Gritting roads and pavements in freezing weather
Facts about our road gritting service and grit bins
We understand that many Swindon residents want to know more about what we do when freezing temperatures create challenging conditions in the borough. Here are some answers to some commonly asked questions about our road gritting service and the grit bins we provide.
- How much grit do you use to treat Swindon's roads and how much does this cost?
- What distance of road do you cover when gritting?
- How do you decide gritting treatments?
- Does spreading salt on top of ice or snow melt it straightaway?
- How many gritters and ploughs do you have?
- How many members of staff are involved in gritting?
- Why are gritters sometimes not spreading salt?
- Why haven’t I seen any gritters out and about?
- What type of grit do you use?
- Do you grit pavements?
- When do you decide that snowploughs should be used?
- When and why do you ‘handsalt’ roads?
- Who is responsible for the M4 and A419?
- How much salt do you have in stock for winter 2018/19?
- Why has a grit bin near me not been refilled?
- Why are grit bins where they are?
- What preparations have you made to ensure the gritting crew are kept safe during COVID-19?
How much grit do you use to treat Swindon's roads and how much does this cost?
It takes 25 tonnes of salt to treat the 200 miles of roads on our gritting routes during freezing weather, and more than double that when it snows. It only takes one teaspoon of salt to treat each square metre of road surface when applied before the road freezes. It costs around £5,000 for all vehicles and drivers to carry out a night’s operation, so it’s important we only do this when we definitely have to.
What distance of road do you cover when gritting?
We concentrate on treating the routes that are most heavily used, which is around 200 miles of roads. Swindon has over 500 miles of roads in total, so those which aren’t treated require extra care when the weather is bad. While we do our best, we cannot guarantee the routes we do treat will always be free of ice. You can see our gritting routes on an interactive map.
As part of our route planning, we have ensured that all access roads to COVID-19 testing sites are regularly treated, to ensure they can remain operational at all times.
How do you decide gritting treatments?
We have two weather forecasting stations. One is near Blagrove Roundabout on Great Western Way and one is on Marlborough Road, just outside Chiseldon. Readings of the current weather conditions are sent from both stations to our specialist weather forecast provider every ten minutes. These readings help to produce two daily forecasts which show the anticipated air temperature, road surface temperature, wind speed and rain or snowfall. If there’s any uncertainty in the information received, we call the forecaster for further information.
We plan gritting treatments from this information. If there are any major changes to the forecast at any time of the day, the forecaster calls our appointed decision maker to let them know. We also receive a two to five-day forecast every day to help us plan ahead. To help us plan ahead, we receive a forecast for the next five days that indicates the weather we can expect.
Does spreading salt on top of ice or snow melt it straightaway?
Salt will not melt ice or snow straightaway. It takes time for the salt to mix with the snow and ice and melt it. Adding more salt will not make this happen more quickly. However, cars driving over the snow and ice will speed up the process because it mixes the salt in faster.
How many gritters and ploughs do you have?
We have eight gritting lorries. Seven of these are put into use when gritting is required. We generally keep the eighth as a spare vehicle in case another one breaks down. We also have eight ploughs.
How many members of staff are involved in gritting?
No-one works on gritting full-time. All gritting staff fit their work in around their other full time jobs at the council during the winter season (mid-October to mid-April).
There are two main teams of trained and qualified gritter drivers made up of seven drivers each. These teams take it in turns to be on standby for gritting work each week for 24 hours a day.
There’s a team of four inspectors to oversee gritting work and act as eyes and ears for the decision makers during the night.
A team of officers monitors forecasts and conditions - and takes the decision on whether to go out gritting. These officers are also on duty 24 hours a day from mid October to mid April during their rostered weeks.
When snow ploughing is necessary, each driver needs a ‘mate’ for safety reasons. On these occasions, we rely on the good nature of any available staff to assist.
Why are gritters sometimes not spreading salt?
This can be deceptive. Gritting vehicles have become more sophisticated, and lorries now dispense the required amount of salt directly down on to the road in a fine spray that you may not see.
However, sometimes a vehicle might not be spreading any salt. This might be because:
- it hasn’t reached the starting point of its treatment route
- it is returning to the depot to refill
- it is driving over a section of road that has already been treated by a fellow driver
Every gritting vehicle is fitted with a GPS system which tracks its route and speed, and it’s part of the inspector’s job to make sure the lorries don’t deviate from their routes.
