This is a great idea:

http://technology.newscientist.com/channel/tech/dn13592-intelligent-paint-turns-roads-pink-in-icy-conditions.html?feedId=online-news_rss20

Thats actually pretty interesting. I wonder how visible it would be when driving 30+ mph though. Meaning, if I'm going 40 mph will I have time to react to the pink road in time to avoid losing control.

Still though, I can defintely see practical usage!