Salting and gritting facts

What is Winter Service?

Winter Service is the salting and gritting service we provide from October through to April (longer if forecasts indicate that cold weather will continue).

This service operates on a standby basis, 24 hours a day, 7 days a week and includes:

You can find full details about how we deal the roads and pavements during Winter in our Surrey Highways Winter Service Policy (PDF).

When roads are assessed to require salting due to low temperatures, icy conditions and/or snow our gritters are sent out to salt roads on the network. For more route information, see our Surrey Winter Online Map.

Do road surface temperatures make a difference?

Yes, when making salting decisions we use weather forecasts, computerised ice prediction systems and information from roadside weather stations to get the most accurate indications of where and when ice is likely to form. However, road surface temperatures and air temperatures are rarely the same and the road surface temperature is also used to make decisions on when to apply salt. we use high-tech road sensors that are able to determine road surface temperature. We currently have 11 road sensors at our weather stations across Surrey, and a further 30 sensors in other locations in the process of being installed this year.

How does salt work?

Salting does not mean that the road surface will instantly become ice free. Salt works by turning the ice or snow surrounding each salt granule into a saline solution which has a lower freezing point than water. The action of traffic helps the salt to be more effective by moving the salt around and eventually melting all the ice or preventing ice forming.

Salt is less effective on road surface temperatures of less than 5°C and so will take longer to melt snow in these conditions. It also melts snow less than 40mm deep and only when traffic moves salt around.

Water freezes at 0°C - the presence of the salt prevents water from freezing until -6°C to -8°C. However, salt starts to become less effective at -5°C and almost ineffective at lower temperatures. In extremely low temperatures, or heavy snowfall, a mix of salt and grit may be used to help vehicles get about.

Rock salt needs vehicles to drive over it to work effectively. Vehicles grind the salt into smaller particles to spread it across the road - this means that grit is sometimes not effective when there isn't much traffic or when there is a lot of snow.

Why is the road still icy?

  • It takes time for the salt to become effective after roads are treated (the more traffic a road has, the quicker the salt will take effect).
  • Rain can wash salt off roads leaving them prone to re-icing. If the rain turns to snow during rush hour, any earlier treatment will be washed away and it isn't possible to re-salt in heavy traffic.
  • If road temperatures fall below minus 7 degrees Celsius the effectiveness of salt diminishes and it will not prevent roads from icing up.
  • If conditions are really bad, access to the roads is not always possible - even for the salt spreaders.
  • Most minor roads and pavements are not routinely salted.

Why are the gritters sometimes not spreading salt?

This can be deceptive. Gritting vehicles have become more sophisticated, and lorries now dispense the required amount of salt directly down on to the road in a fine spray that you may not see.

However, sometimes a vehicle might not be spreading any salt. This might be because:

  • it hasn't reached the starting point of its treatment route
  • it is returning to the depot to refill
  • It is driving on a road that is not on the gritting route.
  • it is driving over a section of road that has already been treated by a fellow driver
  • Treatments are occasionally treated pre-wet (salt and brine mixed) and treatments aren't clearly visible

Every gritting vehicle is fitted with a GPS system which tracks its route and speed, and it's part of the inspector's job to make sure the lorries don't deviate from their routes. The system also records at what time and location the vehicle is treating and this is monitored after each run to ensure routes are being treated correctly.

What should you do if a salt spreader was travelling too fast to be safe?

Contact the team and tell us when and where this happened and we will investigate your concerns. When spreading, salt spreaders should travel at no more than 34mph.

Can you make an insurance claim for a weather-related accident?

Please see our page about insurance claims against the council.

Files available to download

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