I've done a search, but can't find this discussed anywhere.
I drove a series III Prius today with radar cruise control. I noticed that it actually brakes if, for example, you go down a hill which would increase the speed.
I have a 2006 IS250 SL. The radar cruise certainly brakes quite hard if necessary to match the speed of the car in front, but if there's no car in front and you're travelling downhill, the speed will increase unchecked.
Has the Prius just got a better system, or is there's something up with mine?