Greater Cambridge Local Plan: Proposed Submission

Continued engagement on the Transport evidence base.

National Highways welcomes the opportunity to submit representations on the Proposed Submission of Greater Cambridge Local Plan 2024-2045. The Plan seeks to accommodate substantial growth, including provision for at least 48,069 new homes and 73,300 additional jobs over the plan period. Significant development is proposed at Cambridge East, Cambourne North, Grange Farm, North East Cambridge and a number of employment-focused allocations with direct or indirect implications for the Strategic Road Network (SRN).

National Highways is responsible for the operation, maintenance and improvement of the Strategic Road Network in England on behalf of the Secretary of State. Within and around Greater Cambridge, this includes the M11, A11, A14 and A428 corridors and associated junctions. National Highways remains committed to supporting sustainable economic growth and continuing constructive engagement with Greater Cambridge Shared Planning, Cambridgeshire County Council, the Cambridgeshire and Peterborough Combined Authority, developers and other stakeholders throughout plan preparation and examination.

Our handling of development plan consultations is informed by DfT Circular 01/2022: Strategic Road Network and the Delivery of Sustainable Development (‘the Circular’). This sets out how interactions with the SRN should be considered in the making of plans and development management proposals.

In addition to DfT Circular 01/2022, the response set out below is also in accordance with the NPPF and other relevant policies, which helps to ensure that the soundness of the Local Plan is being appropriately considered (from a transport perspective).

Summary Position
National Highways supports the objective of directing growth towards sustainable locations and recognises the emphasis placed within the Plan on public transport investment, active travel and reducing dependence on private car travel.

However, based on the evidence currently available, National Highways is not satisfied that the cumulative impacts of the proposed level of growth on the Strategic Road Network (SRN) have been fully assessed or that all mitigation requirements have been identified, tested, funded and incorporated into the Infrastructure Delivery Plan.

Consequently, National Highways has significant concerns regarding the soundness of the Plan in relation to effectiveness and justification. Nonetheless, it is acknowledged that discussions are ongoing and that the process of agreeing a Statement of Common Ground will commence following the Regulation 19 consultation.
These representations should be read alongside the findings of TN01, prepared by AECOM on behalf of National Highways. TN01 is appended to this letter.

Strategic Observations Strategic Transport Modelling
The most significant issue relates to the adequacy and transparency of the strategic modelling evidence supporting the development strategy. AECOM's review concludes that additional strategic and operational modelling evidence is required, together with supporting assumptions, validation information and sensitivity testing, to demonstrate that:
• the proposed level of growth can be accommodated on the SRN;
• cumulative impacts have been fully assessed;
• proposed trip budgets are robust and achievable;
• mitigation measures are effective and deliverable; and
• mitigation requirements are reflected within the Infrastructure Delivery Plan.

Whilst National Highways acknowledges the Plan’s reliance on trip budgets and monitor-and-manage approaches across several strategic allocations, such approaches must be supported by a transparent evidence base demonstrating how trip budgets have been derived, how compliance will be monitored, and what interventions will be implemented if trip budgets are exceeded. In accordance with DfT Circular 01/2022, strategic highway implications should be identified and addressed through the plan-making process rather than deferred to planning application stage. As presently drafted, a number of key elements remain insufficiently evidenced. These concerns are reflected within the requirements of DfT Circular 01/2022, which sets out expectations for strategic transport evidence and engagement with National Highways during plan-making.

•With regard to the DfT Circular 01/2022, a Local Plan should provide appropriate evidence base needs to ‘provide a robust assessment of any positive and negative impacts on the SRN and inform a transport strategy and the Strategic Environmental Assessment (SEA) for the study area that aligns with the safe operation and long-term integrity of the SRN’ (paragraph 26 of Circular 01/2022. Further to this, in accordance with paragraph 33, robust evidence is required including demand forecasting modelling of the future development. The models will inform the analysis of alternative solutions by accounting for the effects of possible mitigation scenarios and mode share shift. It should be noted that Paragraph 29 outlines where new connections and capacity enhancements to the SRN are considered necessary, these should be identified during the plan-making process and should identify appropriate mechanisms for the delivery of strategic highway infrastructure. It should be noted that there cannot be any presumption that the infrastructure will be funded through a future Road Investment Strategy (RIS).

Noise and Drainage
Aside from traffic generation from development sites, when land is allocated within proximity to the SRN, the increased number of residents can give rise to other issues. It is likely that these locations will be impacted by noise pollution from the SRN National Highways will not allow noise barriers, and other structures on its land. In addition, National Highways will not accept third party connections to its drainage systems as highlighted within paragraph 59 of the Circular 01/2022. Paragraph 59 also states that developments must not add extra run off to existing systems where existing informal or formal connections exist.

Conclusion
National Highways remains committed to working positively and collaboratively with Greater Cambridge Shared Planning and key stakeholders to support the progression of the Local Plan. Discussions are ongoing and we welcome the opportunity to engage with the Local Plan team regarding a Statement of Common Ground.

