Navigation and traffic data

When our car navigation systems all use Google Maps and (anonymously) report back their GPS locations, it suddenly gets far easier for Google to provide up to date traffic data, then use that to provide traffic avoidance as part of directions. Of course you don't want to tell everyone to take alternative routes, but you can tell them, aggregately, to spread out a bit by taking other roads.

Mokalus of Borg

PS - Of course, traffic surveys can tell you most busy roads based on time of day.
PPS - I'd expect a sophisticated navigator to be able to use that data automatically.