Heart of South West Local Transport Board M5 Junction 25 Capacity Improvements Major Scheme Business Case - June 2016
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Heart of South West Local Transport Board M5 Junction 25 Capacity Improvements Major Scheme Business Case June 2016 1
STRATEGIC CASE
Scheme Name M5 Junction 25 Capacity Improvements Date May 2016
Case for Change
Strategic Fit
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 Figure 1. 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. Along this corridor there is a roundabout junction that provides access to the Hankridge Farm retail
park and a large signalised crossroads junction that links the A358 with the A38 route to Monkton Heathfield and Bridgwater
beyond.
Figure 1 Existing arrangement
2
The growth aspirations for Taunton
The Heart of the South West Strategic Economic Plan (SEP) 2014 – 2020 establishes Taunton is one of the key urban
centres around which a large proportion of growth is assumed to take place.
The SEP also recognises that junctions along the M5 motorway are at or reaching capacity and therefore new development
close to these junctions cannot take place without associated infrastructure improvements.
The SEP shows that the HotSW area has a lack of supply of commercial office space compared to the average for the rest
of the England. The strategy supports an increase in the supply of the right types of sites in the right areas to be attractive to
business.
The adopted Core Strategy (2012) for Taunton Deane outlines a requirement for 13,000 dwellings to be built within the
Taunton Urban Area by 2028. The latest Census data indicates that there are currently around 50,000 dwellings in Taunton
Deane so this represents an increase of approximately 27%. In addition to these new homes the Core Strategy states that
9,500 jobs will be provided through a range of employment land uses. The most recent Census data (2011) indicates around
54,000 people in employment within Taunton Deane in 2011, so this is equivalent to a 15% growth in employment
opportunities.
Key strategic sites within Taunton include Monkton Heathfield, Nerrols Farm, Comeytrowe and Staplegrove; these are
shown in
Figure 2. A number of smaller sites are also proposed across the town. Of these development sites the Monkton Heathfield
urban extension (4,500 dwellings and 40,000 sqm of employment land uses) is located closest to Junction 25, however all of
the development sites would be affected by (and have an impact on) the junction because it forms the main strategic access
between the town, the motorway network and the A303 strategic route. Junction 25 is the main gateway to Taunton from
the strategic road network as well as being the point at which the two strategic routes between London and the South West
join. This makes it a focal point for journeys into and out of Taunton for business, goods, commuters and leisure. The retail
and business parks in close proximity of the junction are afforded easy access and this makes them very attractive and very
popular.
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, although eventual land uses have not been identified at this time however
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 cemented the intention to bring forward the SES with a commitment to develop and adopt a Local
Development Order (LDO) for the site. In planning terms this action sets the policy intent and increases the level of certainty
that the site will be delivered. 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. A key consideration for the LDO is
likely to be certainty of infrastructure improvements at M5 J25.
3
Figure 2 Key strategic development sites
The Taunton transport package
The key to managing growth in Taunton is a package of transport measures across a broad range of modes that provide
opportunities for travel. Taunton has an excellent base level of commuting by non-motorised modes and the strategy for
managing growth is set in this context. Whilst most commuting trips are short Taunton is also a location of inward
commuting from the surrounding area and outward commuting to Bristol and Exeter.
Table 1 Mode share for journeys to work (2011 census –workday population)
Taunton Deane South West England
Work mainly at or from 11% 13% 10%
home
Underground, metro, 0% 0% 4%
light rail or tram
Train 1% 1% 5%
Bus, minibus or coach 3% 5% 7%
Taxi 0% 0% 0%
Motorcycle, scooter or 1% 1% 1%
moped
Driving a car or van 59% 59% 54%
4
Passenger in a car or 5% 5% 5%
van
Bicycle 6% 3% 3%
On foot 13% 12% 10%
Other method of travel 0% 0% 0%
to work
A number of key studies have taken place that shape the needs and set out the intentions regarding infrastructure
improvements and non-infrastructure activities that form the Taunton transport package. This work included robust transport
modelling processes and culminated in the Bridgwater, Taunton and Wellington Future Transport Strategy 2011 – 2026
(http://www.somerset.gov.uk/EasySiteWeb/GatewayLink.aspx?alId=43105). The strategy considers a number of scenarios
and makes the case for investment to be targeted -
new or improved cycling and walking routes
improvements to increase public transport use and reduce car reliance
improvements to intelligent transport technology to help direct travellers and manage roads more effectively
new highways infrastructure to ease congestion at pinch points
Walking and
cycling
Intelligent
transport
systems
Public New
transport infrastructure
The strategy identified specific infrastructure improvements; an extract of the strategy is included within appendix 1 to show
the location of these improvements. In terms of a spatial strategy the improvements are targeted at the growth areas and on
the key corridors into Taunton town. The River Tone and the main railway line bisect Taunton and these present key
challenges for both motorised and non-motorised users. As part of the strategy SCC has invested in a number of different
crossing points to improve the permeability of the town and increase resilience in the transport network.
Improvements at M5 Junction 25 are a key piece in the Taunton transport puzzle; other schemes that lock in the benefits of
this project are Toneway Corridor capacity improvements, the recently opened Monkton Heathfield Eastern Relief Road and
planned Monkton Heathfield Western Relief Road
The improvements at M5 J25 unlock the strategic employment site but moreover provide for growth across the town.
Implications of not changing
The potential implications of traffic growth at Junction 25 were considered as part of work undertaken by Somerset County
and Taunton Deane Borough Council in 2014 to assess the preferred site allocations outlined in the draft Site Allocations
and Development Management Plan. The full report is included as appendix 2
This assessment work was undertaken using the Taunton Strategic Traffic Model which is a SATURN assignment model
5
covering Taunton, Wellington and Bridgwater. Traffic forecasts for the horizon year were prepared by point loading into the
model the traffic generated by each of the development sites in the Plan, and adding further background growth in line with
TEMPRO forecasts.
