SH1 Cambridge to Piarere

December 2025 Update

18 December 2025

Before you head off for some well-deserved summer fun, read the latest news and updates on the Cambridge to Piarere (C2P) expressway extension project and nearby state highway activities.

Thank you for joining us at our C2P Community Information Day!

Recently we welcomed locals to our Community Information Day to learn more about the C2P Expressway extension Road of National Significance (RoNS) project and other local state highway projects.

It was great to see so many people (150+) drop in between 2pm and 6pm to explore the displays, chat with the project team, and get the latest updates.

This session gave people interested in the project the chance to:

• See our detailed maps showing the designation boundary, expressway route and changes to local roads
• Understand how the expressway will connect with local roads
• See how we will manage environmental considerations like noise, stormwater and landscaping
• Watch an animated fly-through video showing what the expressway could look like once complete
• Meet the project team and ask questions

We were joined by our colleagues on the Hamilton Southern Links RoNS project, summer maintenance and Waipā District Council’s Cambridge Connections team.

We had lots of interest in the project and a variety of other topics, and some really valuable conversations.

We’d like to thank everyone who came along and contributed with their questions and feedback. Your input helps shape the future of our transport network.

Couldn’t make it? All the project information sheets and posters are available on our project website. The fly-through video is also available.

• Cambridge to Piarere

To find out more about the other projects we featured: 

• Hamilton Southern Links
• Waipā District Council – Cambridge Connections

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What's happening next on C2P?

We are now planning a programme of early works that will help us meet our resource consent requirements and be ready to start construction when funding is available.

We are preparing management plans and planning for removing trees and vegetation. This includes relocating lizards as well as installing bat roosting boxes to offset future habitat loss.

To date funding has been approved for design, consenting, property acquisition and the early works packages. We are aiming to begin construction in late 2026/early 2027, subject to construction funding being confirmed.

Unearthing our ancient greywacke

The rock and soil samples pictured here tell a fascinating geological story. They contain complete to highly weathered greywacke, a type of basement rock that forms the foundation of much of our region’s landscape. When unweathered, greywacke is prized for its strength and durability, making it an excellent material for roading and construction.

This formation is remarkably old - dating back approximately 160 to 100 million years, originating during the Mesozoic era.

Over millions of years, exposure to natural forces such as water, air and biological activity has caused extensive weathering.

This process transformed solid greywacke into what geologists call “rotten rock”, which fractures easily and breaks down into clays and silts. These fine deposits now fill the cracks and crevices within the rock, shaping the soils we see today.

The samples pictured are from the Manaia Hill Group and were found in multiple boreholes across one hillside within the southern end of the project, in the hills near Piarere.

By collecting core samples from a series of sites along the planned expressway route, we gain valuable information to help design the road, reusability of materials and the stability of materials for ‘cut slope design’.

While this general area is home to a lot of greywacke deposits overlain by the occasional ignimbrite - the greywacke is popular with a number of quarries in the district - this also means we have to plan for the challenges weathered greywacke presents to road design, cut design and reusability. Unfortunately, the good unweathered greywacke is at a depth we are unlikely to reach.

To date we’ve identified 3 geological units – Hinuera Formation, Ongatiti Formation and Manaia Hill Group - all of which require different design techniques and standards.

Unweathered greywacke is very hard and strong, making it excellent for roading material. It’s often quarried and crushed for use in road base layers because of its durability and ability to bear heavy loads.

Highly weathered greywacke (also known as ‘rotten rock’) is much weaker and breaks down easily into clays and silts. Building a road directly over this material can be problematic because it loses strength when wet, can be unstable and lead to settlement or slumping and may need to be removed or stabilised before construction.

So, in short:
- Fresh greywacke - great for roads
- Weathered greywacke – a poor foundation, needs treatment

The festive season is nearly here

This is our last newsletter for 2025. We’ll be back on deck with all the latest C2P news in February-March 2026.

Our road crews are also getting a well-earned rest over the break. From midday Friday 19 December 2025 to midnight Sunday 4 January 2026 there’s a nationwide roadworks shutdown in place, so everyone can get to where they’re needing to go nice and easily.

Keep across our works across the Waikato and Bay of Plenty by signing up to the regular state highway maintenance programme newsletter:

• Waikato state highway maintenance programme
• Bay of Plenty state highway maintenance programme

For real time travel planning, check out our Journey Planner.

Steer clear of stress - your summer road safety guide!

Whether you’re heading for the beaches, the lakes or the city, the best gift you can give your whānau is arriving safe and sound. 
Before you hit the highway, let’s make sure your journey is as smooth as your summer playlist. Here are some easy tips to keep you safe and stress-free.

Plan like a pro! Use our NZTA Journey Planner to check peak times and road conditions. Give yourself plenty of time - holidays are for relaxing, not racing.

Chill and adjust - Summer weather can be unpredictable. Slow down in wet or busy conditions and keep a safe following distance. Patience beats panic every time.

Nap before you navigate - Long drives can be tiring. Get a good night’s sleep, take regular breaks, and keep your phone out of reach. A quick water or coffee stop is better than a risky shortcut! Take snacks and games for any children in the car and share the driving to stay fresh. 

Give your car a TWIRL - Before you go, give your car a quick check: Tyres (minimum tread 1.5mm), windscreens, indicators, road ready wipers and lights. (And when you check your windscreen - make sure your WOF/COF/RUC are up to date!).

Click before you cruise - It’s simple - seatbelts save lives. Make sure everyone clicks in before you roll out.

Share the sunshine - Holiday traffic can test your patience. Take a deep breath, smile, and let others merge. A little kindness goes a long way.

Enjoy the sunshine, the laughter, and the memories—but keep safe in the driver’s seat. Have a merry festive season and a happy summer and we’ll be back in your inbox early next year!

More information

For more information on the SH1 Cambridge to Piarere, contact us at c2p@nzta.govt.nz

Visit our website nzta.govt.nz/c2p