A closure was scheduled to begin in June but was moved forward.
NZTA regional transport systems manager Mark Owen said the road's long-term resilience was a priority because it was prone to slips from heavy rainfall, which overflows the stormwater drains.
"The Remutaka Hill road is a lifeline for Wairarapa communities and the only direct vehicle route to the Wellington region," he said.
"This resilience work is necessary to ensure that safety of road users and help prevent future slips and road closures from happening in the event of heavy rainfall in the Remutaka mountain range."
Two high-priority sections would be strengthened from late May to early June to prevent erosion and slips causing lengthy road closures and disruption to people's journeys.
Two culverts that are due for an upgrade will be worked on at the same time.
Other works include building retaining walls, adding new culverts and expanding capacity for existing culverts to manage stormwater overflow.
Eight remaining sites identified in the engineering analysis report would be strengthened in the next few years, subject to funding.
Owen said the NZTA was advising people to plan ahead as the lengthy road closures could cause disruption.
"The Remutaka Hill Rd is steep, narrow and winding which makes it a challenging environment to work in," Owen said.
"Having it fully closed to traffic at night during the main period of the works is essential to ensure the safety of our team.
"Working at night encounters less traffic, and therefore less disruption to road users.
"However, there will still be some impact on motorists during the day with the stop-go in place, so we're advising everyone to plan ahead."
Although the closure could have an effect on transport businesses, McCarthy Transport Masterton branch manager Pete Maclean said, "as long as they don't impinge on us in the daytime [the closures] won't affect us at all".
Maclean said, "Most of [their work is done] outside of those hours.
"We generally have trucks dispatched at the yard from 2 o'clock onwards, so if [drivers] have to wait at the gate for half an hour before they go over the hill it's not too much of an issue for us."
Access over the hill would be available for emergency services and night workers throughout the night-time closures with an escorted vehicle service.
Bookings for this service must be made in advance by emailing remutaka@nzta.govt.nz
Travel arrangements for traffic during the night-time closures:
Sunday May 16-Friday May 21
9pm-4am full road closure
Advanced bookings for escorted vehicle service required [remutaka@nzta.govt.nz].
[The road will be fully open from 5pm Friday through till 9pm Sunday night].
Sunday May 23-Friday May 21
9pm-4am full road closure
Traffic convoys will be escorted over the hill by a pilot vehicle. No bookings required.
From Hutt to Wairarapa 10.30pm and 12.30am.
From Wairarapa to Hutt 11.30pm and 1.30am.
[The road will be fully open from 5pm Friday through till 9pm Sunday night].
Sunday May 23-Friday May 28
The Remutaka Hill road will be closed from 9pm to 4am each night and under stop/go traffic management at all other times.
