PLANS for an A303 tunnel at Stonehenge have been altered over concerns it would ruin the winter solstice.

The proposed western tunnel entrance has been moved about 50 metres south in a bid to stop headlights spoiling the sunset on the shortest day of the year.

The project will still involve turning a section of the A303 into a dual carriageway and a 1.8mile tunnel past the World Heritage Site.

The Department for Transport (DfT) and Highways England have also decided to run a bypass north of Winterbourne Stoke.

The amended scheme is set to cost £1.6billion, up £200million on previous estimates.

More than 9,000 people responded to a public consultation on the plans earlier this year.

Project director Derek Parody said: “People were concerned about the portal and the route and its interference with the winter solstice line.

“They were also concerned about the western route going through the world heritage site severing a number of the key monuments within that western end so, by moving the route further north and aligning it much closer to the existing A303, all the issues relating to the alignment with the winter solstice have been resolved and issues about severance of key barrows groups and proximity have been resolved.”

The key sites highlighted were the RSPB reserve at Normanton Down and long barrows discovered in the line of the initial proposal.

Heritage groups that manage the area, including English Heritage, The National Trust and Historic England, have welcomed the revised proposal that will make the setting of the stones more tranquil and allow visitors to enjoy the attraction without the sound of traffic.

Secretary of state for culture Karen Bradley said: "Stonehenge has captured the imagination of people around the world for centuries and is a site of global importance. With over one million visitors a year it is one of the jewels in the UK's crown and it is important that we preserve it for generations to come. This investment from the government will help make the visitor experience much more enjoyable and this is good news for local residents and businesses who will benefit from the new route."

Work is likely to start in 2021 and take around four years.

Highways England chief executive Jim O’Sullivan added: “Highways England is committed to delivering a high quality, modern road on this vital route between the South West and the rest of the country.

“The A303 and the World Heritage site has suffered from congestion for many years. This scheme will enhance, protect and restore tranquillity to one of the UK’s most iconic landscapes.

“We have listened to feedback from consultation and believe this preferred route will help improve traffic flow, reduce rat running on the surrounding roads, bringing improvements to local communities and benefits to the South West economy.”

The A303 upgrade between Amesbury and Berwick Down is a key part of the government’s £15 billion road strategy.

Transport secretary Chris Grayling said: “This government is taking the big decisions for Britain’s future and this major investment in the South West will provide a huge boost for the region.

“Quicker journey times, reduced congestion and cleaner air will benefit people locally and unlock growth in the tourism industry.”

“The scheme will also support 120,000 extra jobs and 100,000 new homes across the region, helping us build a country that works for everyone.”

The Stonehenge Alliance and Campaign for Better Transport said the scheme would cause "severe and permanent damage" to the archaeological landscape of the World Heritage Site (WHS).

Kate Fielden of the Campaign to Protect Rural England said: “We are shocked at Highways England’s indifference to [world heritage experts] Unesco’s advice.

"The project needs a complete re-think, not a minor tweak which still threatens major harm to this iconic landscape. The potential risk of loss of Stonehenge’s World Heritage Status casts shame upon our country and those responsible for caring for our heritage.”

Chris Todd from Campaign for Better Transport, said: "Progressing with this damaging scheme in the face of the concerns raised by Unesco is a gravely flawed decision.

"The scheme either needs to be abandoned altogether, or the whole process rerun with a full range of options which do not result in any harm to the World Heritage Site, including non-road building solutions." 

Unesco’s World Heritage Committee previously urged the government to explore options that would not impact on the outstanding significance of the site, including a southern bypass and “longer tunnel options to remove dual carriageway cuttings from the property”.

Salisbury MP John Glen said: "The announcement today of the preferred route for the A303 upgrade near Stonehenge shows that the project remains on track. This critical new infrastructure will alleviate traffic problems and rat-running in nearby villages and slash journey times to the West Country. 

"Stonehenge is a major bottleneck and barrier to unlocking the economic potential of the region. The existing road also dissects important archaeology within the UNESCO World Heritage site.

"Today’s announcement by Highways England is an important step forward. After extensive consultation, a twin-bore tunnel and a bypass north of Winterbourne Stoke has been revealed as the favoured option. 

"I’m pleased the project team has taken on board feedback from archaeologists. English Heritage and the National Trust both strongly supported a tunnel. 

"This has been a controversial process – it would have been impossible to reconcile the views of everyone and still deliver a viable solution that is in the best interest of the World Heritage site.

"We need to remember that this is a strategic road and a project of national significance, which is not being funded from local transport budgets. Improving local roads is a separate issue and one which I remain fully committed to.

"There now begins a process over the next year of further consultation leading up to the formal planning process. I will be doing my utmost to ensure that the remaining concerns are fully addressed and the needs of local people taken into account."