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How do the road gritters know when to go out?

We all know the problems that the winter weather can cause when we need to travel. Whether it's a short journey within your local area, or a longer trip using major routes, ice and snow can be a real headache. To top it off, icy car parks can also wreak havoc just as you think your journey has come to an end.

How gritting companies use our weather forecasts to help them make decisions

As well as forecasting national and local weather for the public, the Met Office works behind the scenes with organisations across the country to make sure that everything possible is done to keep roads open and safe during the winter months. Gritting companies will use their bespoke forecast information, but they also have access to forecasters in order to ensure that they are making fully informed decisions.

Met Office receives a range of weather-related queries from gritting companies

Depending on the weather conditions at any given time, the enquiries the Met Office receives can be very varied. If temperatures are low but showers are forecast, gritters might ask for detailed information on the timing and heaviness of the rain in order to work out whether the grit will get washed away. If forecast information indicates that the temperature is likely to stay above freezing, customers will need to understand how confident we are that this will indeed be the case. More detailed localised information in this respect can help them decide to grit certain areas but not others.

How road surface temperature is different to air temperature

Critically, when it comes to the need to grit roads and car parks, it is the road surface temperatures that the gritters are concerned with, not the air temperature. Factors such as the angle of the sun at a given point of the winter, the length of the night, and whether there is cloud cover all affect surface temperatures, with grass, tarmac and glass windscreens reacting differently due to their diverse properties.

So next time there's a cold snap and you're wondering whether you'll need your thermals, forecasters are probably on the phone to a gritting company not far from you to help them decide whether they need to grit the roads that day.

For more information on how Met Office forecasts help gritting companies, visit http://www.metoffice.gov.uk/roads