CAT IIIb RVR minimums are limited by the runway/taxiway lighting and support facilities, and are consistent with the airport surface movement guidance control system (SMGCS) plan. Operations below 600 ft RVR require taxiway centerline lights and taxiway red stop bar lights. If the CAT IIIb RVR minimums on a runway end are 600 feet (180 m), which is a common figure in the U.S., ILS approaches to that runway end with RVR below 600 feet (180 m) qualify as CAT IIIc and require special taxi procedures, lighting, and approval conditions to permit the landings.