Bedford Borough Transport Model Draft Local Plan Assessment Report
Plan for submission evidence base
Representation ID: 10257
Respondent: Central Bedfordshire Council
5. Approach to Modelling Preferred Growth Scenarios
5.1 Within our previous consultation response on the draft strategy options in 2021, we stated that we would want to ensure that the full extent of planned growth within the then recently adopted Central Bedfordshire Local Plan, has been taken into account when considering the growth options and their potential impacts. In deciding the sites, infrastructure and numbers of jobs to be modelled, an ‘uncertainty log’ is completed to inform what is included in each modelling scenario. It is not stated in the final iteration of the modelling when this was most recently completed so it would be useful to have sight of this document as it is likely that sites in the adopted CBC Local Plan that were not subject to a live application or planning consent at this time, may not be included in the impact assessment of the proposals and we would like to ensure the overall cross boundary impact of development in areas such as the A1 and A421 corridors will be captured fully.
5.2 If all relevant sites have not been included, we would request that some sensitivity testing is completed to include the impact of allocated sites within our Local Plan, particularly to inform the mitigation schemes to address cross boundary impact. We are happy to work with BBC to suggest the scope of this work.
5.3 In terms of the assumptions for opening years of major infrastructure in Central Bedfordshire which has been included in future scenarios, the estimated completion dates listed in the reports and shown below are unlikely to be achieved, particularly those listed that are linked to CBC development sites (namely the accesses for the Marston Valley site and the mitigation scheme related to the Marston Gate site). Whilst these schemes are featured in the applications for these sites, they are very much still under discussion and will differ from the eventual consented schemes and delivery timescales. Whilst it is currently anticipated that the Junction 13 improvements may meet the identified delivery date of 2025, it is considered that based upon most recent discussions, the Marston Valley Access Arrangements for phase 1 and 2 may not be delivered until at least 2025 and 2030 respectively.
5.4 Specifically in relation to the A6 to M1 Link Road, it was previously anticipated that the appointed contractor would start on site within the 2021-22 financial year. However, this has been delayed due to the need for CBC to exercise the use of our CPO powers to acquire all of the land required to ensure the delivery of the entire link road and avoid any uncertainty (in terms of land ownership). This will undoubtedly have an impact upon the delivery of the scheme which ultimately means the 2023 operational date for the link road referenced below is now unrealistic.
Figure 1- excerpt from Table 2.2, Bedford Borough Transport Model – New Settlements and the A6
5.5 Large proportions of the proposed growth are reliant on connection stages 2 (and 3 in some cases) of East West Rail being operational and this risk should be recognised within the evidence as it is as not yet known what will feature in the DCO, so delivery timescales are subject to uncertainty as indeed is the scheme itself. The reports do not make reference to the way the EWR scheme has been re-phased, in that some decisions about the future of the Marston Vale line will now form part of the Development Consent Order in addition to what was agreed through the Transport and Works Act Order for the Western Section.
5.6 With regard to potential mitigation options, the reports state that: ‘within this assessment of the proposed preferred strategy for the Local Plan 2040, widening of the A421 to three lanes between the A6 and A603 Junctions has been assumed. This extends the current three-lane section between the Western Bypass (Marsh Leys Junction) and the A6 to the east, with a new lane-gain / lane-drop arrangement assumed at the A603 Junction.’
5.7 In our view, assuming this is as a scheme which will be completed by 2030 for modelling purposes when there is no formal commitment to a scheme of that nature from National Highways nor any obvious funding stream or commitment for inclusion in RIS 3 is not acceptable, particularly when it is listed as a key mitigation scheme to deliver the growth strategy. It is also outside of the red line boundary in the DCO for the A428 Black Cat to Caxton Gibbet scheme. Whilst it is understood that assumptions are required for modelling purposes, this critical mitigation scheme has a very high level of uncertainty.
5.8 It appears that although extensive, the ‘key junctions’ list forming the main part of the assessment and listed in appendix N of ‘Assessment of Local Plan Options 2a-2d’ are all within the BBC boundary. We would like to see the full metrics for those that will be impacted by growth outside of the borough boundary, particularly in the CBC area.
5.9 We note that whilst the overall screen-lines validate, none of the Bedford rural links validate individually when looking to the south of Bedford, particularly on the Old Warden Screen-line and the Stewartby Screen-line in the PM peak. The statement is made that the overall screen-lines validate (as the differences between the flows on the individual links balance), however that would mean that any flow assumptions on the links passing through the individual screen-lines in question should be treated with caution.
