Open-road racing-also known as "regularity rallying" or "time, distance, and speed rallying"-is a sport in which the object is to maintain an average speed over a predetermined course. In essence, it combines the elements of road racing-where power, speed, and handling are king-and rallying, which demands a superior degree of precision. Events are typically held in areas of the country that offer some seclusion, as races are generally 60-120 miles in length and take place on closed public highways. With classes that accommodate average speeds of 85 to 160 mph and an unlimited class that throws timing out the window, you'd better be able to ensure that "Farmer Joe" doesn't wander onto the road and scuttle the race. Safety is paramount in this type of event, and often there are hundreds of volunteers, numerous ambulances, and eyes in the sky to alert the ground crews of any issues on the course.
Flat-Out Corvette Racing On Public Roads - Vette Magazine