How, why and when is the network salted?

We salt the highway network to help the safe movement of all highway users, buses, cyclists, motorists and pedestrians. It is important in terms of both road safety and economy.

Our winter maintenance policies follow the principles set out by the Local Authority Association's publication 'Code of Practice for Maintenance Management - Delivering Best Value in Highway Maintenance'. We spread salt to prevent ice from forming on 1,200 miles (1,930 kilometres) of the County network on every night when frost or icy conditions are forecast.

How and when?

Our aim is to ensure that salt is spread on the highway before ice forms. We achieve this by using a fleet of 37 gritters, which are strategically based across the County. These gritters spread about 15,000 tonnes of salt onto the highway network in an average winter, the gritter fleet are equipped with GPS tracking to enable accurate monitoring of where they are and which roads have been treated. Salting is normally completed within four hours and usually before 7.00am.

Rocksalt

We use rocksalt and coated rocksalt as our anti-icing materials. Our gritting fleet spreads salt onto the highway at spread rates between 8 and 40gm/square metre depending on road surface conditions. 8 or 10gm/square metre is normally spread when we expect ice, and 40gm/square metre when we are trying to clear a build up of snow and/or ice. We need to spread salt accurately as it comes from a non-renewable source and in high concentrations can harm the environment.

Salt works by turning the ice or snow surrounding each granule into a saline solution. The action of traffic is essential for salting to be effective by breaking down the salt granules to form a saline solution to either prevent ice from forming or to melt it.

How can we get it wrong?

No matter how accurate the forecast, there are situations where we cannot salt the network prior to icy conditions. Such situations are:

• When rain is followed by rapidly clearing skies, salting will normally start after the rain has stopped (to avoid the salt being washed away). Sometimes temperatures may fall by as much as 5°C per hour and the wet roads may well freeze before we have been able to salt them.
• 'Dawn frost' occurs on dry roads, when early morning dew develops, falls on a cold road, and freezes on impact. It is impossible to forecast with any accuracy where and when this will occur.
• Rush hour snowfall. When rain turns to snow coinciding with the rush hour, early salting cannot take place as it would be washed away and gritters cannot make progress due to traffic congestion. 

We will, however, always carry out salting to remove ice. This is not ideal and salt takes longer to act once ice has formed.

Avoid harsh steering, keep your speed down and beware of vulnerable road users such as pedestrians and cyclists.