The Nissan intelligent transportation system is currently being testing in Japan, and works by letting vehicles talk to other vehicles as well as infrastructure to reduce traffic and accidents. The information exchanged between cars and infrastructure let vehicles have a visual representation of what other vehicles are coming, how fast they're going, and how many cars are in which direction.
The technology also lets cars access "fastest-route" information, calculated by organizing all the data reported from mobile phones, taxi services, and vehicles using this system. How much traffic is on a road is shown via the real time map by thin or thick lines, which then helps your GPS system take the fastest route. Pretty great for when you have to commute back and forth to work—something we're glad to have given up.
The communications portion should be in testing until the end of fiscal '07, and the dynamic route finding will be tested 'til end of fiscal '08. After that, it'll probably be a few years before it's deployed in Japan, and a bunch more before we get them here—if we get them at all.