Plans are in place to stack lorries that lack the paperwork they need in order to minimise any possible disruption at the port of Holyhead.
The move comes following the end of the EU Transition period overnight, the Welsh Government have said.
A temporary contraflow is in place on the A55 eastbound Junction 2 – 4. All HGVs turned away from the port will be redirected back to the contraflow to turn off at Jct 4 and join the westbound carriageway which is reserved for redirected HGVs.
From today ferry operators will require freight customers bound for Ireland to link customs information to their booking and if they arrive without having done so they will not be able to enter the port.
The reasonable worst case scenario published by the UK Government highlights that 40-70% of HGVs arriving at ports after the end of the Transition Period could be turned away as they do not have the right documentation. The peak for turned away HGVs is expected to be in mid-January.
Minister for Transport and North Wales Ken Skates said: “As the second busiest roll on roll off port in the UK, and a vital link with Ireland, it was imperative that we put contingency plans in place at Holyhead to minimise any possible disruption as the EU Transition period ends.
“We will monitor the situation carefully and as soon as it’s safe to do so we will remove the temporary contraflow. While the next few days are expected to be quiet, we know it will become busier as we approach mid-January.
“Our aim is to do what we can to protect the port, town of Holyhead and wider community from any possible disruption.
“We would also urge hauliers to ensure they have the correct documentation to avoid being turned away from the port.”
Lorries without documentation will either be redirected to another site on Parc Cybi, or if no other site is available they will be stacked on the A55 while they arrange the correct paperwork.
It is expected that the first few days of January will be quiet at the port with traffic picking up later next week.
The Welsh Government said that they have been working with partners across the north of Wales on the plans, including Anglesey Council and the ferry companies. The plans will be kept under constant review.
Isle of Anglesey County Council Leader, Councillor Llinos Medi, added: “We support the steps currently being taken by Welsh Government to protect Holyhead’s position as one of the main international gateways and mitigate any potential disruption to the town and its residents.
“Our priority, as a County Council, remains to ensure safe and efficient trade and traffic movement through the Port of Holyhead, whilst also protecting our local communities.”