Part 6: Southern Route Corridor - Combination Option Assessment 23 Southern Route Corridor - Combination Option Assessment 23.1 Introduction 23.2 Description of South Corridor Option 4B 23.3 Engineering Considerations 23.4 Environmental Considerations 23.5 Transportation Considerations 23.6 Cost Estimate 23.7 Conclusions

Part 6: Southern Route Corridor - Combination Option Assessment

23 Southern Route Corridor - Combination Option Assessment

23.1 Introduction

23.1.1 As reported in paragraph 21.9.3, a proportion of Edinburgh bound traffic is assigned under South Corridor Option 2 to the A904 as a more direct route from the proposed replacement bridge to Scotstoun Junction and Edinburgh via the A90 rather than using the new strategic route. A further option, South Corridor Option 4B was therefore defined. South Corridor Option 4B is a combination of South Corridor Options 1 and 2, providing connectivity to the proposed replacement bridge from the A90 and the M9. A new connection to the A90 would be used to facilitate direct access to the north of Edinburgh from the proposed replacement bridge, relieving some of the traffic pressures which may build up on the existing road network through the implementation of South Corridor Option 2 in isolation. This was compared, as a sensitivity check, against the preferred South Corridor Option 1.

23.2 Description of South Corridor Option 4B

23.2.1 With the implementation of South Option 4B, the recently completed M9 Spur would be closed and the Scotstoun Junction removed. The existing M9 Junction 1a would also be removed, a new all movements junction being provided to the M9 northeast of Winchburgh providing direct access to the proposed replacement bridge.

23.2.2 A revised layout at Echline Junction would facilitate access between the proposed replacement bridge, South Queensferry, the A90 and A904. The new dual two lane motorway connecting to the A90 would have priority through the junction area, direct connections to the north of Edinburgh via Barton Junction being formed with the removal of Scotstoun Junction. Traffic wishing to access South Queensferry from Edinburgh would be catered for through the provision of new slip road arrangements to the A90 commencing east of the A8000. The new westbound new slip road would be carried over the new dual two lane motorway on structure, north of Dundas Home Farm, before interfacing with the A904 and A8000 at Echline Junction.

23.2.3 Traffic wishing to access the proposed replacement bridge or the A90 from the A904/A8000 would be catered for with the provision of a new at grade junction to the west of the existing Echline Junction (on the A904). The existing junction arrangement would only serve local traffic and northbound traffic from Edinburgh.

23.2.4 In facilitating connections between the proposed replacement bridge, the A90 and M9, a new junction would be required southwest of South Queensferry. Operating as a single dual two lane motorway on approach to the proposed replacement bridge, a grade separated junction would be constructed providing access to/from the A90 and the A904/A8000 via the revised Echline Junction.

23.3 Engineering Considerations

23.3.1 In the provision of South Corridor Option 4B, the following engineering constraints and technical issues discussed in Part 2 of this DMRB Stage 2 Corridor Report (Chapter 4 - Engineering Assessment) relating to South Corridor Option 1 and South Corridor Option 2 apply:

  • Existing topography
  • Horizontal and vertical geometry of mainline carriageway design
  • Connection to existing A90
  • Junction provision and side roads connectivity
  • Location of BP Pipeline
  • Proximity of residential areas
  • Environmentally significant areas
  • Ground Conditions
  • Possible future multi-modal developments (LRT, BRT, guided buses or trams)

23.3.2 In terms of engineering assessment, none of the elements required in the provision of South Option 4B would preclude it from further consideration. Through the implementation of direct connections to both the A90 and the M9, this option would provide a higher level of service than the sections of existing carriageway that it would replace.

23.3.3 Considering future multi-modal requirements, any requirement for the implementation of a system such as LRT or BRT would be accommodated through the implementation of hard shoulder running, any future public transport system running in parallel to general traffic on the dual two lane motorway.

23.4 Environmental Considerations

23.4.1 Although the likely significance environmental impact differs between route corridor options, no environmental issues were identified through DMRB Stage 2 assessment that would preclude the promotion of any of the options. South Corridor Option 4B was not subject to Stage 2 assessment, but was qualitatively considered following the 25 June 2008 Route Corridor Workshop. Principal factors in relation to South Corridor Option 4B compared to the Stage 2 southern route corridor options are set out below. It should be noted that impact would depend on the mitigation strategy developed through design development at Stage 3.

23.4.2 Although it is the longest of the southern options, South Corridor Option 4B would have slightly less overall land take than South Corridor Option 2 due to the reduced extent of proposed junction arrangements.

23.4.3 In terms of potential impacts on the water environment, South Corridor Option 4B would require the fewest crossings of Swine Burn and the lowest geomorphological impacts on Swine Burn. The impacts on Humbie Reservoir would be similar to those predicted for South Corridor Option 2 (no impacts on this reservoir were predicted for South Corridor Option 1).

23.4.4 In terms of potential ecological issues, South Corridor Option 4B would impact on Swineburn Wood, Ross’s Plantation, Muiriehall and Carmelhill woodland complexes. These areas of woodland would be affected by South Route Corridor Option 2 but not by South Corridor Option 1. There would also be higher potential for South Corridor Option 4B to impact on otter and water vole populations at Linn Mill Burn and Swine Burn Compared to either of the other southern route corridor options.

