The Parapara (SH4) between Whanganui and Raetihi has reopened following the installation of roadside barriers at a high risk slip site two kilometres south of Fields Track.
It opened at 4pm on Wednesday.
NZTA Regional Transport Systems Manager Ross I'Anson said travel would be restricted to a single lane at the site while work was undertaken to remove unstable material above the road.
Stop-go traffic controls will in place.
The unstable material was identified during a regularly scheduled geotechnical inspection earlier this week and the road has been closed since 5pm on Monday while a more detailed inspection has been undertaken to determine how to safely remove the material.
The roadside barriers will protect motorists from falling material while the work is undertaken to remove it.
The work is expected to be completed by the middle of May.