This assessment identified Junction 25 as one of a series of junctions that would need improvement in order to
accommodate the proposed level of growth within Taunton between the present day and the horizon year of the Taunton
Deane Core Strategy (2028).
In terms of traffic volumes, it is forecast that the total peak hour entry flow at Junction 25 would increase to 6,500-7,000 by
2028. This would exacerbate the existing congestion problem, extending the length of queues and making the peak periods
longer and more severe. It is also clear from the traffic model that there would be an increase in the amount of traffic ‘rat-
running’ to avoid congestion at Junction 25 and therefore the overall level of traffic demand at the junction is potentially even
higher than these forecasts. The traffic model indicates that, without intervention, the junction will experience a worsening of
the issues that are evident in the present day. In particular, the traffic model highlights the following:
Insufficient capacity at the M5 southbound off-slip signals.
Significant delay on the A358 westbound approach, with or without the Strategic Employment Site.
An increase in delay to exit Blackbrook Business Park.
Queues and delay on the Toneway eastbound approach.
The resulting reduction in the efficiency of the highway network will increase the costs to businesses that rely on the junction
for their operations and a reduced reliability.
More recently work to update the Taunton Strategic Traffic Model and undertake forecasts for future scenarios has
demonstrated the impact of future growth on the highway network (appendix 11 contains the forecasting report). In the core
scenario the traffic is forecast to grow by 22.6% in the AM peak and 22.3% in the PM peak between 2014 and 2033. This
growth leads to a subsequent reduction in traffic speeds in the peak hours of 13% and 12% respectively.
The forecasts for traffic on the network around J25 are broadly similar to the underlying growth levels however it is greater
on some routes than others; for example:
Traffic on the A358 (through Henlade village) is only predicted to increase by 3% over the period up to 2018 and
then by a further 6% between 2018 and 2033. This is notably lower than for other links in the surrounding network
and is due to capacity constraints at Junction 25 which limit the amount that traffic can grow.
The flow on Haydon Lane (which is an alternative route into and out of Taunton) shows a much higher increase than
the A358 in both future years with traffic increasing by around 40% by 2033. This route is absorbing traffic which
would prefer to use the A358 if there were more capacity and less delays.
Traffic growth on the Toneway corridor is also much higher than the A358 with an increase of up to 25% over the
period 2014 to 2033. As traffic growth on the A358 is limited, this additional traffic on this route is mostly due to
additional traffic from the M5.
Traffic flow on the M5 is predicted to increase by up to 23% between 2014 and 2033 and is similar in both future
years to the overall level of growth across the modelled area.
The need for the Strategic Employment Site
SCC has produced a separate topic paper (appendix 3) to demonstrate the drivers behind the Strategic Employment Site at
J25. Whilst there are sites available in Taunton they do not fulfil the strategic need; they are not appropriately located for
high quality employment opportunities to be delivered; the ‘need’ for the site is qualitative.
Based on the employment sector forecasts, and qualitative input from stakeholder and business consultations it is expected
that higher value office based sectors, combined with research and education uses to be the type of employment space
most appropriate to Taunton, and that which is most likely to be attracted to invest in space at Junction 25. This reflects the
site’s access to the higher skilled resident workers within Taunton and surrounding villages; some of whom have been
travelling long distances to work in Bristol and Exeter. It also reflects the development at Hinkley Point C, the expansion of
the local college and the potential relocations of jobs, particularly higher valued jobs. Office based, and knowledge based
employment is increasing nationally, and along with service based sectors, these jobs are shifting the UK economy away
from its industrial heritage and a dominance of blue collar industries.
There have been significant levels of investment to progress the site by the local authorities and the site developer;
demonstrating the commitment to bring the site forward based on the demonstrated need. A Memorandum of Understanding
is in place between Taunton Deane Borough Council, Summerfield Developments, Highways England, Somerset County
Council, Environment Agency and Heart of the South West Local Enterprise Partnership (HotSW LEP) to support the
delivery of the employment site.
6
HotSW LEP has clearly expressed continued support for the site to be developed to boost growth in the area. The recent
decision by TDBC to expedite the delivery of the site using a Local Development Order further validates the need for the site
in the context of available development land in and around Taunton.
The implications of the employment site
The specific implications of the employment site have been tested in two ways, the traffic impacts and the scheme design
impacts.
An assessment of the impact of the SES carried out by Parsons Brinkerhoff (appendix 4) indicated that even without
development at the employment site, several of the approaches at the junction would be likely to operate over-capacity in
the future, and therefore very little spare capacity would be available to accommodate additional traffic demand. The
assessment concluded that the main impacts of the SES were to:
Worsen the M5 southbound offslip at Junction 25 – this approach would operate over-capacity during the AM peak
period due to traffic heading towards the SES on the slip road and circulatory carriageway.
Worsen the A358 westbound approach (from Henlade) at Junction 25 – this approach would operate over-capacity
in the AM peak with or without the SES site, but it would become significantly over-capacity in the PM peak as well
due to employee trips departing the SES.
Worsen the A358 eastbound (Toneway) at Junction 25 – this approach would operate over-capacity in the PM peak
with or without the SES site, but it would become over-capacity in the AM peak as well due to employee trips
heading towards the SES.
Increase rat running into/out of Taunton via alternative routes such as Haydon Lane and Creech St Michael.
Increase traffic flow along the Toneway corridor.
