I believe the definition changed a year or so ago to at least 50%,rather than ALL DIRECTIONS. A4-in Bookworm's initial posting,the R01 RVR is given as P1500(1e it could be anything greater than that, the max measurable). I doubt circling minima for ANY a/c category would permit a circle to land at an actual value of 1500m repoted RVR.As an aside,you can fly a VISUAL approach down to 800m,presumably by going visual off an instrument approach.HOWEVER,you can't try to buck the system by converting a circling approach to a "visual approach".Got that??!!