One of the problems is single runway airports without parallel taxiways so aircraft have to taxi down the active runway - LTN & LCY come to mind but there must be many other examples.
Going off topic another major issue the configuration in which runways are operated. La Guardia for example is interesting with take offs and landings on intersecting runways allowing around 70 movements per hour, but this works ok and there are plenty of examples particularly in the US. The most complex I have seen is SFO which combines two sets of intersecting close parallel runways - two almost simultaneous take offs in one direction followed by two not simultaneous but closely spaced landing (presumably a heavy must follow a lighter aircraft rather than the reverse). This allows up to 90 movements per hour including a number of heavies which works ok in good visibility but I have seen delays due to "bad weather" in conditions that wouldn't raise an eyebrow at airports like Heathrow.
Taxiing aircraft having to cross active runways is always an issue (ATL, LAX, etc). ATL is interesting in that it is the only example I can think of of a "grade separated" taxiway. (If you haven't seen it aircraft taxi past the end of the runway and an aircraft that is landing off or landing could be directly overhead.)
Last edited by Peter47; 26th Dec 2020 at 09:29.