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Dunedin City Council – Kaunihera-a-rohe o Otepoti
Traffic lights.

Gritting and de-icing

Some roads are gritted or treated with a de-icing agent to alleviate winter road hazards such as ice and frost, but we encourage people to drive to the conditions and be aware of the risks on winter roads.

When will the roads be gritted?

The gritting season usually runs from late May until early September.

When there is a chance of frosts, our contractor conducts patrols in the very early hours of the morning and reports on road conditions. Based on the assessment, the grit truck is sent out to apply grit or CMA. The grit map shows which roads are assessed and the priorities for gritting and de-icing.

Arterial roads (major traffic routes) will be gritted before 7.30am. Gritting is not done at a specific time, but usually starts after 5am or 6am as this is when frost often forms.

This map shows roads that get gritting or CMA, click to enlarge
This map shows roads that get gritting or CMA, click to enlarge.

Which roads will be gritted?

Road gritting is done in the following order of priority:

  1. Arterial routes -  These are the main routes or thoroughfares in and out of the city, such as Kaikorai Valley Road, Stuart Street and Pine Hill Road.
  2. Collector roads - These are other busy roads, such as Ross Street, that feed traffic to arterial routes. They will be done after arterial roads are completed.
  3. Local roads - These are generally not gritted.

If you are not sure whether your street will be gritted, please check the map above.

Why do you grit some roads and not others?

We need to balance costs and benefits. We aim to use our resources effectively by focusing on routes with high volumes of traffic.

Why is my street only gritted in patches?

Grit is laid where it is needed – this may mean a street is only gritted around shady spots, corners and intersections.

Be aware that CMA is clear and looks wet, so it may not always be obvious when it has been applied.

How much grit do you put out?

We follow NZ Transport Agency specifications for grit and CMA. Over a season, we use around 1000 tonnes of grit and 50,000 litres of CMA, but the quantities vary depending on how harsh the winter is.

On roads that have a lot of traffic, grit tends to windrow fairly quickly, so care is always needed.

Do you do any pre-gritting?

Some roads are gritted the night before a frost is forecast as they are difficult to grit in the morning – grit also tends to be left on these roads a bit longer. Examples are Coast Road, Buccleugh Street and George King Memorial Drive.

Do you grit private roads and footpaths?

We do not do private gritting. Please make your own arrangements if you want to organise gritting on private car parks, etc. Footpaths are not gritted.

What about gritting on the state highways?

For any enquiries about gritting of state highways, please call the New Zealand Transport Agency on 0800 44 44 49.

When do you remove grit?

Grit is removed by our contractor within 96 hours of it being spread. If you have concerns about grit not being cleared in your area, please contact us.

Where can I find out which roads are closed?

For information on current road conditions and closures, see road conditions webpage or call us on 03 477 4000.

You can also contact AA New Zealand, or check out AA roadwatch or NZTA traffic and travel information (links are in the related information section).

What should I do if the road I want to use is closed?

Please follow all directions and signs – roads are closed to keep people safe. Note, if you choose to drive on a closed road, you won’t be able to claim insurance.

Who decides whether roads are open or closed?

Roads are closed as a last resort, after all other options have been considered. The Police duty sergeant can request road closures, but only authorised DCC staff and contractors have the authority to close a road.

We will usually only close a road if we can give people a detour into a safer road.

What is calcium magnesium acetate (CMA)?

CMA is a low corrosion, biodegradable alternative to road salt and is used to reduce ice and snow from forming and bonding to the road. CMA helps prevent frosts from forming, is quick and easy to apply, is safer than grit and does not damage the road or road users.

CMA is most effective when used before ice forms and when road surfaces are above -7°C. It can remain effective against ice forming over many nights of dry freezing conditions, but rain or high humidity can reduce its effectiveness.

Our CMA is supplied by Cryotech. For more information, visit their website in the related information section.

What does CMA look like?

CMA is a clear product that comes in both liquid and granular forms. When it is applied, it will often make the road appear wet or damp until it dries.

Where is CMA used?

CMA is applied to selected city routes that have higher traffic volumes, where grit is likely to form windrows and it is difficult to get onto the road to clear it up – see the grit map. As CMA is relatively expensive compared to grit, we can’t use it on all roads.

When is snow cleared?

We don’t grit snow as it does little to improve traction. Once we are certain snow has stopped falling, main roads are cleared. If possible, please avoid driving when it is snowing or when there is snow on the road.

Will the DCC pay for repairs if I crash on icy roads?

No. If you have an accident, please call your insurer. We provide a service to alleviate winter road conditions, but you need to be aware of hazards and drive to the conditions.

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