Following the Scottish Government’s decision of December 2007 to construct a multi-modal Cable Stayed Bridge west of the existing Forth Road Bridge, Jacobs Arup have been engaged in the assessment and review of the roads’ infrastructure route corridor options identified for consideration at the initial project workshops of January 2008.
Nine mainline route corridor options were identified for consideration in the provision of connections between the proposed replacement bridge and existing roads’ infrastructure. Of these options, three were identified to the north of the Firth of Forth, providing connections to the A90/M90, and six were identified to the south, providing a connection to the A90, M9 Spur and M9.
The assessment was undertaken in two stages. First, an initial assessment was undertaken between January and March 2008 with the recommendations being presented at a sifting workshop on 5 March 2008. Following acceptance of these recommendations, the remaining route corridor options were subject to further design development and assessment and the results reported to Transport Scotland in May 2008.
It was recognised that the preferred corridors identified need not be improved over their full length. It was specified that a later stage of project development would be to give further consideration to the form and function of the junctions required and the extent of the road infrastructure improvements to be provided.
The route corridor options to be assessed are as follows:
Northern Route 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.
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 4 - A new offline carriageway connecting the proposed replacement bridge to the M9 northwest of Winchburgh.
- South Corridor Option 5 – A new offline carriageway connecting the proposed replacement bridge to the M9 northwest of Winchburgh and to the M9 Spur northeast of M9 Junction 1a.
- South Corridor Option 6 - Similar to South Corridor Option 4 but with the alignment located slightly further west.
- The assessment of certain combinations of southern corridor options was also undertaken where it was considered practicable.
1.2 Purpose of Route Corridor Options Review
The purpose of this Route Corridor Options Review is to demonstrate the process of assessment undertaken, with respect to each of the mainline route corridor options, whilst taking into consideration the scheme objectives of the Forth Replacement Crossing Project:
- To maintain cross-Forth transport links for all modes to at least the level of service offered in 2006;
- To connect to the strategic transport network to aid optimisation of the network as a whole;
- To improve the reliability of journey times for all modes of transport;
- To increase travel choices and improve integration across modes of transport to encourage modal shift of people and goods;
- To improve accessibility and social inclusion;
- To minimise the impacts of maintenance on the effective operation of the transport network;
- To support sustainable development and economic growth; and
- To minimise the impact on people, and the natural and cultural heritage of the Forth area.
In the initial assessment of the nine mainline route corridor options consideration was given to engineering and transportation issues and environmental impact. Comparative scheme costs were also taken into consideration in the assessment. A plan of the indicative layouts of the route corridor options is contained within Appendix 1. Junction areas were not reviewed in detail during the initial assessment. It was assumed that all existing traffic movements would be catered for. All corridor options were considered on the basis of provision of a dual two lane motorway but no consideration was given to the impact of provision of multi-modal or multiple occupancy transport strategies.
The initial assessment stage was focused on the consideration of options that had significant differences from each other, rather than minor differences.
The further assessment stage took account of the further design development and assessment that was undertaken in the period between the sifting workshop in March and May 2008.
Through comparative assessment, the number of route corridor options to be taken forward to DMRB Stage 2 Corridor Assessment was reduced with appropriate justification being provided for those options not deemed favourable.