Executive summary

EXECUTIVE SUMMARY

This report presents the findings of a study commissioned by the Highways Agency to confirm or otherwise the recommendation of MIDMAN that A556(M) should not proceed but that a full movement interchange at Junction 20 of the M6, ie its junction with M56, should be constructed. The MIDMAN recommendation also recognised that such a strategy would probably require the widening of M6 to D4M between Junctions 19 - 20 and possibly require the widening of M56 to D4M between Junctions 9 - 7.

The study has compared the two road based options in accordance with GOMMMS leading to the production of Appraisal Summary Tables.

The study has used the MIDMAN traffic model refined to include additional minor roads, modelling of junction capacities, reclassification of existing link types, and refinement of zone loading points. Models were developed for the AM peak and inter-peak periods leading to estimated AADT flows. Future year matrices were developed for 2011 and 2026 using MIDMAN forecasts based on their Scenario 2 recommendations. Incremental assessments were undertaken with the base assessment for comparing the two options including M6 widening between J16-19 and M56 widening between J7-6 (see below). Also various options for creating restrictions on A556 with the J20 scheme were modelled; the option of closing the south-facing slips at J19 and reducing A556 to a single carriageway with a 40mph speed limit was the option taken through the remainder of the GOMMMS assessment.

The A556(M) option has been designed as a D2M, whilst the J20 scheme has included the widening to D4M of the M6 between J19-20 and the M56 between J9-7. With regard to the J20 scheme and associated widening of the adjoining motorways, two forms of motorway widening, parallel and asymmetrical, have been assessed leading to a recommendation as to which is preferable in this case.

Both options have been costed using quantities based on 1/2500 scale plans using rates published by Spons. Both options include works on the existing A556 to reduce its scale. The estimates produced were used in the economic assessment of the options.

The study used the latest available environmental data, and in the case of landscape assessment enhanced by site surveys by qualified landscape architects. Similarly, with regard to integration, the assessment of the options was against the latest planning policies. Full consultation has been undertaken with Statutory Consultees (English Nature, English Heritage, Countryside Agency and Environment Agency).

The study has also assessed the impact of the two options on the wider area network, particularly with regard to the SEMMMS strategy.

The study has concluded that the A556(M) is preferred on:

  1. traffic grounds since it caters for all motorway to motorway traffic; the J20 scheme only caters for 35% of this traffic even when restrictions are applied to the existing A556 and access thereto is limited;
  2. cost grounds being some 15% cheaper than the cheapest J20 scheme;
  3. environmental grounds where it is assessed preferable on 5 of the 9 subobjectives;
  4. safety grounds with a saving in accident numbers over a 30 year period 6 times greater than the J20 option;
  5. economic grounds with a robustly positive BCR, compared to a negative BCR for the J20 scheme;
  6. accessibility grounds although this is only a marginal preference;
  7. integration grounds since the scheme is safeguarded in the Development Plan, other impacts on policies being equal between the two options.
  8. deliverability grounds since Line and Side Road Orders have already been made for A556(M); works could thus commence on site in 2005. However the J20 scheme would require further Public Consultation, a Preferred Route Announcement, and detailed design leading to an additional period of 4 years before the scheme could be implemented.

The study also considered in accordance with GOMMMS the need for widening the M56 between junctions 7 - 6, since this section of motorway had been considered in neither the MIDMAN study nor the SEMMMS study.

The recommendations of the study are that:

  1. the A556(M) scheme be reinstated into the Roads Programme without delay at a D2M standard, with associated traffic calming on the existing A556,
  2. the M56 Junctions 7 - 6 be widened to D4M standard, using parallel widening to its north side, this scheme to proceed no later than the A556(M) scheme.

Executive summary

1.0 introduction

1.0 Introduction

1.1 A scheme to provide a motorway standard link A556(M), between the M6 at Tabley (Junction 19) and the M56 at Bowdon (Junction 7) was included in the National Roads Programme from the late 1980s until the 1998 Roads Review.

The design of scheme was developed to such an extent that a Public Inquiry into the Line and Side Roads Orders was held in Autumn 1993, following which, in Summer 1995, the Orders, with various amendments, were confirmed by the then relevant Secretary of State, and made in June 1996. In the summer of 1997 a Value Engineering exercise was undertaken involving Highway Agency staff and their consultants for the scheme, Allott & Lomax.

1.2 Before the scheme could be progressed to a Compulsory Purchase Order Inquiry, it was subject to further Government review, with the result that in the 1998 Roads Review the scheme was remitted to the West Midlands to North West Conurbation (MIDMAN) multi modal study.

1.3 The MIDMAN study1, in December 2001, incorporated within their reporting, under their scenario CS2 which took account of public transport enhancements, a recommendation that a road based solution was required in the A556, M6, M56 triangle. However their recommendation was that A556(M) should not be taken forward. Instead, the traffic to the Manchester conurbation should be diverted further north along the M6 to Junction 20 at Lymm, and then along the M56 eastwards. In order to cater for these movements, the M6 J19-J20 would probably need widening to 4 lanes in each direction; the M56 J9-7 would perhaps need widening to 4 lanes in each direction; and additional free flow links would be required at J20 to cater for the northbound to eastbound and westbound to southbound movements. This diversion of traffic to a longer route would be reinforced by traffic management measures/ restrictions being applied to the existing A556.

1.4 This alternative to the A556(M) was put forward as an Objector's Alternative at the A556(M) Public Inquiry in 1993 and rejected by both the Inspector and the Secretary of State. The MIDMAN study recommendation is recognised as being based on the results of a strategic model and that Junction 20/A556 was on the periphery of the study area with the limitations that has for the detailed qualification of local impact. It suggested therefore that a further, more detailed, study would be required in this particular area before the recommendation could be confirmed or otherwise.

1.5 Some of the MIDMAN findings on environmental impacts, and indeed information included in the relevant Appraisal Summary Table in the 1998 Roads Review, were at variance with evidence presented during the 1993 Public Inquiry. This study has considered these issues, eg landscape impact, in more detail than would normally be available at this stage of scheme assessment but generally the level of data available, particularly on the M56, is in line with that required for a Stage 1 Report as set out in Design Manual for Roads and Bridges, Volume 533.

1.6 A further issue in the A556 Area is the M56 between Junctions 7 and 6. This section of M56 was not considered within MIDMAN nor within the South East Manchester Multi Modal (SEMMMS)2 and the Highways Agency are concerned about its current capacity as a Dual 3 Lane Motorway.

1.7 Babtie has been commissioned by the Highways Agency to undertake a detailed study into the two route options for enhancing the capacity of the motorway network between J19 on the M6 and J7 on the M56. The results of this study to be presented within a GOMMMS appraisal framework. This study is also to include an assessment of widening the M56 between junctions 6 and 7. The brief for the study is included in Appendix 1.

1.8 The present study is a more comprehensive and detailed assessment than was practical within the strategic MIDMAN Study. In developing the study we have drawn upon the MIDMAN strategic appraisal and a range of other sources. The GOMMMS appraisal uses the national criteria as well as the local objectives set by MIDMAN. In this respect the present study is not a stand alone study but is a focused and detailed assessment of the two route options considered at a strategic level by the MIDMAN Study.

1.9 Sections 2 to 8 of this report describe traffic modelling and forecasting work, engineering layouts of the various options, cost estimates and assessment of the schemes against the five main criteria established by the "New Approach to Appraisal"

Section 12.0 provides an appraisal of the two schemes in the wider GOMMMS appraisal framework. This appraisal process has the following four appraisal 'strands'.

The AST's provided in this section, will draw together the findings of Sections 5 to 8 which assess the impact of the schemes on the Environment, Safety, Economy, Accessibility and Integration.

1.10 The study has been carried out in accordance with the directions of a Steering Group chaired by an officer from the Highways Agency. The members of the Steering Group are listed in Appendix 2.


1.0 introduction

2.0 traffic

2.0 Traffic

2.1 Introduction

The MIDMAN Study's primary highway focus was the M6 between Birmingham and Manchester. To address issues relating to "widening options" north of Junction 19, it is essential to have an understanding of the role of the A556 and the specific characteristics of traffic using the route and the problems that are generated by the present network. Although these characteristics are closely related to those of traffic using the wider M6, they are different and a clear understanding of the traffic related issues is essential to inform a more detailed assessment of options for widening north of Junction 19. Section 2.2 decribes this detailed assessment.

In the light of these issues a traffic assessment approach has been developed which builds upon the MIDMAN strategic approach, refined and tailored to address the A556 issues that have been identified. An overview of this approach is given in Section 2.3 and details of the enhancements made to the MIDMAN Highway Traffic Model to provide a robust, detailed assessment are given in Section 2.4. Use of the refined model to forecast highway travel demand, consistent with the MIDMAN study's wider multi-modal strategy are given in Section 2.5. The assessment of a range of options for the two remitted highway schemes are presented in Section 2.6

2.2 Traffic Characteristics and Conditions

2.2.1 The A556 role in the Strategic Network

The A556 is a trunk road running between North Cheshire and South Manchester. The present study focuses on the short section between the M6 (junction 19) and the M56 (Junction 7). This section of the A556 provides a key link in the Strategic Network, in that it facilitates an important movement between two motorways and for other strategic traffic, although the road is not built to motorway standard. It is the signed route into South Manchester and in particular Manchester Airport for traffic approaching from the M6 south. The geography of the motorway network in this area is such that the M6 between J19 and 20 heads north-west to the Lymm interchange (J20) with the M56. The A556 provides a significantly shorter route between J19 and J7 and it was probably for this reason that Junction 20 was constructed without free flow slips between the M6 south and M56 East and vice versa. This section of the A556 provides a key link.

Manchester is a "super-primary" destination within the strategic network and the A556 provides the "gateway" to Manchester for trips from the West Midlands, South East England, London and the South East. Manchester Airport's main road access is via Junction 5 on the M56 and as a consequence the A556 and M6 provide the primary route for passengers and freight movements between the airport and the south.

In addition to its "national" role the A556 provides a sub-regional route for traffic between Cheshire and Greater Manchester. Traffic levels on the northern third of the "inter-motorway" section of the A556 are increased by more local traffic, in particular from Knutsford, when traffic from the A5034 joins the A556 at Bucklow Hill traffic lights.

2.2.2 Traffic Movements

The composition of traffic on the A556 is illustrated by data collected by a Roadside Interview Survey on the A556 south of Mere Crossroads(A50) in 1996. Data was collected from northbound traffic during a six hour period covering the AM and inter-peak period. This data has been expanded to existing AADT flow levels to give an indication of the pattern of one way movements across the day. The analysis has been based on Postcode sectors. Movements are detailed in Table 2.1 and summarised in terms of origin and destination type in Table 2.2. This summary assumes local destinations are those within approximately 12km of the survey location, and long distance origins being south of M6 J16 or North Wales and long distance destinations being beyond Greater Manchester.

Table 2.2 shows over 50% of northbound traffic on the A556 has a long distance origin, whilst only 5% has a long distance destination, indicating the importance of Greater Manchester as a Primary destination. Only one third of the traffic south of the Mere cross roads has a local origin or destination and strategic movements into Manchester, or beyond, account for a majority of movements. A majority of the sub-regional to sub-regional movements are likely to be movements from the M6 to M56. The importance of the A556 for traffic to Manchester Airport is demonstrated by the fact that 8% of trips on the A556 have a destination at the airport.

North of Bucklow Hill traffic levels are higher with an additional 5000 northbound vehicles. These trips principally have origins in Knutsford, and destinations across Greater Manchester.

To summarise the above, the A556 is a key link in the "strategic network", providing access into Manchester and the airport from the M6 and as a consequence the South of England. It also serves a variety of sub-regional movements due to its proximity to Greater Manchester.