The accompanying AECOM Technical note should be used to address evidence gaps and be subject to further consultation with National Highways.

However, at the present time and whilst supporting the Plan’s sustainable movement objectives, National Highways is unable to conclude that the Plan is supported by sufficient evidence to demonstrate that the cumulative impacts of the proposed scale of development on the Strategic Road Network have been fully assessed or that all necessary mitigation measures have been identified and secured.

Continued engagement on the Transport evidence base.

Infrastructure Delivery and Monitoring
Policy I/IID: Infrastructure and delivery

The policy recognises that there are several mechanisms available to fund infrastructure and mitigation measures required to support planned growth and development allocations within the plan period.

Where infrastructure improvements on the SRN are required and are not already identified within the Road Investment Strategy (RIS), National Highways would expect such improvements to be delivered on a developer-led basis, where feasible. These measures should typically be secured through Section 278 Agreements under the Highways Act 1980.

National Highways would welcome explicit reference within the relevant policies to the requirement for developer-led SRN mitigation where necessary to support development proposals.

Infrastructure Delivery Plan (IDP)
SRN Infrastructure Requirements

Upon review of the Greater Cambridge Local Plan Infrastructure Delivery Plan (IDP) Proposed Submission (Regulation 19) Version (July 2026) and Appendix C: Site-Specific Infrastructure Delivery Proformas, the only SRN infrastructure currently identified as essential to support the Plan is the Caxton Gibbet junction improvement, which is being delivered as part of the A428 Black Cat to Caxton Gibbet Improvement Scheme and funded by National Highways.

However, through ongoing discussions with Greater Cambridge Planning Service, it has been suggested that additional capacity enhancements may be required on the A428 corridor beyond the Plan period.
Given that these potential requirements are anticipated to arise outside the Plan period, there is currently no reference within the IDP to any future improvement works that may be required along the A428 corridor.

Our review of the merge/diverge assessment contained within Appendix B of the CGSP Annex 1 Transport Strategy Addendum indicates that the forecast flow assessment supports consideration of enhanced merge and diverge arrangements at the Scotland Road/A428 merge and diverge locations.
Whilst this evidence suggests that future interventions may be required, the most appropriate solution has not yet been established. Further modelling and supporting evidence are required to determine the necessity of any improvements, design, timing and assurance that improvements are brought forward in a timely fashion in line with current capacity and proposed growth.

As set out above, National Highways has not yet been able to reach definitive conclusions regarding the impact of the proposed growth strategy on the SRN based on the evidence submitted to date.

National Highways requires further information and analysis to be provided for review and will continue to engage with Greater Cambridge Planning Service as Greater Cambridge progress their technical work and modelled scenarios.

Should capacity enhancements or mitigation measures ultimately be required to support the planned growth strategy, consideration should be given to identifying these within the IDP. Any such infrastructure would require further development and assessment in collaboration with National Highways to demonstrate that the proposed interventions are technically feasible, safe, environmentally acceptable and deliverable.

National Highways considers that all SRN-related mitigation identified through further assessment should be:
• clearly defined;
• costed;
• assigned to delivery bodies;
• phased appropriately;
• supported by realistic funding mechanisms; and
• incorporated within the Infrastructure Delivery Plan.
The Plan should also provide a comprehensive monitoring framework identifying:
• trip budget triggers;
• review mechanisms;
• intervention thresholds;
• governance arrangements; and
• responsibilities for implementation.

East West Rail Assumptions / Funding
Section C.6 (Cambourne and Cambourne North) of the Greater Cambridge Local Plan Infrastructure Delivery Plan (July 2026) identifies site-specific infrastructure requirements which are “essential” to supporting the planned growth at Cambourne and Cambourne North. However, the funding arrangements for several of these interventions remain uncertain. In particular, the Plan is reliant on infrastructure associated with the East West Rail (EWR) project. Whilst it is understood that discussions with EWR are ongoing, National Highways understands that the current Development Consent Order (DCO) proposals do not include all the infrastructure referenced within the Local Plan.

Further refinement of the funding strategy for the infrastructure required to support the vision-led growth strategy would provide greater confidence in the Plan's deliverability and viability. This is particularly important where infrastructure requirements have been identified, but the scope, responsibility for delivery, funding mechanisms, and cost estimates are still being developed.

Consideration should also be given to the programme and delivery timescales associated with EWR. A significant proportion of the proposed growth strategy appears to be dependent upon EWR delivering key enabling infrastructure, including the new Cambourne station, active travel connections, and associated highway infrastructure. Should the DCO process be delayed, infrastructure requirements not be included within the consented scheme, or construction and delivery timescales slip beyond those currently anticipated, there could be implications for the timely delivery of planned growth. It would therefore be valuable for the Council to set out any contingency arrangements should the required EWR infrastructure not be secured or delivered within the assumed timescales.

Continued engagement on the Transport evidence base.

