You'd imagine that it would take quite a few plows to clear a snow-covered highway, but not quite this many. Keep count as they go through and you'll see a whole 21 plows in formation (and a couple of sand trucks) painstaking passing piles of grey road-sludge to the right and to the right again and to the right again on this highway in Toronto.
There must be a better way to do it, but apparently these guys don't have it and instead have to resort to pure brute force, of the parade variety. It just raises the question: how many snow plows does Toronto have? And where do they keep them all? Or are they constantly engaged in an eternal drive, locked in formation, clearing the snowy roads for eternity? [Reddit]