Appendix 1 to JAR Ops 1.430 (Minimum RVR values for take-off) says:
Note 3: The reported RVR/Visibility value representative of the initial part of the take-off run can be replaced by pilot assessment.
Note 4: The required RVR value must be achieved for all of the relevant RVR reporting points with the exception given in Note 3 above.
JAR Ops has this for landing (1.405 f))
(f) The touch-down zone RVR is always
controlling. If reported and relevant, the mid point
and stop end RVR are also controlling. The minimum
RVR value for the mid-point is 125 m or the RVR
required for the touch-down zone if less, and 75 m
for the stop-end. For aeroplanes equipped with a rollout
guidance or control system, the minimum RVR
value for the mid-point is 75 m.
Note. “Relevant”, in this context, means that part of the
runway used during the high speed phase of the landing down
to a speed of approximately 60 knots.
[Ch. 1, 01.03.98; Amdt. 3, 01.12.01]
Hope this helps
