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Gritting - explaining how it works
Gritting the roads will not always guarantee an ice-free surface so concentration and care is always necessary when driving in winter.
What is grit?
Although most of us call it gritting there is in fact no grit involved. What we spread on the roads is rock salt taken from an underground mine North of Whitby. It is more or less the same as the rock salt you would grind into your food, but of a size and composition for road use.
How does gritting work?
Our goal is to create a layer of salt and water on the road surface to prevent the ice or snow pack from sticking to the road.
When ice or snow is forecast we spread dry salt onto a road surface which we want to dissolve and form a solution of salt and water. It is this solution that melts the ice or snow by lowering the freezing point of moisture on the road surface.
Before salt can become really effective, it needs to be crushed even smaller by the traffic to help it dissolve.
How do you decide when to grit?
We monitor the road surface temperature and how much moisture is in the air and it is these measurements that dictate when we salt. We may not grit even if:
Does gritting always work?
Salt tends to be less effective at temperatures below minus five degrees centigrade (-5°C) and has virtually no effect below -10°C.
Salt has a limited effect on snow and where accumulations occur, ploughing will be necessary before salting can take place and the service will take much longer to deliver. Once snow has fallen we will attach snow ploughs to the gritters and we will reapply the salt to roads until they are sufficiently protected against the forecast conditions.