The Road Investment Strategy is clear that the A303 Amesbury to Berwick Down scheme involves a tunnel of at least 1.8 miles (2.9 kilometres). Highways England is in the early stage of scheme development, looking at options, including the length of tunnel. Consultation on options will take place in 2017 and will involve stakeholders, local residents, businesses, road users and interested parties.
Highways England does not yet have reliable cost estimates for a 2.8 miles (4.5 kilometres), or 4.3 miles (7 kilometres) tunnel. This information would become available during the consideration of options. The A303/A30/A358 Corridor Feasibility Study indicated that the cost estimate for a 1.8 miles (2.9 kilometres) tunnel is in the range of £864m to £1321m.
To date, Highways England has not sought funding outside of their own resources to fund a solution for the A303 past Stonehenge although this does not preclude them from considering other funding sources in the future.