I never could quite understand the climb or descent 500ft if your able to maintain your FL.
If you can maintain your flight level why would you leave the track? If your diverting you would need to descend to below FL285 anyway, or am I missing something?
I understand that descending below FL285 will avoid other tracks but surely staying high as long as you can at +/-500ft would save on fuel and get the same result i.e avoid traffic?