23.4.5 South Corridor Option 4B would have similar potential landscape impacts to South Corridor Option 2. It would cut through the open arable landscape, affect the Area of Outstanding Landscape Quality at Humbie and isolate Dundas Estate by increasing the road infrastructure effectively encircling it. The potential visual impacts on rural properties and South Queensferry would be similar to those predicted for South Corridor Option 2, which overall are higher than those predicted for South Corridor Option 1.

23.4.6 With regard to cultural heritage, South Corridor Option 4B would have the highest overall potential impact on Designed Landscapes of the southern route corridor options. As South Corridor Option 4B passes through areas with generally less development, there may also be higher likelihood of encountering previously unrecorded archaeology, although works within the main area of known archaeological potential (Inchgarvie area) would be similarly affected by all options.

23.4.7 South Corridor Option 4B would have the greatest overall potential for disruption to local residents during construction (such as potential construction noise, traffic, dust etc) due to the extent and length of this option. However, in terms of vehicle travellers there could be disturbance during construction at online works at M9 Junction 1A and in the Echline/Scotstoun area.

23.4.8 South Corridor Option 4B is considered to be the least compliant of the southern route options in terms of plans and policies. It would also have the greatest overall potential impact on core paths and rights of way.

23.4.9 Noise and air quality were not assessed for South Corridor Option 4B, as detailed traffic data was not available. However, it is not expected that air quality or noise would be route option determinants.

23.5 Transportation Considerations

23.5.1 As a combination of South Corridor Options 1 and 2, South Corridor Option 4B through the provision of a dual two lane motorway in tandem with new junctions to the M9 and A904 and a connection to the A90 is expected to provide the following:

  • Improved existing levels of service for private, road-based modes of travel
  • Improved network performance
  • Improved journey time reliability through the provision of new route corridor options for some journeys between central Scotland and Fife.
  • Minimum change to land-based travel choices and integration
  • Improved general accessibility for those with access to private transport
  • Minimal impact on the effective operation of the transport network during times of maintenance.
  • Reduced sustainable development, but increase economic growth

23.5.2 South Corridor Option 4B provides more direct routing for southbound traffic than South Corridor Option 1, but involves a lower speed interchange between the connecting roads to the M9 and A90 with manoeuvring constraints that would impact on the comfort of the route.

23.5.3 A comparison in journey distances and cumulative vehicle kilometres is provided for the route corridor options in Table 23.1 below.

Table 23.1: Comparison of Journey Distances between Route Corridor Options

Option

  

North Corridor Option 1

North Corridor Option 2

South Corridor Option 1

South Corridor Option 2

South Corridor Option 4B

Journey.

Approx %age of Bridge traffic

          

Halbeath to North Bridgehead

60 %

8.5 Km

8.4 Km

      

Masterton to North Bridgehead

15%

4.6 Km

4.4 Km

      

Admiralty to North Bridgehead

20%

2.6 Km

2.6 Km

      

Ferrytoll to North Bridgehead

5%

0.9 Km

0.9 Km

      

South Bridgehead to A90 at Scotstoun (bound for Barnton)

30 %

    

4.0 Km

7.6 Km

4.0 Km

South Bridgehead to M9 East (at Newbridge)

35 %

    

9.4 Km

7.1 Km

7.1 Km

South Bridgehead to M9 West (at Winchburgh)

5 %

    

14.1 Km

8.4 Km

8.4 Km

South Bridgehead to South Queensferry and beyond via A904.

30%

          

Indicative Annual Cumulative Vehicle km’s (2017)

  

553,000

546,000

452,000

451,000

357,000

23.6 Cost Estimate

23.6.1 The cost associated with the construction South Corridor Option 4B is estimated at £417m (excluding VAT).

23.6.2 With reference to the cost estimates provided in Part 1, Chapter 3, of this report, the cost associated with the implementation of South Corridor Option 4B would be comparable to that of South Corridor Option 2 and substantially higher than the cost estimate for South Corridor Option 1.

23.6.3 The cost comparison with South Corridor Option 2 is generated through a reduction in carriageway cross section provision from dual three lane motorway standard to dual two lane motorway standard. Furthermore, with the closure of the M9 Spur, the complexities of the junctions required are significantly reduced with no requirement to integrate Scotstoun Junction or M9 Junction 1a and a lesser requirement for structural crossings of existing roads and railway lines.

23.7 Conclusions

23.7.1 Whilst South Corridor Option 4B would be capable of providing direct access to the A90 and the M9, the land take associated with the implementation of such a scheme would be far higher than that of South Corridor Option 1 or South Corridor Option 2 in isolation. This corridor would also be expected to have higher overall delivery environmental impacts.

23.7.2 In addition, the anticipated cost associated with the implementation of this option would be comparable to that of South Corridor Option 2 and far greater than that of South Corridor Option 1.

23.7.3 Considering the environmental impacts, the cost associated with this options implementation and the amount of existing roads infrastructure made redundant through its provision, South Corridor Option 4B was not taken forward.