1 Executive Summary 1.1 Introduction 1.2 Route Corridor Options Review (January to May 2008) 1.3 DMRB Stage 2 Corridor Assessment (May to August 2008) 1.4 Main Crossing (Bridge) Assessment (January to August 2008) 1.5 Forth Road Bridge Feasibility of Multi-modal Corridor (August to October 2008) 1.6 Main Crossing (Bridge) Assessment (August to October 2008) 1.7 The Managed Crossing (August to November 2008)

1 Executive Summary

Figure 1.1 Preferred Scheme Layout

Figure 1.1 Preferred Scheme Layout

1.1 Introduction

This report provides summary information on the project development work carried out following the announcement to Parliament in December 2007 (see bibliography: report references 2 to 7), and reports on the further development work carried out to define and assess the Managed Crossing Scheme between August and November 2008. It is the final report on the project planning work carried out during 2008 and provides recommendations on:

  • the detail of the road connections to the Forth Replacement Crossing, as shown in Figure 1.1, within the preferred connecting road corridor defined in the DMRB Stage 2 Corridor Report; and
  • the incorporation of the Forth Road Bridge as an integral element of the proposals for use by pedestrians, cyclists, public transport and any future multi-modal facility.

Following the completion of the Forth Replacement Crossing Study, as part of the Strategic Transport Project Review (STPR), it was announced to Parliament on 19 December 2007 that the Forth Replacement Crossing is to be a cable-stayed bridge and that the scheme would be designed to:

  • safeguard the capability of future multi-modal use;
  • provide for pedestrians and cyclists;
  • provide for two lanes in each direction for general traffic;
  • incorporate hard shoulders to relieve disruption due to breakdowns and maintenance activity;
  • provide an enhanced service to West Lothian, and;
  • protect and promote economic development areas in Fife.

Following the announcement on 19 December 2007, the Jacobs Arup Joint Venture was appointed in January 2008 to work as a development partner with Transport Scotland to take the project forward.

1.2 Route Corridor Options Review (January to May 2008)

Nine mainline route corridor options for the connecting roads to the Forth Replacement Crossing were identified: three in the Northern Study Area and six in the Southern Study Area.

An initial assessment reduced the number of options to three in each study area on the basis of environmental impact, cost, geotechnical issues associated with mine workings and economic/ transportation performance. Following this sifting, the remaining route corridors were further assessed in relation to engineering, environmental, transportation and cost considerations in greater detail.

Following this further assessment of the route corridor options, North Corridor Options 1 and 2 and South Corridor Options 1 and 2 were selected for DMRB Stage 2 Corridor Assessment (see Figure 1.2)

Figure 1.2: Route Corridors shortlisted for Stage 2 Assessment

Figure 1.2: Route Corridors shortlisted for Stage 2 Assessment

1.3 DMRB Stage 2 Corridor Assessment (May to August 2008)

The shortlisted corridor options were developed further and assessed in relation to the scheme objectives and the engineering, environmental, sustainability, traffic and economic advantages/disadvantages associated with each.

North Corridor Option 1 and South Corridor Option 1 were preferred. In each case, they had the engineering, cost, environmental and sustainability benefits associated with the maximisation of the use of existing infrastructure. This latter feature of the preferred options contributes to the achievement of the key sustainability objectives of:

  • protecting and enhancing the natural heritage including biodiversity;
  • improving local accessibility and reducing community severance;
  • adopting sustainable resource management in design and construction; and
  • minimising embodied carbon.

In economic terms, whilst recognising the operational benefits associated with South Corridor Option 2, the comparison of Benefit to Cost ratio (BCR) indicated that the North Corridor Option 1 combined with South Corridor Option 1 provided best value for money.

Following completion of the assessment, a sensitivity check was undertaken on a further option, South Corridor Option 4B, a combination option that was defined at the Forth Replacement Crossing Route Corridor Workshop held with Transport Scotland on 25 June 2008. Details of this option are provided in the DMRB Stage 2 Corridor Report (see bibliography reference 3). The option was discounted on the grounds of its greater environmental impact of the infrastructure and its higher cost.

1.4 Main Crossing (Bridge) Assessment (January to August 2008)

A short list of design concepts was developed at a workshop in February 2008 to provide the functionality as listed below and illustrated in Figure 1.3:

  • Dual two lane motorway with 3.3m hard shoulders and a footway/cycleway.
  • Multi-modal (public transport) corridor.

