New Zealand Transport Agency System Management spokesperson Karen Boyt said people should be prepared for delays and should use the National Park road if they could.
"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," Ms 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 Transport Agency has asked people to drive carefully and abide by all traffic management in place.
It encourages people travelling along the Desert Road to check its website on the day as things may change on site and it will be seeking to open earlier if possible.
Details of State Highway 1 Desert Rd closure:
- 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 website to determine when the road has closed: http://www.journeys.nzta.govt.nz/traffic/
- 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.
