I assumed they used antifreeze in places where it freezes. Maybe not applicable in extreme cold, but seems to be good down to -40 or so.

http://www.dot.ca.gov/hq/esc/oe/project_ads_addenda/05/05-0T...

Some customers have indicated that common deicing and dust control chemicals that are used on the highway make excellent choices for antifreeze agents. These include:

* Calcium Chloride (CaCl2)

* Calcium Magnesium Acetate (CMA)

* Potassium Acetate (KAc)

Pretty common on the West Coast, even in Seattle.

I've seen sand used as well as water.