Mr Stevenson spoke at the start of work to convert a two-mile long stretch of the A9 to dual carriageway.
He said: "The A9 is a vital link to north Scotland and the Scottish Government is committed to dualling this route, from Perth to Inverness, on a phased basis."
The A9 is the longest trunk road in Scotland, linking Perth with Inverness and beyond.
Mr Stevenson said he was pleased to be carrying out the groundbreaking ceremony for the 10.4 million scheme, which is the latest in a series of improvements to the road.
The work, at Crubenmore, will see the existing mile-long stretch of dual carriageway near to Etteridge extended for a further two miles.
Mr Stevenson added: "These works will not only bring employment for local people but also significant safety and economic benefits to communities and businesses across Scotland."
Extending the dual carriageway will help reduce journey times on the road and will give motorists greater chance to overtake slower-moving vehicles.
The work is expected to be completed by late summer 2011.