The Dudley Council gritting team, based at the council’s Lister Road depot, will work around the clock to keep more than 480 kilometres of road clear during severe weather. 65 people work in the winter service team and throughout the winter months there are 17 people on standby at any one time.
Dudley Council has a precautionary gritting network. This includes principle roads (A Roads), classified roads (B and C Roads), bus routes, town centres, hospital main entrances to allow ambulance and maternity access, roads which pass the front main entrance of schools wherever access is possible. The team also grit pay & display car parks, pedestrianized areas in town centres, crematoriums and cemeteries and weight restricted bridges on the classified network.
The vehicle fleet includes 8 gritters (each with a plough front) and two 4x4s for accessing smaller entry ways and side roads. Dudley Council’s salt barn holds 6,500 tonnes of salt, which we have stocked in advance of the winter. This is usually more than sufficient (last year we used 3,000 tonnes) but we have suppliers who can bring in more salt should we have an extreme winter.
We utilise the latest detailed weather forecast technology to monitor weather conditions 24 hours a day, 7 days a week. Most domestic forecasts look at air temperature but the winter service team are interested in road surface temperature and moisture levels, as this allows them to assess when the roads will need to be gritted.
There are more than 1,090 grit bins, located across the borough, have also been filled with salt, for people to use on the carriageways and footways as and when needed.
The science of gritting
- Although the process of road salting is referred to as gritting there is in fact little or no grit involved. What is actually spread on the roads is mined rock salt (Sodium Chloride) of a size and composition for road use.
- Rock salt was first used for the purposes of winter road maintenance in the 1940's and is an effective de-icer for areas that receive road traffic.
- It is a hydroscopic material in that draws moisture to it and also draws heat from the environment rather than releasing it.
- The rock salt is spread on to the road in varying rates of spread dependent on the severity of the conditions.
- The effectiveness of rock salt on roads is enhanced by vehicles passing over larger granules and grinding it into smaller particles spread across the road surface area. This then forms a solution with a higher de-icing capability.
- Whilst water freezes at 0°C, the presence of the salt prevents water from freezing until -6°C to -8°C.
- However, salt starts to become less effective at -5°C and almost ineffective at lower temperatures.
- In extremely low temperatures, or heavy snowfall, a mix of salt and grit may be used to aid traction.
- In relation to snow ploughing this provides the ability to remove large accumulations of snow from the centre of roads.
- However it should be recognised that ploughing has limitations in that it effectively skims the road surface leaving around 30-50mm of snow on the surface.
- It can also result in large amounts of snow accumulating at the sides of roads and on footways and following prolonged periods of gritting can reduce the overall effectiveness of de-icing operations by removing slush which has a high level of salt solution.