Although we call it gritting, there is in fact little or no grit involved. What is actually spread on the roads is mined rock salt (sodium chloride).
The rock salt is spread on to the road in varying rates depending on how icy or snowy it is.
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.
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.
Snow ploughs can be fitted to all of our gritting trucks.
Snow ploughing removes large accumulations of snow from the centre of roads.
However, ploughing has its limitations - it effectively skims the road surface leaving around 30-50mm of snow on the surface.
Ploughing can also result in large amounts of snow accumulating at the sides of roads and on footpaths.
Following prolonged periods of gritting, snow ploughing can reduce the overall effectiveness of de-icing operations by removing slush which has a high level of salt solution.