2.2.3 Operational Conditions

The majority of the A556 between J19 and Junction 7 is an undivided 4 lane road, with substandard lane widths in places. The northern 1.5 km is a dual two lane road. At Junction 19 there is a traditional grade -separated roundabout junction with a free-flow link for southbound access to the motorway. The junction has been signalised in the last four years to give improved operational conditions, in particular to avoid queuing back onto the motorway.

The A50 crosses the A556 at Mere crossroads - a skew crossroads with signal control. For safety reasons right turns off the A556 have been banned. Further north at Bucklow Hill, the A5034 from Knutsford and local side roads meet with the A556 at a further signalised junction.

Table 2.1 : Origin and Destination of northbound traffic on A556 South of Mere - AADT estimated flow
Origin Destination Total Percentage
Northern England Bolton/Bury/Rochdale Oldham/Hyde N Manchester E and NE Manchester Manchester City Centre and Salford Cheadle/Stockport S and SE Manchester W Manchester and urmston Sale/Altrincham Airport Local villages/Lymm NW of J20
Local to A556 10 0 47 0 0 32 0 34 0 78 0 24 0 225 1%
West Cheshire/ N Wales 23 0 16 0 0 79 58 42 0 107 16 19 0 361 2%
Northwich Area 116 24 145 24 85 478 223 488 39 817 75 100 0 2613 15%
Winsford/Middlewich/Sandbach 144 24 216 42 242 450 362 453 92 673 164 66 19 2948 16%
Crewe/Nantwich 75 28 218 42 0 230 338 184 94 347 73 23 0 1653 9%
Midlands and Southern Eng 517 195 889 24 689 1507 1066 1411 224 1405 1041 150 24 9141 51%
Macclesfield/Congleton 16 0 0 0 24 32 0 75 0 50 0 21 0 218 1%
Knutsford and Southern Villages 39 0 95 19 46 103 118 0 30 206 78 105 0 841 5%
Total 941 271 1626 151 1086 2911 2166 2688 479 3683 1447 509 43 18000 100%
Percentage 5% 2% 9% 1% 6% 16% 12% 15% 3% 20% 8% 3% 0% 100%  


Table 2.2 : Breakdown of Traffic on A556
  Local Sub-Regional Long Distance Total
Local 3% 3% 0% 6%
Sub-Regional 13% 26% 2% 41%
Long Distance 15% 35% 3% 53%
Total 31% 63% 5% 100%

Bowdon Roundabout forms the northern end of the A556 with access to the M56 slip roads and A56 to both Altrincham and Lymm being catered for by a large diameter at grade roundabout. This has recently be partially signalised to improve operational conditions. Access from the M56 West to A556 South is facilitated by a direct slip off to the A556 (junction 7), but access for northbound A556 traffic to the M56 westbound is not catered for directly, traffic having to negotiate the roundabout before heading south on A556 to the Junction 8 loop.

Given the sub-standard nature of the single carriageway section of the route a 50mph speed limit applies on this section. A range of safety related improvements have been implemented in recent years or are planned however none of these schemes significantly increases the capacity of the route. At the present day the route operates close to capacity throughout the extended peak periods and any "minor incident" on the route or on the M6 north of J19 leads to severe congestion and unreliability of journey times. Right turn movements along the route, and to a lesser degree left turns off the mainline, regularly disrupt the flow of traffic and give rise to unstable conditions and severe hazard. The high level of traffic, high proportion of Goods vehicles and narrow lanes lead to a high level of driver stress. The lack of a full movements junction at Junction 20 means that there is no alternative principal route when problems occur (there is an indirect link via junction 20 but the dumb-bell junction arrangement means significant levels of diversion traffic cannot be accommodated).

Increasing congestion on the A556 and M6 has led to traffic finding alternative routes across East Cheshire, with degradation of traffic and environmental conditions across a wider network.

There is little scope for the road to accommodate increases in traffic levels in future years. In the face of increasing traffic demand, operational conditions will deteriorate rapidly in the near future. The problems of the A556 were appreciated by the Highways Agency leading to the development of the A556(M) scheme which was endorsed by a Public Inquiry in 1993 and which forms one of the two schemes remitted to the wider MIDMAN study.

2.2.4 Safety Issues

The historic safety record of the A556 reflects the sub-standard carriageway, traffic signal junctions and a range of side road and property accesses along the route. An analysis of injury accidents over the last five years is shown in Table 2.3. The 61 accidents in 1997 represent an overall accident rate of 0.667 PIAs per million vehicle kilometres. This is over 50% higher than the default accident rate for an S2 Older road as used by COBA11. The impact of recent safety schemes is evident in the decline in accidents since 1998, to half the previous level. Further safety schemes, in particular an improvement to the Bucklow Hill junction should continue to provide a reduction in accidents in the next few years. However, many sub-standard features of the route will remain and driver's perception of the route will still be poor.

Table 2.3 Historic Accident Analysis - A556 - Tabley to Bowden Roundabouts
Year Link Only Total Including Junctions
Slight Serious Fatal Total Slight Serious Fatal Total
1997 6 8 0 14 50 11 0 61
1998 14 1 0 15 50 10 1 61
1999 11 3 0 14 42 8 1 51
2000 9 0 0 9 36 3 1 40
2001 8 2 0 10 28 2 0 30

2.2.5 Summary of traffic problems

The traffic related problems of the A556 can be summarised as:

The A556 presently provides a sub-standard, but in some respects, a surprisingly effective link in the "motorway network" serving strategic and sub-regional traffic movements. Future traffic growth will lead to increased congestion and unreliability of journey times, will erode recent accident reductions and lead to further degradation of the local environment along the A556. In the face of greater congestion on the A556 drivers will increasingly seek alternative routes across East Cheshire exacerbating the traffic and environmental problems presently experienced as a consequence of traffic diverting off the strategic network.

2.2.6 Conclusions

The A556 has a number of traffic problems and these lead to environmental, and safety problems in the immediate vicinity of the scheme and increasingly across the wider network. The MIDMAN Study has defined a number of local objectives which its proposed strategy seeks to address and these are detailed in Section 9, in addition to the national objectives set out in the "New Approach to Appraisal". For the present study the following local objectives are of particular relevance and need to be considered in assessing any enhancement of the highway network between Junction 19 and Junction 7:

There is a broad range of national and local criteria against which the effectiveness of the two strategies need to be judged. Traffic issues are critical to the correct assessment of many of these criteria including safety and environmental criteria. The traffic assessment needs to be able to provide robust estimates of these impacts to enable a reliable GOMMMS assessment to be completed.

2.3 Assessment Overview

The requirements of the present study are:

The choice of approach was driven by the above requirements, the timescale and the available tools. The timescale, a matter of months, precluded any major data collection exercise or major traffic model development process. The approach was therefore dictated by the available traffic data and models.

Three potential traffic models existed, upon which the assessment could have been based. These are:

The first model was ruled out because the model did not extend south of Junction 18 to include routes that might be used by traffic when testing the motorway widening scheme.

The Sub Regional Model is focused on the Manchester conurbation but does not include an appropriate network within Cheshire. Thus significant additional work would need to be done to enhance the model adequately to represent travel conditions across a wide rural network.

The MIDMAN model was developed as a strategic model, covering the whole of the country with a more refined modelling of the M6 corridor. It was developed to assess at a strategic level options across the breadth of the MIDMAN study area. The MIDMAN consultants recognise their model is not appropriate for making detailed decisions on widening options north of Junction 19. However refinement of their highway model to enable a robust assessment of the alternative schemes, offers a route which builds upon their earlier work.

To provide a robust re-assessment of the two highway options identified by MIDMAN, and to assess the need for widening of the M56 between J7 and J6, it was concluded that a refinement of the MIDMAN highway model would be the most appropriate approach.

The development of this refined model is outlined below. This model has been used to assess a range of options based on MIDMAN's forecasts of highway travel demand. A key feature of the assessment has been the identification of an appropriate and practical Junction 20 scheme, with respect to the management of the existing A556 between the M6 and M56.

The traffic assessment identified the highway improvements required with each of the two widening strategies and provided data for the economic assessment of the schemes using COBA114 and the traffic input into other aspects of the GOMMMS assessment of the strategies.

The level of assessment undertaken has been tailored to the specific needs of the current study. That is, to develop and test the two options remitted to the study, to enable an even handed assessment to be undertaken and a robust recommendation made on the scheme to be taken forward.

2.4 Traffic Model Development

The development and calibration of the A556 Area Traffic Model is fully documented in a separate report (A556 Area Study -Traffic Model development Report - May 2002)5 and is summarised below.

The A556 Area Model was based upon the MIDMAN model, with a sub-area of the latter model being provided by the MIDMAN consultants from their Reference Case and Core Strategy 2 assignments for 2001 and 2026. The area of the cordoned model was defined by Babtie after consideration of the potential area over which re-assignment could occur with the two alternatives to be assessed. Figure 2.1 indicates the area covered by the model.

The scope of the network was enhanced by:

The zone definition within the core study area was refined by the splitting of a number of zones on a proportionate basis. The refined zoning system is shown in Figure 2.2. Consideration was given to further enhancement of the zoning system (which is based on administrative rather than homogeneous traffic zones) but it was considered to be impractical given the timescale.

Checks on the matrix at different stages identified some bias in the key movements assigned to the A556 corridor. Although the MIDMAN study updated their synthetic matrices with observed data on the A556 itself, movements on other parallel routes did not reflect the balance of observed movements across all routes as revealed by RSI data collected in 1996. As a consequence the matrices were updated using data for the A50, A556, A5034 and Ashley Road in the Mere area. The MIDMAN matrices represent strategic movements and analysis of them revealed that short distance trips were largely missing from the matrices. This has had an impact on the level of calibration that could be achieved and more importantly requires care to be exercised in the interpretation of model outputs. At two key locations pre-loads of local traffic were applied to the calibrated model to minimise problems in the use of the model.

Models were developed for the AM peak and inter-peak period, the periods modelled by MIDMAN. Timescale considerations precluded the development of a PM peak model, thus estimates of AADT flows have been generated by factoring the two available time periods, using factors based on available traffic counts. The calibrated and validated models are considered to be appropriate for the assessment of the two scheme options being considered by the present study and to allow a robust decision on the preferred route to be made. The model has been scrutinised by the Highway Agency's modelling experts and been passed as appropriate for forecasting and differentiating between the traffic impacts of the schemes that form the present study.

2.5 Forecasting procedures

2.5.1 Traffic Growth

Future year matrices were developed for 2011 and 2026, based on the MIDMAN forecasts of highway travel demand that flow from their Multi-modal assessment and Reference Case scenarios. This approach ensures consistency with the MIDMAN highway demand forecasts and includes any reduction of demand resulting from public transport proposals included in the MIDMAN package of proposals.

The refined A556 Area Model base matrices were factored by zonal trip end growth factors, determined from the MIDMAN matrices. The overall growth between 2000 and 2011 across the A556 Area Model is 15.9% for the AM peak and 18.1% for the Interpeak. These rates of growth are slightly higher than national low growth (NRTF 14.1% low - 24.1% High) and reflect the constraint to growth in the peak hour that will exist due to general network limitations.

2.5.2 Do Minimum Schemes

The base network was updated to include a number of highway improvements that will be in place before any MIDMAN highway improvements are implemented. These are:

The Poynton, Stockport and MAELR schemes were assessed by the South East Manchester Multi-Modal Study (SEMMMS)2 which recommended design standards for each of these schemes. These recommended standards were incorporated in the model.

2.5.3 Assessment Strategy

The traffic and economic assessment needs to establish the traffic impacts of a number of separate but related elements of highway construction. To enable these impacts to be fully identified an incremental assessment strategy was devised.

The testing of two basic scenarios allows the benefits of a combination of proposals to be quantified on a like basis, whilst also establishing the impacts of individual elements.

