A public inquiry has begun into controversial plans to expand a dual carriageway into a seven-lane highway.
Around 150 people joined a protest against the plans in January
The scheme would see the widening of the A494 trunk road between Ewloe and Queensferry, in Flintshire.
Objectors fear it will increase noise and pollution and are unhappy the speed limit would rise from 50mph to 70mph.
The Welsh Assembly Government said the project had been planned for many years and the inquiry would allow people to express their opinions.
The A494 links the A55 with the north-west of England, bypassing places like Ewloe, Aston and Queensferry.
Congestion is already an issue on the route, the assembly government has said, and this would increase without the work.
But residents from Northop, Queensferry, Ewloe and Aston, on Deeside, formed a coalition committee to oppose it.
The inquiry - which is expected to last three weeks - is being led by an independent inspector and will hear from those for and against the proposal.
Witnesses from the assembly government's team will explain what the road-widening scheme would involved, and why they believe it is vital.
Later in the week objectors will give their evidence and have a chance to cross-examine experts.
The A494 stretch involved is from Ewloe to just beyond Queensferry
On Tuesday, the inquiry heard the assembly government's view that the widening of the A494 would provide an essential link between the A55 and the M56 and M53 motorways, essentially linking north Wales and the north west of England.
But protesters are concerned about the increase in traffic and noise.
Objectors Jim and Jean Henderson told BBC Radio Wales that things were already bad.
Mrs Henderson said: "At night time we can't have our bedroom window open to get to sleep because of the noise and we feel its infringing our rights."
"There's a human rights issue here, you know its just got noisier as the time's gone on," added Mr Henderson.
Terry Maloney, who will also be giving evidence at the inquiry, said he had concerns about the whole scheme. "
"It's passing through two villages actually plus its going to have a big impact on the small community of Queensferry," he said.
"You've got to ask how many villages in Wales will have a motorway passing through the centre of them."
A legal representative for Flintshire council - which is also against the the proposal - is to raise the authority's specific concerns at the inquiry.
Campaigners wanted the inquiry stopped until alternative routes could be looked at, but the assembly government said this would happen after the inspector had made his recommendations.
Around 150 people attended a demonstration against the plans when the final draft of the was unveiled in January.
A Welsh Assembly Government spokesperson said the project had been in the Truck Road Forward Programme for many years.
The spokesperson said: "The whole purpose of the public inquiry is to enable anyone, who has an interest, to have their opinions and evidence heard by an independent inspector so that he can draw his conclusions and make recommendations to the minister.
"It is by this means that the deputy first minister, the minister for the economy and transport, will be able to make a fully informed decision on the merit of the proposals with the benefit of the inspector's recommendations.