 The vehicle can relay the surface friction data back to the control centre, allowing gritting and clearing to be planned so that the vehicles are deployed most efficiently.Surface friction testers often include a water spraying system, to simulate the effects of rain on the road surface before the rain occurs.The sensors are usually mounted to small compact or estate cars or to a small trailer, rather than the large trucks used for other winter service equipment, as the surface friction tester works best when attached to a lightweight vehicle.