5.10 We also have concerns about the public transport element of the model. It appears that the data for the model was collected in 2018, and there was no bus count data for boardings to allow for validation. The levels of patronage for bus and rail are likely to have undergone significant changes since the time the model was prepared due to the impacts of COVID 19; data reviewed by CBC suggests varying degrees of bus passenger recovery post COVID, dependant on the type of service. With this in mind, clarity is sought on the degree to which the impacts shown through the modelling work were linked to assessing the impact of public transport as a mitigation measure.
5.11 Of these scenarios tested, there are flow change diagrams provided for comparison. In Appendix A there are plots for reference case 2030 to 2040 (excluding mitigation) and also the difference between the excluding and including mitigation 2040 scenarios provided, but there do not appear to be plots showing a direct comparison between the 2040 reference case and the 2040 with mitigation scenario and this would be the ultimate end case in terms of comparative assessment. These need to be provided within the supporting evidence to present the full assessment of impact.
5.12 It is also not clear whether within the five iterations of modelling that were run, there was a retest of the future scenarios including the results of potential traffic reassignment, for example as a result of the scheme to widen the A421 south of Bedford. We would welcome some clarity on this as this would also be an important assessment to model the overall impact of growth plus the proposed mitigation package.
6. Particular Areas of Concern from Modelling Results
6.1 From the information provided, our primary concerns regarding the results of the modelling of the preferred growth option cover three broad locations on the highway network:
6.2 It is welcomed that our concerns around capacity of junctions on the A421 corridor has been highlighted by the modelling work. However, having reviewed the technical reports, we have serious concerns about the future performance of this strategically significant transport corridor.
6.3 The modelling outputs demonstrate that there will still be capacity issues on the network within Central Bedfordshire associated with the proposed growth, even when the proposed package of mitigation has been incorporated. In the PM peak hour, the forecasts for the 2040 Local Plan growth forecast including mitigation highlights unacceptable volume over capacity ratios on junctions of the A421 in the CBC area, which demonstrates that the mitigation strategy proposed is not dealing with this issue. There are also junctions on the A421 corridor within Bedford Borough which also appear to have reached full capacity even with the full suite of mitigation measures introduced.
6.4 The report also details the forecasted congestion at A421 / Western Bypass (Marsh Leys) Junction: additional delay and congestion is forecast on several approaches to this junction in all emerging preferred options. This is likely to be due to the quantum of growth assumed in each option to the south-west of Bedford in the area between the A421 and A6. Given the number of approaches and the constraints at the junction, there is unlikely to be scope to significantly improve the capacity at this location. Some minor improvements (such as further signalisation) may result in increased capacity at the junction; however, it may be necessary to consider interventions which remove traffic from this junction to address the additional delays forecast.
6.5 With these findings in mind, and the effect of the widening of the A421 south of Bedford unlocking suppressed demand, the strategy to mitigate the impact of the proposals in this location are severely lacking and needs revisiting and improving.
A1, Black Cat Junction and the A428
6.6 This part of the strategic road network was discussed at length during the CBC Local Plan examination hearings and through our own technical evidence base work we have identified various issues on the A1, caused by both background growth and our own future growth strategy. Our work identifies the A1 as being under significant pressure with the growth outlined in our adopted plan, so in particular the addition of a new settlement at Little Barford will only exacerbate these issues. Indeed, it is shown in the supporting evidence that the growth strategy results in unacceptable volume over capacity ratios (for example at Biggleswade South and Sandy) in the 2040 scenario with local plan growth and associated mitigation. There are no mitigation schemes in the final list for the preferred strategy that relate to the A1, which is at odds with these findings of the modelling.
6.7 It also is not clear why the mitigation strategy results in the movement of vehicles from Vinegar Hill onto the A1 (as per Figure A.19), or why this would also result in an increase in flows through Sandy, not least as the A428 Black Cat to Caxton Gibbet scheme is understood to have been included within the reference case. This should be revisited and made clear.
6.8 It is also noted that the locations for growth in this area are dependent on an EWR station coming forward. Whilst considering locations in close proximity to rail infrastructure is welcomed, it is important to be clear that the plans for EWR are still at consultation stage and a DCO application has yet to be submitted, and as such, there can be no certainty attached to the potential location of any new stations.
6.9 We also have concerns that the preferred growth strategy could lead to an erosion of the capacity of the A428 Black Cat to Caxton Gibbet scheme, which presumably has not been designed and tested considering new sites such as Little Barford. We understand that the infrastructure has been modelled as being in place by 2025, but we have concerns that the scheme’s level of future proofing could be eroded by the significant growth in the area proposed.
