MAJOR plans to introduce a network of subsea tunnels between Shetland's islands have been approved by councillors.
The plans include replacing ageing ferries with tunnels from Shetland's mainland to Yell and from Yell to Unst within eight years.
The 4.2 mile tunnel from the mainland to Yell is expected to cost £402 million. The estimated cost of a tunnel between Yell and Unst has been quoted at £303m.
Elected members on Shetland Islands Council voted on Tuesday to give the greenlight to a business case report recommending a combination of tunnels and enhanced ferry services with new vessels.
Two more tunnels, to the islands of Whalsay and Bressay, could follow in years to come under the plans – which it is estimated could cost £1.5 billion.
Councillors agreed to continued investment in the ferry service to these islands in the medium-term.
The council currently runs ferry services to nine islands, carrying around 750,000 passengers each year on 12 vessels at a cost of £23m per year, but some routes are now struggling to meet demand and costs have risen sharply in the last decade while the fleet is ageing.
Unst is the UK's most northerly island and home to the UK's only spaceport, at Saxavord.
It is thought tunnels could help boost economic activity related to the spaceport.
Speaking after the meeting, council leader Emma Macdonald said: “We have made our position clear today, and with the support of the Scottish and UK Governments we could be driving through tunnels in Shetland in as little as eight years from now.
"Islands with fixed links repopulate, enjoy economic growth and experience a reduction in their average age."
MacDonald said the next step will be to look at potential external funding, with council bosses due to report back on this in September alongside a draft route map.
“We have no ‘do nothing’ options here. Ferries and tunnels are both needed to unlock the potential of Shetland, and both the Scottish and UK Governments have a vested interest in helping that happen," she added.
Inspiration for building a tunnel network in Shetland has come from neighbouring Atlantic archipelago, the Faroe Islands.
There are 23 tunnels in total across the Faroes with four of them under the sea.
The network includes a 7.1 mile tunnel which connects the island of Streymoy to two sides of a fjord on the island of Eysturoy via the world's only subsea roundabout.
The tunnel has halved the driving time between the capital Tórshavn and the islands' second biggest town, Klaksvik.
The Faroes are home to around 54,000 people while Shetland has a population of around 23,000.
Projections for Shetland tunnels have been produced by the engineering consultancy firm COWI which has been working alongside Shetland Islands Council and fellow consultants Stantec.
COWI's timeline allows three years for preliminary work and five years for construction.
