The contract is likely to be worth about US$200 million over the life of the project and is one of the largest transport consultancy contracts ever let in Scotland.

The consultants' team will be led by Alan Seywright of Jacobs. Arup's Mike Glover will act as project manager while Naeem Hussain, also of Arup, takes on the role of main crossing manager for the bridge.

The project cost is put at between US$6.4 billion and US$8.4 billion. Work on the next phase is set to start in January.