This approach has been adopted throughout the traffic and economic assessment. The assessment has been based on the 2011 traffic forecasts, with reference to 2026 to confirm the appropriateness of highway standards.

2.5.4 Junction 20 Scheme

The MIDMAN proposals for a Junction 20 Scheme did not quantify what actions would be taken with regard to the existing A556 to deter traffic from continuing to use this shorter route. Their strategic model could not reflect banning of turning movements etc and "management of the A556 was represented simply by a reduction of speed and capacity and a lengthening of the route to twice it's actual length". The A556 Area Model has been enhanced to allow practical solutions to be modelled.

The development of a practical scheme for the existing A556 has been difficult. The A556 provides a more direct route between the M6 J19 and M56 J7 than the proposed route via Junction 20 (a distance of 8 km compared with 16 km). It is also the signed route at the present day. To be effective a Junction 20 scheme needs to provide a signed motorway route via Junction 20 that is more attractive to drivers, than the existing, downgraded A556. As demonstrated in Section 2.2 many drivers have the alternative option of using alternative routes to the East of the M6 which "cut-off the corner", albeit requiring the use of lower standard roads and travelling through towns such as Knutsford, Holmes Chapel and Alderley Edge. Analysis of traffic movements on the existing A556 reveal that 40% of the peak and 33% of the interpeak traffic is motorway - motorway traffic, ie travelling between the M6 and M56 or vice versa. The A556 also provides a trunk road connection from West Cheshire and Northwich to Manchester and motorway routes around the conurbation and this traffic could be heavily impacted upon by a poorly designed scheme.

To demonstrate the full range of impacts that could occur, four illustrative alternatives were tested. They are:

Traffic assignments on these four basic strategies were undertaken and the impacts are considered below.

2.6 Traffic impacts

2.6.1 Changes in traffic due to Do-Minimum Schemes and widening South of J19

At the present day, in the peak period many links in the wider network are running at or near capacity. As a consequence longer distance traffic is using some inappropriate routes and this is of particular concern to Cheshire County Council, who are responsible for many of these routes. Increased traffic levels in future years will increase journey times and may cause some drivers to re-route. Changes to routing will also be influenced by other highway schemes that are planned. To establish how traffic flows may change, irrespective of which strategy is adopted, the A556 Area Model has been used to quantify these changes.

Proposals for an Alderley Edge bypass and improvements to the highway network around Wilmslow and Stockport, will make cross country routes to the east of the M6 more attractive once these schemes are opened. These Do-Minimum improvements are expected to lead to a 5% rise in traffic, in effect an additional 300 vehicles an hour in the AM peak on the A50/A535/A34 corridor in 2011 compared with the existing network in 2011. The Do-Minimum flows are shown in Figure 2.3.

Widening of the M6 to D4 up as far as J19 - part of the MIDMAN proposals will improve travel conditions on the M6 and there will be a net transfer back onto the M6 from the A50/A535/A34 corridor of 100 vehicles an hour in the AM peak. The improved conditions on the M6 will also draw a further 150 vehicles an hour off the local road network to the west of the M6 to the south of Northwich. The daily (AADT) impacts of widening the M6 are to increase M6 flows by 2700 vehicles with reductions on local roads to the west and east of 900 and 1500 respectively as shown in Figure 2.4. The widening proposals extend south beyond the limit of the cordoned model and thus the full impact of these proposals cannot be reflected. It demonstrates that widening of the M6 to D4 strengthens the strategic role of the motorway.

In the subsequent analysis the impact of any scheme is given with reference to the Do-Minimum Network and in each case daily flow impacts (AADT) are shown.

2.6.2 Impact of widening M56 6-7

The impact of widening the M56 J6-7 to Dual 4 lane, relative to the Do-Minimum network, is shown in Figure 2.5. It thus includes the impact of widening the M6 to the south of Junction 19. Widening between J6 and 7 improves traffic conditions on the link and as a consequence draws more traffic onto the M56 from other parallel East-West routes as indicated by the increased flows on the M56 between Junction 7 and 9. In addition, the widening of the M56 builds upon the benefits of widening the M6 (as shown in figure 2.4). It attracts some further long distance traffic back onto the strategic network, relieving the Alderley Edge corridor of a further 300 vehicles a day and local roads around Mobberley by 600 vehicles a day. There is also a small switch of traffic from the M6 into Manchester via routes through west Manchester to a route via the A556 and M56. The scheme increases traffic on the A556 by a further 800 vehicles to give an increase of 1400 vehicles relative to the Do-Minimum network.

Widening the M56 between junctions 7 and 6 has positive impacts for the wider network:

2.6.3 Traffic impacts of the A556 (M) Scenario

A scenario that includes an off-line Dual 2 lane motorway, parallel to the A556 (in addition to widening the M6 south of J19 and M56 between J6-7), is discussed below. The AADT flow changes of this scenario are shown in Figure 2.6 and the forecast flows in 2011 are shown in Figure 2.7.

The A556(M) scheme provides free-flow links with the M6 and M56, bypassing the existing sub-standard A556. This removes capacity constraints on the existing route between the M6 South and M56 East, to the benefit of strategic traffic and also assists access to west Cheshire. The free flow motorway links lead to travel speeds of 90-100kph compared with overall speeds of 40-60kph in the Do-Minimum on the existing A556 where speeds are depressed by signalised junctions along the route.

Residual traffic flows on the A556 south of the A50 at Mere are less than 2000 vehicles a day and the road can be down-graded south of Bucklow Hill to a local road and traffic calming introduced, with consequent benefits for the local community. Flows north of Bucklow Hill are higher at around 10,000 vehicles a day as local traffic from Knutsford towards Manchester is not served by the A556(M).

The scheme provides a direct link between the J19 and J7, parallel to drivers' existing route and reinforces the strategic role of the motorway network in the area. This is illustrated by an analysis of motorway to motorway movements along A556. In the Do-Minimum, 2011 situation an estimated 14,500 trips a day travel between the two motorways on the existing A556. Widening of the motorway south of j19 and east of J7 as discussed above increases motorway to motorway movements to 15,700 vehicles a day, 39% of all traffic travelling between the two motorway junctions. With the A556(M) scheme in place this increases to 18,900 vehicles a day.

The increase in motorway to motorway traffic is due to the A556(M) and widened M6 and M56, drawing back onto the motorway network traffic that has sought other routes due to the previously degraded level of service, particularly in the peak periods, that was provided on the strategic network. This is illustrated by Figure 2.7 that shows reductions in traffic on the wider network to the east of the M6 of 10-13%. In addition there is a predicted reduction in traffic flow on links to the west of the M6 as traffic is drawn back onto the motorway network. Other impacts of the scheme are a reduction of traffic travelling north of the M6 J20 and on the B5212 through High Legh as traffic takes advantage of the A556(M). Flows on the M56 J7-9 are reduced as traffic from Northwich and further west switches from routes via the M56 west of the M6 to the A556(M).

The A556(M) scheme removes a number of capacity limitations on the immediate network, removing congestion experienced by strategic and other traffic on the A556. In addition it attracts traffic back to the strategic network which otherwise diverts onto the local road network adding to congestion, noise and pollution in communities such as Holmes Chapel, Knutsford, Mobberley.

Provision of a motorway link directly between J19 and J7, increases the capacity of the existing travel corridor. The scheme thus draws back onto the motorway network, significant levels of traffic which otherwise find local roads and lanes an attractive way of avoiding congestion on and around the A556. The traffic which remains on A556 is local traffic which uses the A556 and the A50 or A5034 to access Knutsford , High Legh or Mere.

2.6.4 Traffic Impacts of potential J20 Scenarios

The traffic impacts of a scenario that widens the M6 and M56 through to J6, provides free flow slips at J20 along with various treatments of the existing A556 are presented below.

2.6.4.1 - Option 1

Option 1 provides widening of the M6 and M56 and provision of free flow slips at Junction 20 to facilitate direct movement between the M6 south and M56 East. With this option no restrictions are imposed on the existing A556. This represents a Do-Minimum option in relation to the spectrum of management options that could be imposed on the A556.

As discussed earlier the route via junction 20 is significantly longer than the A556 and without any incentive to use the Junction 20 route traffic is unlikely to transfer. This is borne out by Figures 2.8 and 2.9. The model predicts only 1200 veh a day will use the Junction 20 route, the remaining traffic opting to remain on the routes they would have used with out the Junction 20 improvement. This is illustrated by comparison of figures 2.4 and 2.8 which show very similar traffic impacts. Widening of the motorway links reduces congestion and improves reliability and journey times for existing users of these links. These improvements attract North-South traffic and East-West traffic from parallel routes and are the prime reason for the increased flows on the widened motorway links, only 1200 of the increases in traffic being accounted for by South to West movements.

In summary, without some "management" of the A556, the J20 route is not attractive and the scheme fails to meet the objective of attracting strategic traffic and relieving the A556 and other routes.

2.6.4.2 - Option 2

Option 2, provides widening of M6 J19-20 and M56 J7-9 with free flow slips, as Option 1 but with closure of the south facing slips at Junction 19 to "force" traffic to use the new Junction 20 slips. The A556 has been reduced to a single carriageway, south of Bucklow Hill and a 40mph speed limit introduced.

Figure 2.10 shows the impact of Option 2 across the wider area, whilst Figure 2.11 shows the forecast flows. Closure of the Junction 19 slip roads results in less than 10,000 vehicles opting to use the Junction 20 slips. In the Do-Minimum 14,500 vehicles a day travel between the M6 and M56 and a further 5,000 between the M6 and A56 and both these movements are displaced by the Junction 19 slip closure in Option 2. The proportion of motorway to motorway trips that switch to Junction 20 is only 35% of those similar trips catered for by A556(M). Of the total displaced trips only 50% switch to Junction 20. Closure of the Junction 19 slips means that strategic trips that do not opt to continue to Junction 20 must leave the M6 at Junction 17 or 18. This closure also affects strategic trips heading to Northwich and Knutsford in addition to the "through traffic" discussed above. As a consequence flows on routes to the east of the M6 increase by 11%. Part of this increase is due to drivers travelling to Knutsford having to divert off the M6 at Junction 18. Flows to the west of the M6 increase by 9% as a result of trips to the Northwich area diverting off the M6 earlier and due to trips from Middlewich/Winsford finding non-motorway routes towards Manchester. Again flows on the widened sections of the M6 and M56 are higher due to higher travel speeds, but only about 70% of this additional traffic uses the new slips at Junction 20. Increases in traffic in the M6 corridor north of the M56 are in part due to some drivers opting to continue up to Junction 21a to join the M62 into Manchester, even though this junction experiences significant congestion in peak periods.

Figure 2.10 shows that across the wider network flows increase rather than decrease as a consequence of the scheme. Reductions in traffic are recorded on the M6 and A556 and the route through High Legh due to closure of the slip roads. The increase in flows across the wider network will impact on the local communities, including Holmes Chapel, Knutsford, Mobberley and other smaller communities. Local pinch points on the wider network may need to be improved to mitigate the effects of congestion. Narrowing the A556 is an integral part of the management of traffic on the A556 with this option. Although flows are approximately halved in relation to the Do-Minimum, the reduction in capacity leads to no overall improvement in traffic travel times or driver stress. Indeed, the reduction in road width may exacerbate problems when an incident occurs along the route, or on the M6 north of J19.

