Remember,Like a lot of authorities around the world,one only needs a 'certain' RVR/Vis to attempt the approach.But a lot hangs on the 'legal' required Visual references encountered at DH/MDA..Ergo if one can see the terrain at the MAP one might continue 'Visually'to the field.
At the moment In Canada ,
one only needs'1200RVR' to start the approach,the onus being on the crews'Visual' assessment (regulation)at DH/MDA..If the a/c doesn't arrive on the runway one is in Violation of said Reg'....
