MOTORWAY traffic around Newport is due to be diverted on Friday and Saturday nights for the next year while work is done in the Brynglas Tunnels overnight.
Welsh ministers published a notice on Friday to say that work in the tunnels could start as early as the second day of the Nato Summit on September 5, and will continue for a maximum of 16 months.
The work is due to take place from 8pm on any Friday or Saturday during that time, until 6am the following day.
Both sides of the road will not be closed simultaneously, according to Friday's notice.
The M4 between the exit and entry slip roads for Junction 25a to St Julian's and Caerleon, and Junction 26 for Malpas Road, will be affected, with westbound traffic having to leave at Junction 25a and follow the A4042 and A4051 to rejoin the M4 at Junction 26, and vice versa.
The Argus reported earlier this year that politicians had approved work to boost the tunnel's safety, three years on from a lorry fire which brought the M4 to a halt.
Edwina Hart, minister for the economy, science and transport, agreed to employ contractors to develop proposals for refurbishing and improving “life safety measures” in the tunnels, including lighting.
The westbound tunnel was fitted with temporary strip lighting following the 2011 fire.
In May this year a Welsh Government spokesman said the work would be in both tunnels and would include a new road surface, tunnel lining, drainage, lighting and other works to "increase resilience and improve protection of the traveling public in the event of a fire".
William Graham AM welcomed the plans but warned that they meant more disruption for motorists.