Motocross, having the addition of a horn, lights, effective silencing and a number plate. Enduro riders compete over a longer course (which may include roads); and an enduro event may last between one day and six days (such as the International Six Days Enduro). Some enduro events (known as "multi-lappers") are held on rather shorter circuits, not unlike scramble tracks. "Multi-lappers" are especially popular with novice riders. Rally raid, or "rallies"—A special type of enduro bike with a significantly larger fuel tank for very long distance racing, typically through deserts (e.g. Paris-Dakar rally). Engine capacities tend to be larger, usually between 450 cc and 750 cc. Dual-Sport—A dual-sport bike is a multi-purpose bike, made for on-road and recreational off-road riding. A dual-sport bike may resemble an enduro bike, but since a dual-sport bike is not intended to be used for competition, it may be less rugged, and equipped with dual-purpose tires and with more road legal equipment, such as indicators, mirrors and extra instruments. Most dual-sport bikes require a number plate to be ridden on state and county roads. Track racing—High-speed oval racing, typically with no brakes, nor rear suspension. The engines, fueled by methanol, are long-stroke four-stroke singles, such as JAP and Jawa. They have at most two gears. Some types, such as speedway, and grass-track bikes, are designed to take left turns only. Snow bikes—A snow bike takes a typical dirt-bike and replaces the rear wheel with a single tread system similar to a snowmobile and the front wheel with a large ski. They are much smaller and more nimble than a snowmobile, and they have a tighter turning radius, which lets the rider go where many snowmobiles cannot. The first prototype of motorcycles with a rear tread date all the way back to the 1920s, with failed attempts to bring them onto the market until recent times. Many motorcycles made after the 1990s or later can be fitted with a kit that transforms them into a snow bike. Dual-purpose Dual-purpose motorcycles, sometimes called dual-sport, on/off-road motorcycles, or adventure motorcycles, are street legal machines that are also designed to enter off-road situations. Typically based on a dirt bike chassis, they have added lights, mirrors, signals, and instruments that allow them to be licensed for public roads. They are higher than other street bikes, with a high center of gravity and tall seat height, allowing good suspension travel for