Cyclists, runners and walkers had exclusive access to a section of the Norwich Northern Distributor Road (NDR) prior to it opening to traffic.
Hundreds of people turned up to explore the westernmost part of the dual carriageway on Sunday, between the A1067 Fakenham Road and New Drayton Lane.
One of the more unusual sights along the three-mile stretch included a doctor riding a penny-farthing.
The Pushing Ahead event was organised to demonstrate how new cycle lanes and links have been created as part of the NDR work.
But those opposing the road's development labelled it as a 'vulgar publicity stunt' by Norfolk County Council.
The Wensum Valley Alliance staged a protest during at the opening against what they claimed was a 'massive overspend' on the NDR.
Jenn Parkhouse, chair of the campaign group, said: 'This 'cycle explorer day' is a vulgar publicity stunt. For just six hours today, the council will be feigning interest in recreation activities such as walking, running and cycling.
'Thereafter, they will revert to their obsession with road building.'
The first section of the NDR is due to open next month. Council leader Cliff Jordan said earlier in October that he believed the final cost of the road would be between £200m and £205m.
The council had previously budgeted £179.5m for the development.
Martin Wilby, chairman of the council's environment, development and transport committee, said: 'We are very pleased to give local people a chance to see the road before it's open to general traffic, and to explore the new cycle-ways and links to Marriott's Way and communities such as Horsford and Thorpe Marriott.'
Norwich GP Simon Cooke was among those exploring the NDR on Sunday. The 54-year-old cycled the stretch on his modified penny-farthing.
He said: 'It got a bit hairy when there was a bit of wind, but it was a lot of fun.
'It's a great road, but I had to be a bit careful. Riding this is a combination of being on a skateboard and a tall bike.'
Once complete, the NDR will stretch from the A47 at Postwick to the A1067 Fakenham Road.
The county council is now looking at whether a £160m viaduct could be build to carry it over the Wensum Valley.
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