On the basis of this assessment SCC commissioned Parsons Brinckerhoff to consider potential mitigation options that would
enable the delivery of the SES (appendix 5). The options considered are shown in Table 2
Table 2 Mitigation Options Considered for SES traffic impact
Scheme Details Objective
J25 Signalisation Full signalisation of Junction 25, To provide additional capacity at
including elongation and widening of Junction 25 to offset additional traffic
circulatory carriageway. demand to/from SES.
Haydon Link Road Provision of a new link road between To provide an alternative route between
the A358 and Haydon Lane. Taunton and the SES that would
reduce traffic impact at Junction 25.
The study concluded –
The need for full signalisation of the junction (including associated widening and elongation)
The Haydon Lane Link Road (if implemented on its own) would reduce flow along the Toneway corridor but would
not have a significant beneficial impact to Junction 25
The Haydon Lane scheme would require improvements to other junctions along the routes into Taunton.
There is likely to be additional benefit to Junction 25 if both the signalisation and Haydon Lane link schemes are
implemented together as mitigation options.
Problem Identification
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. Journey time surveys were carried out along the A358
between the A358/A378 Thornfalcon junction and the M5 Junction 25 in 2012 to show the difference between peak and free
flow conditions. The greatest variation on journey times was recorded in the AM peak period. The shortest recorded journey
duration on the AM peak period was 35 seconds and the longest journey was 8 minutes 16 seconds. The average journey
duration during the AM peak was 2 minutes 41 seconds
7
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
route is unpleasant to use and perceived as dangerous. This will act as a barrier to walking and cycling in a town that
currently has a better than the national average share of commuting journeys by these modes.
As indicated in the previous section the strategic modelling that considered the implications of the SES determined that
without intervention the junction will experience a worsening of the issues that are evident in the present day. In particular,
the traffic model highlights the following:
Insufficient capacity at the M5 southbound off-slip signals.
Significant delay on the A358 westbound approach, with or without the Strategic Employment Site.
An increase in delay to exit Blackbrook Business Park.
Queues and delay on the Toneway eastbound approach.
8Objectives and Outputs
The Options Appraisal Report (appendix 6) set out the objectives of the scheme however prior to the submission of this business case SCC has taken the opportunity to
review the objectives and has made minor changes to objectives 2 and 4.
Objective 2 originally sought to “Reduce peak hour traffic congestion at Junction 25 and improve access to Taunton and the motorway”; SCC considers this to be very difficult
to achieve a reduction in congestion whilst still promoting growth. The amended objective remains challenging and demonstrates benefits of the scheme.
With regard to objective 4, this originally sought to compare CO2 emissions across Taunton; it is likely that the benefits of the J25 improvement scheme would be masked by
increases in CO2 across Taunton caused by growth and therefore the objective has been revised. The final objectives for the scheme are set out in
Table 3.
Table 3 Scheme Objectives
Measure of Success Timescale Indicators Dependencies /
Risks / Constraints
Objective 1 - Support the economy Delivery of housing and Five year period Housing numbers / employment Dependent on
in Taunton by facilitating the employment land as indicated by following scheme land delivered prevailing economic
delivery of employment and the Local Plan. opening conditions
residential development.
Objective 2 – Better manage peak Increased throughput of traffic. Five year period ATC data.
hour traffic congestion at Junction Reduced journey time through the following scheme Journey time data extracted
25 and improve access to Taunton junction during the peak hours opening from Dft’s JT datasets
and the motorway. (compared to forecasts
without the scheme in place)
Objective 3 – Improve accessibility Increase in pedestrian and cyclist Five year period Automatic cycle counters Pedestrian and cycle
to Taunton and future development movements through the following scheme provision will be
areas for pedestrians and cyclists. junction using pedestrian and opening improved however it is
cyclist facilities provided by the unlikely to be a step
scheme change due to the
constraints
Objective 4 – Reduce carbon Reduction in emissions shown Five year period Traffic data and DfT Local Growth is likely to
emissions, compared to a non- using DfT Local Authority Basic following scheme Authority Basic Carbon Tool. increase traffic flow.
intervention scenario. Carbon Tool (in comparison with opening
a ‘Do Minimum’ scenario)
9Summary
Problems Scheme Objective Organisation’s Objective Contribution of Scheme
Proposal
Congestion as Improve accessibility to reduce
constraint on Supporting journey time to nearby
1 Ensuring economic well being
employment and economic growth employment and residential
housing development developments
Increase capacity and
Peak time congestion Alleviating Living sustainably, staying introduce signalisation to
2
and queuing congestion safe, being healthy reduce peak time delay and
reduce queues
Increase capacity and
establish segregated
3 Safety issues Safer travel Staying safe pedestrian and cycle routes to
reduce the severity of
collisions
Outputs
The junction was identified for requiring intervention to support the Core Strategy growth as part of the Infrastructure
Delivery Plan which is forecast to deliver 13,000 dwellings. Monkton Heathfield development is closely located to J25; whilst
J25 improvements will not directly enable growth on this site to take place the additional capacity will support the growth by
maintaining existing levels of performance. The strategic employment site will deliver up to 2750 jobs in phased approach;
this is set out in Table 4.
Table 4 Scheme Outputs
Scheme 2016/17 2017/18 2018/19 2019/2020 2020/21 2021+ Total
Outputs
Total 0 0 0 1 4 19 24
development
land (Ha)
Jobs created 0 0 0 150 600 2000 2750
Commercial 0 0 0 30000 1000000 250000 155000
Floor Space
(SQFT)
Businesses 0 0 0 5 15 50 70
created or
safeguarded
Total New 0 0 0 0 0 0 0
Homes
10The Scheme
The Options Appraisal Report sets out the high level options that were considered in advance of the decision for a road
improvement scheme to be developed. This work considered the problems, set objectives and assessed a range of
transportation options to solve the long term problems.
