you need decent machinery to pull the dirt back in effectively. however, rakers could help to spot where big piles of dirt were building up. my take on the Emil crash was that he ended up on a bit of the track which is rarely used at Sheffield, the outside on bend 3. you dont see too many people dive bomb the 2nd bend. It wasnt really a place on the track Emil intended to be at, as he hoped to have blocked holders run. you can see why that part of the track might have been neglected as its usually the 4th bend that sees the overtaking.