Someone was asking for the plans, these are the most up to date:
https://infrastructure.planninginspecto ... 206%29.pdf
For those are interested these are the reasons for the west facing only slip roads at Chybucca (with traffic numbers), the underpass at Chiverton, and the lack of A390 slip road (starts on documment page 60 or PDF page 67):
https://infrastructure.planninginspecto ... REPORT.pdf
From what I've observed a lot of traffic uses Chybucca from the West to access Truro avoiding the congestion around Threemilestone, Treliske Hospital and Highertown. But Truro East traffic uses Carland and Perranporth traffic uses Boxheater (for East) or Chiverton (for West). Would only be useful for Shortlanesend.
8.2 Summary of matters raised that did not result in changes and
why
8.2.1 As summarised in section 8.1, changes to the design of the scheme since
statutory consultation have been influenced by a combination of factors, including
suggestions and matters raised by the public, PILs and stakeholders in response
to the consultation. However, not all suggestions or matters raised could be
accommodated within the design of the scheme, taking into account other
constraints such as environmental impacts, cost of the scheme, land required and
engineering and safety standards.
8.2.2 This section summarises key issues or suggestions raised in response to
consultation that did not subsequently result in a change to the design of the
scheme. It highlights those issues and suggestions that were raised most
frequently; a response from Highways England on all individual matters raised
and suggested changes is provided in section 8.4 to 8.7 of this chapter.
Chiverton Cross WCH Connection
8.2.3 A key issue raised during public consultation was the impact of the relocated
Chiverton junction on WCH connectivity. It was felt by members of the public,
interest groups and statutory consultees that the provision for WCH at the new
Chiverton junction is inadequate, specifically in relation to the proposed
requirement for WCH users to add 1.5km to the journey in order to gain access
between the B3277 from St Agnes and the A390 to Truro. The impact of this on
commuters between St Agnes and Truro, as well as in terms of safety and
encouraging sustainable travel, was found to be unacceptable by many
respondents. It was suggested that a WCH crossing is required at the site of the
existing Chiverton junction, following the ‘desire line’ between the B3277 and the
A390.
8.2.4 Highways England considered the feedback regarding the WCH crossing at
Chiverton Cross and determined that the provision of a crossing at the location
stipulated by respondents would not be feasible due to the impacts of including
the crossing on the project and construction programme. The preferred location of
a cycle bridge is further constrained by the potential effects a crossing in this
location could have on the World Heritage Site.
8.2.5 Although the preferred WCH connection location has been deemed unfeasible for
inclusion in the DCO submission, Highways England has committed to delivering
improved WCH connectivity through the addition of a proposed underbridge
approximately 1km from the preferred ‘desire line’ location stated by respondents.
This underpass [identified as PR2] is detailed in Chapter 12 - People and
Communities of the Environmental Statement (Volume 6, Document Reference
6.2,) and in the PRoW Management Plan (Volume 6, Document Reference 6.4,
ES Appendix 16.1 Outline CEMP Annex P) and in the Public Rights of Way
Plan (Volume 6, Document Reference 6.3, ES Figure 12.4). New off-carriageway
connections are also provided between the realigned B3277 and the realigned
A3075; and between the realigned A390 and the existing A30. These changes
mean that WCH users will be able to navigate Chiverton without travelling on the
main carriageway.
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Segregated A390 slip roads
8.2.6 Concern was raised in response to consultation that the design of Chiverton
junction would result in congestion on the A390 and on the main carriageway of
the new A30. Objection was also raised to the additional 1.5km distance required
to travel from the A390 to Chiverton, due to the eastern relocation of the junction.
It was suggested that additional slip-roads would be needed, particularly a westbound segregated slip-road onto the A30 from the A390.
8.2.7 Highways England has considered the need for an additional slip road in this
location, including west-bound from the A390 onto the A30. Traffic modelling
(using the established SATURN modelling software) has been undertaken during
the development of the scheme, as detailed in the Transport Report (Volume 7,
Document Reference 7.4), The modelling shows that there would be no
significant harmful impacts overall in relation to congestion on the A390 as a
result of the scheme.
8.2.8 Furthermore, a detailed modelling assessment of the proposed Chiverton junction
(using Junctions 9 software) shows that the scheme would not result in significant
impacts such that would lead to queuing and congestion on the new A30. The
assessment shows that the new Chiverton design would significantly reduce
queues on the A390 in comparison to a ‘Do Minimum’ scenario (in which the
proposed scheme is not implemented and the existing A30 remains in its current
form). Therefore, Highways England consider that there is not sufficient demand
for the provision of additional segregated slip roads in this location.
8.2.9 Beyond demand, there are additional constraints to this aspect of the design that
Highways England has taken into consideration. First, under the DMRB, there is a
minimum required spacing distance of 450m between consecutive merges, such
as on-slips for Chiverton junction and the A390. This is required in order to
provide adequate space for vehicles to safely enter and exit the main
carriageway. A second constraint is the close proximity of the World Heritage Site
boundary, which limits the potential alignment and position that the on-slip would
be able to take within the design and safety standards.
8.2.10 Given the lack of forecast requirement and cost implications, the safety and
engineering constraints, and potential impact, Highways England has determined
that the provision of the suggested west-bound on-slip for the A390 should not be
included in the scheme.
Chybucca, east facing slip roads
8.2.11 A key concern raised at statutory consultation, as well as in previous nonstatutory consultation and engagement, was the non-provision of east facing slip
roads at Chybucca junction. A significant number of respondents to the statutory
consultation raised concerns on the impacts that the lack of east facing slips
would have on connectivity, traffic through local roads (rat-running) and
congestion, with some respondents querying the design would represent good
value for money or undermine the principle of the scheme.
8.2.12 During non-statutory consultation on the scheme in late 2016, the lack of east
facing slip roads at Chybucca was raised as a concern. As detailed in the
Scheme Assessment Report (Volume 7, Document Reference 7.6), Highways
England considered this issue in response to the concerns raised at consultation
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and concluded that the predicted traffic flows did not justify the provision of east
facing slip roads at this location as part of the scheme.
8.2.13 Following the Preferred Route Announcement (PRA) in 2017, Highways England
has further assessed the provision of east facing slip roads through additional
traffic modelling. The traffic model was further developed and includes additional
local roads used for rat running. The model demonstrates that the number of
vehicles using the east facing slip roads remains low in comparison to that of
those using the west facing slip roads. The model shows that by 2038, the
demand for east facing slip roads would be 1,764 vehicles per day (528 east
facing on-slip and 1,236 east facing off-slip), whilst demand for west facing slip
roads would be 11,322 vehicles per day (4,799 west facing on-slip and 6,523
west facing off-slip).
8.2.14 Beyond consideration of demand for east facing slip roads, there are other
aspects that would also need to be considered, such as: construction costs,
environmental impacts, increased land take, which would be significant in this
location given the extent of additional earthworks, cuttings and embankments that
would be required to construct the slip roads.
8.2.15 To summarise, the introduction of east facing slip roads has been reviewed by
Highways England following both non-statutory and statutory consultation, and
the decision to provide west facing slip roads only at Chybucca is still supported.
Given that future demand is predicted by the traffic modelling to be low, east
facing slip roads would not address the specific issues of congestion, safety,
network reliability and capacity on the existing A30.
8.2.16 Further detail on the traffic modelling undertaken in this assessment is provided in
the Transport Report (Volume 7, Document Reference 7.4) and details of the
environmental assessment are provided in the Environmental Statement
(Volume 6, Document Reference 6.2).