2.6.4.3 - Option 3

Option 3 represents the ultimate "traffic management" of the A556- full closure of the road between Junction 19 and Bucklow Hill for all except local access. This option impacts on all through traffic, presently using the A556 which in the Do-Minimum amounts to 38,500 vehicles a day. Figure 2.12 shows the impact on traffic flows of option 3, whilst Figure 2.13 shows the forecast flows. With this scheme 14,000 vehicles use the Junction 20 slips, higher than option 2 but the consequence of more draconian measures. Of the traffic routing via Junction 20, only 6,500 are motorway to motorway movements. Other strategic traffic diverts to a range of other routes as with Option 2. Impacts to the east of the study area are broadly similar to Option 2 as strategic traffic diverted by the closure of the A555 route chooses similar routes. This option retains access to Northwich from the M6 and flow increases to the west of the M6 are lower than Option 2 as changes are mainly due to Middlewich/Winsford traffic re-routing to new routes. The scheme prevents Northwich traffic using the A556 to travel towards Manchester. This traffic in part uses the M56 junction 10 to head north east, whilst the remainder seeks alternative routes round and through Knutsford. The A50 and A5034 route from Knutsford to Bucklow Hill is significantly affected and leads to traffic levels north of Bucklow Hill only reducing by about 50%.

Option 3 closes the A556 south of Bucklow Hill, which benefits the local community in environmental terms, however this is at the expense of other communities, in particular those on the A5034, Mobberley, Ashley and Knutsford.

2.6.4.4 - Option 4

With Option 4, restriction of the use of the A556 is based on reducing the road to a single carriageway and imposing a 40 mph speed limit. In practice and in particular in the peak periods speeds along the A556 are regulated by the traffic levels. The traffic impacts are shown in Figure 2.14 whilst the forecast flows are shown in Figure 2.15. This scheme is not discriminatory in that no specific movements are prevented from trying to use the A556. Due to the capacity restriction only a proportion of the total demand can be accommodated on the A556, the remainder finding alternative routes either via junction 20 or the local road network. Only 4,000 vehicles a day opt to use the J20 slip roads, only a quarter of the motorway to motorway traffic. The scheme has a broadly neutral impact on traffic levels to the south of the study area, relative to the Do-Minimum. However the scenario results in a higher level of traffic on these roads than occurs with the Incremental 2 network. So, although keeping the slip roads open at J19 reduces the impact on the network to the south of the scheme, it is at the expense of the usage of the Junction 20 slips. Narrowing the carriageway of the A556 reduces traffic levels on the road, from 38,600 in the Do-Minimum south of Mere crossroads, to 29,600, a reduction of only 25%. A comparison of journey speeds along the A556 between Junction 19 and Bowdon Roundabout is given in Table 2.4.

Table 2.4 - Comparison of Northbound Speeds Junction 19 to Bowden Rbt
  Do-Minimum Option 2 Option 4
AM Peak 38 kph 43 kph 21 kph
Inter-peak 60 kph 55 kph 28 kph

Closure of the Junction 19 slips in Option 2, reduces the demand for travel along the A556 and narrowing the road can be accomplished without impacting on travel times. However with Option 4, using narrowing to reduce traffic levels results in a halving of travel speeds, relative to the Do-Minimum. This leads to congestion along the route throughout the day and a significant degradation of journey quality for all users whether they are making strategic or more local trips.

Demand varies over the day but capacity provided is essentially fixed. As a consequence Option 4 leads to a more uniform flow profile on the A556 across the day and this explains why although the capacity of the route has been halved, the daily flow has only been reduced by 25%. Restriction of the A556 only "displaces" 9,000 vehicles a day from the route, of which only 44% use the Junction 20 slips.

2.6.4.5 - Assessment of Junction 20 Schemes

A broad range of restraint options have been investigated by the above tests, in an attempt to establish the most effective solution.

To be effective, a Junction 20 option needs to attract strategic traffic to travel a longer distance than at present via the new free flow slips. This is the nub of the matter that the MIDMAN strategic assessment was unable to firm up on. The present study has looked at a broad range of traffic management options and none of these schemes is fully effective and transfer is only achieved at a disadvantage to a significant amount of traffic.

The options investigated are summarised in Table 2.5.

Table 2.5 - Summary of Junction 20 Options
  Option 1 Option 2 Option 3 Option 4
Management measure None Close south facing slips at j19, narrow A556 Close A556 completely south of Mere Narrow A556
Targetted approach? No Strategic traffic between M6 and Bowdon No - all users affected No - all users affected
Users Adversely affected None Traffic from M6 south to Knutsford and Northwich All users. Local and strategic All users. Local and strategic
Through trips displaced by management measures None 19,500 40,000 9,000
Predicted usage of J20 slip roads AADT 1,200 9,900 14,000 4,100
Proportion of displaced traffic on slips None displaced 50% 36% 49%
Other adverse impacts None Local network particularly Holmes Chapel area. Trips to Northwich and Knutsford from M6 diverted off M6 Local network particularly Knutsford and Mobberley Local network particularly Knutsford and Mobberley

In none of the cases do the Junction 20 slips fully serve their intended purpose, to provide an attractive route to longer distance traffic. The additional distance involved in using Junction 20 is too great to be attractive to the majority of drivers that the scheme seeks to serve.

The above analysis clearly indicates that, some management of the A556 or access to it, is required if traffic is to be encouraged to use the newly constructed slip roads at junction 20. At the present day, the A556 is the signed route from the M56 to the M6 South and if a Junction 20 option were implemented traffic would be signed via Junction 20. The traffic model cannot take account of the impact of signing and it is accepted that the estimated usage of the Junction 20 slips is likely to be under-estimated by the model.

The above analysis has demonstrated that it is not possible to develop management measures that are targeted at re-routing strategic traffic and are effective at achieving this. The A556 at present provides a direct and reasonably effective link in the strategic network. Any junction 20 solution involves "persuading" drivers to use a less direct route and thus does not meet their aspirations. This is reflected in the above analysis which shows drivers, including those making strategic trips prefer to route to lower standard routes.

Option 2 is reasonably targeted but only transfers a half of the displaced trips to the new slip roads. It has the disadvantage of most of the options that it increases traffic levels on the wider network, particularly in southern Cheshire, with consequent congestion and environmental impacts for residents in the area. It does not lead to any appreciable improvement in traffic conditions on the existing A556 (compared with the Do-Minimum) but equally nor does it lead to a significant worsening of conditions as occurs with Option 4. In relation to motorway to motorway traffic, the scheme is not effective in retaining and encouraging strategic traffic onto the motorway, with only 35% of motorway to motorway trips retained on the motorway network. In terms of practicality and acceptability, Babtie consider that Option 2 is the most appropriate option to take forward to the economic assessment and GOMMMS appraisal, along with the A556 (M) Scenario. This decision was endorsed by the Steering Group.

2.6.5 Comparison of Scenarios

The A556(M) Scenario and the selected Junction 20 Scenario are compared below. The Junction 20 Scenario includes widening the M6 J19-20, M56 J7-9, closure of the south facing slips at Junction 19, provision of new slip roads at Junction 20 and narrowing of the existing A556 south of Bucklow Hill to a two lane single carriageway. A summary of the impacts is shown in Table 2.6 below.

Table 2.6 Summary of Scheme Impacts
  DO-MIN A556(M) M6 J20 (Opt 2)
Existing A556 traffic levels (2011) 38, 600 - 50, 3000 1, 200 - 9, 900 20, 300 - 34, 000
A556(M) traffic levels (2011) N/A 49, 200 N/A
M6 J20 slips traffic levels (2011) N/A N/A 9, 900
SW Screenline S. of Northwich 30, 000 Decrease by 2,500 Increase by 3,300
SE Screenline S. of Knutsford & Alderley Edge 50, 000 Decrease by 6,000 Increase by 5,300
NE Screenline S. of Ashley 10, 000 Decrease by 1,400 Increase by 1,200
Impact on Strategic Traffic (m'way to m'way) 14,500 18,900 - Additional 4,500 trips attracted back to motorway network 6,600 use J20 slips - 7,900 Trips displaced to local road network
Impact on communities N/A Reduction of traffic through towns and villages Increase in traffic through towns and villages
Traffic conditions on Existing A556 N/A Most traffic transferred to parallel motorway Traffic halved but congestion levels not improved

The two scenarios have opposing traffic effects. The A556(M) enhances the motorway network by providing a direct link between J19 and J7 and attracts strategic traffic onto the motorway, re-enforcing the strategic role of the M6 and M56. The reduction in traffic across the local road network is to the benefit of the local communities, reducing congestion and consequent environmental problems. It removes 80 - 90% of traffic from the A556 to the parallel A556(M), to the benefit of the properties fronting the existing road, but to the disadvantage of a number of properties close to the new motorway.

The Junction 20 Scenario displaces strategic, motorway to motorway, traffic from the A556(M) with only 35% of it transferring to the new Junction 20 slip roads, the remaining traffic opting to use a range of A class, B class and C class roads across the Cheshire network. Closure of the slip roads also impacts on traffic from the M6 with a local destination in the Knutsford/Northwich area that is forced to leave the M6 at Junction 17 or 18. These increases in traffic will increase the adverse impacts of traffic experienced in communities such as Holmes Chapel, Knutsford, Mobberley. The local Highway Authority may need to develop schemes to alleviate pinch points on the local road network to mitigate the impacts of the Junction 20 scheme. Narrowing of the A556 south of Bucklow Hill and the lowering of the speed limit to 40mph is a integral part of the scheme. Traffic levels on the A556 are roughly halved but there is no significant change in journey speeds along the route as identified in Table 2.1 of 40-60 kph.

To quantify the wider area impacts of the two scenarios, an analysis has been undertaken of the network within which flow changes for the two schemes are encompassed. Links have been categorised by flow level and change in flow as shown in Figures 2.16 and 2.17. The analysis method is detailed in Appendix 3.

These figures show that the whilst only 11 kilometres of the network have an increase in traffic of more than 10% with the A556 (M) scheme, 111 km of network experience this level of increase with the Junction 20 scheme. Likewise, the A556 scheme reduces traffic by more than 10% on 132 km or route, whilst the Junction 20 scheme reduces traffic on only 39 km of the network.

In conclusion, the two scenarios have markedly different traffic impacts and in terms of the traffic related objectives set by the wider MIDMAN study the A556(M) performs better, as discussed in more detail in section 9.

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2.0 traffic

3.0 engineering

3.0 Engineering

3.1 Standards used in option design

The A556(M) was the subject of a Public Inquiry in 1993, at which stage it was presented as a dual 3-lane motorway (D3M) scheme. Subsequent to the publishing of the Line and Side Roads Orders in 1996, a Value Engineering Exercise was instigated by the Highways Agency, one of the outcomes of which was a reduction in standard of the A556(M) scheme to a dual two lane motorway (D2M). This standard, D2M, has formed the basis of the assessment in this study.

The MIDMAN study concluded, as part of their Scenario 2, and in particular their assessment of the J20 scheme, that the M6 between J19-20 would probably require widening to dual 4-lane motorway (D4M) and the M56 between J9-7 would perhaps require widening to D4M. Given the time limitations imposed on this study, Babtie assumed that both sections of motorway would be widened to D4M and this formed the basis of the assessment in this study. This assumption was accepted by the Steering Group as the pragmatic way forward, with the standards to be confirmed by the traffic and economic modelling and analysis.

The M56 Junctions 7 - 6 is treated in the study as a 'stand-alone' scheme and since the brief was to investigate capacity problems, a D4M standard was used as the basis of any required increase in capacity.

3.2 Description of A556(M) Scheme

3.2.1 Introduction

The proposals involve the construction of a new motorway between the M6 and M56, west of the existing A556 route. There would be free flow junctions with the M6 and M56, and two intermediate grade separated junctions with the existing A556, one located north of the M6 and one south of the M56. There would be full access to the Knutsford Motorway Service Area (MSA) from both the M6 and the new scheme. The proposals also include the closure of the south facing slip roads at Junction 19 on the M6 and their reinstatement connecting the M6 with Northwich Road. This scheme is principally that for which Line and Side Road Orders were made in 1996 and subsequently modified following a Value Engineering Review in 1997.

