In reply to parishiltons, & the statement that "having a R/W separation standard published, with defined conditions is way better, safer & more professional than running things pretty close occasionally. Either you have a separation standard, or you don't". I totally agree. I was not in any way trying to extol the virtues of "running things tight"; merely stating that this was necessary at times. The separation standard involved may not have been immediately apparent, but was generally covered by the old MATS Pt.1 "let out" of, "nothing in this manual shall prevent the ATCO from using his discretion in order to ensure the safety of a/c etc."
I just intended to illustrate that the individual ATCO had, at times, facilitated max. R/W utilization.; &, to indicate that I was not averse to the idea of the very minimum of adequate separation standards. But, I very much doubt that it will be possible to squeeze even more out of a system which is running very much at the tightest of margins.
Simply, we have reached, or very nearly have, the limit at the busiest of aerodromes.. When ATCOS "ran things pretty close", they did it professionally & safely & there was room to manoeuvre if the intended consequence (max. safe R/W utilization) was not going to be achieved. It strikes me that if you run things at their tightest, you will not be left with any alternative action possibilities. There is, despite your faith in "squeezing", an absolute limit beyond which we cannot go.