The project's pre-feasibility study estimates that only 6,000 vehicles a day are likely to cross the bridge, well below the estimated 10,000-15,000 a day that use the 25-kilometre-long King Fahd causeway between Saudi Arabia and Bahrain. 'From an economic point of view you would never build such a link,' says a one leading Gulf-based bridge engineer. 'The traffic figures are so low that it is close to not being feasible.'

However, the project has far more significance than just being a transport link. The agreement, which was signed on 11 June by Qatar's Crown Prince Sheikh Tamim bin Hamad al-Thani and his Bahraini counterpart Sheikh Salman bin Hamad al-Khalifa, was a clear public commitment by the Gulf's smallest two states of their intention to bring their two economies more closely together.

The two governments have looked at using the bridge as an energy corridor carrying electricity power lines and a gas pipeline alongside, to meet Bahrain's growing energy requirements. Sources close to the project in Doha also suggest that a number of artificial island developments could be built along the route of the causeway. 'Adding a pipeline would make it more viable,' says the engineer. 'So would combining tourist and residential island developments with the project. But that is not what these kinds of projects are about. They are mostly political. And that is why it is called the Friendship Bridge and its aim is to bind these two countries together.'

The design is likely to share many similarities with the King Fahd causeway. A pre-feasibility design carried out by Denmark's COWI, which designed the Saudi-Bahraini crossing, has about half of the crossing built up on an embankment with the other half on a series of short bridges of about 50-metre spans. However, the final details have still to be announced. Initially it was intended that the project would be offered to contractors on a design-and-build basis. Now, it is understood that the inter-governmental committee responsible for developing the project is considering a more conventional procurement route, with the detailed design being carried out by the client.

The Bahrain-Qatar Causeway is the biggest in a wave of major bridge projects in the Middle East, particularly in the Gulf, as governments seek to develop their road and rail infrastructure in order to meet the challenges of rapid economic expansion.

According to data gathered by MEED and MEED Projects, about 20 major bridge schemes worth an estimated $12,000 are planned or under way in the region. Hundreds of smaller bridge structures such as rail bridges, highway interchanges, flyovers, and airport piers that are part of larger transport projects take the total value of regional bridge projects up to an estimated $20,000 million.

Without doubt, the capital for Middle East bridge building today is Dubai. Faced with crippling traffic congestion, which many warn could seriously harm the emirate's future economic prospects, the government is ploughing billions into upgrading its transport network.

Critical to alleviating Dubai's congestion problem is removing the chronic traffic bottleneck over Dubai Creek. Currently, some 16,000 vehicles an hour cross the creek. By 2020, Dubai's authorities estimate that the figure will to jump to about 43,000 an hour, far exceeding the 19-lane capacity currently provided by the three existing crossings the Garhoud and Maktoum bridges, and the Shindagha Tunnel.