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.
There's one lane blocked and queuing traffic due to an accident involving three vehicles involved on the M4 Westbound at J26 A4051 (Malpas Road).
Lane two of two is blocked by the accident, which is located adjacent to the entry slip road.
The A4232 Butetown Tunnel Eastbound is blocked and there's stationary but light traffic due to an accident between Stuart Street and A4234 Central Link/Pierhead Street (Queensgate Roundabout)
Emergency services are arriving at the scene. It's not clear how long the road will be blocked.
The eastbound carriageway of the M4 is closed between J38 A48/Margam offslip and J37 A4229/Pyle due to an accident. Traffic Wales is warning of delays as all three lanes are currently closed.
Both South Wales and Mid and West Wales fire services are at the scene. A South Wales Fire Service spokeswoman said it is believed three cars have been involved in a collision and a car had also broken down nearby.
A South Wale Police spokesman said there had been a number of accidents on the M4 following a hail shower. He said no one suffered any significant injuries.