Protestors opposed to the creation of a a total of seven lanes on a dual carriageway have been demonstrating in Flintshire.
Around 150 people attended the protest
The final draft of the proposals for the A494 Queensferry bypass were unveiled to civic leaders on Wednesday.
Critics say they fear major disruption during the work, with increased traffic and noise once it is complete.
The Welsh Assembly Government said the route suffers from congestion which would increase without the work.
Protestors gathered outside the Deeside Leisure Centre where civic leaders were given a chance to see the plans before they go on public display from Thursday to Saturday.
The A494 links the A55 with the motorways linking with the north-west of England, bypassing places like Ewloe, Aston and Queensferry.
It has a speed limit of 50mph, but the plans would see it turned into an seven-lane road, with speed limits of up to 70mph.
Residents from Aston on Deeside had their say on the development at a public meeting in August 2006.
The multimillion pound scheme will involve demolishing a number of homes which were bought by the authorities when the plans were drawn up 15 years ago.
Four residents' groups have formed a campaign group, the Coalition Committee, which will be holding its own exhibition on the development.
The committee is pushing for a public inquiry and urging anyone living in the communities around the A494 to make their views known to the assembly government ahead of the 9 February deadline for objections.
Speaking before the demonstration, coalition committee chairman, local councillor George Hardcastle said: "This is the residents' last chance to stop this development.
"They need to get down to the leisure centre on Wednesday afternoon to show the assembly how they feel.
"This will not only affect Aston residents, the knock-on effects will really hit people throughout the county, so we're hoping for the biggest demonstration yet.
"Next week, we're having our own exhibition to expose the reality of this development. When people see the plans and listen to the assembly officials, I don't think they get the extent of the impact this is going to have."
Mark Isherwood, Conservative Assembly Member for north Wales, said: "The knock-on effects of this development will be felt by people throughout the country, and in light of the overwhelming opposition, I would urge the Assembly Government to revisit this decision."
'Disruption to lives'
An alternative exhibition will be held at Aston Park Community Centre on 19 and 20 January.
The assembly government said the route provided the main link between north Wales and the UK motorway network and suffered from "serious congestion problems".
The statement added: "This congestion will get worse. Without improvement, this will adversely affect the economy of the area and cause disruption to local peoples' lives.
"The existing road does not meet current design standards. The scheme will improve safety. The carriageway will also be screened from the adjacent housing wherever possible by landscape mounds and noise barriers."