Matt Cuckston said: “I can’t see the incident, it’s about 15 cars ahead of me.
“But the air ambulance has just landed on the motorway about 15 minutes ago. I thought they were reopening the eastbound carriageway but they just let a few cars past before the air ambulance landed.
“The lorry driver next to me can see it, and he says it [the lorry] has overturned.
“He said there is debris on both sides of the motorway and the lorry has gone into the barrier.
“The appears to be near the junction with the A329M.”
He added: “When we first drove up to the accident there was a lot of people running around at the front, there was a lot of confusion, they were trying to do something.
“This was before police or the ambulance arrived.”