Non Technical Briefing Note

Non Technical Briefing Note

Somerset County Council Interim Assessment of Hinkley Point C

Development Impacts.

1. Introduction

Somerset County Council has been engaged with EDF Energy and their transport

consultants Savill Bird & Axon (SBA) for a considerable period of time undertaking joint work to develop a transport assessment (TA) through a Planning Performance

Agreement (PPA). The Council have appointed consultants JMP to undertake this

work on our behalf steered closely by County Council staff.

The required TA is wide ranging; broadly covering:

· detailed workforce and visitor assumptions;

· accommodation assumptions;

· materials and freight assumptions;

· vehicle routing and management;

· park and ride location and size calculations;

· studies of bus/ rail/ walking/ cycling opportunities;

· control mechanisms;

· travel plans;

· road safety impacts;

· traffic incident management;

· traffic congestion impacts and environmental impacts;

· design of the required highway access arrangements for specific sites; and

· required highway mitigation improvements.

The applicant’s progress in preparing the TA has at times been slow, particularly on the issue of traffic impact and the identification of required highway mitigation and

improvements. The applicant’s ‘Stage2a consultation’ proposals for highway improvements were not based on a robust quantification of the impacts of the development, and at that point the Council identified the following potential risks:

·  The Council may get to a point where we need to agree a statement of common ground and local impact report without a robust and jointly agreed evidence base having been completed; and

·  EDF may choose to submit a Development Consent Order to the Infrastructure Planning Commission containing sub-standard highways improvements that are not derived from a robust and jointly agreed evidence base.

In response to those risks the Council commissioned JMP to undertake an interim

assessment of the potential impacts of the Hinkley C development outside of the PPA process, using the agreed future year traffic models and using agreed development assumptions where possible, filling in any gaps in data with their own assumptions.

The purpose of this work was to enable the Council to reach a view on the likely scale of highway improvements that may be required to mitigate or offset the impact of the development, and address the strategic issue of whether required improvements were likely to comprise minor changes to the network as suggested by EDF, more significant changes possibly involving considerable land acquisition, or a Bridgwater Northern Bypass. Although the work has involved the development of individual junction designs for assessment purposes, it should be noted that these will need to further develop once EDF finalise a number of operational assumptions which at the time of writing are still not yet tied down.

Difficulties were experienced during the joint modelling activity in terms of getting the

future year traffic models to operate effectively due to high congestion forecasts. The

level of demand within the 2016 models was such that the models were unlikely to yield comparable results between a ‘with’ and a ‘without development’ scenario. The network appeared to be operating at or beyond capacity and was frequently saturated with little or no vehicular movement able to occur. The models were stabilised during April by JMP as part of the joint work by developing a method to spread a realistic amount of traffic into the ‘shoulders’ of the peak traffic hours, reflecting what would happen on the ground in congested conditions (i.e. people

travelling earlier and later to avoid severe delays). This ‘peak spreading’ results in

significant congestion outside of the ‘traditional’ peak hours and is estimated to result in a removal of about 2.5% of ‘trips’ from the network to reflect the fact that under these conditions some people will simply choose not to travel.

The future traffic situation has therefore been forecast as one where there is

considerable ‘peak spreading’ even before the Hinkley development traffic is added,

and the Council will need to consider the extent to which such extended periods of

congestion will be acceptable.

At the point of writing EDF have still not finalised the number of workers who will be

working in each of the shifts that they outlined in the ‘Stage2a consultation’ documents, and this decision could have a big impact on how many people will be travelling in the peak hours and the associated impact on congestion levels and required mitigation.

The ‘non-work’ travel undertaken by construction workers from their accommodation

has yet to be quantified so is not included in this assessment. The likely severe additional impact of workers leaving the area in the PM period on Fridays, and the

effect of seasonal traffic pressures particularly on the M5 have also yet to be properly

quantified and understood. The assessment therefore reflects an average weekday

situation.

2. Overview of the Outcomes of Somerset County Council’s Interim Assessment.

The outcomes of the interim assessment and a summary of the key outcomes and associated issues are set out below:

·  Peak hour traffic will worsen considerably by 2016 affecting more junctions and ‘spreading’ over longer periods in the day, even before the Hinkley development traffic is added, due to levels of development already committed. Some people will choose not to travel.

·  The Hinkley development traffic has a significant effect on congestion in 2016 leading to longer queues at more junctions. The development traffic will increase delay across the town by about 10% when averaged across the day over and above the already worsening conditions in 2016, with up to 40% increase in delay in the early evening.

·  EDF’s proposed ‘stage2a consultation’ highway improvement package does not mitigate or offset the Hinkley development traffic, indeed it worsens the situation and generally results in longer queues at more junctions although there are locations where some benefits are experienced. Two of the junction improvement schemes proposed by the applicant could not be made to work in the traffic model.

·  The proposed alternative highway improvement package performs much better than EDF’s stage2a package. This larger scale package resolves a large number of the traffic congestion issues created by the Hinkley development, performing particularly well in the PM period and providing a good degree of ‘betterment’ at many locations where it more than offsets the Hinkley impacts.

·  The larger scale package does not completely offset the Hinkley traffic impact on all junction approaches and residual problems remain particularly on the western end of the A39 in Bridgwater at West Street and on the eastbound approach to Broadway/ Taunton Road junction, as well as at A38/ Wylds Road, M5J23 and Bath Road/ Puriton Hill. Further refinements to the junction designs are currently underway and already showing improved performance so it is considered that many of the residual issues can be resolved.

·  It is important to note that although a package of junction improvements appears to be able to largely offset the impact of the Hinkley development, this will still leave levels of congestion that are significantly worse than today’s conditions, as discussed in the 2016 ‘reference case’.

·  An important issue will be to consider the extent to which the overall scale of works assumed in the larger scale package would be acceptable and deliverable on a realistic timescale given that significant land acquisition will be required.

·  As the larger scale package provides a degree of ‘betterment’ at certain locations beyond what is required to offset the Hinkley development it may be possible to slightly scale-back some of the land-take requirements for some improvement schemes whilst still mitigating the Hinkley traffic impact. Further work will be required to establish this once the overall level and distribution of development traffic is finalised by EDF.

·  The Bridgwater Northern Bypass also performs much better than EDF’s package and offsets the Hinkley development traffic at most locations.

·  The larger scale package provides a higher degree of ‘betterment’ (i.e. shorter traffic queues) than the bypass at a number of locations in Bridgwater and performs marginally better than the bypass in terms of reducing overall delay to traffic across the road network when considered cumulatively across all time periods.

·  The bypass is however more successful then the larger scale highway package as currently modelled, in terms of limiting the number of junctions experiencing increased traffic queues as a result of the Hinkley development. In other words the bypass results in fewer problems occurring but does not provide as much extra capacity at individual junctions as the larger scale package. This may change with further work on the larger scale package and of course a key consideration is also the deliverability of the bypass.

·  The assessment considers all the information available at the time it was undertaken but many EDF operational issues such as the proportion of workers allocated to shifts and visitor numbers have yet to be finalised. The assessment can therefore only be considered as an interim view on the implications for highways and transport. Even though certain matters such as seasonality and Friday peaks are not yet fully quantified, the assessment does robustly set out the strategic choices for transport which are unlikely to change although the precise nature of particular improvements at specific locations will of course evolve.

·  EDF are proposing to undertake a further stage of consultation on potential highway improvements and have indicated they may wish to use the outline junction improvement designs that have emerged from this interim assessment as a means of identifying the likely worse-case land acquisition requirements for consultation.