West of England - Outline Business Case
Project Title: A4174/Wraxall Road Roundabout Signal Scheme
Project Owner: Richard Gillingham, South Gloucestershire Council
Promoter and partners: South Gloucestershire Council
Description of Intervention:
Wraxall Road Roundabout is located on the A4174 Avon Ring Road in South Gloucestershire south- east of Kingswood and north-west of Cadbury Heath (see below). The northern and southern arms of the roundabout are the dual carriageway A4174. The side-road arms of Wraxall Road Roundabout are Wraxall Road to the west and Tower Lane to the east.
A4174/Wraxall Road Roundabout
To the north the A4174 continues through the A420 Roundabout that provides access to Kingswood and forms a major arterial route into Bristol. Further north the A4174 continues through the East Fringe to the M32 and the A38 beyond that to the west. The A4174 terminates some 3.6km to the south at Hicks Gate Roundabout at the intersection between the A4174 and the A4 with the latter providing a key strategic route into Brislington and Bristol, to the west, and towards Bath in the east. Wraxall Road Roundabout currently experiences congestion with delays mainly on the side-road arms during the weekday morning peak period of nearly 30 seconds according to journey time data, and delays of over a minute on most approaches during the weekday evening peak period. Delays on the A4174 southbound approach are nearly one and half minutes during this period. There are a number of development sites in the North and East Fringe that are either committed or in the planning process. This includes major development of the Cribbs Patchway New Neighbourhood (CPNN), Charlton Hayes and at Harry Stoke. Whilst some distance from the site, the size of these developments could mean that they will still influence traffic volumes and affect travel behaviour in the vicinity of Wraxall Road Roundabout. In addition, the JSP Plan aims to build approximately 44,000 new homes beyond what has already been committed in the West of England between 2016 and 2036. In order to achieve this, five SDLs
West of England - Outline Business Case have been identified where additional large-scale greenfield development is proposed to occur. There are two SDLs that have potential significance in relation to Wraxall Road Roundabout, namely: • Land at Bath Road Brislington, with 750 new homes and mixed-use development and relocation of the Bath Road Park and Ride to land adjacent to Hicks Gate Roundabout; and, • North Keynsham, with 1,500 new homes and 50 hectares of employment floorspace proposed, new local centre, primary school and mixed tenure marina. This represents a total of 2,250 dwellings and 50 hectares of employment land to be located between two and three miles to the south of Wraxall Road Roundabout which is likely to increase demand for travel through the site. As well as land-use development, the Joint Transport Study (JTS), which has been prepared with the aim of providing a long-term direction for the transport system within the West of England up to 2036, also includes a proposal for a new motorway interchange at M4 Junction 18a. This scheme has the potential to significantly increase volumes using this section of the A4174 through providing a more direct link between this part of the A4174 and the M4. Collectively, future land use developments and proposals for the wider highway network are therefore likely to give rise to increased demand for travel on the highway network surrounding Wraxall Road Roundabout. At the same time businesses in the area, such as at the Bristol Bath Science Park, have a reasonable expectation that they will be able to function without the cost of traffic congestion unduly affecting their business operation. The proposed intervention to improve and signalise the roundabout is therefore required because Wraxall Road Roundabout is currently congested and is forecast to operate well in excess of capacity, particularly in the weekday peak periods by 2036. This will progressively cause increased levels of congestion at the roundabout with high levels of queueing and delay. This will act as a constraint to housing and employment growth in the area and increase costs to businesses operating within the area. The proposed scheme consists of modification of the existing uncontrolled roundabout layout to a fully signal-controlled ‘through-about’ arrangement. Specifically, it comprises the following elements: • Widening of the A4174 approaches to three lanes with four lanes at entry with three lanes providing high capacity for the dominant A4174 through-traffic movement; • Provision of a three-lane highway link for A4174 through-traffic across the middle of the roundabout; • A merge on exit arrangement for A4174 through-traffic from three lanes to two over a distance of circa 100m; • Traffic signals at each entry and conflict point would manage the flow of traffic safely and efficiently. The initial layout for the scheme is shown on drawing 673847.BK.36.01-007. The total cost of this scheme is estimated £5.855 million (base year price in 2018). It is expected that construction will start 2020 and be completed by 2022.