During the design process a more detailed analysis of options has been undertaken in order to achieve the preferred
package. This analysis considered the main constraints, benefits and costs of the various infrastructure improvements to
find the best package. Figure 3 shows a simplified version of the thought process that led to the preferred design.
The preferred option and lower cost alternatives have been discussed with Summerfield and with TDBC as key
stakeholders. A summary of this process is provided in Table 3. Whilst delivering a lower cost option would be preferable it
is essential that the scheme delivers the maximum value for the public investment. This not only includes providing
additional capacity for growth and the access to the SES but also potentially supporting Highways England on the A358
dualling scheme.
Fundamental to getting roundabouts to work efficiently is managing the amount of traffic that is circulating at any one point in
time, if too much traffic is allowed into the system then it will jam up. The preferred option provides capacity for growth
around the existing J25 roundabout by elongating and widening the road space; this allows more vehicles onto the
roundabout at any one time. The main limitation of the existing roundabout is the A358 eastbound exit (at the Toby
Carvery); the culvert that bridges the Broughton Brook is only wide enough for three lanes of traffic, one of which is
eastbound. This narrowing requires traffic to merge and limits the throughput of the whole junction because there is such a
large demand for this exit. The preferred option removes this constraint and this action, combined with the other changes to
the roundabout mean there is an increase in available capacity.
The scope of the improvements is shown in appendix 7. 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.
o 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 Southbouth off slip
A new toucan crossing on new link road between new roundabout and M5 J25 roundabout close to the new
roundabout.
11Figure 3 Scheme Development Process
12Figure 4 Summary of Cost Reduction Options Considered
Scheme Description / Diagram Objectives TDBC comments Summerfield Commentary
option Growth Congestion Walking and comments
Cycling
1 The option diverts the A358 westbound traffic onto a new link across the Delivers some Increased capacity at New TDBC would not Does not provide This is the lowest cost option to deliver an improvement
western edge of the Gateway park and ride site, through farm land and joins wider growth the main junction will infrastructure support this option suitable access to to J25.
the roundabout at M5 J25 between the existing A358 entrance and the but not J25 provide for additional to be because it would SES Does not deliver the growth objective as does not
southbound motorway on-slip. The link will have two lanes along its entire Strategic throughput of provided not deliver the SES. provide access for SES.
length and there are no junctions proposed off the link, traffic would flow in Employment vehicles. Due to along new Unclear where local contribution would come from
in a westbound direction. Site local rat running it is link, existing which could render this option undeliverable.
likely that some infrastructure Will need additional investment to provide access to
congestion will to be SES; delivering this will cause disruption to all
remain at the upgraded westbound A358 traffic.
junction however it where The option was not costed as it was discounted
will have the ability to possible. because it does not have local support and does not
deal with additional deliver all of the objectives.
vehicles during the
peak periods.
2 The same as option 1 but provides a roundabout as an access to the Delivers some Increased capacity at New TDBC do not have Whilst it provides The additional cost comes with the benefit of providing
strategic employment site. wider growth the main junction will infrastructure a high level of access this will not a point of access for the strategic employment site
and SES provide for additional to be support for this be seen as high however the arrangement is far from ideal. All SES
throughput of provided scheme; whilst it quality access and traffic from Taunton will need to travel via the A358 and
vehicles however all along new could deliver the will be seen as a turn right at Ruishton Lane and past the Park and Ride;
Eastbound traffic link, existing SES it does not negative to putting additional pressure on this junction.
from SES will need infrastructure provide longer term potential occupiers Furthermore, all traffic from SES travelling east along
to go through the to be growth and will and sub-standard A358 will need to go all the way around the main
main roundabout upgraded require future compared to other roundabout; reducing the ability of this junction to deal
where infrastructure M5 locations with growth. This increases journey time and distances,
possible. investment and compromising the benefits of the scheme.
disruption. The option was not costed as it was discounted
because it does not have local support and does not
deliver all of the objectives
133 The same as option 2 but provides an eastbound single lane link from the Delivers some Increased capacity at New TDBC would Provides adequate The eastbound link reduces the pressure on A386 /
main roundabout to the SES junction. wider growth the main junction will infrastructure support this access Ruishton Lane / P&R junction set out above and
and SES provide for additional to be scheme but have enables good access from Taunton and M5 to the SES.
throughput of provided concerns about A single lane link in the eastbound direction could be
vehicles. along new disruption in the delivered by providing the infrastructure for this link only
Journeys to and / or link, existing longer term and the however in the longer term it is likely that the link will
from SES do not infrastructure impact this could need to be a dual carriageway when it connects to an
have to travel to be have on the improved A358 (Highways England scheme). Providing
unnecessary upgraded business the base infrastructure at this stage would be more cost
distances. where community and effective and limit disruption in the longer term.
possible. travelling public.
This option has been costed at £16.69m – this includes
all works to upgrade the main J25 roundabout.
4 The same as option 3 but provides an additional lane on the eastbound link Delivers wider Removing the extra New TDBC have strong Provides high The benefits of dualling the eastbound link at this stage
between J25 and the SES access roundabout and makes the link between growth to 2033 trips from the infrastructure support for this quality are two fold -
the SES junction and A358 / Ruishton Lane / Park and Ride junction two and SES roundabout provides to be scheme as it uncompromised It will be more expensive for HE to deliver the dualling
way. max available provided provides wide access in the future than the additional cost to SCC / LEP at
capacity to manage along new ranging befits for this time; a long term saving to the public purse.
congestion. link, existing Taunton beyond Should HE need to deliver the dualling it would be
infrastructure the delivery of the disruptive to the traffic using, potentially having a
to be SES. significant impact on the operation of J25; this is an
upgraded unnecessary cost to the local economy.
where
possible. This option has been costed at £18.02m – this includes
all works to upgrade the main J25 roundabout.
