The Welsh Government has promised fast-tracked measures to alleviate congestion on the M4 at Newport, while a special commission will consider longer-term solutions.
First minister Mark Drakeford confirmed on Tuesday that the M4 Relief Road, which his government had spent £44m developing, would not be progressed because of the cost and environmental damage.
He acknowledged the strong views for and against the scheme but said there was a consensus that capacity, resilience and the environment on the M4 corridor around Newport had to be addressed, through local and regional solutions.
Transport minister Ken Skates will announce details of the new commission on Wednesday, including timescales.
Mr Drakeford said: 'In advance of the commission’s work, the minister will implement a series of fast-tracked, targeted interventions to alleviate congestion on the M4, for example: actions to expedite recovery of vehicles; enhanced traffic officer patrols; live journey time information to inform better transport choices; and a behavioural campaign to reduce accidents and incidents and to make maximum use of existing lane capacity.'
The newly released report of the scheme’s public inquiry reveals that the planning inspector, the late Bill Wadrup, concluded there was a 'compelling case for the scheme to be implemented'.
This would have involved building 14 miles of new alignment across the Gwent Levels, in line with Labour’s manifesto promise in the 2016 Welsh election.
Mr Drakeford said continuing austerity, Brexit and lack of progress on the Comprehensive Spending Review could result in Wales’ budget being 'even lower in the future than it is today'.
He also said he would have blocked the scheme on environmental grounds in any case, because he attached 'very significant weight' to adverse impact on the wildlife and historic landscape of the Gwent Levels.
Paul Davies, the Welsh Assembly’s Conservative leader, said Mr Drakeford was 'kicking this decision into the long grass' by setting up the commission. He said the 'foot on the windpipe of the Welsh economy' caused by M4 congestion would clearly continue.
Mr Drakeford countered that the fast-tracked measures would alleviate problems sooner than the new road could have done, and that the Welsh economy’s future depended on many things, not 'one stretch of road'.
Plaid Cymru leader Adam Price welcomed Drakeford’s decision but said eight years had been lost and major expenditure incurred. 'We have to find a better way, surely, of making these decisions.'