Waka Kotahi NZ Transport Agency has announced the preferred site for the roundabout to replace the dangerous intersection of State Highway 1 and State Highway 29 at Piarere.
The location will be to the northwest of the existing intersection.
Funded by the NZ Upgrade Programme, this location is part of a transport corridor between Auckland, Hamilton, and Tauranga.
Waka Kotahi regional manager infrastructure delivery Jo Wilton said the roundabout would improve safety on a high-volume traffic route.
"This intersection is among the most dangerous on the New Zealand roading network," she said.
"The new roundabout will ensure that all traffic has a safe and efficient way of making any type of movement, be it straight ahead or turning. Vehicle speeds in roundabouts are significantly lower, which minimises the impact of any crash that might still occur."
The preferred site considers a number of factors, including initial technical assessments of stormwater, ecology, archaeology, and geotechnical information.
Discussions with affected landowners are continuing, as is the finalisation of the detailed technical assessments required to complete design, the lodgement of the notice of requirement, and regional consents.
Lodgement of designation and consents for the SH1/29 roundabout is expected to happen later this year, with construction expected to start in 2022, subject to negotiations on property acquisition and RMA proceedings.
Once started, construction is anticipated to take about two years to complete.
Replacing the current intersection directly with the roundabout is not practical due to the high traffic volumes, safety considerations, and the resulting disruption on SH1.
The Government recently confirmed the direction and funding commitment for these safety improvements at Piarere, through the NZ Upgrade Programme.
When the NZ Upgrade Programme was initiated, a number of the projects, including the SH1/29 roundabout, were in their early stages of development, with detailed project information still being established.
Since then, Waka Kotahi has worked to get a better understanding of project risks, scope, costs, and timeframes.
For the SH1/29 roundabout, this work resulted in an updated cost estimate of $40 million to deliver the project. The same scope and transport benefits will be delivered.
The detailed business case for the longer-term Cambridge to Piarere corridor (Waikato Expressway extension) was recently presented to the Waka Kotahi Board and their decision will be available soon.