Quick Drive AI

Hey guys,
Im new to Trainsim, been playing a few Quickdrive routes with my favorite locos on NS Coal District. What controls the randomly generated trains? I noticed a lot of NS stuff that I pass on sidiings, but also my U30s from the Feather River route showing up during a quick drive... how do I change this?
Thanks
Kyle
Im new to Trainsim, been playing a few Quickdrive routes with my favorite locos on NS Coal District. What controls the randomly generated trains? I noticed a lot of NS stuff that I pass on sidiings, but also my U30s from the Feather River route showing up during a quick drive... how do I change this?
Thanks
Kyle