Figure 1.3: Forth Replacement Crossing Bridge Cross Section
(No utilisation of Forth Road Bridge)

Figure 1.3: Forth Replacement Crossing Bridge Cross Section

Bridge options were developed to carry the multi-modal public transport corridor in the central area of the bridge (as illustrated in Figure 1.3 above), or in the lower level of a double deck structure. Given the very high cost of this provision for multi-modal public transport, a decision on the preferred bridge option was deferred pending the outcome of further investigations on the suitability of the Forth Road Bridge to take part of the overall crossing traffic.

1.5 Forth Road Bridge Feasibility of Multi-modal Corridor (August to October 2008)

A more positive prognosis for the Forth Road Bridge emerged during 2008. The second internal cable inspection carried out by FETA in early 2008 indicated that cable deterioration was not as rapid as had been feared. The technical feasibility of replacing the cables was also confirmed by a report published early in the year by FETA, although disruption to users and the consequential adverse impacts to business and the economy was such that it was not considered practical in the absence of a replacement bridge. Accordingly, a technical assessment of the capability of the Forth Road Bridge to work alongside the Forth Replacement Crossing was commissioned. With the new bridge being designed to carry general traffic and all heavy goods vehicles, the technical assessment of the Forth Road Bridge considered a range of options for rail based light rapid transit public transport together with footway loading and reduced highway loadings. All options were assessed to be geometrically feasible in that they could be accommodated within the available width of the bridge. All but one of the options reduced the load on the main cables. Modifications to the movement joints on the bridge would be required but could be provided within the parameters required for a rail based tram.

All of the options were assessed as having positive potential. The load reduction would mitigate the loss of cable strength that had already occurred and extend the period before cable replacement or augmentation became necessary. If the current dehumidification scheme being undertaken by FETA is a success, this work could be deferred indefinitely.

1.6 Main Crossing (Bridge) Assessment (August to October 2008)

  • The appraisal of the condition of the Forth Road Bridge provided confidence that it can make a contribution to the project. Although not capable of meeting the future needs as the main crossing, it was concluded that it can support future public transport requirements and accommodate non-motorised users (pedestrians and cyclists). The opportunity to use the Forth Road Bridge in this way has allowed the development of a flexible, narrower replacement bridge of high quality and significantly reduced cost. The proposals for the Forth Replacement Crossing and Forth Road Bridge working as part of a managed crossing strategy are illustrated in Figures 1.4 and 1.5.

Figure 1.4: Forth Replacement Crossing Cross Section
(Utilising Forth Road Bridge)

Figure 1.4: Forth Replacement Crossing Cross Section

Figure 1.5: Forth Road Bridge Cross Section

Figure 1.5: Forth Road Bridge Cross Section

A 3 mono-tower cable stay bridge with a single box girder deck was recommended as the preferred option for the Forth Replacement Crossing.

Figure 1.6: Artist’s impression of 3 mono-tower cable stay bridge

Figure 1.6: Artist’s impression of 3 mono-tower cable stay bridge

1.7 The Managed Crossing (August to November 2008)

Options for optimising the scheme definition were considered, having regard to the outcome of the Stage 2 Corridor Report and the assessment of the potential use for the Forth Road Bridge. The key considerations were that:

  • The Stage 2 Corridor Report concluded that the Full Corridor Scheme need not be implemented in full and that project planning work should be progressed to give further detailed consideration to the form and function of the junctions required and the extent of the road infrastructure improvements provided within the preferred corridors (see Section 4).
  • The Forth Road Bridge could be capable of adaptation for multi-modal use, including future tram/light rail use, and it was determined that this would be taken forward as a planning assumption (see Section 5).
  • The scheme, which has been defined to take account of the combined output from these separate exercises, is referred to as the Managed Crossing Scheme. The Managed Crossing Scheme will provide high quality approach roads to the new bridge. The existing junctions at Admiralty and Ferrytoll will be enhanced to protect and promote the developing area of Rosyth and to provide good quality connections for local communities. A new junction will be provided at South Queensferry and Junction 1a on the M9 will be enhanced to facilitate new access to the bridge from West Lothian.

Analysis indicates that, for the majority of the time, the existing bridge and road network operate without congestion. Peak period congestion is largely due to the close junction spacing along the A90/M90 corridor and driver reaction to that. Much of the congestion and queuing which is observed during peak periods at present is due to the interaction of traffic joining busy traffic on the main carriageway at closely spaced junctions. It is proposed that this is addressed by the use of Intelligent Transport Systems with local junction improvements (see Figure 1.7).

