In traveling series and special events, individual time trials of one or two laps pit drivers against each other and themselves for the fastest qualifying speed. Starting positions for preliminary heats and feature races may be determined using an “invert,” or reverse qualifying speed. For example, in an invert of 5, the 5th fastest qualifier starts first on the inside in the pole position, and the fastest qualifier starts 5th. Often, the driver who won the last feature race in that class will start directly behind the invert, followed by the rest of the field in the order of their qualifying times. In some races, starting positions may be decided randomly through a drawing, or by a roll of the dice.
The term “heat” is occasionally used for part of the main event when it consists of two or more parts, but most of the time, heats refer to shorter, preliminary races, usually 8 laps, with a small number of competitors. Depending on the number of entries in that class, there are usually 2 or 3 heats with an equal (or nearly equal) number of cars in each heat. Racers are assigned to heats using an even/odd distribution based on qualifying laps so that each heat has a mix of times. Heats narrow the field by determining who moves on to the feature race, and sometimes the starting positions. They get the cars and the fans warmed up, and build excitement for the main event. Heats provide the driver and pit crew with one final opportunity to tweak the vehicle before the feature race begins. The feature race is the longest and most important race of the night for each class.