A snowmobile, also known in some places as a snowmachine, or sled, is a land vehicle for winter travel on snow. Designed to be operated on snow and ice, they require no road or trail. Design variations enable some machines to operate in deep snow or forests; most are used on open terrain, including frozen lakes, or driven on paths or trails. Usually designed to accommodate a driver and one passenger, their use is much like a motorcycles and an all-terrain vehicle (ATVs) intended for winter use on snow-covered ground and frozen ponds and waterways. They have no enclosure except for a windshield and their engine normally drives a continuous track or tracks at the rear; skis at the front provide directional control.