West of England - Outline Business Case
Market Failure (including why the private sector cannot resolve):
The West of England is failing to meet its economic potential, and housing and economic growth is sluggish, in part due to the need for improved transport infrastructure. The East Fringe of Bristol is a major economic hub within the region with the Bristol and Bath Science Park situated just north of Wraxall Road Roundabout. There are also two Strategic Development Locations (SDLs) located between two and three miles to the south of Wraxall Road Roundabout representing a total of 2,250 dwellings and 50 hectares of employment land. Wraxall Road Roundabout currently experiences congestion during weekday peak hours, particularly during the evening peak, and is forecast to experience severe congestion in future. The A4174, which passes through the roundabout, is a key strategic route in the Greater Bristol area providing a link between the A4 and Bath in the south to the M32 and the M4. The route also provides access to new housing and employment areas such as the Bristol and Bath Science Park. These congestion problems cannot be mitigated solely through private sector projects; public sector investment is needed as well. The increased capacity of critical pinch-points such as Wraxall Road Roundabout is essential to the development of the region’s infrastructure, to meet the housing and economic growth ambitions. It is therefore proposed that the roundabout be improved in order to increase capacity and facilitate growth. These improvements are proposed for the following reasons: • To reduce congestion, thereby reducing delays and removing barriers to economic growth.
State Aid Position
The scheme is considered to be state aid compliant in accordance with details provided in the State Aid: The Basics Guide issued by BIS in July 2015. The proposed project is for improvements to an existing roundabout which forms a part of the public highway network. This infrastructure is currently in the ownership of the Local Highway Authority and would remain so following improvements. The proposed improvements would benefit the local highway network and increase network resilience. We advise that WECA seek further legal advice to confirm the above position should they have any concerns in this regard.
Rationale including alignment with strategic aims:
The Strategic Economic Plan (SEP) prepared by West of England LEP outlines how the region will achieve sustainable economic growth over the plan period. Specifically, the SEP was prepared to support the West of England’s attempts to secure government funding to assist economic development in the region between 2015 and 2021 through the Local Growth Deals initiative. Within this context, the SEP aims to facilitate the creation of more than 25,000 jobs and develop an economy worth around £25bn per year (which also contributes some £10bn to the Treasury annually). The LEP vision is to encourage sustainable economic growth and the creation of substantial numbers of new private sector jobs. The SEP positions the West of England as ‘the city region of choice for a sustainable future’, based on the region’s legacy of innovation, world class university and research facilities, strong visitor economy and high quality of life. The SEP highlights that expansion of these sectors will be driven by a number of ‘levers of growth’, including investment and promotion and places and infrastructure. In particular, infrastructure is presented as a key enabler of growth in the region. The Wraxall Road Roundabout
West of England - Outline Business Case capacity improvements would contribute to the LEP vision by improving accessibility and reducing congestion, making the area more attractive to businesses. There are a number of adopted policies in the South Gloucestershire Core Strategy that the Wraxall Road Roundabout signal scheme is geared towards. These being: • Policy CS1 High Quality design – Developments should respect and enhance the character, distinctiveness and amenity of the site and its surroundings. Flood risk, personal safety and the disposal of waste materials should also be considered. • Policy CS5 Location of development – Most new developments will take place within the communities of North and East fringes of Bristol and the development of existing transport improvements such as the delivery of the Greater Bristol Bus Network and the planning for the WoE transport package and future schemes; • Policy CS2 Green Infrastructure - Seeks to ensure that existing and new Green Infrastructure is planned, delivered and managed as an integral part of creating sustainable communities and enhancing quality of life. • Policy CS7 Strategic Transport Infrastructure – Priority will be given to strategic infrastructure proposals that reduce congestion and improve accessibility by transport modes other than private cars.
Options appraisal:
The option generation process involved determining types of junction improvements that could be implemented. To assist in this process a series of scheme objectives were devised for the scheme, which were defined based on the current transport problem and future transport situation, as well as guiding policy documents. These objectives were as follows: • To improve traffic flow along the A4174 Ring Road and reduce delays to these arms; • To improve air quality in the vicinity of the roundabout compared to a Do-Nothing situation; • To improve the road safety performance of the roundabout; • To maintain capacity, or improve delays where possible, on Wraxall Road and Tower Road side-road arms; and • Facilitate/accommodate growth from housing and other infrastructure schemes. Based on these objectives, as well as examination of site opportunities and constraints carried out as part of the option generation process, three broad signal-controlled junction types were identified as potentially suitable solutions: • Fully/partially signalled roundabout; • A signal-controlled intersection/cross-roads; and • A signalled through-about. The initial sifting did not identify any ‘showstoppers’ that would prevent delivery. All options were therefore brought forward for further development and refinement. Four options were therefore developed to a level of detail such that their ability to meet the scheme objectives could be assessed and to enable appraisal under TAG. Table 1 summarises the five options developed.
