Here's my solution: Every radio station broadcasts a small burst of modulated data within its station identification. This data gives the frequencies of nearby radio stations which play similar music. When your car drives to the edge of the station's range, it automatically checks these frequencies; if one of them has a stronger signal than the others, it'll switch to that one. Thus, you can listen to classic rock on a coast-to-coast drive without ever having to hunt around on the radio dial.