Major Scheme Business Case Summary Report for Programme Entry

Transcription

1 Paper A Heart of South West Local Transport Board Major Scheme Business Case Summary Report for Programme Entry M5 Junction 25, Taunton July

2 SCHEME SUMMARY Scheme Name M5 Junction 25, Taunton Date 7 July 2016 Scheme Scheme Description The existing situation M5 Junction 25 (M5 J25) is a large five-arm grade separated roundabout with a 3-lane circulatory carriageway beneath the motorway mainline as shown in Error! Reference source not found.. The motorway off-slip arms operate under full time signal control to reduce traffic queuing back onto the motorway at peak times. To the east of the junction there is a signalised junction with Ruishton Lane which also forms the access to the Park and Ride site. The A358 is single carriageway here, with two westbound lanes and a single eastbound lane (restricted by the structure over the Blackbrook watercourse). There is a merge-in-turn in the eastbound direction immediately after the exit from Junction 25, and this is a source of congestion at peak times. East of the Park and Ride junction the road widens to two lanes in both directions but reduces back to a single lane through Henlade village; also a source of congestion at peak times. Henlade village is a declared Air Quality Management Area. Beyond Henlade village the A358 extends south east and connects with the A303 at Ilminster. To the west of Junction 25 the A358 is a dual carriageway (known as the Toneway corridor) which provides access to the Taunton urban area. Figure 1 Existing layout The growth aspirations for Taunton The Heart of the South West Strategic Economic Plan (SEP) establishes Taunton as one of the key urban centres around which a large proportion of growth is assumed to take place. The adopted Core Strategy (2012) for Taunton Deane outlines a requirement for 13,000 dwellings to be built within the Taunton Urban Area by In addition to these new homes the Core Strategy states that 9,500 jobs will be provided through a range of employment land uses. 2

3 The Taunton Deane adopted Core Strategy and submitted Site Allocations and Development Management Plan both refer to the need for a second Strategic Employment Site (SES) to complement other employment allocations within the borough. The preferred site for this development is to the south east of Junction 25. This development will cover a 25 hectare site and may include a Business Park and industrial units.it is estimated that the site will provide over 3000 jobs and hence a significant boost to the local economy. Highway capacity and traffic impact at Junction 25 are recognised as key constraints associated with the delivery of this potential development site. In December 2015 TDBC confirmed their intention to bring forward the SES with a commitment to develop and adopt a Local Development Order (LDO) for the site. Once in place the LDO is equivalent to planning consent for any uses which adhere to the LDO s parameters. TDBC have estimated that the LDO will be in place in mid-2017 The Existing Problems at M5 Junction 25 M5 Junction 25 is heavily used at peak times and carries a total traffic volume of around 5,000 vehicles during the weekday peak hours. Average hourly inter-peak volumes are in the order of 3,500 vehicles with about 6% of traffic being HGV s (the proportion of HGV s on A358 is 9%). Junction 25 experiences high levels of traffic congestion at peak times with queues frequently extending along the A358 towards Henlade and occasionally back up onto the mainline M5. The key problems at the junction can be summarised as follows: Some entries are not signal controlled and therefore have limited capacity when circulatory flows within the roundabout are high (there are not enough gaps in the traffic to allow vehicles to enter the roundabout). M5 Southbound off-slip entry is under pressure due to high motorway flow conflicting with high circulatory flow. Width restriction over the Blackbrook watercourse limits eastbound exit capacity on the A358. The junction has limited facilities for non-motorised users, a cycle and footpath runs around the southern side of the junction however users find crossing the southbound M5 on-slip difficult due to the lack of priority and accelerating vehicles The Proposed layout It is not possible to increase the capacity of the junction within its current footprint. Following consideration of a range of options the layout shown at Figure 2 below is proposed. The main components of the scheme are - A new link between A358 / Ruishton Lane / Park and Ride junction with footway /cycleway along one side and a new roundabout to the south of the park and ride site A new link between the new roundabout and the existing M5 J25 roundabout on an embankment and crossing Broughton Brook with a new structure with footway / cycleway along each side (not shown) Elongating the existing M5 J25 roundabout on the eastern side Widening the existing circulatory arms (underneath M5) to accommodate an additional lane Moving the pedestrian / cycle facility to behind the bridge supports by removing some of the sloping embankment. Signalisation of o M5 J25 / Blackbrook Park Ave o M5 J25 / A358 Toneway o M5 J25 / new link road Realignment of signals at M5 J25 / M5 Southbound off slip A toucan crossing on the new link road between new roundabout and M5 J25 roundabout close to the new roundabout. 3