M1 Junction 13
6.10 It is stated that for the preferred option, and in particular for the AM Peak hour, the forecasts show that there is an increase in delay on the A421 southbound off-slip to M1 Junction 13 via Salford Road. High levels of congestion are forecast in this area in the reference case forecasts and therefore any additional traffic at this location will lead to an increase in delay. The forecast increases in delay at this location is likely to be predominately due to the additional traffic attracted to the corridor with the widening of the A421 to the south of Bedford.
6.11 Mitigation to accommodate the development proposed within the CBC Local Plan was agreed by Highways England for J13, but it is not clear that any additional capacity could be accommodated moving forward. This is a key junction, which will be impacted by growth within CBC, Milton Keynes (MK) and BBC and the severity of the future and indeed current issues are not addressed adequately within the supporting evidence.
6.12 Both the A1 and M1 junction 13 were considered during the CBC Local Plan examination, and capacity constraints were acknowledged, but the requirement for the BBC growth strategy to address and contribute to solving these issues is not addressed at all in the supporting evidence. It is considered that a resolution to these issues will require a strategic partnership approach due to amount of growth being proposed in this area from the different authorities, including Bedford, Milton Keynes and Central Bedfordshire, as well as due to the levels of growth that could be delivered within the area as a result of the EWR proposals and the resulting implications for the strategic road network.
Junctions over capacity in Central Bedfordshire
6.13 Modelling for the preferred option also indicates various junctions in Central Bedfordshire that will be close to or over capacity, with a volume-capacity ratio of greater than 95% and in several cases 100% or above (for example the junction of Bedford Road and Woburn Road at the parish boundary of Marston Moretaine and Lidlington). In addition to provision of a key junctions list detailing those outside the Bedford Borough Council boundary as well as within it as mentioned above, and notwithstanding the issue of model validation on some links, BBC should propose mitigations to address these issues and seek to ensure suitable funding is secured to enable solutions to be put in place.
7. Mitigation Strategy and Infrastructure Delivery Plan
7.1 The mitigation strategy for the preferred growth option falls short in a number of areas:
a) Overreliance on uncertain schemes and those outside of the authority’s control
b) No solutions to mitigate the negative impact of the mitigation proposals, such as releasing supressed demand back on to the A421 by widening it between the A6 and Cardington Road
c) No overall solution to cross boundary capacity issues on the A421
d) No consideration of the impacts on the A1 and the future function of this strategically important corridor. Bearing in mind the known constraints here, this would likely involve the need for large-scale intervention, such as realignment. CBC would welcome the opportunity to be involved in such work. As stated in our previous response, we would question whether growth could be considered in these locations without a commitment to such interventions, which would undoubtedly require government funding
e) No references to the ongoing study to look at potential schemes to deal holistically with issues at M1 junction 13, which should in part be funded from developer contributions related to sites in the submission plan such as Kempston Hardwick. This scheme, when developed, should also be referenced in the IDP. The scheme modelled in the reference case related to the Marston Gate development is small scale and related directly to the impact of that scheme and is also still subject to live application. Transport is not deemed a definite issue for discussion with Milton Keynes Council in the Duty to Cooperate statements - nor is J13 referenced in the MOU with National Highways (though the A1 is).
f) The plans for EWR are still at consultation stage and a DCO application has yet to be submitted, as such, there can be no certainty attached to the potential location of any new stations
7.2 We do however, support and welcome the approach to sustainable links such as bus routes between the intended new station at Stewartby Hardwick and Wixams station and would be very happy to discuss the nature of these routes for mutual benefit of our residents, but only as part of a robust mitigation strategy which covers not only the Bedford Borough area, but all areas that are deemed to be affected negatively by the preferred growth option outlined.
7.3 Central Bedfordshire Council first raised concerns about the findings of the initial modelling exercise at a Duty to Cooperate meeting held in February 2022. We appreciate that since that time we have had ongoing technical discussions with BBC Officers and their consultants and have been provided with further information which has been helpful to understand the issues in more detail. However, it is clear that a specific strategy is also required to work with neighbouring authorities such as CBC to agree a joint approach and this is yet to be addressed in any of the technical reports.
7.4 Despite the modelling report stating that: ‘this assessment forecasts that, based on the assumptions underpinning the Bedford Borough Transport Model, the potential site allocations for the proposed preferred strategy for the new Local Plan in 2040, and the inclusion of the proposed package of mitigation measures, average travel conditions do not worsen within the borough and does not result in locations where junction delays are forecast to increase significantly from those forecast at the end of the adopted Local Plan in 2030’ this is referring to ‘average’ conditions and those of Bedford Borough only, which is short sighted given the overall growth aspirations for the Arc area which is referenced in policy DS2.
7.5 The proposals, even when mitigated, have an unacceptable impact on the CBC highway network and an approach to rectify this is required as a matter of urgency.