Drag boat racing is a form of drag racing which takes place on water rather than land. As with land-based drag racing, competitors race their vehicles for the lowest elapsed time (low ET) over a straight race course of a defined length. There are three standard drag race course lengths, 660 feet (1/8 mile), 1,320 foot (1/4 mile), and the most common length, used in professional drag boat racing, 1,000 feet (3/16 mile plus 10 feet). Unlike drag racing on land, which begins from a standing start, drag boat racing begins from a short rolling start to a point that cannot be passed until the green "start" light illuminates. There are numerous categories of professional and sportsmen classes based on various engine configuration, fuel type, hull design and propulsion types. The premier category of drag boat racing being the Top Fuel Hydroplane class which is the water based equivalent to Top Fuel Dragsters capable of covering the liquid quarter mile in less than four seconds with a top speed of around 260 mph (400 km/h). The biggest event on the drag boat calendar is the LODBRS World Finals which takes place at Firebird Raceway Phoenix, Arizona.