The A465 is blocked in both directions and there's queueing traffic after an accident between the Glynneath Interchange and the Rhigos Roundabout.
The A465 between Glynneath and Hirwaun has now reopened, South Wales Police say.
One person was taken to hospital earlier in the evening after 12 vehicles were involved in a collision.
South Wales Police say 12 vehicles have been involved in a crash on the A465 between Glynneath and Hiwaun this evening.
One person has been taken to hospital with injuries not believed to be serious.
The road remains closed as emergency services work to clear the area.
The A465 Heads Of The Valleys Road is closed in both directions after an accident between the A470 Ffrwd Road (Cefn Coed Roundabout) and Lower Vaynor Road.
The A465 Heads of the Valleys Road is blocked Westbound between the Rhigos Roundabout and Glynneath Interchange.
A470 Ffrwd Road is closed after an accident at the A465 Heads Of The Valleys Road (Cefn Coed Roundabout).
The A465 is blocked in both directions after an accident between the B4521 (Mardy) and Old Hereford Road (Llanvihangel Crucorney).
Fog is reducing visibility on the A465 Heads Of The Valleys Road between the A40 Monmouth Road / A4042 (Hardwick Roundabout) and the B4560 Llangynidr Road (Garnlydan / Llangynidr).
The A465 Heads Of The Valleys Road Westbound exit slip road is closed because of smoke blowing across the road at the A4143 (Llanfoist Interchange).
One lane is closed for emergency repairs after an accident on the A465 in both directions between the Resolven Roundabout and the Aberdulais Roundabout.