Historic England, the National Trust and English Heritage welcome the ICOMOS/UNESCO report  which recognises the benefits a tunnel of at least 2.9km could bring to the Stonehenge World Heritage Site, if it is designed and delivered well.
The report by the International Council on Monuments and Sites and the United Nations Educational, Scientific and Cultural Organisation is the result of an advisory mission to the World Heritage Site in October 2015. The report mirrors the views held jointly by Historic England, the National Trust and English Heritage, in acknowledging that a fully-bored tunnel of at least 2.9km could help to significantly improve the World Heritage Site and that the design and location of all aspects of the road improvement scheme need to be carefully and fully considered .
The report acknowledges that a solution needs to be found for the A303 traffic bottleneck , and commends the UK Government for its proactive and collaborative approach . The report highlights the scheme’s potential to become a best practice case for the management and design of substantial infrastructure in a World Heritage Site  and states that any scheme must both protect the Outstanding Universal Value of the World Heritage Site and also benefit road users whether they are local, national or international .
The report highlights the recent improvements to the Stonehenge Landscape, namely the removal and grassing over of the A344 road, undertaken by English Heritage in partnership with the National Trust to reunite the Stonehenge monument with the wider landscape, as a success story and a vision of what could be achieved with the A303 .
Helen Ghosh, Director-General for the National Trust says: “We welcome this report which recognises the unmissable opportunity the Government’s road improvement scheme presents finally to address the blight of the existing A303 and the recommendation that heritage is put at the heart of any proposed scheme. At the moment the A303 cuts through the middle of the World Heritage Site, compromising its integrity and harming the setting of many monuments.”
Duncan Wilson, Chief Executive of Historic England says: “We share the mission’s view that the design and location of all aspects of the road improvement need to be very carefully considered. But with sensitive design there is a real opportunity both to deal with the problem of the current A303 and to deliver significant public access and landscape quality benefits to the World Heritage Site. We will work closely with Highways England and other partners to ensure that the mission’s advice is fully taken on board.”
Kate Mavor, Chief Executive of English Heritage, says: “We are delighted that the mission recognises the benefits our recent improvements have brought to the World Heritage Site. Provided that it is designed and built in the right way, a tunnel would reunite the wider landscape around the ancient stones, helping people to better understand and enjoy them.”
In 2014 Historic England, English Heritage and the National Trust welcomed the Government’s announcement that it would be committing to a new tunnel of at least 2.9km to remove the A303 from the Stonehenge Landscape as part of its Road Investment Strategy. At present there are no detailed designs, but all three heritage and conservation organisations are committed to working closely with Highways England to ensure that only schemes which protect and enhance the World Heritage Site are progressed.
 The Report on the joint world heritage centre / ICOMOS advisory mission to Stonehenge, Avebury and Associated Sites is an initial report published by ICOMOS and UNESCO containing comments and recommendations following an advisory mission to the World Heritage Site in October 2015 to consider the Government’s proposal for a new road.
 “The mission considers that the project for the relocation of the existing road underground into a tunnel of at least 2.9km could readily adopt appropriate well-established construction methods and spatial planning approaches. Hence with good design and construction controls, the tunnelled length of road would be expected to have beneficial impact…However, the siting and design of the tunnel portals and, approach cuttings / embankments, entry/exit ramps, mitigation measures and the temporary construction works…will require rigorous investigation, evaluation, interative design and assessment…”[Page 24]
 “The A303 is one of the main routes from London to the southwest of England. Sections have been upgraded to dual carriageway status, though one third of the road remains single carriageway. On the A303 between Amesbury and Winterbourne Stoke (the section including Stonehenge) traffic flows are above the capacity of the road…” [Page 6] “The land surface comprised grassland and farmland used for cultivation and grazing with local areas of woodlands crossed by a congested A303 with slow moving traffic.” [Page 9]
 “The current efforts of the UK Government, its strategic decision to address the long running traffic problem and develop a project which would sustain the Universal Value of the property should be highly commended.” [Page 6].
 “The A303 road improvement project has the potential to become a best practise case regarding the governance of the project, the design implementation and management of heavy infrastructure within a World Heritage property.” [Page 24]
 “The aim must be to conserve OUV and improve the setting of the world Heritage site and the quality of life of all users of the road system, be they local users, national users or international users.” [Page 9]
 “The A344 case illustrates well the benefit that the removal (tunnel) of the A303 could bring to the World Heritage Site as a whole.” [Page 6]