The Desert Road will be closed for part of Wednesday morning to allow urgent safety work to be carried out.
The road near the Waihohonu Bridge, on SH1 between Waiouru and Rangipo, is currently down to one lane after a truck crash last week caused extensive damage.
New Zealand Transport Agency spokeswoman Karen Boyt said the state highway would be closed from 7.30am Wednesday for up to an hour and a half while structural engineers carry out a detailed assessment of the damage both on and off the road. This will determine what future repairs are needed.
The second closure, from around 10.30am Wednesday for up to an hour and a half, will allow a temporary barrier to be installed to protect road users. This will enable the road to opened to two lanes.
Boyt said people should be prepared for delays and should use the National Park road if they can.
"We understand the inconvenience this closure may cause and we'd like to apologise in advance for any disruptions. The damage to the bridge is extensive and we need to complete this work to keep the public safe.
"Once the work is finished we should be able to open the road to two lanes while we look at what other repairs need to be carried out," Boyt said.
A temporary speed limit will be put in place near the crash site because of the reduced lane widths on the bridge.
The truck and trailer rolled in icy conditions, with the trailer ending up partially submerged in the river below the Waihohonu Bridge. No-one was injured in the crash.
Details of SH1 Desert Rd closures:
• First closure from around 7.30am Wednesday up to 9am for a detailed damage assessment.
• Second closure from around 10.30am Wednesday until up to 12pm for the installation of safety barrier.
• People should use the NZTA website to determine when the road has closed.
• People should use an alternative route such as State Highway 49, 4 and 47.
• The detour could add up to 40 minutes to a journey.