Some of the work was to have been completed in the week the lockdown started.
Partridge says temporary speed limits of 30km/h will be in force.
Partridge said the NZTA had been working closely with contractors and Construction Health and Safety NZ to plan a safe return to work after the end of the level 4 lockdown.
"We will be implementing a range of new measures to ensure the health and safety of our workers and road users, including restricted access to sites, requirements for workers to maintain physical distancing, and the use of additional protective clothing," he said.
The transition back to on-site work will be different for every project, and the timing will depend on the nature and complexity of work sites, Partridge said.
He said road users should expect to see more work sites up and running across the region.
Travel will still be restricted during alert level 3, but Partridge said more workers would be on the roads and motorists are urged to be patient, cautious and comply with all temporary speed limits to keep workers safe.