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Winter Gritting Routes Map | Winter Maintenance Strategy
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Why do we salt the highway network? | How and when? | Which roads are salted? | Snow Clearance | Weather Forecasting and Decision Making | Rocksalt | Cycleways and Footpaths | How can we get it wrong?
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.
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.
With 3,000 miles (4,830 kilometres) of County maintained roads, it would be prohibitively expensive to treat the entire network. 1,200 miles (1,930 kilometres) are normally treated, i.e. about 40% of the network. The Government Highways Agency is responsible for salting all trunk roads and motorways within the County. In total, 41% of the road network in Cheshire is treated when icy conditions are anticipated.
Roads which are salted are dealt with in the following priority order:
Priority 1 Routes
are all ‘A’ Class carriageways, and designated routes to A & E Hospitals. Then in order to maximise efficiency and scale of economy, other classes of carriageway which are required to be driven as part of the route, in linking up the ‘A’ Class network, will also receive this level of treatment. These will be as identified on the Winter Gritting Route Plans;
Priority 2 Routes
are other major commuter roads (‘B’ class), major commuter/distributor roads carrying 4 service buses or more per hour between 06.00 and 10.00am, roads serving emergency services/public transport centres/comprehensive and secondary schools/higher education establishments, roads with gradients greater than 10% and carrying more than 1000v/day and main access roads to rural communities/villages. Third party funded Public Highways are also treated, however this will only continue for the duration of the external funding being made available. These will be as identified on the Winter Gritting Route Plans;
Other Carriageways
it is Not considered practical because of resources and costs to pre-treat all highways and Other Carriageways will not be pre-treated. The aim is that these will only be post-treated to remove ice or snow only after all the Priority 1 and 2 routes are treated and open to traffic and when snow or ice is likely to persist for a continuous period of 24 hours. This will also depend upon available resources.
Whenever snow is forecast we aim to pre-salt all the priority 1 and priority 2 routes prior to it falling. However this is not always possible, for example when it starts as rain and turns to snow. When this occurs salting is delayed until the rain stops in order to prevent the salt from being washed away. This situation can be even more difficult if it occurs during the rush hour as traffic congestion impedes the gritters progress.
Once snow has fallen we will continue to work around the clock until all roads are clear. Priority 1 and 2 roads will be cleared first, followed by all other roads, although we sometimes have to return to the priority 1 and 2 roads before all the other roads are clear, to ensure they remain clear of ice and snow. This will often be necessary towards the end of the day, especially when the snow has been thawing all day and evening temperatures fall below freezing causing the melt water to freeze.
During periods of snow we deploy our fleet of 37 gritters equipped with snow ploughs and 3 snow blowers. We also have a network of farmers that we can call on to help clear the roads. However, salt will not instantaneously remove snow or ice. The action of traffic is essential for salting to be effective by breaking down the salt granules to form a saline solution which melts the ice.
Weather Forecasting and Decision Making
The Meteorological Office provides us with weather forecasts which include road surface temperature information. The forecasts form part of our computerised Ice Prediction System, the system is monitored 24 hours a day throughout the winter and gives the Winter Maintenance Duty Officers the latest weather information as well as actual road surface temperatures and other information from various sensor sites around the County. This information enables the Duty Officers to make their operational decisions. Precautionary salting is carried out when there is a clear probability of ice or snow, in that wet road surfaces are expected to fall to or below 0º Celsius.
The Ice Prediction System allows the Duty Officer to make a more accurate assessment of the need for salting - this results in a reduction of the risk of failing to salt when required but also provides a saving in costs since the number of unnecessary road salting is reduced.
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, is environmentally unfriendly and can damage vegetation.
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.
Ever wondered why it's brown? Find out on our Frequently Asked Questions page!
Cycleways are salted where they form part of the 1,200 miles (1,930 kilometres) of salted roads. Footpaths alongside carriageways and other cycleways are not treated except where frosty/icy conditions last for several days. Footpaths and cycleways may then be treated when we have the capacity to do it.
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.
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