14Constraints
The improvements are geographically constrained by a number of factors –
M5 motorway and the structure that carries it over the top of J25
Residential properties and businesses alongside A358
A358 Broughton Brook culvert
Gateway Park and Ride site
Flood zone / watercourses
Topography of the surrounding area.
Other constraints include funding and time. In terms of finance the local funding that is available is limited to the developer
contributions that can be achieved from the site and the level of CIL or New Homes Bonus that can be made available by
TDBC. It’s clear from the flood risk, archaeology and topography of the SES that it will have a number of financial
challenges for delivery. It has already been established that bringing utilities to the site will be expensive due to the location
of the nearest connection points. The developer has indicated that a contribution of £1.5m will be available for the scheme
however due to the cost of servicing the site it will be necessary to forward fund the contribution from other sources. TDBC
has committed to investing New Homes Bonus funds into transport infrastructure, in December 2015 the Council approved
a planned expenditure of £2.5m over four years.
Inter-dependencies
In late 2014 the Government confirmed investment in the A303 / A358 / A30 route to provide an Expressway between the
M3 and the M5 along this route. Subsequently three specific sections of the corridor identified for improvement to in the
Highways England (HE) Roads Investment Strategy 2015 to 2020, these are -
A303 Amesbury to Berwick Down
A303 Sparkford – Ilchester dualling
A358 Taunton to Southfields
The development of the schemes and their confirmation through the Development Consent Order process is likely to take a
number of years and it is not anticipated that work will commence before 2020.
SCC’s improvement to M5 J25 is not directly dependent on HE’s work to bring forward the A358 improvement. HE
considers the SCC improvement as committed development; they are taking account of SCC’s designs for J25 in their work.
Given the likely timing of a preferred option being available SCC has consider how best to evaluate the likely scenarios
within the appraisal of the J25 scheme in order to determine the long term benefits of the investment. SCC has worked with
the Independent Technical Advisor to design sensitivity tests that allow the potential impact of HE’s improvements to A358
to be understood as well as possible at this stage. The Technical Advisor was keen to understand the longevity of the
investment by the HotSW LEP and whether a future upgrade to the A358 would change the long term benefits provided by
SCC’s proposed scheme.; these tests are in addition to those that were agreed within the Appraisal Specification Report
(appendix 8), they are SCC’s and the ITA’s assumptions about the scheme and do not seek to set out any particular position
nor pre-empt the work that HE has to do. They should only be considered as a guide to whether an investment in J25 at this
time represents good value for money in the longer term.
SCC considers that HE has three broad options when designing the connection of the improved A358 with the M5 –
1. Route all strategic traffic through the existing J25 and upgrade this junction where necessary
2. Route some strategic traffic through J25 and take some traffic on a new link to join up with M5
3. Route none of the strategic traffic through J25
SCC considers option 3 to be very unlikely given the potential cost and the stated aspiration to create “a new Expressway to
the South West”. It is highly likely that the local traffic wishing to travel to Taunton and West Somerset still pass through J25
in each of these scenarios. Therefore SCC has carried out sensitivity tests to ensure the benefits of SCC’s J25
improvement will still be achieved.
Bringing the scheme forward at this time means there will be immediate (on completion) and longer term benefits to the local
economy. The lack of clarity around the details of the HE scheme mean that it would not be possible for TDBC, SCC and
local stakeholders to plan the delivery of development in the vicinity of J25 and this would significantly hinder economic
growth in this area.
15Stakeholders
A Memorandum of Understanding has been developed and signed by partners working towards the development of the
strategic employment site. This is attached as appendix 9.
Key stakeholders will include –
Taunton Deane Borough Council
Summerfield Developments
Highways England
County and Borough Councillors
General public
16ECONOMICS CASE
Scheme Name M5 Junction 25 Capacity Improvements Date May 2016
Economic Summary Value for Money
Category
PV Benefits (£m) £164.2m
PV Costs (£m) £15.2m Very High
BCR 10.8
Assessment Approach and Assumptions
The transport economics for this business case have calculated using the TUBA software package, based on underlying
SATURN modelling. A number of supporting documents have been produced, these are included as appendices as follows:
Appraisal Specification Report (ASR) (Appendix 8)
Local Model Validation Report (LMVR) (Appendix 10)
Forecasting Report (Appendix 11)
Economics Report (Appendix 12)
Appraisal Summary Table (AST)(Appendix 13)
A review of the existing Taunton Strategic Traffic model (SATURN) took place in 2014 and concluded it should be updated
to improve the outputs and better comply with WebTAG guidance. The methodology for the update is outlined in the ASR
and is expanded within the LMVR (appendix 10).
The Forecasting Report (appendix 11) outlines the methodology that has been adopted to prepare future year traffic
forecasts for the appraisal of the M5 Junction 25 scheme. Forecasts were prepared for 2018 (as the assumed opening
year) and 2033 (as the design year, 15 years after opening). Modelling covered AM, Average Interpeak, and PM hours.
It has been necessary to prepare a number of different future year scenarios for the appraisal however the core scenario
reflects the most central forecast and is the best available prediction of future outcomes given the current understanding of
local factors influencing demand and supply. The overall level of traffic growth in this scenario has been constrained to
NTEM and is therefore consistent with government forecasts. The most recent DfT National Road Traffic Forecasts have
been used as a basis for the growth in freight trips. Further sensitivity test scenarios include a lower growth scenario, a
higher growth scenario including the Strategic Employment Site adjacent to Junction 25 and a scenario reflecting emerging
proposals from Highways England regarding improvements to the A358 corridor between the A303 and M5.
