the Outlaw wrote:
Sometimes the sand is mixed up with salt (keeps the pile unfrozen).
Perhaps the road crews throw it down as a preemptive deicer.
There must be some reason to throwing sand on an otherwise dry road.
My guess would be visibility. Seattle drivers don't REALLY know what it takes to keep a road clear and the top people at WADOT probably know that, so to keep pressure off themselves the plows are probably there just to be seen 'doing something'. I'm sure it probably helps to a point because of whatever is mixed in with the windshield assassinating sand but I'd rather seem them pre-soak the roads with liquid deicer like they used to.