cac_sabre,
Thanks for the explanation on both those matters. All makes sense now and seems like there needs to be major changes to the infrastructure (i.e. stop bars) for any improvement in the movement rates during Low Vis Ops.
kimberleyex,
Airports like LAX and LHR are far better equipped to handle that sort of weather. Low Vis taxi routes, Stop Bars, better taxiway lighting, Ground Radar etc etc. But they do have many more movements, and many many more days with very low vis so the money spent on that sort of equipment is definitely justifiable.
As for airborne delays, (getting off topic) LAX achieve most of their separation through extra track miles and speed control in the terminal area - but they do have 4 parallel runways to play with! LHR when busy is amazing to watch and their controllers are top notch. 10-20 mins holding is about as bad as I've seen unless the weather is ****ty and they still only have 2 parallel runways.
To put it in perspective, number of movements in 2009:
LAX - 634,383
LHR - 466,393
PER - 118,704
Cheers