The Manawatu Gorge, the main route south from Hawke's Bay, is on track to reopen on May 18 after being closed due to a large slip.
Two slips hit last Monday night, with one of them about 3500 cubic metres and expected to take three weeks to clear.
The other slip, of about 200cu m at the southern end of the gorge, has already been cleared.
According to the New Zealand Transport Agency, good progress had been made by contractors working through the weekend despite bad weather halting work yesterday.
NZTA highway manager Ross I'Anson said work on clearing the large slip began on Thursday afternoon after an assessment by geotechnical engineers.