Call to make M4 three lanes on each side around Swansea
Calls are being made to expand the M4 motorway around Swansea - adding an extra lane on each side.
The stretch between junctions 44 (Swansea East) and 48 (Pontarddulais) currently has two lanes each way.
But Swansea council leaders want it increased to three, to help cope with more traffic pressures from thousands of new homes being built in the area.
The Welsh Government, which controls the M4, said it could not comment.
Swansea's local development plan has homes earmarked for both the Penllergaer and Pontarddulais areas which would be built by 2025.
Council leader Rob Stewart stressed he wanted to avoid potential traffic issues.
"We are talking about putting an extra lane in," he said.
"The Welsh Government does have extra capital means in the settlement and we need to make a bid for them.
"I've already indicated to the first minister we will be coming to them with a request.
"The houses are not going to be built overnight but its about having a prepared plan for the residents around them."
The M4 reduces from three lanes to two at junction 38 (Port Talbot) and remains that way until the motorway ends at junction 49 (Pont Abraham).
However, Stuart Cole, professor of transport at the University of South Wales, does not support extra lanes on the motorway.
"The answer is not to add another lane," he said.
"There's no justification in my view for building another two lanes on that motorway.
"The evidence suggested to me is that traffic is coming through drivers trying to get from one side of Swansea to another and trying to avoid the centre where there's serious congestion."
Prof Cole said he believed "high quality, high frequency" buses which operate from large satellite park and rides on various outskirts of the city would work better,
The aim would be for them to run daily from 06:00 to midnight.
"It works in Dublin and it works in Edinburgh so why can't it work in Swansea?" he added.
But Mr Stewart hit back saying Prof Cole's comments relate to a separate issue.
"The M4 upgrades we are talking about are several miles to the north of the city and would assist both Neath Port Talbot and Carmarthenshire," he said.
"We are already investigating regional transport opportunities as part of the city deal planning and city developments."
A Welsh Government spokesman said they would not be able to comment until Swansea council has discussed its future development plans in detail with them.