Clearway
Clearway is more effective once laid and constantly adjetated ie vehicles or AC passing over it constantly. If it is laid, diliuted with the snow or ice already on the floor and left alone it will freeze. A guy at Dusseldorf airport once told me if they have cleared the runways and clearway is working, they would employ runway sweepers during quiet periods even if there was no snow, in order to adjetate the clearway, and it worked. RAF airfields are to quiet!