Last updated 13:00 28/12/2009
His skill behind the wheel is because the bar has been set higher for him, and now, according to his family, the 19-year-old has become the second – and youngest – New Zealander with Down syndrome to get a driver's licence.
Clayton passed his learner licence test two years ago with a score of 100 per cent, and in early December he achieved an 82 per cent pass for his restricted licence.
"It's not that hard," he said.
He has now progressed to a natty little Mercedes-Benz smart car.
"I help Mum and Dad put the wine in boxes, tape them up and take them to the supermarkets in my smart car," Clayton said.
He also enjoys driving to the local video store to get movies and a Subway sandwich, and to the gym, where he continues a disciplined training regime for his sport of powerlifting.
Clayton recently returned from his first Special Olympics National Summer Games in Palmerston North, where he won three gold medals and a silver.
His parents Jeff and Sophie Marr say it has been "quite a process" helping their son achieve independence, and has taken a fair bit of lateral thinking.
The building blocks were the same as for their other children, Sean, 18, and Alex, 16, who also learned to drive in a rural setting.
Clayton had ridden a motorcycle from a very young age, when the family lived at Okiwi Bay, Mr Marr said.
"When they started driving, they had `paddock cars'. If they can, all young people should learn to drive on a farm so that when they hit the road, all they have to think about is the rules."
Clayton has learned precision driving. "Work in the vineyard means there's only a few centimetres' clearance down each side of the row. Clayton spends 25 hours a week on the tractor and he's only ever run over one post," Mr Marr said.
Mrs Marr said Clayton had an automatic "paddock car", but kept looking at his feet on the pedals. "So Jeff took him there at night so he couldn't see his feet."
Another step was the addition to the family fleet of a special "scooter car", which Sean found for sale on Trade Me. The 50cc scooter, which is registered as a moped, has two seats, side by side. The family intend to make it available to other families teaching special needs youngsters to drive.
Support and encouragement from the Automobile Association and a driving instructor convinced the Marrs to let go.
"It was a big decision to put Clayton out there on the road, from his perspective and for other people," Mr Marr said.
"We took him in to the AA and they were encouraging, and we enrolled him with Kevin Bannan Driving Tuition. The instructor said, `I think he could get there'. He had to get everything spot on, so in a way it was harder for him."
They also firmly believe Clayton's success is partly linked to him attending the Nelson Marlborough Institute of Technology's Supported Training Programme. It was announced recently that the programme has been axed to make way for a new one.
"It's important young people with Down syndrome keep in touch with mainstream kids. One reason they achieve so much this way is because they set goals against their peers," Mr Marr said.
Clayton said his aim now was to get his full licence and take a friend on holiday to Wellington.