More confusion....
<<The airfield is required to implement safe guards when the VIS drops below 400m in order to allow movements.>>
No, it's 600m. ATC decides when to implement LVPs and the criteria for commencing LVPs are as follows:
The IRVR (or meteorological visibility if the IRVR system is unserviceable) is less than 600 metres; the IRVR to be used to determine the commencement of these procedures is the TOUCHDOWN reading. If this position is unserviceable the MID-POINT reading is to be used instead;
OR
The cloud ceiling is 200ft or less;
irrespective of the serviceability state of the ILS, lighting, standby power etc.
Mad_jock said: "with these new mega high towers the airport can be in to LVP's and no RVR's being reported because the cloud is broken at 100ft and the tower can't see the runway."
Don't understand you Jock... The height of the control tower is irrelevant to LVPs as RVRs are measured at the runway and cloud is measured from the ground. At many airports RVR is measured automatically and the only ATC involvement is in reading the measurements to pilots.