Traffic Wales is reporting severe delays on the M4 through Newport this morning.
The congestion starts at J29 Castleton to J26 Malpas.
There is also heavy queuing traffic on the A4232 eastbound towards Cardiff Bay.
There are long delays on the A465 westbound after a broken down vehicle leads to road closures.
The incident has occurred between the A4109 Glynneath interchange and the B4242 Cwmgwrach roundabout.
Diversions are in place.
The M4 Eastbound entry slip road has closed and there is heavy traffic after an accident involving a car and a lorry at J47 A48 / A483 (Penllergaer/Swansea West Services).
Emergency services are on scene after the car involved has ended up facing the wrong way.
There is a diversion in place and traffic will have to head West on the M4 to J48 and turn around to head East.
Alternatively, traffic can head along the old A48 (running parallel with the motorway) to J46 (Penllergaer)
Traffic is queuing on the A470 southbound from Nantgarw to Coryton this morning as many return to work from the Christmas break.
Traffic Wales are warning of congestion and delays to drivers between the Coryton Interchange and Abercynon due to poor driving conditions.
More road traffic is expected around Wales as Arriva Trains Wales stages a 24-hour walkout over pay and working conditions.
There is heavy traffic on the A485 due to an accident involving two vehicles near the North Road.
Drivers are being warned of blocked roads between Lampeter and Tregaron.
The A547 between Rhyl and Colwyn Bay is closed after an accident near Ffordd Talargoch.
Police say there's already heavy traffic in the area affecting Rhuddlan and Prestatyn.
North Wales Police are attending the scene and diversions are in place.
This morning's accident has led to long delays on the major routes into the capital.
The M4, A470, A48 East and Westbound and the A48M all have delays.
There are no estimates on when the A4232 will reopen.
One lane is blocked and there's very slow traffic after an accident on the M4 Eastbound between J34 A4119 (Miskin) and J33 A4232 (Cardiff West And Services).
A multi-vehicle collision has closed the A465 Eastbound between Llandarcy and Neath.
There's queueing traffic, but diversions have been put in place.
There's very slow traffic after an accident, now on the hard shoulder, on the M4 Malpas Straight Westbound between J26 (Malpas Road) and J27 (Highcross).
There's congestion on the M4 to J25 (Caerleon). All lanes have been re-opened.