"It was the airbags in the truck that saved me, and the way the truck's actually landed, rather than rolling over.
"It's quite scary."
The truck landed on its wheels, gouging part of the motorway out - Mr Greig's partner Angela Rotherham, sitting by his side and holding his hand, joked he had "parallel parked it".
Nursing a fractured vertebrae in his lower back, Mr Greig is confined to his bed, tilted at a 45 degree angle, until he's fitted with a back brace.
He expects to be discharged from hospital with his brace tomorrow, and is looking forward to being back at home.
It will be four to six weeks before the fracture is healed, and he will be off work until then.
Mr Greig has no qualms about getting back behind the wheel, but admitted, "you don't know until you get in the cab".
He considers himself lucky - apart from the fracture, the crash left him with only a few scratches on his face, a cut on his lip, and some skin off his left thumb.
And despite the airbag having "splattered in my face", his glasses weren't even knocked off in the crash.
"It's pretty phenomenal, really," he said.
He also knows how bad things could have been if the crash had happened at a busy time of the day.
"It's just scary to think about really. It could have been a massive fatality, people could have landed on the car, cars could have come around the corner and run into you. It's pretty scary.
"As unlucky as it was, it was pretty lucky."