Key Points:

Work to widen a section of State Highway 6 in Central Otago's Kawarau Gorge is expected to be completed this week after "better than expected" weather.

Traffic has been restricted to a single lane near the Roaring Meg, about 15km west of Cromwell, causing delays for motorists since February 20.

But Transit New Zealand Central Otago area engineer John Jarvis said subject to weather conditions the widening work should be completed this Friday.

"In the first week of work we have experienced better than expected conditions, which means that we can remove safely more rock to further improve the width of the road," Mr Jarvis said.

Large scale excavation in one of the narrowest parts of the Kawarau Gorge was impossible because of hillside instability, so contractors were carefully removing and scaling back sections of protruding rock.

Traffic delays of up to 10 minutes were expected between 8am and 5pm until Friday.

The road section undergoing widening is near the site where three army soldiers were killed in a Unimog crash in February 2005.

Privates David Partington, 17, of Taranaki, Shane Ohlen, 21, of Wellington, and Ashley Goodwin, 19, of Motueka, died after their Unimog left the road and plunged 100m down a steep bank into the Kawarau River.