3.2.2 The Main Line

Commencing from the south, the M6 would be widened symmetrically to dual 4 lanes from the new south facing slip roads from Northwich Road to where the A556(M) connects with the M6.

Between a point just south of Tabley Hill Lane and Junction 19 the existing sub-standard M6 horizontal alignment would be improved and the existing south facing slip roads at Junction 19 would be removed in order to facilitate the provision of the north facing slip roads from the MSA to the M6 (see Section 3.2.3). After the MSA overbridge the northbound carriageway would develop into 5 lanes, 2 lanes forming the northbound carriageway of the new scheme which would diverge from the M6 immediately north of Northwich Road, pass under Tabley Hill Lane and then turn in a northerly direction to cross over the M6 approximately midway between Tabley Hill Lane and Junction 19. It would then cross under Swain's Walk and converge with the southbound carriageway of the A556(M) in the vicinity of Moss Lane.

The mainline would be a dual 2-lane motorway. It would pass under Chester Road, then under Bentleyhurst Lane, and turning northward to run approximately parallel to the A556 Chester Road, it would pass under the A50 Warrington Road, the Hulme Barns Farm accommodation bridge, Bucklowhill Lane and Chapel Lane. The mainline would then turn eastwards, crossing Millington Hall Lane and passing under Millington Lane before passing under New Hall Farm accommodation bridge and Chester Road.

Immediately south of the M56 the carriageways would diverge with the southbound carriageway joining the M56 just west of Bowdon Link. The northbound carriageway would pass under the M56 and westbound Bowdon Link before merging with the realigned eastbound slip road from Bowdon roundabout and joining the M56 in the vicinity of Ryecroft Covert.

The scheme would be lit in the vicinity of the free flow motorway interchanges, but the central section would not be lit.

3.2.3 Side Road Arrangements

Wherever it is necessary for a side road to cross the scheme, where possible the structure would be constructed at right angles to the mainline, and off the existing line of the side road thus enabling access to be maintained on the side road during the construction period.

Commencing from the south, Sudlow Lane would cross over the M6 on a new structure to the south of the existing, which would have to be demolished to accommodate the new south facing slip roads to the MSA and Northwich Road. Sudlow Farm accommodation bridge over the M6 would be demolished and not replaced. Northwich Road would form part of J19, receiving the south facing slip roads from the M6. Northwich Road would be realigned to the north in order to construct the new bridge over the M6. Both of the slip road junctions with Northwich Road would be roundabouts, and the length of Northwich Road between the roundabouts would become a dual carriageway. To the west of the western roundabout Northwich Road would become a wide single carriageway to its junction with A556 Chester Road.

Tabley Hill Lane would cross over the M6 and the A556(M) links on a new structure located to the south of the existing; Swain's Walk, a bridleway and private means of access, would be carried over the A556(M) links on bridges; Moss Lane would be realigned to the north in order to construct the new structure carrying it over the scheme and also to facilitate the removal of two acute bends to the east of the mainline.

North of Moss Lane, the intermediate junction between the new scheme and A556 Chester Road would be sited (see Section 3.2.4). The new structure taking Chester Road over the scheme would be to the west of the existing line, with Chester Road constructed as a wide single carriageway between the 'dumb-bell' roundabouts. The existing gaps in the central reserve on the length of Chester Road between this junction and Junction 19 would be closed, turning movements being via the roundabouts.

Bentleyhurst Lane would cross over the scheme on a structure to the north of the existing line; the A50 Warrington Road would cross the mainline on a structure constructed as close as possible to the existing line on the south side in order to maintain the highway standards of the A50; an accommodation bridge for Hulme Barns Farm would be constructed some 250 metres north of Warrington Road.

The structures carrying Bucklowhill Lane and Chapel Lane would be constructed to the north and south of the existing lines respectively. Millington Hall Lane would be severed by the scheme. Access to the eastern length of the lane would be via an improved junction with A556 and access to the western length would be via an improved junction with Millington Lane; Millington Lane would cross the mainline on a structure south of the existing line and an accommodation bridge for New Hall Farm would be constructed some 220 metres north of Millington Lane.

Yarwoodheath Lane bridge, which carries an accommodation track and a public footpath, would be demolished and not replaced. During the Public Inquiry there was no request from the affected owners for a new bridge since a large area of land to the south of M56 currently served by the bridge would be required for the A556(M). Ryecroft footbridge would be rebuilt some 20 metres to the east of the existing structure.

The construction of the new scheme would also include an improvement to the existing A556 between the proposed roundabout adjacent to Mereside Farm and Bucklow Hill. Between these two points Chester Road would be reduced from a four lane to a two lane single carriageway road, thus allowing the substandard bend to be improved and right turning facilities provided at Millington Hall Lane and Millington Lane. A further amendment to the A556 would be provided in the vicinity of the M56 underbridge where the carriageway configuration would be revised to allow for the addition of an extra lane. This would be done by reducing the existing lane and central reserve width.

Since the A556(M) would remove a significant amount of traffic from the existing A556 between Bucklow Hill and the proposed junction at Tabley, concern was expressed in the Public Inquiry in 1993 that if no physical measures were applied to the carriageway it would be attractive to 'boy racers' and the like. The format of any measures was never agreed with Cheshire County Council so for the purpose of this exercise it has been assumed that the carriageway would be narrowed to 7.3 metres. The proposals are shown on the drawings in Appendix 5 and have been included in the scheme cost estimates in section 4.

3.2.4 Junction Strategy

3.2.4.1 M6/A556(M)/MSA Interchange

Commencing from the south, the existing sub-standard south facing slip roads into the Motorway Service Area would be replaced by new slip roads commencing south of Sudlow Lane. These slip roads would not only provide access into and out of the MSA from the south but would also extend to provide a highway access to and from Northwich Road. These slip roads would provide access for both Northwich and Knutsford traffic; in the case of Northwich traffic there would be redistribution of traffic such that it approaches the Northwich Road/Chester Road junction along Northwich Road instead of, as at present, from Junction 19. This increased volume in traffic requires the widening of Northwich Road between the M6 and Chester Road, and the improvement of the existing traffic signal controlled junction by the addition of a 'G-turn'. The slip roads would be located in such a position as to allow for the expansion of the Service Area.

North of Tabley Hill Lane the northbound A556(M) link would merge with the slip road carrying traffic from the MSA to the new scheme. Northbound traffic leaving the MSA wishing to access the M6 would use a new slip road from the MSA running parallel to the northbound carriageway of the new scheme joining the M6 immediately south of Junction 19. In a southerly direction, a slip road for vehicles on A556(M) wishing to access the MSA would diverge off the mainline immediately south of Swain's Walk; this slip road would merge with the southbound slip road from the M6 before entering the MSA. The southbound slip road from the M6 would diverge from the M6 south of Junction 19, go under and then over the northbound and southbound carriageways respectively of the new scheme before merging with the southbound MSA slip road from the new scheme. This overall junction arrangement ensures that all traffic movements between the M6/A556(M) and MSA, plus movements between M6 and A556(M) and M6 and A556 are catered for.

3.2.4.2 A556(M)/A556 Junction at Over Tabley

At Over Tabley a junction between the A556(M) and Chester Road will be provided by means of grade separation and north facing slip roads. Two new roundabouts will be constructed on Chester Road. This junction would cater for traffic between Northwich and A556(M) and would help to ensure maximum relief to the existing A556 between this point and Bucklow Hill.

3.2.4.3 A556(M)/A556 Junction at Rostherne

At Rostherne a junction between the A556(M) and Chester Road will be provided by means of grade separation and a roundabout. The roundabout will be situated at Mereside Farm and a slip road will link the A556 and the southbound A556(M). This slip road will carry all southbound traffic from Altrincham, except that travelling to Knutsford. Northbound traffic will enter the existing A556 in the vicinity of the existing M56 bridge. This overall junction layout will cater for traffic between Altrincham and A556(M) and would ensure maximum transfer of traffic onto the A556(M).

3.2.4.4 M56/A556(M) Interchange

Immediately south of the M56, the two carriageways of the A556(M) would diverge with the southbound carriageway joining the M56 just west of the Bowdon Link. The northbound carriageway would pass under the M56, under the M56 westbound Bowdon Link, to merge with the realigned eastbound slip road from Bowdon roundabout and joining the M56 in the vicinity of Ryecroft Covert. The existing eastbound slip road from the M56 to Bowdon roundabout would be realigned to accommodate the alignment of the northbound carriageway of the new scheme. This junction layout provides free flow between M56 and A556(M).

3.3 Comparison of Parallel Widening and Asymmetrical Widening

3.3.1 Introduction

Two forms of motorway widening to give dual 4 lane carriageways are assessed in this report, and both forms, parallel and asymmetrical, have been applied to both M6 and M56 to allow a comparative assessment in line with GOMMMS.

3.3.2 Parallel Widening

The proposed layout is shown on Drawing Nos. 7201914/YA/002 in Appendix 4. The principle behind this layout is to construct a whole new carriageway outside the existing trafficked carriageways to minimise interference with traffic flows. The centreline of the widened motorway is offset from the existing centreline by 21.9 metres, to a position 6 metres outside the existing back of verge. Once the new carriageway is constructed, traffic is transferred to it from the nearest existing adjoining carriageway, which is then widened to accommodate the fourth lane before being utilised by traffic in the 'opposite' direction. The redundant carriageway is then landscaped with part of it retained for access, either emergency or during maintenance work on the motorway. Parallel widening has the advantage of minimising disruption to traffic during construction and moving the motorway away from sensitive locations. Additional land is generally only required on one side of the motorway and the choice of the widened side takes account of important engineering and environmental features, while providing for extensive landscape treatment and, where necessary, noise barriers.

3.3.3 Asymmetrical Widening

The proposed layout is shown on drawing No. 7201814/YA/001 in Appendix 4. The principle behind this layout is to limit the extra amount of land required, and to purchase that land on one side of the motorway only. The centreline of the widened motorway is offset from the existing centreline by 3.6 metres, with the edge of the widened carriageway being positioned 2.4 metres beyond the back of the existing verge.

Asymmetrical widening has the advantage of minimising the landtake, but 2-way contraflow would be required during construction causing significant congestion which could lead to traffic diverting off the motorway.

3.4 M6 J19-J20 (as part of J20 scheme)

3.4.1 The Main Line

Although the MIDMAN1 study recommends that the M6 motorway be widened from the south as far as J19, it was always the intention that the A556(M) would include the widening of that section of M6 affected by the A556(M) scheme, i.e. the section from a point south of Sudlow Lane to where the A556(M) scheme diverged from the M6. To allow a true comparison to be made between the two overall options, the widening of M6 as part of the Lymm Interchange solution has been taken at the corresponding point, i.e. south of Sudlow Lane.

To limit the impact on Knutsford MSA, symmetrical widening would be utilised from south of Sudlow Lane to the tie-in of the north facing slip roads from Junction 19, Tabley. Also, as incorporated in the A556(M) scheme, the sub-standard alignment of the M6 between Northwich Road and the north side of J19 is improved.

From the point north of J19, two widening schemes, parallel and asymmetrical have been designed for the remaining length of M6 as far as Junction 20. The widening has been applied to where the M6 to M56 eastbound and M56 to M6 southbound slip roads diverge from the M6, with the M6 remaining as a dual 3-lane carriageway through J20. The widening has been applied to the west side, this being the side recommended by Pell Frischmann in their earlier proposals for M6 widening. This decision of widening the west side of M6 has been confirmed by Babtie after assessment of relevant factors. The full length of the M6 within this option, being of D4M standard, would be lit.

3.4.2 Side Road Arrangements

It has been assumed that every existing crossing of the M6 motorway, be it a county road, farm accommodation bridge or footbridge, will require to be incorporated in any widening scheme, but will also require to be maintained in use during the construction of the widening works. To achieve this all the new bridges, except those specifically indicated otherwise below, would be built off line from the existing structure, which would be demolished once the 'diversion' was in use.

