What some tracks do if they have wall is to build the catch fence where it comes all the way down to the top of the wall and it's mounted flush to the edge that is closest to the track,therefore when you flip you go into the catch fence and can't even land on top of the wall,or like Ascot used to be there was a dirt shelf made by putting dirt behind the wall until it's level with the top of the crash wall then they had old car tires stacked up on top of the wall and dirt shelf which really cushioned the blow of landing up there.No sharp edges or or narrow pieces of concrete to land on in either one of these applications.