For the test of the A358 improvements in particular, it was necessary to make a number of assumptions about the scheme
given its early stage of development. However, the scenario that has been tested was discussed and agreed with the ITA
for the LTB and reflects the best estimate following discussions to date between SCC and Highways England.
Initial reference case demand forecasts were prepared according to the typical methodology outlined in WebTAG and
variable demand modelling has been undertaken to incorporate demand responses into these forecasts. Trip distribution
and trip frequency responses were modelled as these were considered to be most important factors in this case.
The environmental appraisal has been carried out for the scheme and covered noise, air quality, landscape and townscape,
historic environment and water environment. The report of this work has been included as appendix 14.
An ecology study has been carried out on behalf of the developer and this is included as appendix 15. It concluded that
there were no overriding ecological constraints to the development of the site and development could be undertaken in
accordance with biodiversity policies within the NPPF and TDBC Core Strategy. The study did suggest that, depending on
the development proposal, further survey could be undertaken to determine the presence of important hedgerows, invasive
plant species and the potential presence of protected and notable species. If any of these species were found, the potential
adverse impacts could be mitigated through careful design. The report concludes by suggesting Phase 2 ecological surveys
that would provide a complete ecological baseline, against which the potential ecological impacts on the proposed
development could be assessed
A social impact appraisal has been carried out and is included as appendix 16, the AST for the social appraisal can be
found as table 2 in the report or as appendix 16a. The scheme is appraised to be beneficial in terms of its social impacts.
Some aspects are beneficial, with the remainder being neutral. None have been found to be adverse. The quantitative
17aspect of the appraisal concerned accidents, which showed a £3.1 million net benefit over the 60 year appraisal period
(discounted to 2010), albeit this is considered to be in effect zero or neutral in the context of modelling uncertainty. Journey
Quality and Security also showed social benefits, scoring a large and slight benefit respectively. This means that users will
experience more positive perceptions of the schemes locale, particularly with regard to the locales cleanliness,
environment, a reduction in frustration and fear of accidents.
Key Risks, Sensitivities and Uncertainties
A number of scenarios have been tested to provide comfort that the scheme represents good value for money. The lack of
clarity around the detail of the future Highways England scheme at this stage has necessitated two scenarios are tested to
understand the impact of a potential scheme. These are set out in Table 5.
Table 5 Description of the scenarios that were assessed
Scenario Description
Core Scenario (without The forecast which is constrained to TEMPRO and is the best
SES) available prediction of likely outcomes.
High Growth (with SES) The equivalent to the growth in the core scenario plus additional
traffic demand associated with the Strategic Employment Site at
Junction 25.
Low Growth A reduced growth forecast based on the WebTAG approach for
uniformly factoring down traffic growth in the matrix for the Core
scenario
HE A358 improvement Includes the Highways England scheme to create a dual
carriageway link between the A303 and the M5 at Junction 25.
HE A358 improvement with Includes the Highways England scheme to create a dual
free flow slips carriageway link between the A303 and the M5 at Junction 25 with
a free flow connection to the M5 south of Junction 25 and would
be expected to remove traffic demand from Junction 25..
The relative merits of each of the scenarios are set out in Table 6.
Table 6 Cost and Benefit results for each scenario.
BCR
Travel Time Indirect Tax Total
Scenario VOC Benefits (adjusted
Benefits Benefits Benefits
ITA)
Core Scenario
£159.154m £-9.276m £8.018m £164.234m 10.8
(without SES)
High Growth (with
£205.793 £-7.212m £9.707m £206.281m 13.6
SES)
Low Growth £98.224m £-7.213m £8.018m £96.452m 6.3
HE A358
£156.936m £-11.598m £9.336m £152.876m 10.0
improvement
HE A358
improvement with £48.352m £-2.054m £3.140m £49.438m 3.2
free flow slips
Appraisal Summary Table
AST and worksheets are included within the environmental appraisal summary report (appendix 13).
An ecology study (appendix 16) has been carried out on behalf of the developer; the AST can be found as appendix 16a.
18Impacts Positive Monetised and Non-Monetised Impacts Scale of Impact
not Included in BCR
Air Quality Net improvement in exposure to NO2 and PM10 but these are very small. Neutral
Impacts Negative Monetised and Non-Monetised Impacts Scale of Impact
not Included in BCR
Noise Potential for noise increase due to new road layout and increased traffic Slight adverse
flow. (NPV -£492771)
Landscape and Loss of agricultural land and vegetation cover including trees and
Slight adverse
townscape hedges; changes to local landscape character; changes impacting on the
reducing to neutral by
composition of views, particularly to the east. Vegetation and built form
year 15.
on or near J25 limits views towards the site which minimises impacts.
Historic environment Likely to impact on the setting of nine listed buildings; direct impact on Moderate adverse
regionally important heritage asset should the remains of one be
present.
Water environment Site within Flood Zone 3 and close to water courses. Impact on water Large adverse
quality can largely be mitigated through construction management. Loss
of floodplain will need mitigation through the provision of water storage at
an alternative location.
Historic environment issues have been included within the risk assessment as they could potentially impact on the cost of
the scheme.
Water environment issues have been included within the risk assessment.
