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What is gritting?
Despite the name, gritting rarely involves grit (a mix of sand and stones) at all. Gritting involves spreading rock salt onto roads and pavements to prevent ice forming or to help melt snow and ice.
In Derby, we grit roads using rock salt which has been coated in molasses. The molasses helps the salt to dissolve quicker and stick better to the road surface, making it more effective than uncoated salt.
When the salt dissolves in surface water (helped by vehicle and foot traffic to crush it) it lowers the freezing temperature of the water. Instead of freezing at 0° any moisture freezes at -6° to -8°.
Why, when and where we grit
As Highway Authority, we are responsible for keeping roads safe. This includes a statutory ‘duty to ensure, so far as is reasonably practicable, that safe passage along a highway is not endangered by snow and ice’ (Highways Act 1980).
Our primary gritting routes include:
- All A (principal) roads and B (classified) roads
- Important access roads (but not all bus routes)
- Other roads that enable access to critical buildings such as hospitals, fire and police stations, major food distribution centres, the city centre, the railway station and bus station
If there is prolonged heavy frost, ice or snow then we will consider treating other roads on a priority basis. This depends on resources being available as our priority is the primary routes.
Pedestrianised areas and footpaths in the city centre and shopping centres will also be treated when the forecast indicates that rain is likely to be followed by freezing conditions, or when snow is forecast. This treatment will normally be carried-out outside normal shop opening times.
How do you grit the roads?
The salt is spread evenly on to the road surface using our fleet of gritters. We spread anywhere between seven and 30 grams of salt per square meter of road (depending on weather conditions).
When icy conditions are forecast we will grit the primary routes in Derby as a precaution.
We use four gritting vehicles and have one on standby. We can have these vehicles on the road within one hour if the forecast changes.
When do you decide to grit?
The weather forecast is checked at least once a day throughout winter (between 1st October and 30th April).
Our forecast provider, DTN (formerly MeteoGroup) advises us of the possibility of freezing road surface temperatures, ice or snow and gives an approximate time when we might expect this to happen.
As well as being updated with regular national forecasts and local information for nearby weather stations, we monitor a network of sensors embedded in roads across Derby. Each is connected by cable or mobile phone technology to our automatic weather station (grey box by the roadside) and measures road and air temperatures, rain, dew and salt levels.
The sensors are sited either on a representative stretch of road (no nearby trees, buildings or bridges, which offer some protection from the cold), or traditional cold spots. The weather stations then beam back information for us to monitor.
All of this information helps us decide if we are going to grit the roads. Most of the time, we treat roads in the early morning or late at night when there is minimal traffic on the roads and before ice can form.
You can find out more about how we keep roads safe over winter in our Winter Service Policy.
What happens when snow is on its way?
Our snow clearing operation will take place when heavy and continuous snow settles. We can quickly attach snow ploughs to the front of our gritting vehicles so they can clear roads and grit at the same time. Snow ploughs only work effectively when snow is more than 3-4cms deep; they cannot work on roads that have road humps or similar traffic calming measures.
We concentrate on primary routes such as access to hospitals, fire and police stations and other important facilities whilst it’s snowing or if there are strong winds causing drifting.
Once the main roads are clear, we will begin to work on other roads.
It may not be possible to clear every road, and some roads may have to be left to thaw naturally as our vehicles cannot fit down narrow roads.
Highways England clears motorways and trunk roads, such as the A61, A38 and A6 in Derby. Derbyshire County Council clears all roads in the county from the city/county boundary. You can see who is responsible for roads on our gritting route map.
Find out where your nearest grit bin is located using our map.
Grit bins have been provided to allow residents to help spread salt on the roads and footways in their neighbourhood that aren’t part of our gritting routes. It should not be used on private driveways and footpaths.
How do I report an empty grit bin?
We aim to keep all of our grit bins full as far as possible. If your nearest grit bin is empty during cold weather, please telephone Streetpride on 0333 200 6981 (9am to 3pm, Monday to Friday) and we will re-fill it for you as soon as we can.
How can I clear snow and ice?
The government website provides advice on how to clear snow and ice on the road, path or cycleway safely. This is especially useful if you live in an area that is not routinely gritted by us.
Travelling in winter conditions
Winter can present some very difficult driving conditions.
- Make sure your journey is absolutely necessary.
- If you do need to drive, stick to main roads that have been treated with salt (driving on salt actually helps it to melt the ice).
- Make sure you check the status of the roads around the city, and the county, before travelling in cold weather or when snow is forecast.
- When driving, travel at a lower speed and leave extra room between you and the car in front. Stopping distances increase on wet/icy roads.
- Make sure your car is well maintained. Tyres should be well inflated and have a deep tread. Make sure that there is sufficient anti-freeze in your coolant to prevent your radiator freezing overnight or while driving. You should also check your battery to make sure it is charged if you have not used your car for a while.
- If driving behind a gritter, make sure to leave plenty of space in front and do not attempt to overtake, there may be un-cleared snow ahead of the vehicle or ice.
- Check the latest traffic information from Highways England.
Emergency Winter Kits
Everyone should consider having an Emergency Winter Kit in their car. Carrying the following items could be lifesaving if you were to become stranded:
- Ice scraper and de-icer
- Torch and spare batteries - or a wind-up torch
- Warm clothes and blankets for everyone
- First aid kit
- Jump leads
- A shovel
- Road atlas
- Sunglasses (the low winter sun and glare off snow can be dazzling)
- A portable phone charger
- In addition, before commencing your journey supplement your emergency kit with food, hot drinks and any medication that your or your passengers may need.
How much salt do you have?
We have 4000 tonnes of salt stored in our barn – more than enough to last us for the average winter.
Why hasn't the grit melted the ice and snow?
Spreading salt on its own has a very limited melting effect. This is why we need vehicles to drive and people to walk over it. This helps mix the salt with the ice and snow creating a saline solution which has a lower freezing point. Only then will the snow and ice begin to melt.
It's freezing outside, why haven't you gritted?
Our decision to grit roads depends on a number of factors including:
- road surface temperature (different from air temperature),
- how much moisture is on the road and
- the amount of salt on the road (from previous gritting runs).
Roads tend to hold heat much better than other surfaces so even if the air is forecast to be freezing, the road surface may be several degrees warmer. If the weather has been dry and there is little or no moisture on the road surface then ice cannot form. In addition, if we have gritted in previous days and our sensors tell us that there is still a high volume of salt on the road surface (enough to prevent ice forming) we don’t need to spread more salt.
I can't see any salt on the road - have you gritted?
If you can’t see any salt on roads along our gritting routes – that’s a good sign! It means the salt has dissolved and been crushed into solution and is doing its job.
We do the majority of our gritting runs in the early hours of the morning so you might not always see our vehicles on the roads.
Why don't you grit all the roads in Derby?
It isn’t possible to grit Derby’s entire road network because of the time, machinery and costs involved. We have four main gritting routes which treat 272km, which is 35% of the highway network.
Can I have a grit bin for my street?
Requests for a grit bin are considered individually and involve an inspector carrying out an assessment of the road. It is important that when we allocate a new grit bin they need to be located where they will be of the most benefit. The types of locations we would consider placing a new grit bin would be those with:
- sharp bends
- steep gradients
- potentially dangerous road junctions
- exposed locations
Salt from grit bins is meant for use on the roads and footpaths and should not be used on private paths or driveways.
My road is very icy - can you send someone immediately to grit it?
Please contact us and we will record and consider your request, although it will be subject to route priority, current weather conditions and whether our gritters are available.