3 Forth Replacement Crossing Route Corridor Options Review (January to May 2008)
Nine mainline route corridor options were identified. Three options were identified in the Northern Study Area, providing connections to the A90/M90. Six options were identified to the south, providing connection to the A90, M9 Spur and M9.
Figure 3.1: Mainline Corridor Options
A sifting workshop was held with Transport Scotland on 5 March 2008 following an initial assessment of the nine route corridor options in relation to environmental impact, cost, geotechnical issues associated with mine workings, and economic/ transportation performance. Three options in the Southern Study Area (South Corridor Options 4, 5 and 6) were not deemed to be viable. The route corridor options carried forward for further assessment were as follows:
3.1.1 Northern Study Area Corridor Options
- North Corridor Option 1 – An online upgrade of the existing A90/M90 route corridor between Ferrytoll Junction and Halbeath Interchange
- North Corridor Option 2 – An offline scheme providing a new mainline carriageway between the proposed replacement bridge and Halbeath Interchange
- North Corridor Option 3 – A combined option requiring the online upgrade of the A90 between Ferrytoll Junction and Admiralty Junction with a new section of offline carriageway being provided between Admiralty Junction and Halbeath Interchange.
3.1.2 Southern Route Corridor Options
- South Corridor Option 1 – A short offline section of new carriageway connecting the proposed replacement bridge to the A90 south of Echline Junction.
- South Corridor Option 2 – A new offline carriageway connecting the proposed replacement bridge to the M9 north of Winchburgh.
- South Corridor Option 3 – A new offline carriageway connecting the proposed replacement bridge to the M9 Spur northeast of M9 Junction 1a.
- South Corridor Option 4A – An additional option identified for assessment at the sifting workshop of 5 March 2008; a combination of South Corridor Options 1 and 2 providing direct connections to the A90 and the M9.
3.2 Corridor Assessment
Following further assessment of the above route corridor options, the following options were recommended for DMRB Stage 2 Corridor Assessment:
- North Corridor Option 1
- North Corridor Option 2
- South Corridor Option 1
- South Corridor Option 2
3.3 Rationale for Route Corridor Option Removal
3.3.1 North Corridor Option 3
North Corridor Option 3 was not found to provide any benefits over North Corridor Option 1 or North Corridor Option 2. It was the least effective option in meeting the scheme objectives and, of the options available, it provided the least amount of junction functionality, limiting local access connectivity. In addition, of the northern route corridor options available, this corridor was assessed to generate a deterioration of local air quality at the highest number of properties.
3.3.2 South Corridor Option 3
Whilst the South Corridor Option 3 mainline could be implemented fully in association with the proposed replacement bridge, the junction arrangement required to the M9 and M9 Spur was assessed to be complex, requiring multiple structures to implement. The proximity of existing roads and the Falkirk-Fife Railway Line to the proposed junction location makes the provision of connections to all routes extremely difficult. A substantial number of departures from standard would be required. South Corridor Option 3 would also require the greatest number of residential property demolitions when compared with the other southern route corridor options available.
3.3.3 South Corridor Option 4A
Whilst South Corridor Option 4A was found to be capable of providing direct access to the A90 and the M9, the land area required would be far greater than that of South Corridor Option 1 or South Corridor Option 2 in isolation. This corridor is also expected to have the greatest ecological, visual and landscape impacts of the southern route corridor options and would require a high number of water crossings.
Further, the cost of this option would be greater than that of either South Corridor Option 1 or South Corridor Option 2 in isolation.
Figure 3.2: Route Corridors shortlisted for Stage 2 Assessment