Policy S/CBN: Cambourne North

National Highways recognises the strategic importance of Cambourne North and the opportunities arising from East West Rail and the Cambourne to Cambridge public transport corridor. However, Cambourne North represents one of the largest allocations within the Plan, ultimately proposed to deliver approximately 13,000 dwellings and substantial employment development.
An estimated 2,670 dwellings will be delivered in Cambourne North within the plan period. It is proposed that a further 10,450 dwellings will continue to develop beyond the plan period.

National Highways' principal concerns are:
• potential need to provide interventions on the A428 including new public transport and active travel bridges and potential changes to junctions and slip roads requiring additional mainline A428 lanes that are significant works without available funding streams or deliverability assessments;
• insufficient evidence regarding the derivation and validation of the MoDES
methodology;
• inadequate information regarding traffic distribution to affected SRN junctions;
• insufficient information regarding calibration and validation of the CaPCAM model;
• limited evidence demonstrating the ability of the A428 corridor and associated junctions to accommodate development traffic;
• lack of clarity regarding cumulative impacts alongside East West Rail and other strategic growth locations; and
• insufficient evidence regarding the accessibility and effectiveness of proposed mitigation measures.

The Plan should not rely solely on future monitoring arrangements. Evidence is required now to demonstrate that the allocation is deliverable and that any required mitigation can be secured and funded. National Highways therefore requests modifications requiring:
1. Clarifications on strategic modelling and operational modelling (junction assessment and merge-diverge). This is in order to demonstrate likely mitigation requirements on the SRN.
2. Provision of modelling assumptions and validation.
3. Quantification of development impacts at Caxton Gibbet, Cambourne Junction, Scotland Road and other affected SRN locations.
4. Identification of all necessary SRN mitigation measures and clarity on their scope and deliverability.
5. Inclusion of those measures within the Infrastructure Delivery Plan.
6. Ongoing engagement with National Highways regarding crossings, structures and infrastructure affecting the A428 corridor.

Further to the above, we recognise that technical work is ongoing regarding scenario testing for Cambourne North. We shall continue to engage with Greater Cambridge beyond the Regulation 19 consultation period.

Continued engagement on the Transport evidence base.

The policy includes an agreed trip budget framework and substantial commercial and residential intensification. National Highways remains concerned that additional evidence is required regarding:
• impacts on A14 Junction 33;
• cumulative interaction with wider growth proposals;
• robustness of proposed trip budget assumptions; and
• contingency measures should agreed trip budgets not be achieved.

National Highways therefore requests:
• further junction capacity assessment;
• sensitivity testing;
• identification of mitigation triggers;
• monitoring arrangements; and
• intervention measures linked to exceedance of trip budgets.

National Highways also reiterates that any environmental mitigation relating to A14 traffic impacts must be located outside the highway boundary unless otherwise agreed.

Continued engagement on the Transport evidence base.

This strategic allocation comprises approximately 4,500 homes and significant employment development adjacent to the A11 corridor. AECOM's review identifies a number of substantive concerns, including:
• absence of TRICS-based employment trip generation evidence;
• lack of TEMPro growth application and supporting assumptions;
• concerns regarding junction modelling methodology;
• uncertainty regarding internalisation assumptions and education trip assumptions;
• limited evidence demonstrating future operation of the A11/A1307 junction; and
• insufficient evidence regarding cumulative impacts on the SRN.
National Highways therefore requests that the transport evidence be updated and independently verified before the allocation can be considered fully justified.

Continued engagement on the Transport evidence base.

National Highways notes the proposed 220,000sqm employment allocation adjacent to Junction 25 of the A14.

Further evidence is required regarding:
• trip distribution assumptions;
• TEMPro growth application;
• operational modelling outputs;
• mitigation requirements at the A14/B1050 junction;
• accommodation of freight traffic; and
• future travel planning measures.

The allocation should only progress where evidence demonstrates that impacts on the SRN can be appropriately mitigated.

Continued engagement on the Transport evidence base.

The allocation proposes a major new city district including approximately 8,000 homes and significant employment development. Although the Plan includes an indicative trip budget, National Highways is not yet satisfied that sufficient operational assessment has been undertaken to
demonstrate impacts on:
• A14 Junctions 34 and 35;
• the wider A14 corridor;
• M11 corridor interactions;
• cumulative effects alongside neighbouring allocations; and
• resilience should trip targets not be achieved.

Further operational modelling and mitigation identification are therefore required.

Continued engagement on the Transport evidence base.

National Highways supports the principle of additional managed HGV parking provision in the area. However, the allocation is expected to generate substantial freight and employment traffic and further evidence is required regarding:
• trip generation;
• SRN trip distribution;
• impacts on the A14 Junction 24/24A complex;
• operational performance;
• mitigation requirements; and
• sustainable transport measures.

Compliance should be achieved with the expectations for Services as set out in Annex A of the DfT Circular 01/2022. An operational assessment should be undertaken and any resulting mitigation secured through the Plan.