The winter service includes precautionary salting of all carriageways and the more important footways in advance of forecast ice and snow.
Since 2007-08, pre-wetted salting has been used on all four Trunk Road Units.
Pre-wetted salting involves spreading dry salt and brine in the proportion of 70% dry salt to 30% of fully saturated brine with a salt concentration of around 23%. The addition of the brine to the dry salt takes place at the point of spreading and has the following main advantages:
Salt requires to go into solution before it becomes effective in preventing ice formation. The addition of the brine has the effect of reducing, if not eliminating, the time lag before the salt becomes effective after spreading.
The brine minimises the amount of dry salt removed from the carriageway by the draught from the spreading vehicles, road traffic and strong cross winds. More salt adheres therefore to the road surface after spreading and this can increase the length of time the salt lasts without retreatment.
The brine ensures that the “ bounce” of salt crystals onto the road side verges during spreading is minimised and that the greater proportion of the salt spread is contained within the carriageway. This leads to reduced corrosion on roadside structures and environmental benefits.
The changeability of the Scottish weather patterns means that even with this new and improved method of precautionary salting ice formation on roads can still occur. Motorists should be aware therefore that there will still be times when motorways and trunk roads will not remain completely free of snow and ice.