West of England - Outline Business Case
Table 1: Options considered Option Description Option 1a Introduction of partial signal control with the Wraxall Road arm left uncontrolled Option 1b Introduction of full signal control to all roundabout entry arms Option 2 Replacement of the roundabout with a signal-controlled intersection Option 3 Replacement of the roundabout with a signal-controlled ‘through-about’
The operational impacts of the proposed improvement options were assessed using a VISSIM micro- simulation traffic model of the Wraxall Road Roundabout and the immediate surrounding highway network. This model simulates the weekday morning and evening peaks, as well as inter-peak period, and is based on 2018 observed traffic flows and conditions. The existing layout and four scheme options were tested for base year (2018) traffic flows, with selected options also tested for a 2036 forecast year (Option 1b was discarded following base year modelling because of similarity to Option 1a but comparatively poor performance in terms of congestion). Traffic growth between the base and forecast years was derived using the GBATS4 SATURN model. Cordon flows were extracted from the 2021 and 2036 with the latter including M4 Junction 18a. The difference between the 2021 and 2036 volumes was calculated to estimate growth between the base and 2036 forecast year. To ensure that growth reflected congestion present in the base VISSIM model, the SATURN growth was adjusted using a Congestion Index. The AM and PM base VISSIM models were run to derive mean peak hour speeds at network bottlenecks. This was divided by the free-flow speed to calculate a Congestion Index, which was applied to the growth. The resulting growth was applied to the peak hour and applied pro-rata to the shoulder hours retaining the original in-flow profile from the base models. The 2036 forecasting work also assumed that some form of improvement would be implemented at both the A4174/A420 and A4174/Marsham Way Roundabouts. This was so that the Wraxall Road options could be tested without capacity constraint at these adjacent roundabouts either limiting the arrival flow of traffic at Wraxall Road Roundabout, or congestion on the approaches extending back to and interfering with a scheme at Wraxall Road. In addition, to ensure that the traffic flows were robust the Saturn model included the proposals for M4 Junction 18a in the derivation of flows. This ensures that these improvements would be contemporary with other proposals and offers a suitable capacity solution for the assessment period. The results from the tests carried out showed that Options 1a and 3 would deliver an improvement in network conditions during the busier and more congested weekday PM peak period in the 2018 base year. This equates to a reduction in mean network delay per vehicle of nearly 15 seconds. However, during the relatively less trafficked AM and IP periods, these options all marginally increased queuing and delay at Wraxall Roundabout. This is caused by increased lost time due to the inter-green period under signal operation. Options 1b and 2 were predicted to provide little or no network benefit in 2018 and indeed were expected to increase localised queuing and delay in all periods modelled. The assessment of Option 1a, 2 and 3 in the 2036 forecast year showed that, because of traffic growth and increased congestion, all options provided some benefit over the existing layout, this included benefits during both peak and interpeak periods. Option 3 performed the best out of all the options tested under 2036 traffic delivering the lowest queuing and levels of delay on the A4174 arm in all periods, as well as reduced congestion on Tower Lane during the PM. However, this was at the
West of England - Outline Business Case cost of increased delays on the side-roads during the AM, although this was relatively minor compared with the benefits provided to the A4174. Option 1a also performed well in the forecast year, particularly with regard to operational conditions on the Wraxall Road approach. However, during the AM peak queuing and delays A4174 southbound arm were very high with this option providing no improvement over the existing layout. Option 2 similarly provided limited benefits for the A4174 southbound approach in the AM. At the same time, this option was expected to result in significant increases in queuing and delay on the Wraxall Road approach in most of the time periods modelled. All options have been subject to an environmental baseline, utilities, GI and FRA desktop studies which all have been compiled into the DfT EAST Options Five Case Assessment. The following points briefly summarise the assumptions of the economic case calculations used to derive the Present Value of Benefits (PVB), Net Present Value (NPV) and Benefit Cost Ratios (BCRs) for Options 1a, 2 and 3: • In line with WebTAG guidance, a proportional approach was taken in the derivation of Transport Economic Efficiency impacts associated with the scheme. Derivation of scheme benefits is based on the travel time savings obtained from the VISSIM model for the AM (07:00 – 09:59), IP (12:00-13:59) and PM (16:00 – 18:59) peak periods. Vehicle operating cost savings and accident cost savings have not been accounted for in the economic assessment; • Journey time changes were split by vehicle type; • Car based delay reductions were split across three trip purposes; • Travel time changes were converted to an annual total using an expansion factor of 252; • Scheme opening Year: 2022; • Modelled years: 2018 and 2036; • Appraisal period: 60 years; • Price base year for discounting: 2010; • Discount rate 3.5% for 30 years from scheme opening and 3% thereafter; • Optimism bias added to scheme costs: 44%; and • Value of Time assumptions WebTAG databook December 2017 (WebTAG Table A 1.3.2). The key outcomes of the EAST options assessment are summarised in Table 2 below. The assessment shows that the key differences between the options relate to traffic performance (which is the key issue to meet the objectives), and the economic case.