Change in Benefit or Cost required to Change in New Value for Likelihood of
change Value for Money category Benefit or Cost Money Category New Value for
Money Category
Value for Money Statement
The scheme is considered to have a very high value for money for the core scenario with a BCR of 10.8. SCC considers
the high growth scenario more likely as the scheme facilitates the delivery of the SES, this has a BCR of 13.6 and therefore
exhibits better value for money than the core scenario. Whilst the SES will take some time to be completely built out the
scenarios that consider the impact of the A358 improvement demonstrate that in the longer term the scheme offers good
value for money.
Whilst there are non-monetised adverse impacts of the scheme SCC considers that the most significant of these will be
mitigated through the scheme development and in the case of the water environment will develop a phased whole site
approach with the SES developer.
19FINANCIAL CASE
Scheme Name M5 Junction 25 Capacity Improvements Date May 2016
Summary Financials
Overall Cost of £18.02 LTB £12.9m Available £15.9 m Contingent £m
Scheme Contribution Budget Liabilities
Scheme Costs
Main Expenditure Items (include FY 14/15 FY 15/16 FY 16/17 FY 17/18 FY 18/19 FY 19/20 FY 20/21 Total
project income separately) (£m)
Design (inc surveys, site 0.175 0.325 0.151 0.151 0.801
investigations etc)
Preliminaries 0.200 0.688 0.688 1.575
New link road and junctions 5.708 5.708
Upgrades to existing roundabout 2.172 2.172
Main contractors OH&P 0.032 0.374 0.162 0.568
Contingency 0.06 0.713 0.309 1.082
Inflation 0.065 0.559 0.253 0.877
OB @44% 0.388 3.338 1.511 5.237
TOTAL COST 0.175 1.07 11.531 5.246 18.02
Budgetary Impact Summary
Forecast Net Budget profile (£m) FY 14/15 FY 15/16 FY 16/17 FY 17/18 FY 18/19 FY 19/20 FY 20/21 Total
Total Required Budget 0.175 1.07 11.531 5.246 18.02
Total Local Contribution (Secured) 1.5 1.5 3
Total Local Contribution (Unsecured) 2.122 2.122
Total LTB Requirement 0.175 1.07 10.031 1.624 12.9
20Anticipated Funding & Financing Arrangements
In addition to the LGF contribution SCC has secured funding from two sources. Appendix 17 contains a letter of support from Taunton Deane Borough Council which sets out their
commitment to providing £1.5m from the council’s resources. Appendix 18 contains a letter from Summerfield Developments confirming financial support for the scheme of £1.5m.
In addition to this SCC has submitted a bid to Highway’s England’s Growth and Housing Fund for a £4.0m contribution to the scheme, it anticipated that the results of this bid will be
known by the end of June 2016.
Financial Risks
A full risk register has been included as appendix 19. A QRA has not been carried out at this stage due to the level of design that has been carried out; a 44% optimism bias has
been included within the financial overview.
The key financial or funding risks that have been identified are:
Risk Mitigation status Calculated Risk Value
Scheme costs greater than funding package Amber – awaiting output of HE GHF bid, scheme cost reductions £4.0m (value of bid)
considered.
Land acquisition Green – land costs covered by OB Not calculated
Historic environment Green – archaeological surveys to undertaken once PE Not calculated
confirmed.
Cashflow Green – developer contributions will be phased as the site is built £1.0m
out
Upturn in the market leading to cost increases Green – inflation has been included and the procurement route Not calculated
will ensure the most cost effective solution has been found.
Accounting and Budgeting Issues
The issue of cashflow due to phased developer contributions has been highlighted on the risk register; SCC will determine the most appropriate mechanism to manage this prior to
the final business case being submitted.
21Additional Notes
A detailed independent cost estimate is attached as appendix 20. NB -the cost estimate does not include – landscaping, inflation or OB.
Since the submission of the expression of interest and subsequent inclusion with the GD2 the design for the scheme has changed which has resulted in a change to the cost of the
scheme. The initial scheme, similar to that described as scheme 1 in Figure 4 did not include a junction to access the SES. In this scenario the new link between A358 and J25
was to be temporary in order to widen the Broughton Brook culvert. In consultation with the developer, TDBC and the LTB ITA the scheme evolved to the current proposal. This
proposal includes a dualled link between the existing J25 roundabout and the new SES access roundabout; this will facilitate a link into HE’s A358 improvement in the longer term,
however should HE’s preferred option not require all the capacity that this link provides will be possible to reduce the scale of the eastbound carriageway with an approximate
saving of £1.33m.
22COMMERCIAL CASE
Scheme Name M5 Junction 25 Capacity Improvements Date May 2016
Introduction
The key output from this project is the completion of the required highway improvements to programme and to budget. The
programme also needs to ensure that the works are undertaken safely and with as little disruption to the travelling public as
possible.
Success of the project will also be measured against reduction in congestion, the support given to economic growth and
safer travel.
Capability and Skills
It is SCC’s intention to employ a dedicated project manager to oversee the development and construction of the scheme
once the funding package has been confirmed. The PM will provide end to end oversight of the project
The outline design to achieve planning permission will be managed through SCC’s Engineering Design Team of SCC
whose Service Manager is Richard Needs. Richard has undertaken similar roles on a number of Major Schemes within
Somerset, including North West Taunton Transport package, Taunton Gateway (Park & Ride), Taunton Third Way and
Bridgwater Colley Lane Southern Access Road which is due to commence construction later this year.
SCC’s Engineering Design Team will be supported during the design and site supervision phase as necessary using
additional / specialist resources available through the County Council’s Engineering Consultancy Contract – currently let to
WSP Parsons Brinckerhoff.
Procurement activities will be managed by SCC’s Commercial and Procurement team with a view to ensuring a competitive
process that achieves best value for money and minimises exposure to risk.
