Temperatures are set to fall this week, with ice and possibly some snow forecast, and Sheffield’s gritters are ready to treat the roads. One thing is certain, we’ll all have a good moan if they get it wrong.
There are five weather stations across the city providing up-to-the-minute weather forecasts. This helps Streets Ahead contractor Amey to determine when there is a need to grit our roads.
Contrary to belief, over 60% of the city’s highway network is gritted in priority order. That is 610 miles of urban and rural roads and can take up to 8.5 hours to complete a full gritting run. Priority 1 routes include main arterial roads linking Sheffield to other towns and motorways. Priority 2 routes are bus routes, link roads, roads where public service facilities are located, and rural routes. Snow is also cleared from city centre pavements, but pavements across the city are not gritted anymore.
As the temperature drops to near freezing point the gritters will be out, but it isn’t grit they are spreading. It is rock salt. And the salt used comes from mines of ancient underground deposits in Cleveland, County Antrim, and below the Cheshire town of Winsford, and lowers the freezing point of moisture. Pure salt is the most effective pre-treatment, but grit is often added once snow has started to lay and compact.
The pre-treating of the highway network mitigates the formation of ice and snow, although traffic is needed to make it effective. Very often, when an area has slush or rainfall, it washes the salt away and makes the road vulnerable again, necessitating them to be re-gritted a second time before the weather freezes.
In 2003, the Highways Act 1980 was amended to place Sheffield City Council (and others) under a legal obligation to keep the roads clear. According to the amendment: “A highway authority are under a duty to ensure, so far as is reasonably practicable, that safe passage along a highway is not endangered by snow or ice.”
It is a far cry from Victorian times when sand was shovelled off the backs of horses and carts, and although the switch to motor vehicles greatly improved operations, it wasn’t until the development of the first spinning salt distribution gritter in 1970 by Ripon-based Econ Engineering that the process was speeded up.
Today, Econ supply 85% of the UK’s rock salt spreaders and even have a dedicated gritting museum with fully restored vintage road maintenance vehicles, gritters, spreaders and snowploughs.
Whilst rock salt has been the choice for generations it can have a negative effect on soil and plants, interfering with the nitrogen cycle, and causing roots to absorb salt instead of important minerals. Salt water can also drain into soil affecting insects and can disturb the eco-system in watercourses. In addition, sodium chloride can be harmful to animals. And let’s not forget that it can cause damage to road surfaces.
As you might expect, alternative methods are being sought including urea (used in the production of fertilizer), potassium chloride, calcium chloride, potassium acetate (all incredibly expensive), beet juice, cat litter (yes, you read right), sand, ashes, and stone grits. Other eco-friendly alternatives being explored are cheese brine, garlic salt, potato juice, pickle brine and coffee grounds.
But for now, it seems rock salt will be here for a while because it remains cheap and readily available.
Finally, the truth surrounding gritter lorries in the summer. In very hot weather when tar is at risk of melting the gritters spread salt. This absorbs moisture from the air and cools the tar and creates a non-stick road surface.
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