Cerbus, what many don`t realise is that the ATCO`s have very little input into the procedures that they have to use. Instructions come from a higher power then that which employs us and we just have to make it work.
Minimum spacing on final is 5 miles or vortex whichever is greater and as mentioned earlier to keep the 5 miles until touchdown requires increased spacing. This is not down to controller ability it is because the rwys do not operate independantly so a departure must be rolling in the gap between an arrival touching down and the next arrival reaching 2 miles, sounds like plenty of room but it`s not.
I can only speak for the Tower side of things and unfortunately a lot of our restrictions on taxiway usage and crossing points are driven by the inability of some pilots to follow taxy instructions and to stray across red stopbars onto active runways, it is set to get worse with the withdrawal of even more routes and crossings.
Quite a few of our guys have worked at some of the busiest Units, Heathrow, Gatwick, Atlanta, Lax etc and it is very frustrating to try to increase the movement rate when we are given restrictions which make that ever more difficult.