the top six cars from each group qualify for a second session. The cars that finished seventh or worse are lined up by their times, with the best of these times starting 13th. The twelve remaining cars run a 15-minute session, after which the top six cars move on to a final 10-minute session to determine positions one through six on the grid.

The Iowa format was instituted in 2012 with major modifications (times set based on open qualifying session in second practice, positions 11th and back in odd positions raced in the inside heat,