Highway maintenance frequently asked questions

What is the resealing (chip sealing) process?

Prior to resealing we identify any areas of the road base (also known as the pavement) that require strengthening, and these are repaired in advance, known as a ‘pre-reseal repair’.

When we come to reseal a road, we first apply a thin layer of bitumen or emulsion onto the existing road. Then a layer of sealing chip is applied onto the bitumen/emulsion. The sealing chips are rolled into the bitumen to provide initial bond. The road is then re-opened to traffic under a temporarily reduced speed limit of 30km. Loose chips are swept up and the site is road marked, normally within 48 hours of sealing, at which point the temporary speed limit is increased to 50km. Further sealing chip compaction occurs by managing the traffic over the site, and after a few days the site is swept again and the temporary speed limit removed.

Why is resealing work undertaken during summer?

Warmer spring and summer months are the best time for resurfacing as daylight hours are longer and the warm temperatures and dry air help the new seal stick to the road surface. Warm weather helps ensure the new seal becomes strong and long lasting.

Bitumen and emulsion are liquids when they are hot and hard when cold. They can crack in cold weather, return to a liquid state in high temperatures, and wet road conditions during sealing will affect the bond between the bitumen and the road, leading to chip seal failures.

During the peak summer months it is a balance to programme as much work as we can before schools return, while the roads are quieter, whilst also minimising the effect on people’s holiday travel.

Why is there traffic management when nobody is working on site?

Even when there is no one on site working, we may leave temporary speed limits, signs and cones in place to protect road users. We need to consider reduced visibility, temporary surfaces, weather and changes to the road layout that people may not be used to.

When motorists disregard traffic management, they put their safety, that of other road users and our road workers at risk.

Why isn’t maintenance work completed at night?

Where possible, we work at night to minimise disruption to drivers on key routes. However, night work presents a number of risks for road workers. We are also restricted by various factors, such as noise restrictions, which are intended to ensure residents adjacent to works are treated considerately too.

We also need to consider our proximity to other infrastructure, such as overhead power lines, which may pose a health and safety risk to our teams on the ground.

Why don’t we use asphalt on all state highway roads?

Asphalt is a significantly more expensive surface when compared to chipseal, and as such we need to use a mix of asphalt and chipseal surfacing to provide a network of roads that can be well-maintained into the future. We tend to use chipseal on long straight sections of state highways that have lower volumes of traffic.  Asphalt tends to be used on tight corners, at intersections or high-volume sections of road, where the stress factors related to vehicle movements are increased.

Why do you reseal roads?

The seal on a road is like paint on your house – it keeps water out of the structure underneath. Like paint, the seal breaks down over time and starts to let water in.

When the surface of a road starts to break down it indicates that it is time to reseal. The ideal time to reseal is just before any damage occurs, so your road may still look like it is in good condition when we complete the reseal.

You completed a renewal last year, why are you sealing the road again this year?

All renewals receive a ‘second-coat’ seal the year after they are re-built. This is due to the initial renewal only including a single coat of chip seal, which is then allowed to settle for approximately 12 months. The second coat is then added to provide a thick, durable layer of chip seal, waterproofing the surface underneath. This process prevents ‘flushing’, which is where the bitumen rises to the surface of the road, making it shiny and slippery.

Why are there so many potholes on the roads?

Potholes can occur for a number of reasons, however water is the primary cause. With our older pavements, if there's a crack in the road surface, or a displaced stone, it will allow water to sit in the road surface. As vehicles drive over the ponding water, tyres create hydraulic pressure, forcing the water down into the pavement. Over time, as vehicles continue to run over the pothole, it'll grow in size as weakened areas break off. Sections of road that are due for renewal are often the worst affected areas as the pavement and surface are weaker and are starting to fail.

Potholes will often appear during heavy rain events, and we're seeing these events occur more frequently now due to climate change.

I damaged my car on a state highway road, what should I do?

Drivers should have insurance for their vehicles in the event of any damage that occurs on the road. Your insurer should be your first point of contact if your vehicle is damaged. If appropriate, your insurer would then get in touch with Waka Kotahi.

Alternatively, you can complete the Request for compensation for vehicle damage form if you'd like Waka Kotahi and the relevant road maintenance contractor to investigate the matter directly.

Request for compensation for vehicle damage form