Commencing from the south, Sudlow Lane would cross over the M6 on a new structure to the south of the existing. The existing bridge, along with Sudlow Farm accommodation bridge, would have to be demolished to accommodate the resited slip roads from Knutsford MSA. Sudlow Farm accommodation bridge would not be replaced.

Northwich Road would be realigned to the north in order to construct the new bridge over the M6; this shift to the north will assist the resiting of the slip roads from the MSA. Tabley Hill Lane would also be realigned to the north.

Old Hall Lane bridge would be rebuilt on line, with the road closed whilst the new bridge is built. There appears to be a convenient alternative route via the B5391 Budworth Road and the A556 to allow the side road to be closed for a limited period. The footbridge carrying the public footpath between Winterbottom and Hollowood Farm will be reconstructed slightly to the north, whilst the accommodation bridge some 1km to the north, would be rebuilt on the south side of the existing.

Cann Lane would be diverted to the south to avoid impact on property sited on the north side of the existing road; also the accommodation bridge/public footbridge linking Northwood Lane and The Ashes would be rebuilt on the south side. Similarly the combined access/footpath bridge to Crowley Hall will be relocated on the south side. Finally, at the northern end, the accommodation bridge adjacent to Sebastapol Covert would be relocated on the south side.

3.4.3 Junction Strategy

Commencing from the south, the existing sub-standard slip roads servicing the MSA would be replaced by full standard slip roads. The south-facing ones would commence 200 metres north of Sudlow Lane, the north-facing ones north of Northwich Road.

The realignment of M6 to remove the substandard horizontal radius would necessitate the demolition of the two existing interchange bridges at Tabley. It is proposed that these bridges be replaced by a single bridge, wide enough to accommodate a dual carriageway, located in the centre of the existing interchange. A dumb-bell roundabout arrangement would be incorporated; dependent upon whether traffic restrictions are imposed on A556 north of Junction 19, the dumb-bell roundabouts could be traffic signalled controlled.

The proposals for M6 both parallel and asymmetrical widening are shown on the drawings in Appendix 5.

3.5 Lymm Interchange (J20 scheme)

3.5.1 Introduction

Lymm Interchange currently links the M6 Motorway (Junction 20) with the M56 Motorway (Junction 9). However, the layout of the interchange does not afford free-flow for all movements. Traffic travelling north on the M6, wishing to turn east towards Manchester and traffic travelling west on M56 wishing to turn south towards Birmingham are required to travel up to the Interchange with the A50 (Junction 20), sited some 1km north of M56. This interchange takes the form of a priority dumb-bell roundabout and as well as serving the A50 also provides access to the adjacent 'Truckstop', which provides service area facilities for commercial vehicles. It is considered that this junction would not cope with the additional volume of traffic diverted from A556. Owing to the convoluted layout of the existing Lymm Interchange the only feasible way to cater for the movements described above is to provide free flow links to the south east of the existing interchange.

3.5.2 Main Line

The M6 northbound to M56 eastbound link commences in the vicinity of Crowley Hall and heads on a left-hand curve before following a radius of 720 metres to cross Intack Lane immediately west of Intack Farm, which would be isolated between this link and the M6. The link then crosses the M6 at a skew of 45° some 200 metres south of Swineyard Lane bridge, and then Swineyard Lane itself immediately east of that lane's junctions with Withers Lane. The link passes within 20 metres of the private residence, Crowthorne, where a retaining wall would be required to save the property, before crossing Fanners Lane and through three properties, Green Croft, Burnaby and Ash Dene. It then crosses the M56 at a skew of 39°, following a right-hand radius of 720 metres to cross the A50 some 50 metres south east of its junction with Broadheys Lane before joining the M56 eastbound carriageway in the vicinity of Big Wood.

The M56 westbound to M6 southbound link commences immediately east of the existing A50 bridge at Primrose Hill and follows a 720 metre radius left-hand curve to pass north of Rowlinson's Green before crossing Fanner's Lane. It then passes through Stores Farm as it crosses Swineyard Lane, and continues on the left-hand radius to cross Intack Lane some 50 metres west of Moss Oaks Farm before joining the M6 southbound carriageway in the vicinity of Sebastapol Covert. The links, being part of the motorway interchange, will be lit.

3.5.3 Side Road Arrangements

The eastbound link isolates Intack Farm by placing it between the link and the M6 Motorway. The engineering layout incorporates a bridge to allow access to this property but it may be, if this option is progressed, that it is deemed more beneficial to both Highways Agency and the property owners, to 'take' the property. Both links then bridge over Swineyard Lane, before crossing Fanner's Lane, which will be stopped up. The eastbound link then affects Withers Lane at its junction with the A50. Withers Lane would be diverted to the north, and the A50 bridged under the new link.

The proposals are shown on the drawings in Appendix 5.

3.6 M56 Junction 9-7 (as part of J20 scheme)

3.6.1 The Main Line

The M56 is currently D2M through Lymm Interchange, gaining lanes to become D3M where the east facing slip roads tie in. The proposed scheme is for an additional lane gain to occur where the 'Lymm free-flow links' tie-in to produce a D4 motorway. This widening of the M56 is proposed on the north side between Primrose Hill (the A50 Crossing) and Junction 7 at Bowdon, with the 4-lane carriageways being continuous through Bowdon Interchange. Where the M56 passes under West Lane, a retaining wall will be required to limit the impact on the private house, Newlyn. The whole length of the M56, within this option, being D4M standard, would need to be lit.

3.6.2 Side Road Arrangements

As with M6 widening, it has been assumed that every existing crossing of the M56 will require to be incorporated in the widening scheme, but will also require to be maintained in use during the construction period. To achieve this all the new bridges would be built off-line from the existing structure which would be demolished once the diversion was in use.

The shift of the M56 to the north to accommodate widening commences west of the current A50 bridge. The A50 will remain on its current alignment but to achieve this a temporary bridge will be required during construction.

Meg Lane would be diverted to the west to limit the impact on Greatoak Farm. Beechtree Lane, which currently runs parallel to the M56, will be diverted further to the north to a new T-junction with West Lane, which itself is diverted to the west to cross the M56. Agden Lane would be diverted to the east onto its original line but this would result in the demolition of Agden House.

Reddy Lane, which goes under the M56, would remain on its current alignment, the existing bridge being extended on its northern side. The bridge also accommodates an access track for Booth Bank Farm. This track would need realigning on the north side of the M56. Coe Lane, which becomes a private road to Hope Cottage and a public footpath, will be diverted to the west.

The A556 Chester Road crossing presents major engineering difficulties. The proposed solution is to build a new bridge on line in two halves. A diversion is not possible due to the constraints of the Nag's Head on the west side and the loop to the M56 on the east side. Traffic delays during construction would be significant enough to result in traffic using local roads to avoid delay.

Yarwoodheath Lane, which is a private road and public footpath would be diverted to the east.

The proposals for M56, both parallel and asymmetrical widening are shown on the drawings in Appendix 5.

3.6.3 Existing A556

As described in Section 2, if the Junction 20 scheme proceeds, measures would need to be applied to the existing A556 to limit its attractiveness to traffic which currently uses it. The measures which have been taken through the assessment are as set out in paragraph 2.3 option 2 i.e. removal of South facing slips at Junction 19 and narrowing of the A556 to 7.3 metre wide single carriageway between J19 of the M6 and J7 of the M56. The cost of these measures have been included in the scheme cost estimates in section 4.

3.6.4 Junction Strategy

The M56 Junction 7 will remain the same layout in principle as exists. However the eastbound off slip will require relocating to the north to accommodate the motorway widening, and the westbound offslip will be diverted to the west to allow a new bridge to be built over M56. This latter proposal may be reconsidered if this option progresses; closure of the link during construction may be an option.

3.7 M56 Junction 7-6

3.7.1 Main Line

To the east of Junction 7 the widening of the M56 is proposed to be on the north side so there is no impact on Rostherne Mere, a RAMSAR site and Site of Special Scientific Interest. However, as the M56 approaches the River Bollin, the widening will be done symmetrically to limit the impact on the Bollin Valley. This symmetrical widening is then carried through to Junction 6, the termination point of this study. Currently, the M56 is a D3M through Junction 6, picking up a fourth lane east of Junction 6. There will therefore be a lane drop eastbound and a lane gain westbound west of this junction.

3.7.2 Side Road Arrangements

Ryecroft footbridge would be rebuilt east of the existing structure. Hardy's Covert bridge, which carries a private road to Ashley Hall and a public footpath, would be rebuilt to the east of the existing. Both the railway and Cow Lane pass under the M56 and in both cases, the existing bridges will be extended on the north side. Ashley Road will be diverted to the east to avoid any additional impact on Tanyard Farm. The accommodation bridge for Thornsgreen Farm will be resited on the west side.

Where the M56 crosses the River Bollin, the form of widening is symmetrical with a loss of hardshoulders. The existing river bridge will therefore remain unchanged with no additional impact on the River Bollin. Finally, Sunbank Lane which is carried over the M56 will be closed whilst a new bridge is built on-line. There is a convenient alternative route via the interchange with the Wilmslow Road.

The proposals for this section of M56, both parallel and asymmetrical widening are shown on the drawings in Appendix 5.

3.8 Conclusion

3.8.1 The A556(M) scheme would be predominantly D2M standard with free flow interchanges with both the M6 and M56. Its scheme length is 11.5Km and it requires no property demolition.

3.8.2 The J20 scheme requires the widening of the M6 on the West side between J19 and J20 and the widening of the M56 on the North side between J9 and 7 to D4M standard. The scheme length is 21.2Km and it requires the demolition of 5 private houses.

3.8.3 The M56 between Junction 7 and 6 requires widening to D4M standard. The widening to be on the North side to West of the crossing of the River Bollin, where symmetrical widening is proposed. The length of the widening is 5.0Km and no property demolition is required.

3.8.4 With regard to motorway widening, both parallel and asymmetrical forms of widening are considered to have merit and are taken forward throughout the following assessment.


3.0 engineering

4.0 scheme cost estimates

4.0 SCHEME COST ESTIMATES

4.1 General

4.1.1 The approach taken with respect to preparation of the Scheme Cost Estimates follows closely that adopted previously for Estimates prepared at OPR stage for the A556 (M) Scheme.

4.1.2 The format of the estimate is based on the Highways Agency's Works Commitment Submission pro-forma (TR 415 rev. 8/90).

4.1.3 We have assumed that all surplus material can be re-used in areas contiguous with the Scheme and therefore does not attract a premium for Landfill Tax. These particular areas are shown on the Landscape Plans in Appendix 7, since they are considered to be an integral element of the landscape proposals.

4.2 Methodology

4.2.1 With respect to the Main Works Contract for most of the cost elements quantities have been measured and set against items taken from the Method of Measurement for Highway Works. Reference has been made to the Engineering Plans, Moss highways computerised modelling information, Highway Construction Details published by Highways Agency, in order to produce a Bill of items to be priced. For Preliminaries a percentage of the Main Works Total (before Preliminaries) of 12.5% has been used with costs for traffic management added separately.

4.2.2 Rates have been established by reference to published data namely "Spons Civil Engineering and Highway Works Price Book 2002"6 as well as in-house cost data, cost information from the Highways Agency and uplifted to an estimate base date of Q4 2001.

4.2.3 With respect to some cost elements and other Sections (e.g. Traffic signs and Road Markings) where it is not possible to properly quantify and rate such work a percentage based on the Main Works Total has been used.

4.2.4 No Allowance has been made for Accommodation Works, as they cannot at present be defined.

4.2.5 De-trunking costs for works to the existing A556 are shown under 'Other Works'.

4.2.6 Contingency and VAT have been included in the Scheme Cost Estimates at 10 and 17.5 % respectively, on all elements of the works.

