Spreading salt on its own onto our roads has a very limited melting effect. This is why we need cars and vehicles to drive over it which then mixes the salt with the ice and snow creating a saline solution which has a lower freezing point (usually -6°c). Only then will the snow and ice begin to melt.
We use 6mm crushed rock salt to melt ice, or to prevent ice from forming on the road surface during winter and this is spread onto the roads by our six purpose-built gritters. The spreader at the rear of the gritter is designed to give an even distribution of salt across the road and spread the salt at a controlled rate. Our gritters are fitted with the latest Satellite Navigation systems to aid the driver, making salt spreading more efficient, saving salt and reducing waste. The gritting vehicles also have attachments that enable a snow plough to be fitted when needed.
Salt must be spread onto the road surface before the roads become icy, or before snow starts to fall. This is known as precautionary salting. We aim for our drivers to begin gritting at least two and a half hours before freezing temperatures are expected, or four hours before snow starts to fall.
Every effort is made to avoid the need to treat our roads during peak traffic periods, or when school children are arriving or leaving their schools. This is because our gritters can become delayed in traffic and can get stuck along with the cars, buses and lorries that they are trying to help. If this situation is likely, treatments can be brought forward or delayed until later.
A map of the gritting routes is published through our online mapping service at maps.derby.gov.uk.
It isn’t possible to grit Derby’s entire 744km (465 miles) of road network because of the time, machinery and resources it would take and the costs involved.
Our six gritting routes cover 275km or 171 miles which is 37.5% of the total road network and we prioritise to make sure our critical routes are covered.
Derby’s roads are usually gritted before the road surface temperatures fall below zero and this is usually timed to avoid peak traffic times. This is to avoid the gritting vehicles becoming stuck in traffic queues.
Gritting may also be carried out in the early hours of the morning, again about two and a half hours before the road surface temperatures are forecast to freeze.
Trunk roads are the responsibility of the Highways Agency. These roads are:
We currently buy our rock salt from Compass Minerals, a salt mining company based in Chesire. More information about our rock salt can be found on the Compass Minerals Website.
When snow has been forecast we spread rock salt on the roads to stop snow from settling and becoming compacted. However, much more salt is needed to melt snow than to prevent ice forming.
Salt alone has very little effect on snow once it has started to settle. There is little we can do until it becomes deep enough to snow plough (about 30mm or just over 1 inch deep). This may lead the public believing that we haven’t gritted the roads, when in fact we already have. The actions of snow ploughing, spreading salt and vehicles running on the snow will all help to turn the snow to slush and clear the roads.
Please contact us and we will record and consider your request, although it will be subject to route priority and current weather conditions and whether our gritters are available.
There is a responsibility on everyone to drive carefully especially during winter weather. You can find out more seasonal driving advice from the Highways Agency.
You may be travelling on a road that is not part of a main gritting route or you may be on a road before it has been treated. If this is the case, slow down and drive with caution.
Salt spreading does not make roads completely safe. It is commonly believed that rock salt will immediately disperse ice and snow and that the roads are safe to use in a normal manner. This is not the case and the movement of the traffic is needed to mix the salt with the moisture on the road surface for it to be totally effective, so please drive responsibly in these conditions.
The Met Office issue regular forecast updates on the TV, and the radio. Warnings may be given about the road conditions - pay attention to these warnings, set your alarm for earlier to allow more time for your journey. If the weather is forecast is likely to be really severe think about whether your journey is necessary.
You can view the government's snow advice that provides information for members of the public that wish to clear ice or snow from footpaths where they live.
This is because of the time it takes to grit or clear snow from our footpaths. We only grit footpaths in the city centre where rain has been forecast followed by freezing temperatures, or where there is persistent snow or ice.
We grit our footpaths in the city centre and the main district shopping centres where there are a higher numbers of pedestrians.
With over 1,829 kilometres (1,141 miles) of footpaths in Derby and gritting every single one is not possible – so our efforts have to be concentrated on areas that will benefit most people.
No you will not be liable for a claim should someone have an accident as a result of you spreading grit.
Grit bins are provided and are placed in locations where difficulties are likely to be experienced by road users. They help you and other motorists to spread salt on the road or footpath if you are having difficulty.
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:
Salt from grit bins is meant for use on the roads and footpaths and should not be used on private paths or driveways.
Often grit bins become the focus of vandalism, or used as a rubbish bin. For this reason we may decide to return a grit bin to our depot for cleaning or repair. This is usually done over the summer months. We can remove a grit bin if we have a request to do so, as long as the other people in the area also agree that it is no longer necessary.
We do not supply grit to the public or for private use. A local builder’s merchants and other suppliers usually sell rock salt/grit for private use.
Our decision to go out depends on two specific weather factors: The road surface temperature and potential road surface moisture. Although the air temperature may be freezing, this doesn’t indicate that the roads will be. Typically the road surface holds heat better than the air and therefore will not always freeze. We have a dedicated weather station in the city that tells us the current state of the road surface along with air temperature, wind speed and precipitation. These stations along with others in Derbyshire help our forecast provider produce a detailed forecast for the city. The forecast includes expected minimum road surface temperatures and moisture levels.