US ATC - Cleared to land
I have operated many times into US airports and have become used to their habit of clearing you to land when there is traffic in front of you and departing. The logic would appear to be that you land at your discretion subject to the runway being clear and this makes sense in good VMC.
However I recently operated into DTW (Detroit Metro) in borderline Cat 1. Cloud was overcast at 100', met vis was 1/4SM and RVR were right on the Cat 1 limits at about 2400'. LVPs were not in force(!). With all this, we were still cleared to land with traffic ahead of us. The only way we had to assess whether the preceding had cleared the runway was observing his TCAS trace reach ground level and then disappear as he presumably turned off his transponder after landing.
Would any US air traffic bods care to comment? At what stage do you stop these "clear to land - number 3" type clearances?