Jeez, Dick, you make it hard.
There shouldn't be different risk levels anywhere across the airspace. The OAR should calculate the risk at points all across the system, then find an airspace classification, and a set of other things like radar, and try to level out the risk so that no-one flying in a passenger plane is exposed to higher or lower levels of risk than anyone else.
And no, CASA hasn't set a risk level, and no, the US NAS system hasn't determined a risk number - they just rely on years of experience. IF they measured risk levels like CASA wants us to do here, they'd probably get the fright of their lives. And no, we shouldn't say their experience is better than ours, because it isn't. We're just as safe as they are, and we don't have any higher or lower number of accidents or incidents.
Anyway, I don't want to play any more, and maybe all the other wouldbe participants should just refrain from posting and starve the oxygen from this debate [yeah, I know, I should have listened to my own advice!].
One good thing - NAS will all be over soon when the White Paper is published. Absolutely nothing you can do about it, Dick, and I can't wait for this to end.
Sorry Dick, but you lose, and common sense finally wins.