Table 2: Summary of how the scheme options meet the five cases
Option Strategic case Economic case Financial case Commercial case Management case (£m) Option 1a: Reasonable fit High BCR Financially Has a commercial Has a management case Partial signal with strategic Affordable case with the Wraxall objectives Rd. arm uncontrolled Option 2: Signal Reasonable fit High BCR Financially Has a commercial Has a management case controlled with strategic Affordable case intersection objectives
West of England - Outline Business Case
Option 3: Signal Excellent fit High BCR Financially Has a commercial Has a management case controlled with strategic Affordable case ‘through‐about’ objectives
Following examination of the four options, Option 3 signalled through-about is recommended to be taken forward at Wraxall Road Roundabout. This option provides the greatest benefit to traffic flow along the A4174 whilst delivering some benefit to the side-roads arm. It provides the greatest enhancement in terms of capacity and will facilitate growth better than the other options and provide improvements in journey time reliability and network resilience. As such, Option 3 therefore meets the strategic objectives of the scheme better than Options 1a and 2 whilst providing a high value for money with a BCR of 9.56.
Synergies with Other Projects/Programmes/Sector Initiatives:
The scheme will cater for developments that are currently underway as well as existing committed developments, whilst also allowing for some growth beyond this. The scheme will support strategic development at: • Land at Bath Road Brislington, with 750 new homes and mixed-use development and relocation of the Bath Road Park and Ride to land adjacent to Hicks Gate Roundabout; and, • North Keynsham, with 1,500 new home and 50 hectares of employment floorspace proposed, new local centre, primary school and mixed tenure marina. The scheme will also facilitate localised traffic growth associated with a potential new motorway junction at M4 Junction 18a.
Outcomes including wider socio-economic benefits:
The improvements to Wraxall Road Roundabout will increase capacity on a major node in the highway network, alleviating highway congestion in the short- and medium-term. This will reduce delays, thereby providing economic benefits, and reduce vehicle emissions, delivering a positive environmental impact and improving the sustainability of the road network. With ongoing development in employment and housing in the area, the improvements will stimulate growth and ensure growth occurs that could otherwise be prevented by the presence of a ‘pinch- point’ of restricted capacity within the highway network. In addition to the support of employment and housing growth described above, the scheme will also directly provide construction jobs. The economic assessment undertaken has monetised the benefits and costs of the scheme and suggested that the total present value of benefits (PVB) will be £51.1m compared to a total present value of costs (PVC) of £5.855m. This gives a net present value (NPV) of £45.76m and a high benefit- cost ratio (BCR) of 9.56. In addition, a desk-top based economic impact analysis has estimated the scheme impacts on Land Value Uplift, jobs and Gross Value Added (GVA). Land value uplift benefits associated with the roundabout improvements have not been included in this assessment as DfTs latest guidance states that the analysis presented in terms of jobs, GVA and homes can only be used to inform the strategic case of scheme, whilst the economic case can comprise of the metric Land Value Uplift as a sensitivity test BCR. However, the Land Value Uplift has been estimated at £15.5m for housing (2010 discounted prices) and £0.36m for employment land.
