Open-road racing is a form of regularity rally carried out at high speeds on closed public highways, most commonly in sparsely populated parts of the Southwestern United States. Competitors attempt to set specified average speeds which can range from or higher along courses ranging between in length. At the lower speeds, unmodified productioncars can be used, while straightforward safety modifications can permit powerful sports cars to reach speeds of.
All these organizations have similar rules and regulations. Drivers and optional navigators compete to set a specified average speed over the measured course, which is typically 50-90 miles in length. 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. Speed classes are chosen by the driver, with constraints according to their racing experience, the performance potential of their car, and the safety requirements set by the organizers. As an example, in the Silver State Classic Challenge there are currently four main classes, in which cars can achieve target speeds between 95 and 180 mph. 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 an Unlimited Class, in which drivers compete to set the fastest possible time over the course.
Touring (Speed classes: 95, 100, 105, 110 mph)
Stock street cars with regular 3-point seatbelts may be run in this class. A handheld fire extinguisher must be fitted, while gloves and Snell approved motorsports helmets must be worn by drivers and navigators. First-time drivers must run in this class unless they have appropriate motorsports experience. At no time may the car exceed the Tech Speed of 124 mph.
In addition to a handheld fire extinguisher, gloves and Snell helmets, the car must be fitted with 5-point or 6-point harnesses for the driver and navigator. Open cars must have a rollbar fitted. At no time may the car exceed the Tech Speed of 140 mph.
Grand Sport (Speed classes: 130, 135, 140, 145, 150 mph)
In addition to the above equipment, all cars must be fitted with a rollbar or equivalent roll-over protection. Drivers and navigators must wear fireproof racing suits. At no time may the car exceed the Tech Speed of 168 mph .
Super Sport (Speed classes: 155, 160, 170, 180 mph, and Unlimited)
In this class, specialist race cars are necessary. A full roll cage, fuel cell and onboard plumbed fire extinguisher are required. Cars in the 160 and 170 mph speed classes may not exceed the Tech Speed of 180 mph at any time. Cars in the 180 mph and Unlimited classes have no specified maximum speed.