Almost 7,000 people have walked through a multimillion pound tunnel, regarded as a feat of engineering, before it opens to motorists this summer.
The £371M Hindhead Tunnel in Surrey will relieve major congestion for people travelling between London and Portsmouth.
The Highways Agency said the tunnel will offer drivers faster and safer journeys - enabling many commuters to avoid unsuitable country roads on their way to and from work.
Almost 7,000 people took part in the 2.9km walk - for which tickets sold out in less than 24 hours. But plenty of people were unable to get their hands on tickets, with thousands left disappointed.
A Highways Agency spokesman said: “We are delighted that so many people were able to come and see the tunnel up close, and hope that people enjoyed seeing just what a huge engineering achievement building the tunnel has been.
“The A3 Hindhead Tunnel is a vital road improvement, with real benefits for road users and local people alike, and unrivalled environmental benefits too. We are looking forward to opening the new road this summer.”
Project co-ordinator Caroline White, of Hindhead Together, a partnership of eight agencies involved in the A3 Tunnel project, said it was a “once in a lifetime opportunity”.
It was organised by Hindhead Together as a gesture of thanks to the many communities following more than 25 years of lobbying, planning and discussion.
White said: “This has been a chance for the local people and those interested in the project to come and take a look at it close hand.
“It’s a prize-winning tunnel project which everyone has been very pleased to see after first being in the offing some 30 years ago.”