Traffic delays to the west and south of Dunedin city are expected to last at least several weeks.

A large slip has opened up a crack in Portobello Road, which is slowing motorists around Turnbulls Bay.

Work to repair the road will take about three weeks, during which time traffic is being diverted.

There's also major roadworks on State Highway One through the city's southern suburbs.

The New Zealand Transport Agency is spending almost $300,000 resealing parts of the highway between Green Island and Fairfield.

That's in addition to the ongoing Caversham Highway development, for which work is now concentrated at Lookout Point.