 Nothing keeps West Sussex moving more than the gritters. The big yellow vehicles that help drivers literally get a grip in ice or snow. We're at one of West Sussex County Council's four highways depots to see behind the scenes, to watch the gritters at work. Twenty-four vehicles serve twenty-one routes across the county. We find out how often those gritters go out, where they go, and how it's been decided which roads get gritted and which ones don't. All types of road problem are a top priority for the County Council, which has pledged to spend millions to tackle flooding and an increasing number of potholes. And that's apart from salting and gritting the roads. Regular briefing reports are received by the man who oversees the county's roads to ensure he's on top of the situation. The roads we do are the heaviest news. So it's the A roads and the B roads that are our responsibility. We also do the main roads that lead to hospitals, to colleges, to emergency services, to railway stations and such like, which amounts to about 900 miles. We obviously help local communities to help themselves. We have something like 350 salt bins around the county. And in addition to that, parish councils, something like 180 parish councils have one tonne bags delivered to them, which we replenish on a priority basis. As well as grit for the bins and bags, the County Council organised big society funding of £5,500 to buy this mobile salt spreader for villagers in the Lavent Valley. It's lunchtime and decision time on the roads, deciding if the gritters go and where. A 24-hour forecast is the key to the decisions which will be made. West Sussex has been split into three forecast areas, which can be quite different from each other. And with each, there are three options. Gritting one or more areas, not going at all, or simply delaying the decision till five in the evening when there'll be another forecast. Sophisticated weather systems can even measure road temperatures using buried sensors. But even when a decision has been taken, the game can be changing all the time. The forecasts have been of low confidence in terms of the type of weather that's coming along. This most recent snow event has been much longer than was predicted and hasn't had the snow and warmer weather behind it as was originally predicted. Four thousand tonnes of rock salt are currently held at the West Sussex depots, salt that can melt snow even at temperatures of minus 21 degrees Celsius. It doesn't even have to feel particularly cold for the roads to freeze because in winter the roads can be as much as four degrees colder than the air temperature. Just one inch of snow means 80,000 tonnes of the white stuff to be cleared. And one thing you can be sure of, there is enough salt and grit to last the winter and to keep the vital roads of West Sussex moving.