A stretch of the A30 through Cornwall is closed in both directions after a serious crash involving an overturned lorry and a car.
Devon and Cornwall Police were called to the crash on the dual carriageway near Zelah, between the A39 at Carland Cross and the A390 at Penstraze at about 13:50 GMT.
One person has been potentially seriously injured, the force said.
National Highways said diversion routes were in place around the closure.