Figure 1.7: Use of Intelligent Transport Systems on the M42 in England (photograph courtesy of Highways Agency)

Figure 1.7: Use of Intelligent Transport Systems on the M42 in England (photograph courtesy of Highways Agency)

1.7.1 Environmental and Sustainability Considerations

The potential adverse environmental impacts for the Managed Crossing Scheme are less than those identified for the Full Corridor Scheme.

In terms of resource use, preliminary calculations have been undertaken to provide a high level comparison of the embodied carbon of materials associated with the two scheme alternatives. The results show that the Full Corridor Scheme, which would have more roadworks, earthworks and bridge deck compared to the Managed Crossing Scheme would require approximately102,000 tonnes more embodied carbon than the Managed Crossing Scheme.

1.7.2 Capital Cost Estimate: Comparison

Table 1.1 sets out the capital cost estimates for the Full Corridor Scheme (as at July 2008 and as modified in October 2008) and the Managed Crossing Scheme, all at Q4 2006 prices. Outturn prices allowing for the cost of capital and an estimated inflation range are also detailed below.

Table 1.1: Comparison of Capital Cost Estimates


Full Corridor Scheme
(as defined July 2008)
Costs (£m)

Full Corridor Scheme
(as modified Oct 2008)
Costs (£m)

Managed Crossing Scheme
(Oct 2008)
Costs (£m)

Network Connections North




Network Connections South




ITS and Supervision




Main Crossing




Approach Viaducts




Sub-total excl risk, OB and VAT




Risk allowance




Optimism bias




Sub-total excl VAT




Non Recoverable VAT




Total incl. Risk, OB & VAT




Uplift to outturn costs:

Addition for Cost of Capital (Annual Managed Expenditure) and inflation to 2016

1,114 to 2,114

857 to 1,747

525 to 1,145

Total Outturn Cost Range (2016)

3,200 to 4,200

2,630 to 3,520

1,720 to 2,340

1.7.3 Whole Life Cost Estimate Comparison

In additional to the capital costs, operations and maintenance (O&M) cost profiles detailing the long term operating costs and lifecycle refurbishment costs have been estimated.

The assumption is made in the Full Corridor Scheme that the Forth Road Bridge, a listed structure, would be managed on a care and maintenance basis although not used for traffic. Its usage under the Managed Crossing Scheme as a public transport corridor is assessed to require a higher level of operation and maintenance cost input.

Table 1.2: Whole life cost comparison

Cost Element

Costs at Q4 2006 prices (£,000s)

Full Corridor Scheme (as modified Oct 2008)

Managed Crossing Scheme

Construction Costs excl VAT (from Table 1.1)



O&M Costs

Network Connections



New Bridge



Existing Bridge



O&M sub total



Lifecycle Refurbishment Costs

Network Connections



New Bridge



Existing Bridge



Lifecycle cost sub total






1.7.4 Economic Assessment

The economic assessment considers the monetised benefits of the options for the Forth Replacement Crossing and compares these benefits to the costs associated with its construction and maintenance in accordance with the requirements of the Scottish Transport Appraisal Guidance (STAG). In this exercise, all costs are rebased to 2002 prices and are discounted to 2002 in line with the practice for transport schemes. The maintenance costs associated with retaining the Forth Road Bridge are included in this assessment.

Table 1.3 provides a comparison of the Benefit to Cost Ratio of the Full Corridor Scheme and the Managed Crossing Scheme.

Table 1.3: Economic Appraisal - Full Corridor and Managed Crossing Schemes

Full Corridor Scheme

Managed Crossing Scheme

Present Value of Benefits



Present Value of Costs



Net Present Value



Benefit to Cost Ratio (BCR)



The Benefit to Cost Ratios (BCRs) provide a comparison of the transport costs without the tested investment (but in this case including the refurbishment of the existing bridge) and the transport and investment costs with the investment.

In addition to the above, the wider economic impact of closure or restricted use of the Forth Road Bridge, without a replacement crossing, on the local economies of Fife and the Lothians and the national economy of Scotland, would be very significant.

FETA have assessed that cable replacement would be the preferred method of restoring the strength of the suspension cables and that it would be possible to undertake. However, if carried out without a replacement bridge to carry traffic during the period of the works, the disruption caused would reduce business turnover by £1,320 million and reduce business turnover by £1,085 million in Scotland as a whole with an associated loss of jobs of 3,200, many of which would be permanent.