Both lanes of State Highway 3 through the Manawatu Gorge are now open for the first time in more than a month.
The highway has been reduced to one lane since a slip in early April.
The Transport Agency said contractors had installed about 2000 square metres of rockfall netting at the site of the slip.
The gorge was last closed by several massive landslips in 2011, and reopened in November 2012.
Transport Agency spokesperson Anthony Frith said millions had been spent upgrading the alternative route, Saddle Road.
He said the Tararua District Council was continuing to make that road wider with more passing lanes to make it suitable for heavy traffic so that it can continue to be used in case of further slips in the gorge.