its value, is appropriate.

1.2 Overview

1.2.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

1.2.2 However, there are some significant concerns with the approach taken within the SPD to calculate the
contributions, and the approach does not accord with CIL Reg 122 tests used to govern financial contributions – the contributions sought would not be ‘directly related to development’ nor ‘fairly and reasonably related in scale’. The following points are of particular note:

• The modelling evidence base upon which the infrastructure is based does not make appropriate allowance for changes in travel behaviour nor seeks to mitigate impacts through sustainable travel initiatives – thus, the extent of the mitigation may not represent a cost-effective means of mitigating the impacts of development.

• A 535 dwelling per annum (dpa) ‘cap’ artificially inflates the contribution value per dwelling – the infrastructure identified by the Transport Study accompanying the Local Plan is capable of accommodating a greater quantum of development.

• No allowance is made for any potential funding grants – improvement of the A27 has been identified historically as a priority location in the Road Investment Strategy (RIS).

• The SPD penalises development coming forward towards the end of the plan period.

• The relationship between number of bedrooms and trip generation is not linear.

SECTION 2 Transport Evidence Base

2.1 Overview

2.1.1 Land at Maudlin Farm in Westhampnett has been identified in the Chichester Local Plan (2021 – 2029):
Proposed Submission under Policy A10, which allocates the land for the development of:

• 265 dwellings, including 4 serviced self/custom build plots.
• Specialist accommodation for older persons, to include a component of care or support.
• Provision of on-site public open space and play area.
• 3 gypsy and traveller pitches

2.1.2 A review has been undertaken of the Reg 19 consultation on the 2021 – 2039 Proposed Submission
version of the Chichester Local Plan and, in particular, the Transport Study supporting this work upon which the proposed SPD is based. There is considerable disconnect between the proposed mitigation strategy and the objectives of the National Planning Policy Framework and contemporary guidance on how development should be mitigated. For example:

• The transport strategy places little emphasis on the role that sustainable travel has to play in mitigating the traffic impacts of development. This includes the impact of behavioural change arising post-pandemic; the delivery of large strategic sites with the ability to accommodate
trips within the development site through the provision of internal services and facilities; andthe potential for strategic scale sustainable travel improvements being delivered alongside planned development.

• A blanket ‘predict and provide’ is taken to trip derivation, with trip generation forecasts significantly greater than that used in other authorities across the West Sussex area – by comparison, the Mid Sussex District Council study recognises the opportunity for sustainable travel behaviours and incorporates a ‘Decide and Provide’ methodology into the assessment. This consequence of this rigid approach to assessment is that it significantly overestimates the likely traffic impact of planned development, by potentially as much as traffic equivalent to that of an additional 1,900 dwellings.

Modelling scenarios tested whether the proposed package of local plan mitigation could cater for a greater quantum of development, with the outputs indicating that a 700dpa strategy could be accommodated. Potentially, an even greater quantum of development beyond 700 dpa could also be accommodated but this remains untested. Capping the number of dwelling means that the proposed mitigation strategy goes beyond mitigating the impacts of
development and provided capacity in excess of that required to accommodate development.

2.2 Outcomes

2.2.1 As a consequence of the deficiencies in the modelling base, an unnecessarily large burden is being
placed upon planned development – the proposed mitigation can accommodate a much greater rate
of growth. An increase in the level of planned development would enable the cost per dwelling to be reduced accordingly, and the direct mitigation of development impacts only, as opposed to the provision of additional capacity beyond that required, would reduce the infrastructure costs placed upon planned development.

2.2.2 In addition to this, a greater emphasis on mitigating the impacts of development using means of encouraging sustainable travel may result in a more cost-effective approach to managing the impacts of development. This would enable greater investment in other infrastructure (both transport and nontransport) improvements.

2.2.3 It is apparent that the contributions identified in the SPD would not satisfy the following CIL Reg 122 tests:

• Fairly and reasonably related in scale and kind to the development – the scale of the contribution far exceeds what is necessary of the planned development. The burden created by the artificial capping of growth and by requiring mitigation that extends beyond mitigation
of development traffic could be reduced by a more cost-effective approach to the mitigation strategy or by spreading the cost of the improvements across a greater quantum of development.
• Not directly related to the development – the SPD requires funding of mitigation that goes above and beyond direct mitigation of the traffic impacts of planned development.

SECTION 3 SPD Methodology

3.1 Number of Dwellings

3.1.1 The emerging CDC Local Plan (2021 – 2039) has placed a development cap on providing a total of 9,630 homes across an 18-year period, equating to 535 homes per year.

3.1.2 Of these, approximately 6,000 are committed, having an extant planning permission or a ‘resolution to grant’. There are now only 3,551 homes left before the development cap is reached.

3.1.3 The remaining unfunded £27m for the two proposed junction improvement schemes has been divided by the remaining number of homes (3,551) to calculate a per-dwelling contribution. At a ‘per dwelling’ ratio, this equates to £7,600 approximately per dwelling. There are no known mechanisms within existing consents to secure ‘top up’ contributions, and thus any committed developments have a much lower level of burden placed upon them. It is reasonable to assume that committed development will
not have provided additional contributions towards other mitigation required to mitigate the impacts of planned growth, and thus planned development that has yet to come forward will be required to pay full contributions towards these aspects as well as the uplifted A27 contributions.