Why haven’t I seen any gritters out and about?
We have eight gritting vehicles to treat the 200 miles of roads on our gritting routes. It takes around three hours for one vehicle to treat its entire route. The vehicles normally start gritting at least four hours before the forecast says that the road surface temperature is going to reach freezing point.
If it has snowed, it’s likely that gritters will be on the road continuously. However, it may be three to four hours before they pass the same point twice, as they will have to return to the depot to be refilled with salt.
When we have heavy snowfall occurs, our priority is to keep our resilient network open. The gritters will then be fitted with snowploughs and stay mainly on 'A' and 'B' roads, meaning that other roads may not be treated as often.
What type of grit do you use?
For our normal salting operations, we use a product called Thawrox+. This is rock salt generally mined within the UK with the addition of a by-product derived from the sugar refining process. There are several benefits to using this product as opposed to the traditional pure rock salt including:
- It’s less corrosive to steel and aluminium
- It causes less damage to concrete and asphalt road surface
- It’s more free-flowing which makes it easier for the gritting equipment to spread without it blocking up the mechanism
- It remains active on the carriageway surface for longer so we do not have to treat it as often
If we have to treat structures like footbridges, we can’t use the normal Thawrox+ salt because, even though it’s less corrosive than pure rock salt, it could still damage the reinforced concrete structure. In these cases, we spread a product which contains urea as its active ingredient which is much less corrosive. We can’t use this urea product as our main de-icing material though, as it costs about 16x more per tonne than the Thawrox+.
Do you grit pavements?
There are over a thousand miles of pavements, alleyways and cycle paths in the borough. We do not have the extensive resources it would require to grit these. There are 493 grit bins in the borough that residents can use to treat pavements and pedestrian areas with salt.
When do you decide that snowploughs should be used?
There needs to be at least two inches of snow on the road before we use ploughs. This is because ploughs run about one inch above the road surface. We cannot scrape snow ploughs along the road surface as this would wear out the rubber blade out within minutes.
Two members of staff are required to operate each snow plough safely. You can read about how we are protecting our staff during the pandemic below.
When and why do you ‘handsalt’ roads?
All our gritting routes are designed so that we can access the roads by gritting lorries. When we experience severe snow conditions we try to treat other roads, particularly those on hills.
However, due to accessibility or safety concerns sometimes we cannot use our gritting lorries. In these cases, we send smaller vehicles loaded with salt which our gritting staff then spread by hand. We usually prioritise roads for treatment, but when handsalting steep hills we apply salt to footways to improve safety for pedestrians.
Who is responsible for the M4 and A419?
The A419 and the M4 are managed by Highways England.
How much salt do you have in stock for winter 2020/21?
1,850 tonnes of salt have been stockpiled in readiness for the 2020/2021 season. This is enough to treat our gritting routes 74 times. More salt is on provisional order in case we experience snow or prolonged cold spells. This will become easily available if it's needed.
Why has a salt box near me not been refilled?
In the winter we rely on the public to notify us of empty salt boxes, because we cannot monitor how much they are used. We respond quickly to reports of empty bins during winter, but when we get heavy snow we may have to prioritise our deliveries. You can report an empty or damaged salt box online.
Why are salt boxes where they are?
There may be a salt box in your area but not on your road. We put them in the most hazardous areas, considering:
- gradient of roads and pavements
- speed of traffic
- whether there's a safe area for the bin on public land that doesn't cause an obstruction
- If there's anyone in the local area who would be able to spread salt
You can view an online map of salt box locations.
You can also request a new location for a salt box.
What preparations have you made to ensure the gritting crew are kept safe during COVID-19?
We have carried out a full and robust risk assessment to ensure our crews are kept safe while at work. Some of the precautions we are taking include:
- Only one member of our crew will be operating a gritting lorry at a time
- Only one driver will be allowed into the site office at a time to pick up keys, their route details and record sheets
- The inside of all gritting lorries will be cleaned before and after use
- The staff break area has been sufficiently spaced out to ensure social distancing is maintained
- If we need to deploy our ploughs, for safety reasons, two members of our crew are needed in the cab at all times. To minimise the risk, we have ensured there is sufficient space between the driver and ‘mate’.