Simple, effective and possibly life-saving idea, France's Eurovia is developing a thermosensitive road varnish that changes color to indicate freezing and dangerous conditions.
Like a Hypercolor t-shirt, the road could turn pink (or any other indicative color) when surface temperature is below freezing and returning to neutral once it warms back up. Not only a boon to motorists, but it helps out the environment and saves some cash by eliminating unnecessary salting of roads. Several roadways in France are currently being used for durability and usability tests. Pending results, we could even see color changing sidewalks in years to come.
Also on Cool Hunting: Luminescent Gravel