The car could have some sort of wireless (4G, WiFi, etc...) to download updated/detailed data for new routes when it needs it, and store locally what it will li

The car could have some sort of wireless (4G, WiFi, etc...) to download updated/detailed data for new routes when it needs it, and store locally what it will likely need again in the future. Since the car knows where it's going, as long as it has some idea of when it will be in range of a wireless access point, it can plan when and how it will download the rest of the trip information on the way. As long as the car has basic route information and knowledge about where it will be able to connect to servers with updated information. Cars could drive anywhere with basic road info, and download updated and more detailed information (intersection metadata, possible closures, etc...) only as needed. It doesn't always need to be in wireless range, it just needs to know when it will be so it can plan accordingly.