What is road grit?
The most common material used to treat road surfaces prior to freezing is rock salt. Rock salt is mined from underground mines. It can also be combined with grit which helps to provide traction and grind up the salt. Rock salt is a brown colour because it is unrefined and contains impurities, so it is often referred to as grit.
How does gritting the road work?
Grit works by lowering the temperature at which water freezes. It relies on the action of vehicle tyres to be spread over the road, so requires traffic to be effective.
When do we grit?
To decide when to grit we receive weather forecasts from our Forecast Provider. However no matter how accurate the forecast, there are situations where the network cannot be gritted prior to icy conditions. Some of the situations are as follows:
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When rain is followed by rapidly clearing skies, salting will normally start after the rain has stopped (to avoid the salt being washed away). Sometimes temperatures may fall by as much as 5 degrees per hour and the wet roads may freeze before salting has started or completed.
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"Dawn frost" occurs on dry roads, when early morning dew develops, falls on a cold road, and freezes on impact. It is impossible to forecast with any accuracy where and when it will occur.