3.1.4 The result of this is that there will be a disproportionate impact on development at the ‘tail end’ of the plan period, which is required to make up a significant proportion of the cost of the infrastructure required to mitigate the entirety of the planned growth, of which some two thirds is already permitted.

3.1.5 Therefore, it is not in keeping with the ‘fairly and reasonable related in scale and kind”, as required by
CIL Reg 122, as the remaining development is expected to mitigate the impact of development that has already obtained consent. Similarly, it also fails to adhere to the ‘necessary to make the development acceptable in planning terms’ – the level of the contribution is actually necessary to make already permitted development acceptable in planning terms, not the development to which it will be applied.

3.2 Ratios

3.2.1 CDC acknowledges the outcomes of the viability testing and recognises that dwellings do not all have
the same impact on the A27. Paragraph 4.19 of the A27 Chichester Bypass Mitigation (August 2023)SPD states:

‘Smaller dwellings generally have fewer occupants who drive and own a car and therefore have a generally smaller impact than is the case with larger dwellings where the larger number of occupants would, on average, own and drive more cars.'

3.2.2 Using guidance on the future mix of dwellings within the district contained within the latest Housing and Economic Development Needs Assessment (HEDNA), CDC has employed a scaled approach when considering the range of dwelling sizes that may come forward. This equates to a contribution rate of £3,049.16 per bedroom (£7,623 / 2.5) which would provide the following contribution scale:

• 1 bedroom - £3,049
• 2 bedroom - £6,098
• 3 bedroom - £9,147
• 4+ bedroom - £12,197

3.2.3 The number of trips generated by a dwelling does not have a linear relationship to the number of bedrooms it comprises (i.e. a four bedroom dwelling will not result in double the number of trips compared to a two-bedroom dwelling). Larger family homes are typically occupied by families where the children are not of driving age or have access to their own vehicle. However, in using a linear
relationship, the methodology in the SPD assumes that a family of 5 that includes three school age children will generate four times the number of vehicular movements than a professional couple living in a 1-bedroom property.

3.2.4 The TRICS database has been filtered to calculate a generic trip rate based upon surveys comprising
of just two-bedroom dwellings and filtered again for just four-bedroom dwelling surveys, shown in
Table 4.1 [within attachment].

3.2.5 The TRICS assessment identifies that a four-bedroom dwelling will generate an additional daily vehicle
trip rate of 0.174 per dwelling compared to a two-bedroom dwelling. This represents an increase of just 5%, and not double as outlined by CDC, demonstrating that factoring the level of A27 contributions on a per bedroom basis does not result in a contribution that would be ‘directly related to the development’ nor ‘fairly and reasonably related in scale and kind’.

3.3 Additional Funding

3.3.1 Even though the proposed improvement package goes beyond the mitigation of development impacts and addresses existing issues / introduces additional network capacity, the SPD makes no indication that further alternative means of funding the improvements will be sought and introduces no mechanism to reduce the level of contribution sought from development should further funding awards be made.

3.3.2 National Highways has included the A27 Chichester By-pass in their current RIS 3 funding review. It is
acknowledged that there is no certainty at this time for inclusion of any scheme within the RIS3. However, funding was previously identified (c. £100m) towards improvement of the Chichester Bypass, which was subsequently lost as consensus could not be reached between the local authorities as to the preferred approach. Having previously been recognised as a location where intervention is
necessary, it is not unreasonable to assume that a funding award will be made.

3.3.3 Similarly, the SPD focusses solely on residential development, and it is unclear as to whether similar
contributions will be sought from other use classes which have the potential to increase usage of the A27. Clarity should be provided in respect to the level of contribution that may be sought from other floor space, to ensure fair and equitable mitigation of impacts consistent with the requires of CIL Reg 122.

SECTION 4 Conclusion

4.1 The principle of development funding mitigation required to accommodate planned growth is accepted, and the development of an SPD providing a clear means to calculate site specific contributions is welcomed.

4.2 However, the SPD fails to provide an appropriate mechanism for contributions to be secured in accordance with the CIL Reg 122 requirements, particularly those of ‘relatedness’ and ‘proportionality’.

4.3 To ensure that this can be achieved, the following recommendations are made:

1 Further modelling of traffic impacts should be undertaken through the Transport Study, allowing for ‘Decide and Provide’ principles to trip forecasting, a greater emphasis on sustainable travel and for changes in travel behaviour following the pandemic – some means
of sustainable mitigation are commented upon briefly within the Study, but it fails to build upon this.

2 Reconsider the mitigation strategy, to allow for infrastructure only that is necessary to mitigate the impacts of development and more cost effective means of mitigating the impacts of development, in line with the requirements of CIL Reg 122 and paragraphs 57 and 111 of the National Planning Policy Framework.

3 The artificial 535 dpa cap places an undue burden on planned development at the ‘tail end’ of the plan. The cap should be lifted and a greater quantum of development, of at least 700 dpa, be permitted.

4 Consider alternative means of deriving financial contributions that reflect the impact of development, recognising that there is not a linear relationship between the size of a dwelling and its trip generating properties.

5 Encourage, and make allowance for, the award of further funding streams to assist with delivery of the project. Provide clarity as to the level of contribution that may be sought from use classes other than residential.