Currently there are four main classes, each of which has several subclasses, where drivers must achieve target speeds between 95 and 180 mph (152.888 and 289.682 km/h). The classes specify safety equipment levels required for cars, drivers and navigators, and a maximum "Tech Speed", which may never be exceeded. Radar traps are hidden along the course to enforce this rule. There is also a fifth 'Unlimited Class', in which drivers compete to set the fastest possible time over the course, with no maximum speed restrictions.
The 'Silver State Classic Challenge' (also known as the 'Nevada Open Road Challenge') is an authorized Open Road Racing event that has run since 1988 on a long stretch of State Route 318 in Nevada, United States, which is closed for the occasion. Drivers and optional navigators compete to set a specified average speed ("Target Speed") over the 90-mile (144.841 kilometres) course. The start and finish time for each car is recorded against a GPS clock, and the average speed is calculated from the elapsed time. In each speed class, the winners are driver and navigator to achieve the speed closest to their target speed.