The green flames coming from behind the race cars in this video represent the airflow created by a car during a race. The animation of airflow has been developed by ESPN and SportsVision using real-time information--a car's location and speed--derived from GPS. The information is put into a computer model that uses computational fluid dynamics to create the graphic of green flames. The technology will be used for the first time this Sunday during the NASCAR Nextel Cup race, the Allstate 400 at the Brickyard in Indianapolis.