Roads in winter
Salt levels and how salt works
We now start winter with about 39,000 tonnes of salt in stock. This is roughly what we expect to use in an average winter. A few years ago we only started with 8,000 tonnes.
However, with national salt shortages happening in recent winters our pre-winter salt stocks are now much higher. This reduces our need to re-stock during the winter period when salt supplies may be short.
How salt works
Grit (or crushed rock salt) is meant to stop ice forming on the road surface. It works by going into solution and lowering the freezing point of water on the road surface. But, even when a road has been gritted ice can still form. For example, a shower of rain after we have gritted can wash the salt off the road surface and it can then freeze. Or, a drainage problem on land next to it may cause water to run across the road and again wash salt off. For these reasons great care is always needed in sub-zero conditions.
How much grit is spread?
We follow national guidance and take account of the current conditions. Typically salt spread rates vary from 10 to 40 grams per square metre. In difficult conditions, for example, if it's snowing, we will treat our main roads continuously with successive grits, so in these conditions we use a lot more salt.
It's snowed and the roads are white - you haven't gritted!
Grit is meant to stop ice forming on the road surface and then snow sticking to it leading to a build up of thick ice. However, grit will generally not stop snow lying on roads, unless the snowfall is very light indeed.
So, when snow falls it will generally lie on roads and we need to plough and then grit again to clear it.
Grit also relies on the mechanical action of tyres to make it work well. That is why in snow conditions the tyre tracks turn black while much of the rest of the road remains white.
In very heavy snow conditions our grit lorries add coarse material such as sharp sand to the rock salt to give traction for vehicles and to help the break-up of snow layers.