West of England - Outline Business Case
Project Spend Profile and Cost Breakdown
Development Phase Delivery Phase Total Cost (£000s): 18/19 19/20 20/21 21/22 - Capital Sought £161 £1,327 £2,549 £2,649 £6,687 Revenue Sought 0 0 0 0 0 Total £161 £1,327 £2,549 £2,649 £6,687 The figures in the table above include inflation. Costs are based on a 2018 base year price of £5.855 million (construction cost £5.238 million, the remainder preparation and design, supervision, SGC overhead and contingencies). A range of outturn costs has been calculated, based on differing ranges of inflation. The central case is used to present the project spend profile above, which assumes inflation of 2.5% per annum from 2018 to 2020, then 4% per annum thereafter. Scheme opening year is assumed to be 2022. Minimum forecast range: £6.2 million (inflation 1% below central case and delivery 1 year earlier). Maximum forecast range: £7.3 million (inflation 1% above central case and delivery 1 year later). Source and Commitment of Match Funding:
The proposed scheme would be classified as an early investment intended to provide the infrastructure to allow for JSP growth and unlock committed developments in the area (such as CPNN, Horizon 38 and FEA). The scheme is not specific to individual developments; thus match funding contributions have not been considered. The scheme preparation and construction costs are expected to be met by South Gloucestershire Council and recovered through a recharge to WECA.
Public Match Source Amount (£000’s) Secured/ Status
Private Source Amount (£000’s) Secured/ Status Match
Delivery Issues, Key Milestones, Track Record and State of Readiness:
Expected date of completion and submission of Full Business Spring 2020 Case
West of England - Outline Business Case
It is anticipated that the scheme be will under Permitted Development rights and will not require an Environmental Impact Assessment. The scheme is currently at an outline stage and further design work will need to be undertaken to produce a Final Business Case.
Dependencies, Key Risks and Viability: Please outline scheme dependencies, list 5 key risks and mitigation actions, and consideration of financial viability. (see risk rating key at end of form)
The scheme offers excellent value for money. The total scheme cost of £5.855 million for the recommended option represents a significant investment but is within the range expected for this scale of highway works. There are no dependencies that would impact on scheme delivery.
Top 5 current risks RAG Proposed mitigation measure Mitigated rating RAG rating 1. Changes to other schemes Amber Early understanding of the effects of Amber changes to other schemes. 2. Need to secure funding Amber Timely issue of final business case Amber illustrating scheme has a very high value for money. 3. Public support Amber Early consultation with the public Amber 4. Inflated or additional scheme Amber Most reliable estimates applied in cost Green costs schedule using rates verified by independent Quantity Surveyor. Utilities that may be impacted have been considered and included in the costs. Costs include contingency. 5. Buried services or other site Amber Buried services have been considered Green issues preventing delivery at this early stage in design along with other potential site constraints. Further consultation with statutory undertakers to be carried out as part of C3 enquiries at detailed design
Submitted by: Paul Macnamara
Contact details (email/phone): [email protected] / 01454 867829
Date of submission: 16 October 2018
West of England - Outline Business Case
Approval of the Outline Business Case:
Senior Responsible Name: Richard Gillingham Owner from promoting Signature: organisation
Date: 18/10/18
Section 151/Chief Name: Nina Philippidis Finance Officer of promoting Signature: organisation
Date: 22/10/18
Risk rating key:
West of England - Outline Business Case
Annex A: Logic Model
Context and Rationale Traffic signal improvements to A4174/Wraxall Road Roundabout to increase capacity and reduce queuing and delay. Supports growth committed in the South Gloucestershire Core Strategy and planned growth in the JSP. Supports existing and proposed sustainable transport infrastructure.
Objectives Resources/ Input Activities Outputs Direct & Indirect Impact Outcomes The aims/ objectives of the In order to achieve the In order to address the We anticipate that, once We anticipate that if We anticipate that if scheme are: set of activities to fulfil aims and objectives we accomplished these activities accomplished these outputs accomplished these activities these aims/ objectives will accomplish the will produce the following will lead to the following will lead to the following we need the following: following activities: deliverables: change: changes in service, organisation or community: • Improve traffic flow along • Scheme funding • Design • A higher-capacity signal • Reduced mean network • Support committed the A4174 Ring Road • Project team (e.g. • Utilities controlled through-about delay during peak provision of dwellings • To improve air quality in design and • Construction arrangement at the periods of around 100 and planned the vicinity of the engineering) • Project Management junction seconds and reduced employment growth roundabout • Stakeholder and • Environmental total vehicle delay of • Stronger local economy • To improve road safety public support mitigation approximately 400 hours • Additional indirect job • To maintain capacity, or • Site supervision by 2036; provision associated with reduce delays where • Reduced queuing and construction of the scheme possible, on side-road delays on the A4174 of
arms up to eight minutes during the busiest peak • Facilitate/accommodate period growth from housing and • Improved journey time other infrastructure reliability schemes • Reduced emissions