Did you know that Harbor drive is closed during Summerfest? That makes perfect sense, since there are 50,000 people coming and going from the gates. It would be a nightmare if that road were open during the festival. There is one vehicle that does travel that road during the fest. The artist shuttles move up and down that road all day.
If you want a glimpse of who is about to play, or who just performed, peek into the windows of those shuttle buses. Most of the buses are picking up musicians that wait at the south lot. Some of the biggest acts are brought to the festival grounds by other means, but your rank and file touring bands come and go via shuttle.