Almost 7,000 people have walked through a multimillion pound tunnel, regarded as a feat of engineering, before it opens to motorists this summer.
Tickets for people interested in taking part in the walk through the £371 million Hindhead Tunnel in Surrey on Saturday May the 14th sold out in less than 24 hours last month.
Up to 10,000 people who had registered an interest in joining the 1.2 mile (1.9km) walk on the A3 were left disappointed as organisers were unable to allocate more places.
Those who got a ticket walked through the tunnel before it opens in July to thousands of cars and lorries on their journey from London to Portsmouth, relieving major congestion.
Among those walking were four generations of one family, a two-and-a-half week old baby and a 92-year-old woman who completed the full distance without help.
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.
Ms 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.''
The Highways Agency said the A3 Hindhead project will mean quicker, more reliable journeys on a safer road and remove rat-running traffic from unsuitable country roads around Hindhead.