GPS devices are already seeing rapid adoption, and they are helping, but they alone are not enough: Most use signposted speeds to calculate trip times, don't have real-time traffic data, and don't take into account the changes in traffic flows that occur on different days and at different times of the day (or because of special circumstances, such as accidents, bad weather, etc).
That's about to change! Devices will get real-time traffic movement data from sensors in commercial fleets, buses, road sensors, police, emergency services, and even cell phones. With that information and some clever software, a GPS could find out what the best route is based on current conditions and not just on a static map. Potential fuel savings are huge. Still, nothing beats telecommuting. ::Turn left. No right. I mean left