The cruise control system as fitted in our cars (Gen5, Gen5.5, Gen6 and Gen6.5 Camry/Aurions) are all basic speed control systems that work perfectly well on flat roads. On uphill roads, depending on gradient and torque output of the engine, it will force the transmission to downshift if it senses that it is not keeping up with the set cruise speed, which if you are not expecting the downshift action may cause a slight panic moment for the driver. This is particularly the case with the 4cyl models where a surging effect can be felt when travelling over minor undulations with cruise control set because it is unable to maintain the set constant speed. On downhill roads, as described in a previous post, the cruise control does nothing except cut all throttle input. For Gen5 and Gen5.5, because the throttle is controlled by throttle cable and part of the cruise control system consists of a mechanical device daisy-chained onto the cable, the device simply releases the throttle cable to a point that it believes is zero throttle input, but in fact there is still a tiny amount of throttle input being registered hence one can still feel throttle input. This is probably one reason why Gen6 and beyond switched to drive-by-wire technology where zero throttle input actually means zero throttle input. The cruise control systems where brakes are applied on downhill roads are actually called Active Cruise Control systems where the it can instruct the braking system to apply the brakes; Merc S Class and high end Lexus technology. Previous posts also mentioned the experience of a 'speed hold' function when the car is travelling downhill. This is completely separate of the cruise control system and is actually a function of the auto transmission as fitted to Gen6 Camry/Aurion and beyond and is something that Toyota Japan have fitted to a lot of their auto transmission cars, I think, 2 generations ago. -m_luke