 These vehicles are often multi-purpose, and can be fitted with other equipment such as brushes, lawnmowers or cranes—as these operations are generally unable to run during heavy snowfalls, there is generally little overlap between the different uses, reducing the size of the fleet required by the agency or contractor.Modern winter service vehicles will usually also have a satellite navigation system connected to a weather forecast feed, allowing the driver to choose the best areas to treat and to avoid areas in which rain is likely, which can wash away the grit used—the most advanced can even adapt to changing conditions, ensuring optimal gritter and plow settings.Most run on wheels, often with snow chains or studded tires, but some are mounted on caterpillar tracks, with the tracks themselves adapted to throw the snow towards the side of the road.