We receive regular detailed weather forecasts predicting conditions on roads in Cumbria and we will send out gritters whenever ice formation or snow is forecast.
To prevent ice forming on our Priority 1 and 2 roads we spread 6mm crushed rock salt at a rate of 10-15gms per square metre. If freezing conditions after rain is forecast, we spread salt at a rate of 20-40gms per square metre dependent on the amount of moisture present and road surface temperatures that are expected.
We have pre-planned salting routes that allow all Priority 1 routes to be treated within 3 hours and Priority 2 routes to be treated within 5 hours of a decision to salt. Once the decision is made to pre-treat these roads, sufficient time must be allowed to complete the gritting operations before any ice forms. On the few occasions that ice does form the rate of spread has to be increased to 20-40gms per square metre to melt the ice.
Treatment of Snow
When snow depths exceed 30mm to 50mm it is best removed by ploughing. Each pass of the plough is supplemented by a salt spread at 20gms per square metre to prevent snow from compacting and so ease subsequent ploughing.
Treatment of hard packed snow or persistent ice
The formation of hard packed snow and ice will be rare on Priority 1 and 2 routes. On the remainder of the highway network where it is likely to occur, it can be treated using higher rates of spread. However, below minus 10oC or where snow or ice is more than 20mm thick, great care is needed as the use of salt alone can result in an uneven and very slippery surface. In these circumstances we spread a mixture of sharp abrasive grit and salt to break up and melt the hard packed snow or ice.