The busy road's being made two lanes in both directions between Segensworth and Titchfield - it's due to take 18 months.
Huge Aircraft Carrier Section To Be Assembled
A 750-tonne section of the UK's biggest aircraft carrier has set sail on its first sea voyage to be assembled with the rest of the giant warship, which will be based at Portsmouth.
The aft island of HMS Queen Elizabeth left BAE Systems' Scotstoun yard on the River Clyde in Glasgow, sailing under the Erskine Bridge and out to the Firth of Clyde as part of a 600-mile journey around the north coast to reach Rosyth in Fife.
The section, which will host the carrier's air traffic control centre, is the last major section of the HMS Queen Elizabeth to be made on the Clyde and has been completed ahead of schedule, BAE said.
It was loaded on to the barge earlier this week before workers welded it in place ready for its journey.
HMS Queen Elizabeth and another aircraft carrier, HMS Prince of Wales, are the largest warships ever constructed for the Royal Navy.
The first is due to be launched in 2016.
Six shipyards around the UK are involved in building various parts of the ships, which are ultimately being assembled in Fife. Once complete they will be 280m (919ft) long and weigh more than 65,000 tonnes.
They are being built by the Aircraft Carrier Alliance, a partnership of BAE Systems, Babcock, Thales and the Ministry of Defence.
Angus Holt, Queen Elizabeth Class block delivery director for BAE, said:
"The delivery of the aft island is a huge milestone for the aircraft carrier programme and we are extremely proud to have achieved this. The island has been completed to an exceptional standard which is testament to the skills and talent of our workforce here on the Clyde.
"Once the island has arrived in Rosyth the full scale of the nation's flagship ship will be revealed for the first time."
About 10,000 people have worked on the construction at various stages and crews of 1,600, including pilots, will populate each ship when they are in service.
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