The Hindhead Tunnel will open to traffic next Wednesday.
Secretary of State for Transport Philip Hammond will open the tunnel, which is the longest of its type in the UK and is part of a four mile bypass for Hindhead village in Surrey.
The £371m road scheme will eliminate a notorious congestion hotspot at the Hindhead crossroads and will restore peace and tranquillity to the Devil's Punchbowl - an internationally prized area of countryside - and for people living in and around Hindhead.
Southbound traffic will be the first to use the tunnel, with northbound traffic being introduced to the new road a few days later. The first traffic will be escorted through the tunnel in convoy, and the old road will remain in use in the meantime.
Construction work on the scheme began four-and-a-half years ago, in January 2007. It is being opened within budget and on schedule.