There are delays of up to 20 minutes on the A303 in in both directions between A30 (Upottery) and A358 / B3168 Station Road (Southfields Roundabout, Ilminster).
The road is closed due to a serious accident. Two vehicles were involved.
Air ambulance attended the scene. One person was airlifted to Frenchay Hospital in Bristol. Police say the person is seriously injured.