4.3 Conclusions

4.3.1 The Total Estimated Scheme Cost for the A556 (M) is £116M. The total estimated scheme costs for the M6Junction 20 Widening Scheme options (Parallel and Asymmetrical) are £161M and £131M respectively.

4.3.2 A high level risk analysis has been undertaken on the two options of A556(M) and J20. This analysis indicates that the contingency of 10% allowed on the A556(M) scheme is of the right order but for the J20 option it should be double that allowance mainly due to the specific risk of the outcome of a public inquiry. However, both options have been estimated using a 10% contingency allowance to avoid criticism of bias.

4.3.3 The Total Estimated Scheme Costs for the M56 Junction 7 to 6 options are £34M and £29M (Parallel and Asymmetrical) respectively. Similarly to the J20 option, a risk analysis indicates that the contingency should be of the order of 20% but a figure of 10% has been used in the estimates

4.3.4 The traffic management costs are estimated at:

J20 Scheme:
Parallel Widening £2.20M
Asymmetrical Widening £3.86M

M56 J7-6
Parallel Widening £1.50M
Asymmetrical Widening £2.61M

and show a significant cost penalty, in traffic management terms, for asymmetrical widening.


4.0 scheme cost estimates

5.0 environmental assessment

5.0 Environmental Assessment

The environmental assessment is based primarily on available information. This information has been collated from a number of sources including consultation information provided by statutory and non-statutory consultees, review of previous Environmental Statements and new fieldwork undertaken for the Landscape and Visual Assessments. Despite the historical nature of the information obtained from the Environmental Statements, they cover the M6 widening option and the A556(M) option in reasonable detail. While the M56 widening options have not been covered by specific environmental assessments, consultations have provided information to allow for assessments to be undertaken at a similar level of detail for these options.

5.1 Noise

5.1.1 Approach/Methodology

The method for assessing noise was based on the principles of the guidance contained in GOMMMS Volume 2, Section 43. However because the area of impact was so extensive the method was adapted as follows:

The assessment was based on the year 2011 for consistency with the MIDMAN study.

5.1.2 Impacts of A556(M) Scheme

The proposed road would affect traffic flows over a wide area extending as far as Junction 17 of the M6 to the south and to Wilmslow in the east. Noise levels may be expected to decrease noticeably (by more than 1dB LA10 (18Hr)) at houses fronting sections of the A50 and the A535. The occupiers of almost 400 properties might expect an improvement in their noise climate.

Seven residential properties stand within 50 m of proposed new road. These might expect noise levels to rise substantially to above 70dB LA10 (18Hr).

5.1.3 Impact of J20 Scheme

The proposed road would affect traffic flows over a wide area extending as far as Junction 17 of the M6 to the south, to Wilmslow in the east and west of the M6 as far as Middlewich. The general effect would be to reduce traffic on all-purpose roads in the area of junctions 19 and 20 of the M6 whilst increasing traffic on a network of roads to the south and east.

Noise levels may be expected to decrease noticeably (by more than 1dB LA10 (18Hr)) at approximately 100 houses fronting roads where traffic would reduce. However traffic would increase by more than 25% on approximately 50Km of highway and over 700 houses fronting these roads could expect a noticeable increase in traffic noise.

Seven residential properties stand within 50 m of proposed new slip roads at the motorway junction. These might expect noise levels to rise substantially to above 70dB LA10 (18Hr).

5.1.4 Impact of Junction 7 - 6

The changes in traffic flows resulting from the widening can be expected to be less than +25 or -20%. Consequently changes in traffic noise would be insignificant.

The worksheets 4.1 are included in Appendix 8, except for M56 J 7 - 6 where no properties would experience a change of more than 1dBA.

5.1.5 Summary of Noise Impacts

A566(M) M6 J20, M6 J19 - 20 and M56 J9 - 7. Parallel Widening M6 J20, M6 J19 - 20 and M56 J9 - 7. Asymmetrical Widening M56 J7 J9 Parallel Widening M56 J7 J9 Asymmetrical Widening
+29 population win -37 population lose -37 population lose No net change No net change

5.2 Air Quality and Greenhouse Gases

5.2.1 Approach and Methodology

The method for assessing air quality objective was based on the principles of the guidance contained in GOMMMS Volume 2, Section 43. However because the area of impact was so extensive the method was adapted as follows:

The assessment was based on the year 2011 for consistency with the MIDMAN study.

5.2.2 Impact of A556(M) Scheme

There would be a redistribution of traffic over a wide area. Lengths of the A50 between Knutsford and Holmes Chapel would see a reduction of up to 54% in traffic flow and, between Holmes Chapel and Alderley Edge flow would reduce by more than 30%. In total more than 1500 residential properties front sections of road that would experience reductions of more than 10% in traffic flows whilst just 180 houses front roads that would see more than 10% increases.

As a consequence there would be a significant reduction in kerbside concentrations of oxides of nitrogen and particulate matter (PM10) over a total length of more than131 kilometres of road. However concentrations would rise alongside some 11 kilometres of highway. There would therefore be a net improvement in local air quality.

The assessment of greenhouse gases is based on the prediction of carbon dioxide emissions. This showed that the expected reduction of traffic on many roads would result in a reduction in emissions of some 26,000 Tonnes/year.

5.2.3 Impact of J20 Scheme

There would be a redistribution of traffic over a wide area. Between Junction 19 of the M6 motorway and Mere, traffic on the A556 would fall by more than a half and the A50 between Mere and Sworton Heath would see a 25% reduction. However there would be substantial lengths of highway where traffic flows would increase. In total some 309 residential properties front sections of road that would experience reductions of more than 10% in traffic flows whereas more than 1500 houses front roads that would see more than 10% traffic increases.

As a consequence there would be a significant reduction in kerbside concentrations of oxides of nitrogen and particulate matter (PM10) over a total length of some 33 kilometres of road. However concentrations would rise alongside some 111 kilometres of highway. There would therefore be a net deterioration in local air quality.

The assessment of greenhouse gases is based on the prediction of carbon dioxide emissions. This showed that the expected increase of traffic on many roads would result in an increase of emissions of more than 60,000 Tonnes/year.

5.2.4 Impact of M56 Junctions 7 - 6

The impact of the scheme would be limited. Traffic flows would change by more than 10% on just 4km of road. As a consequence there would be a significant reduction in kerbside concentrations of oxides of nitrogen and particulate matter (Pm10 ) alongside these roads. Air Quality at 183 frontage properties would improve significantly.

The emissions of Greenhouse Gases would also reduce. It could be expected that total emissions of CO2 would fall by 866 Tonnes. This compares with a figure of 3313K tonnes from UK transport sources for the year 1996.

The worksheets 4.3 for Air Quality and 4.5 for Greenhouse Gases are included in Appendix 8.

5.2.5 Summary of Local Air Quality Impacts

Summary of Local Air Quality Impacts
A566(M) M6 J20, M6 J19 - 20 and M56 J9 - 7. Parallel Widening M6 J20, M6 J19 - 20 and M56 J9 - 7. Asymmetrical Widening M56 J7 J9 Parallel Widening M56 J7 J9 Asymmetrical Widening
Concentration weighted for exposure: PM10 -509, NO2 -303 Concentration weighted for exposure: PM10 1084, NO2 6126 Concentration weighted for exposure: PM10 - 509, NO2 6126 Concentration weighted for exposure: PM10 -27.4, NO2 -208 Concentration weighted for exposure: PM10 -27.4, NO2 -208

5.2.6 Summary of Impacts on Greenhouse Gases

Summary of Impacts on Greenhouse Gases
A566(M) M6 J20, M6 J19 - 20 and M56 J9 - 7. Parallel Widening M6 J20, M6 J19 - 20 and M56 J9 - 7. Asymmetrical Widening M56 J7 J9 Parallel Widening M56 J7 J9 Asymmetrical Widening
Reduction in CO2 = 26250 tonnes Increase in CO2 = 61377 tonnes Increase in CO2 = 61377 tonnes Reduction in CO2 = 866 tonnes Reduction in CO2 = 866 tonnes

5.3 Greenhouse Gases

This sub-objective is included in 5.2 above.

5.4 Landscape

5.4.1 Introduction

5.4.1.1 This assessment has been prepared by Randall Thorp, Landscape Architects, on behalf of Babtie, and as part of the Highways Agency detailed Appraisal of the A556 Area.

5.4.1.2 The purpose of this assessment is to compare the landscape impacts arising from the proposed A556(M) motorway scheme; with the alternative options of widening the M6/M56 and building new links at the Lymm interchange; and to consider the widening of the M56 between junctions 7-6, which is supplementary to the two options above.

5.4.3. Site inspections were undertaken to assess the effects of the options on all potential receptors. The receptor plans, landscape working papers and site notes have not been included in the Appendices because of their volume but are available to interested parties from either Highways Agency or Babtie Consulting Engineers, both in Manchester.

5.4.2 Methodology And Scope Of The Assessment

5.4.2.1 This assessment has been prepared in accordance with advice contained in:

5.4.2.2 This assessment is based on the following original research and investigation:

5.4.2.3 The landscape proposals for the A556(M) scheme in 1992-3 have been reviewed and where necessary modified, to take into account changes in circumstances. Landscape proposals for the M6/ M56 widening and Lymm interchange, and for the M56 junction 7-6 widening have been developed alongside this assessment, to ensure that the landscape and visual impacts of each of the proposals are minimised.

5.4.2.4 In assessing the impact of change on a landscape it is necessary to consider the importance of that landscape and its features on the various levels on which it is valued. This study has been guided by the Countryside Commissions 1998 study (see 5.4.3 below) for a description of the area as seen at national level, and by national designations of protected landscapes and features. At the local level it has been guided by the Cheshire County Council 1994 study (see 5.4.3) which describes the landscape in more detail.

5.4.2.5 However since both these studies consider this study area as part of larger units of landscape, we have refined the descriptions to give a true picture of the areas under consideration, by deleting references to features not found within the study area. This is particularly applicable to the area north of the M6 J9-7, which at national scale is part of the Mersey Valley, of which it is the edge, and not at all typical of the description of the area in the 1998 study.

5.4.2.6 The Cheshire County Council study includes strategies and landscape guidelines for conservation and restoration of each area, which have been used to design the landscape mitigation proposals for the three schemes.

5.4.2.7 Potential areas where surplus excavated material could be disposed of have been shown on the plans. The assumption has been made that these areas would be returned to agriculture at gradients to suit the type of agriculture and natural topography.

5.4.2.8 For the widening schemes the landscape proposals have been drawn for parallel widening, and the assessment of impact made on that basis. However while making that assessment a judgement was made and noted as to whether the effects of asymmetrical widening would be significantly different.

5.4.2.9 The relatively slight variations in level across the topography of the study area, made determination of a visual envelope impractical, so all potential receptors within or close to 1 km of the proposed works, were checked.

5.4.2.10 Assessment of impact has been made for the year of opening, and fifteen years later, for day and night, for winter only.

5.4.2.11 The field survey has been guided by the descriptions and importance given to the landscape and features at national and local level, and for ease of survey the study area has been divided into small areas of relatively consistent character, and designed the mitigation and assessing impacts on this detail level, prior to summarising the impacts for each option.

5.4.2.12 The landscape proposals have been prepared in accordance with the same principles as were used for the A556(M) proposals in 1993, with the following principal objectives:

  1. To integrate the proposed roads into the existing landscape.
  2. To reduce the impact of the proposed roads on adjacent land and properties.
  3. To provide interest for the road user.

To achieve integration the landscape proposals rely on those features which are listed as characteristic of the area in the Countryside Commission 1998 study, and the landscape guidelines in the CCC 1994 study.