4 Figure 2 Proposed layout Highways England are currently developing proposals for dualling the A358 between Ilminster and the M5 at Taunton, as part of the upgrading of the complete A303/A358 route between the M3 and M5 at Taunton to dual carriageway Express Way standard. The scheme for dualling the A358 is in the first Roads Investment Strategy, with a target commencement date in Spring The proposed route for the A358 will not be clear until Highways England initiate consultation later in The proposed M5 Junction 25 layout shown above would be compatible with a southern bypass route for Henlade. Scheme Objectives The scheme to improve capacity at M5 Junction 25 has four objectives:- Objective 1 - Support the economy in Taunton by facilitating the delivery of employment and residential development. Objective 2 Better manage peak hour traffic congestion at Junction 25 and improve access to Taunton and the motorway. Objective 3 Improve accessibility to Taunton and future development areas for pedestrians and cyclists. Objective 4 Reduce carbon emissions, compared to a non-intervention scenario. Summary of Options Assessment In developing the M5 Junction 25 proposals an Options Assessment report was produced which considered the following options:- Signalisation, widening of the circulating carriageway and realignment of entries Widening and extension of motorway slip roads A Haydon Lane link road to access the employment site A new motorway junction north of Junction 25 Enhancement of the existing park and ride service 4

5 Improved public transport along A358 corridor Demand management and smarter choices The OAR concluded that the first option, signalisation of the Junction 25 roundabout, was the most appropriate option. Stakeholders A Memorandum of Understanding has been developed and signed by partners working towards the development of the strategic employment site. Key stakeholders will include Taunton Deane Borough Council Summerfield Developments Highways England County and Borough Councillors General public There has not yet been a public consultation exercise about the M5 Junction 25 proposals. 5

6 FINANCIAL SUMMARY Main Expenditure Items ( m) 14/15 15/16 16/17 17/18 18/19 19/20 20/21 Total Design (inc surveys, site investigations etc) Preliminaries New link road and junctions Upgrades to existing roundabout Main contractors OH&P Contingency Inflation TOTAL SCHEME COST Scheme Funding Funding Source Funding Amount ( m) Total Local Contribution (Secured) Total Local Contribution (Unsecured) Total LTB Requirement TOTAL LTB Contribution Total Scheme Cost ( m) LTB Contribution ( m) From SEP Total Scheme Cost ( m) LTB Contribution ( m) Variation in Scheme Cost Variation in LTB Contribution ( m) 0 6

7 VALUE FOR MONEY STATEMENT Assessment Detail Initial BCR 10.8 The Business Case has been reviewed, discussed with Somerset, and an amended submission received. The forecasting and assessment use standard transport economics, compliant with WebTAG. There is some uncertainty in the assessment pending clarity from Highways England regarding the route and timing of the A358 dualling. Adjusted BCR 10.8 No other benefits monetised Non-Monetised Impacts Balance between beneficial impacts relating to travel and adverse relating to the local environment. No adjustment to BCR required Beneficial impacts from: Reliability Journey Quality Security Adverse impacts from: Noise (slight) Landscape (slight) Historic environment (moderate) Flooding (large) Water quality (slight) Key Risks, Sensitivities and Uncertainties in the Assessment There is a degree of uncertainty at present about the scale of quantified benefits which the scheme will deliver over time, pending a clearer understanding of the nature and timing of the A358 dualling. There is also some uncertainty about the cost of the Junction 25 scheme Sensitivity tests completed for Low and High development scenarios these give BCRs ranging from 6.3 to The Strategic Employment Site at Junction 25 is not included in the Core and Low growth scenarios, but is included in the High growth scenario. Further sensitivity tests were conducted to reflect the impact of the A358 dualling. The BCRs range from 10.0 if the A358 is dualled to Junction 25, to 3.2 if the dualling includes free flow slip roads linking the A358 directly with the M5 (south). While the current assessment is that the scheme would result in Very High Value for Money there is some risk that it may fall into the High category. Value for Money Category Very High 7

8 DELIVERABILITY Key Risks to Delivery The inter-relationship of the scheme with both the Strategic Employment Site and the Highways England A358 dualling scheme introduces significant risk to the timescale for delivery. There are a number of procedural risks The Local Development Order for the Strategic Employment site; planning consent for the Junction 25 scheme; land acquisition; approval to work on the Highways England network; drainage consents, etc. Financial risks the cost estimate is at this stage not fully developed and this introduces uncertainty. Environmental Impact Overall slight adverse impact on natural and historic environment. The main concerns are the impact on water resources and biodiversity, and on listed buildings and a regionally important archaeological heritage asset Social and Distributional Impact Overall the scheme is appraised to be beneficial in terms of its social impacts, with some being positive and the others neutral. Journey Quality shows significant social benefits, which safety and security are also positive. Physical activity, access to services and affordability are all neutral. RECOMMENDATION Independent Transport Advisor Recommendations It is recommended that the Local Transport Board:- 1) Approve Programme Entry for M5 Junction 25 Capacity Improvements as part of the LTB Programme; 2) Note that the proposed layout for the scheme is contingent upon the promotion of the Strategic Employment Site by Taunton Deane BC through a Local Development Order, and the development by Highways England of proposals for dualling the A358 between Ilminster and Taunton. 3) Note that the cost estimate for the scheme will be further refined, and in view of the inter-relationship with the Strategic Employment Site and A358 a further report is to be considered before the scale of the financial contribution from the Growth Deal 2 programme is determined. In the interim the indicative allocation remains at 12.90m 4) In view of the scale of the current estimate the promoters should make every effort to secure additional external funding. 8