A PROPOSAL to bore an extra M4 tunnel at Brynglas could face ten years of delays if government officials tried to get it built because of opposition.
That's according leading transport expert Professor Stuart Cole, who said turning the Southern Distributor Road into an expressway was a quicker and cheaper option that would solve the problem of the Brynglas Tunnels.
The Welsh Government is consulting on four proposals to tackle congestion, safety and pollution on the Newport stretch of the M4.
One of the schemes, known as option D, includes building a new tunnel at Brynglas and expanding the motorway to four lanes between junction 24 and 29.
Prof Cole, of the University of Glamorgan's Wales Transport Research Centre, said: "With option D there will be a lot of opposition and opposition invariably means delay."
The public inquiry process could last ten years, he said.
"The problem is that the capacity at the existing Brynglas Tunnels is inadequate for the traffic it is expected to take," he said.
"We need to find a short term solution. Waiting ten years is not a short term solution."
Option D has already sparked opposition on both sides of the existing tunnels, with campaigners fearing many homes could face demolition.
Prof Cole also argued that building work would inevitably cause traffic disruption while costs could rise from the estimated £550 million.
The transport professor said a better and cheaper scheme was option C - upgrading the SDR with new junctions to allow free flowing traffic.
That could solve the capacity issue at the Brynglas Tunnels with a solution that could be "implemented within three years rather than ten or more", he claimed.
He said the estimated cost of £300 million for the upgrade work was for the "Rolls Royce" version, and the cost could be brought down with fewer intersections and more bridges where users can't access the road.
He said option B, a £45 million proposal to improve the SDR's roundabouts with signal controls at all junctions, is just "messing around".
The professor added he couldn't see the point of option A, which would see a new road built south of Newport, when an existing road could be modified.
The consultation continues until July 6. For more information and to respond visit www.m4cemconsultation.com