Particular consideration has been given to the visual impact of the roads on the rural landscape, including public footpaths, and on views currently enjoyed by residents. The effects of both road lighting and vehicle lights have been considered.

5.4.2.13 The landscape plans are drafts, and will be subject to change when a final option has been selected. At that time proposals will encompass all the habitat types needed to provide mitigation, eg ponds and herbaceous layers. At the present stage the proposals have been limited to those elements that have been assessed as of primary importance in mitigating the effects of the proposed engineering works.

5.4.2.14 The landscape design elements which have been used include ground modelling, vertical barriers, and planting. Ground modelling not only accommodates surplus spoil from the works but provides permanent screening. Where possible, gradients of mounding facing away from the roads will be gentle, designed to blend in with the natural landscape, and to return the land to agriculture. The road side gradients are steep to minimise land take. Vertical barriers as screens have only been proposed in those few locations where space is very limited.

5.4.2.15 The planting is intended to:

  1. Screen the roads and vehicles on them.
  2. Provide shelter
  3. Filter particular pollution
  4. Provide interest to road users
  5. Achieve integration into the existing landscape framework in terms of pattern and species
  6. Extend and create habitat corridors

Species used would generally be locally occurring trees and shrubs.

All hedges would be planted with occasional trees. All areas of tree planting would contain a mix of tree and shrub species (but are described in the following text as 'tree' planting for brevity).

5.4.3 Description Of The Landscape Character And Planning Constraints Within The Study Area

5.4.3.1 Figure 5.5.1 illustrates the general topographic context of the A556 study area. The study area comprises a roughly triangular area based on the existing M6/M56/A556 roads, with an eastward extension along the M56 from junction 7 to junction 6.

Thumbnail Image of Figure 5.5.1

Figure 5.5.1 - Full size map (JPG 143KB) 

5.4.3.2 The topography of the study area is gently undulating (see Figure 5.5.4 in Appendix 7). The village of High Legh, situated within the M6/M56/A556 triangle, lies on a low ridge of 72-75m od. which falls away gently in all directions, draining into the River Bollin in the north, and giving onto the gently undulating Cheshire Plain in the south.

5.4.3.3 North east of High Legh, Agden Brook cuts into the landscape in a relatively steep sided valley, and passes under the M56 just west of junction 7 to flow to the River Bollin. The A556 extending south from the M56 junction 7, is aligned along the watershed between Agden Brook to the west and a more complex landscape to the east containing the meres of Rostherne, Mere, and Tatton and a number of small brooks also draining north under the M56 to the Bollin. Figure 5.5.3 identifies designated landscape features and landscape area designations.

Thumbnail Image of Figure 5.5.3

Figure 5.5.3 - Full size map (JPG 132KB)

5.4.3.4 Figure 5.5.2 illustrates the landscape character areas around the A556 study area. The landscape character of the area has been described at two levels. A broad brush description of large national landscape character areas was undertaken by the Countryside Commission and published in a number of volumes in the series "The Character of England's natural and man-made landscape" 199813. A more detailed description of landscape character was published by Cheshire County Council in 1994. This identifies the breakdown of national character areas into smaller regional character areas, and also identifies smaller scale landscape units exhibiting more local differences within the regional areas. The boundaries of the National character areas, and the small scale landscape units identified by Cheshire County Council are shown on Figure 5.5.3. All of the Cheshire landscape units fall within the 'East Cheshire Plain', region.

Thumbnail Image of Figure 5.5.2

Figure 5.5.2 - Full size map (JPG 144KB)

5.4.3.5 The Countryside Commission assessment adopts the M56 as the broad northern limit of National Landscape Character Area, 6.1, "the Shropshire, Cheshire and Staffordshire Plain", and most of the study area therefore falls into this area. The area north of the M56 and west of the A56 (junction 7 of the M56) falls into area 60, "the Mersey Valley". The area north of the M56 and east of the A56 falls into area 55, "the Manchester Conurbation".

The Cheshire Plain around the Study Area

5.4.3.6 The Shropshire, Cheshire and North Staffordshire Plain is a large area, the key characteristics of which are given by the Countryside Commission as:

  • Extensive gently rolling plain interrupted by sandstone ridges, the most prominent being the Cheshire Sandstone Ridge
  • A unified rural landscape, with strong field patterns, dominated by dairying which merges with more mixed and arable farming to the north and south-east.
  • Mosses, meres and small field ponds are scattered throughout. Subsidence flashes occur to the east of the Cheshire plain.
  • Boundaries are predominantly hedgerows, generally well managed, with abundant hedgerow trees which are mostly oak. Metal railing fences occur locally on estates.
  • Woodlands are few and are restricted to deciduous and mixed woods on the steeper slopes of sandstone ridges, and some of the wetter areas. There are also locally extensive tracts of coniferous woodland. The plentiful hedgerow trees, particularly in Cheshire, give the appearance of a well-wooded landscape.
  • Large farmsteads regularly spaced throughout with dispersed hamlets and few market towns.
  • Buildings are predominantly red brick with warm sandstone churches and, in the national park, occasional very distinctive black and white half-timbered buildings.
  • Extractive industries generally small-scale but widespread - sand, gravel, salt, sandstone, peat.

5.4.3.7 Much of the landscape within the study area, particularly to the south of the M56, accords with this description. It is a rural landscape of mixed and arable farming, with strong field patterns, well managed hedgerows and plentiful hedgerow trees. The meres and mosses to the east of the A556 around Tatton Park are notable features in the landscape, as are the large estate landscapes which are concentrated in this vicinity and of which Tabley and Tatton are described in the more detailed Cheshire Landscape Assessment. Development within the study area is typically rural with small settlements and numerous isolated farms well served by public footpaths which link into a network of small lanes and farm tracks. The market towns of Knutsford, and Lymm, are situated on the edge of and just beyond the study area.

5.4.3.8 The Cheshire Landscape Assessment identifies two distinct landscape units around the M6 and A556, with the A556 providing a clear boundary between them: the Frandley character area and the Tatton area.

5.4.3.9 The Frandley area lies around the M6 and extends as far as the A556. It is described as follows:

Landscape Character

Part of the Cheshire Plain, characterised by medium to large-scale farmland. The hedgerows are dominated by mature, sometimes over-mature, oaks with very few young hedgerow trees. The hedgerow condition is variable. The land use is principally pastoral, but arable use increases towards the north and is associated with a decline in hedgerow condition. Typical features are small ponds with copses. There are farmhouses scattered across the area with an older network of lanes remaining. In contrast to this, the area is bounded to the north by the M56 and 2 main 'A' roads cross the area.

General Strategy

Although much of this area is relatively intact and should be conserved there is a need for restoration where the characteristic features of hedges and hedgerow trees are beginning to break down.

Landscape Guidelines
  1. Promote maintenance of intact hedgerow system through Hedgerow Grant Scheme.
  2. Replant hedgerow oaks to maintain a major element of the Cheshire Landscape
  3. Consider planting small copses and woodlands in field corners and adjacent to ponds
  4. Conserve remaining ponds
  5. Scope for small to medium-scale woodlands in a farmland context.
  6. Scope for medium to large-scale woodland near Stretton airfield and Whitely Reed.

5.4.3.10 The Tatton character area encompasses the mosses and meres to the east of the A556 and around the Tatton Park Estate, which is owned by the National Trust. This area is described as follows:

Landscape Character

An area of woodland parkland centred on Tatton Hall and estate. It remains a good parkland structure with a mixture of woodland and individual trees. On the periphery, bounded by the M56 and A556, Rostherne Mere and adjacent agricultural fields continue the wooded appearance. Within the landscape, Tatton is an important feature, being a large contained area of woodland visually prominent when viewed from the surrounding area.

Landscape Strategy

As a large area of established park woodland and related wetland features, the landscape strategy should be to conserve the existing character.

Landscape Guidelines
  1. Support the management of existing woodlands, using available woodland grants, and parkland features, using Countryside Stewardship.
  2. As part of woodland management, there should be a replacement of timber and parkland trees to provide continuity
  3. Conserve parkland features, including extensive areas of unimproved grassland and significant water bodies.

5.4.3.11 The Mersey Valley around the M56 J9-7 proposals and the A556(M) tie in to the M56

The Mersey Valley National character area extends from the estuary at Liverpool into the Manchester Conurbation. The Countryside Commission describe the key characteristics of the Mersey Valley as:

  • A very distinctive river-valley landscape focusing on the Mersey, its estuary and associated tributaries and waterways, although the Mersey itself is often obscured.
  • A range of landscape types, including salt marshes around the estuary, remnants of semi-natural mosslands and pockets of basin peats towards Manchester, with the broad river valley in between.
  • Broad linear valley with large-scale, open, predominantly flat farmland supporting substantial bands of mixed agriculture.
  • Trees and woodland are scarce and are mainly associated with settlements
  • Field pattern is regular and large-scale, often defined by degraded hedgerows.
  • Large-scale highly visible industrial development, particularly at the river crossings of Runcorn, Widnes and Warrington.
  • The valley has a dense communication network with motorways, roads, railways and canals producing a large number of bridge crossings. Power lines are also prominent along this corridor.
  • Distinctive cultural landscape with major towns of Runcorn, Warrington and Widnes having much in common in relation to past and existing development pressures.

5.4.3.12 The landscape within the study area is on the edge of the Mersey valley area and has a transitional character between Cheshire Plain and Mersey valley. Cheshire County Council have described land adjacent and to the north of the M56 as the Bradley landscape unit. It is described as follows:

Landscape Character

Urban fringe farmland on the northern end of Cheshire Plain where the landscape is increasingly under pressure A mixed arable and grassland landscape with medium to large-scale field pattern, the hedgerows are moderately intact with some loss of hedges due to complete removal. There is a low density of hedgerow trees but with some isolated copses and small woodlands. There is a gradual rise before dropping down to the Mersey Valley, producing a more open aspect with some long views out to the north, south and east.

Landscape Strategy

The Cheshire Plain character is under threat from both the urban fringe influences and from arable farming taking over from dairying and it is felt restoration is the most appropriate policy.

Landscape Guidelines
  1. Plant up copses and small woodlands into the existing hedgerow and pond pattern.
  2. Restore hedgerow and hedgerow trees
  3. Consider creating a woodland buffer zone on urban edge
  4. Restore ponds
The Manchester Conurbation and Ashley landscape unit around the M56 Junction 6-7 Proposals

5.4.3.13 The study area does not pass right into the built up area although housing extends close to the existing motorway on the north side around junction 6 of the M56 at Warburton Green. The Bollin Valley, which forms the County boundary, more or less defines the edge of the urban area. The key part of the Countryside Commission description of the Manchester Conurbation relevant to this study is therefore in respect of the river valleys, other than the Mersey, which are described as:

More sinuous and narrow than the Mersey, but nevertheless form important countryside corridors throughout the area. Many of these have large areas of woodland along their valley sides providing a buffer with neighbouring urban development. These valleys are also important as recreational areas with large expanses of playing fields, numerous golf courses and water treatment works set within an overall managed countryside. Numerous country parks and victorian urban parks are associated with the river valleys, often connected by recreational trails.

All the river valleys contain sizeable areas of open grassland and other semi-natural habitats. There are many pockets of farmland within the river valleys, many of which are viable farmsteads though many are given over to urban farming uses such as horticulture. Part of the river valleys and corridors associated with the canals have areas of derelict land.

5.4.3.14 The Cheshire Landscape Assessment identifies the landscape to the north and west of Tatton and alongside the M56 as the Ashley landscape unit. The character, strategy and guidelines are described as:

Landscape Character

An area of small to medium-scale farmland without a major settlement to the east of Tatton Park and to the west of Manchester Airport. The farmland is mainly pasture, including areas of horse-keeping, with a high number of over mature hedgerow trees in relatively intact hedges. This gives a parkland appearance without evidence of clum