Procurement Strategy & Sourcing Options
In developing the procurement strategy for this scheme SCC has considered current capacity for delivering major highways
infrastructure, the complexity of the project and the fixed budget and has determined that the best options for procurement
is to let a design and build contract for the scheme once planning permission has been obtained.
SCC has programmed this procurement exercise to take place commencing with the publication of the OJEU notice and
PQQ in September 2016 with a view to awarding a contract in April 2017. This will allow for planning permission to be
sought from SCC under Regulation 3 of the Town and Country Planning Act 1990 to SCC as the planning authority before
the issue of the invitation to tender so that potential contractors are aware of the planning conditions.
The report detailing the reasons for the chosen procurement strategy is included as appendix 21.
Financing Arrangements and Payment Mechanisms
SCC intends to use an NEC 3 Option A form of contract with the objectives to achieve cost certainty, reduce exposure to
risk, have an efficient process and maximise opportunities for innovation and value engineering.
The contract will be let on a fixed price basis where this is only adjusted through compensation events. Payment is made
for each group of completed activities or for each activity which is not in a group.
Risk Allocation and Transfer
The risks associated with compensation events will be borne by SCC as the employer under the contract. All other risks
associated with the construction works which are not defined as compensation events will be carried by the contractor.
23Contract Length
It is anticipated that the contract will be 36 months, this is sufficient to allow for mobilisation, detailed design, construction,
post-construction activities.
Human Resources Issues
The availability of experienced engineering project management resources is somewhat limited given the number of large
construction projects that are currently ongoing; this has been included as a risk in the risk register.
24MANAGEMENT CASE
Scheme Name M5 Junction 25 Capacity Improvements Date May 2016
Introduction
This Management Case describes the management capability of SCC and outlines the proposed management structure
and processes of the project. It demonstrates that the management provision for the project is considered robust and
provides confidence that the successful delivery of the project can be achieved.
The management processes described are established and proven having been applied to similar projects previously
undertaken by SCC. The project is considered to be achievable as the deliverables (highway improvement works) are
familiar to the County Council who have a track record of implementing such projects. The structure of the Council supports
the delivery of highway improvement works projects and Council officers have experience in the delivery of such projects. In
addition, the Council can use the support of its engineering consultants through a framework agreement to support the
delivery of projects.
Evidence of Similar Projects
SCC has considerable experience of delivering complex highway schemes. Whilst the majority of schemes have been
successfully delivered SCC understands that there are risks to all schemes and is in a good position to manage these risks.
Examples of recent projects are – Huntworth Roundabout (under construction), Yeovil Eastern Corridor (under
construction), Taunton NIDR (under construction), The Bridgwater Way LSTF (complete), Taunton Gateway (Park & Ride)
(complete) and Taunton Third Way (complete).
Programme / Project Dependencies
A key unknown is the Highways England preferred option for improving A358. This has been described in the
Interdependencies section. It is anticipated that there will be more clarity regarding the options for this improvement that
can be fed into the design work for the scheme. SCC and Highways England are working closely together through the
development of both schemes.
Governance, Organisational Structure & Roles
Director of Economy &
Senior Responsible Owner Community Infrastructure Project Manager To be appointed
Operations
During 2015-16 SCC has carried out a wholesale review of governance for the delivery of a full range of highway schemes
to ensure the processes are robust and up to date. New area based infrastructure delivery boards have been introduced to
supplement the existing Programme Management Office (PMO) and the Highway Improvement Schemes (HIS) Board.
The HIS Board meets monthly to address issues raised across the entire county highway schemes and improvements
programme. Members include the County Council’s Cabinet Members for Highways & Transport and Business, Inward
Investment & Policy.
The PMO reports to HIS Board and its key role is to plan and coordinate the development of new highway infrastructure
and their subsequent programming, design, management and implementation.
The area based boards meet monthly to review activity, spend and to provide strategic guidance and decision making to
support project delivery. Accountability for the projects sits initially with Commissioning and is then handed over to
Operations as the project moves forward.
The project organisation chart for implementing the project, highlighting key project roles and links between the roles, is
shown in Figure 5.
25Figure 5 Governance Structure
Are governance arrangements in place? Yes
Risk Management Strategy
At this stage of the project the risks have yet to be quantified.
The key risks that have been identified are:
Risk Mitigation status Calculated Risk Value
Funding Amber – Awaiting outcome of HE GHF bid Not calculated
Performance of junction if works Amber – Awaiting outcome of funding bids Not calculated
not progressed
Historic Environment Green – Survey work to be undertaken once Not calculated
business case is approved
Water environment Green - discussions with EA and Summerfield to Not calculated
determine appropriate mitigation strategy
Impact on Gateway Park and Green – Ongoing discussions with Transporting Not calculated
Ride Somerset positive – engagement with operator
required
Implications of proposed Green –Engagement with Transporting Somerset Not calculated
schemes on any prospective ongoing.
new P&R operations contract
The project risks will be managed in accordance with SCC’s corporate risk management strategy; this has not been
appended to the business case but can be provided.
The risk assessment (included as appendix 19) follows the Red-Amber-Green (RAG) assessment methodology matrix
which considers both impact and likelihood. All the risks within the register are either designated as a ‘green risk’ at the
outset or can be mitigated to ‘green risks’. The remaining risk which is an amber level risk at the outset is associated with
utility diversions; if they are not completed to programme this could introduce both delay and increased costs into the
scheme. This can be mitigated by early engagement with the utility companies in order to provide accurate and robust costs
and timescale estimates. Whilst this will mitigate the risk to some extent, it will not be able to mitigate it wholly and as a
result it remains identified as an amber risk.
Has a risk management strategy/plan been completed? Yes
Have key risks been identified and managed? Yes
26You can also read
