Greater Cambridge Local Plan Preferred Options

Please find comments from National Highways in response to your public consultation.

National Highways (NH) have been engaged with the Greater Cambridge Local Plan (GCLP) team for over a year, collaboratively engaging regarding the effect of the emerging GCLP on the Strategic Road Network (SRN) as the plan develops; and mitigation necessary to deliver the local plan proposals. National Highways has been appointed by the Secretary of State for Transport as a strategic highway company under the provisions of the Infrastructure Act 2015 and is the highway authority, traffic authority and street authority for the Strategic Road Network (SRN). The SRN is a critical national asset and as such we work to ensure that it operates and is managed in the public interest, both in respect of current activities and needs as well as in providing effective stewardship of its long-term operation and integrity.

There are a number of comments NH would like to address as part of the current consultation period, ending 13/12/2021 as detailed at point •First Proposals (preferred options) consultation (Autumn 2021); in the timetable below:

The Local Plan sets out the future land use and planning policies for the Greater Cambridge area
until 2041, establishing the areas for growth and the impact that this growth may have on the area
during this time period. The timeline for the Local Plan is as follows:
• First Conversation Consultation (Winter 2020);
• Publication of initial evidence base findings (Autumn 2020);
• First Proposals (preferred options) consultation (Autumn 2021);
• Draft Plan Consultation (Autumn 2022);
• Proposed Submission Plan Consultation (2023);
• Submission to Secretary of State (2023/2024); and
• Examination and Adoption.


1. The impact that each strategic allocation site would have on the SRN should be established in the Local Plan so that the impacts can be suitably mitigated.
2. The locations of the ‘Cambridge urban area other small allocations and windfall sites’ and ‘South Cambridgeshire other small allocations and windfall sites’ should be established and the level of growth and any impacts on the SRN should be identified so they can be suitably mitigated.
3. The locations for employment should be identified in the Local Plan and the impact that these sites would have on the SRN should be established and mitigated where required.
4. The reason for the discrepancy between housing growth figures in different parts of the Local Plan should be clarified.
5. The development quantum for all potential development site allocations should be clearly stated in the upcoming Local Plan.
6. Modelling or assessments should be undertaken regarding the development sites and their potential effects on the SRN as part of the further development of the Local Plan.
7. The Local Plan should include recommendations for all planned developments to include Transport Assessments taking into consideration the surrounding SRN network. Where there are junctions on the SRN where a significant increase in traffic flows is predicted, full junction capacity assessments should be undertaken taking into account committed developments and relevant future assessment years as per National Highways guidance set out in DfT Circular 02/2013, so that any impacts can
be identified and mitigated as necessary.
8. The inconsistency between the employment rates set out in the Employment Land and Economic Development Evidence Study and those set out in the Greater Cambridge Local Plan: Topic paper 1: Strategy (2021) should be explained.
9. The Infrastructure Delivery Plan should be updated to include any SRN junction mitigation works that are identified as part of the Local Plan junction modelling work.
10. There are a number of inconsistencies between different Local Plan documents with regard to the level of proposed housing and employment growth in Greater Cambridge. Clarification on the correct level of growth in Greater Cambridge should be provided.
11. There is insufficient information provided on the SRN to allow any conclusions to be made. It is recommended that further information is provided for the SRN links and junctions within the vicinity of the local plan area so that the base (and, hence the impact) of the proposed Local Plan can be fully understood.
12. SATURN modelling plots or outputs should be provided to National Highways for all SRN junctions in the vicinity of the Local Plan area, demonstrating likely changes in vehicle flows, volume over capacity ratio (V/C) changes and delays so that the locations where impacts are likely to be seen can be identified (and subsequently detailed junction modelling undertaken and impacts mitigated as necessary).


The Transport Evidence Report (TER) has been reviewed separately and NH provides their summary below:

Material concerns
1. There is a lack of evidence given in the TER to demonstrate the impact of the Local Plan proposals on the SRN. It is not possible for NH to understand the impacts of the performance of the SRN or its junctions compared to a typical 2041 baseline without the Local Plan.
2. Modelling has assumed that the M11 has been subject to material capacity enhancements between J8 and J14 (Girton interchange) as part of the Local Plan modelling. The detail of the enhancements assumed is unclear, but there are no M11 improvement schemes in RIS2, nor are there any significant schemes in the RIS3 pipeline.
It is likely the modelling overstates the capacity of the M11 and its junctions, which will understate the impact of the Local Plan development proposals and show an optimistic view of the SRN performance.

Moderate concerns
3. Details of the future network do not show the A14 Cambridge to Huntingdon Improvement Scheme. This scheme would not be included in either the 2015 (CSRM2 E-series) or 2019 (CSRM2 Fseries) Base Year models and so should be included in the forecasts. It is expected that this is an omission in terms of the documentation. However, this should be clarified as failure to have included the scheme would be a major concern.
4. It is noted that the report states the CSRM2 series Base Year models are compliant with DfT’s Transport Analysis Guidance (TAG).
However, no evidence of this is supplied and there is no understanding of the level of validation of the SRN in the Base Year. Clarification on the performance of the SRN in the Base Year should be sought to understand the level of uncertainty prior to the forecasts being developed.
5. The TER is lacking in detail on the methodology for developing the forecast year demand. Whilst it is not anticipated that the Local Plan growth will be constrained, it is unclear how the 2041 Baseline aligns to NTEM and if the assumed level of growth is appropriate. Information on the housing trajectories and employment levels
assumed should be supplied alongside this. The Uncertainty Log should be provided to support the 2041 Baseline assumptions.
6. There is no detail on how the internalisation of jobs assumed within the Greater Cambridge Local Plan modelling compares to internalisation levels achieved elsewhere (either best practice, or elsewhere in the local area). On this basis it is not possible to gauge whether the levels assumed are appropriate or if an optimistic assumption has been taken. Clarification on the levels of internalisation assumed and how this applied to real-world outturn should be supplied.

Minor concerns
7. The extent to which the supply and demand assumptions were reviewed between the Options assessment and the Preferred Options testing is unclear. Guidance from the DfT (TAG) will have changed in this period, as – potentially – will scheme details/assumptions from both national and local promoters.
8. Within the Preferred Option reporting, comparisons to a 2015 base are made despite the text noting the model has been updated to a 2019 base year. Likewise, no evidence of the level of validation achieved for this updated model and how this is aligned to TAG guidance has been presented. Clarification on the comparisons should be provided as well as evidence on the level of validation achieved.

National Highways look forward to further engagement on the proposals, in relation to the comments made herein.