I do it quite often that i try new sets with the ai. Just fill the grid with 19 AIs and have a bit of fun. They drive quite well untill it gets crowded. Especially at the start when a lot of cars are side to side. One of them always ends up slamming his brakes, since there wasnt enough room for him. Then the rest of the crowd starts to rearend him. Doesnt happen everytime, but often .