Nice improvement, but it's still based on other vehicles and not temporary terrain changes like bridges and overpasses.Adaptive cruise uses a radar module that is hidden in the grille of the vehicle, or sometimes behind the emblem in the grille (if you've ever seen a Lexus, or Cadillac with the smooth emblem in the grille, thats how you can tell) to gauge the distance from the vehicle in front of you, and keep a preset distance.
Lets say you set the adaptive cruise for 75MPH, and someone gets in your lane doing 65, the car will automatically slow, and keep that preset distance until that vehicle moves out of your path, and will then resume 75. Some GM systems will even completely stop the vehicle, and maintain itself in stop and go traffic.