In the late 1980s and early 1990s the number of cars attempting to enter each race was as high as 39. It was too dangerous to have that many cars on the track at the same time. A "pre-qualifying" session was used. The teams with the worst record over the last six months would need to pre-qualify. This including all new teams. Only the four fastest cars from this session were then allowed to the main qualifying session. The slowest cars from the pre-qualifying session were listed in race results as "Did Not Pre-Qualify" (DNPQ). Pre-qualifying was ended after when many of the small teams left the sport.