I am having the same problem as mentioned in consumer complaint: ODI case number: 10188438 (component: Vehicle speed control:cruise control). Whenever I start up a steep or slightly steep hill with the cruise control on, the car doesn't start to accelerate soon enough. Then, it appears to accelerate all at once. I have started accelerating the car myself, rather than allowing the cruise control to accelerate, on hills. As stated in the previous complaint, the cruise control works fine on fairly level ground.

- High Point, NC, USA

The car's cruise control behavior on level ground is fine, but on rolling hills it's totally egregious, and indicates to me that this feedback control system may be close to instability and therefore potentially dangerous. I think that the control algorithm used is dreadfully sub-optimal, and has such long internal control-loop processing delays that its reactions to changing road conditions are alarming. What I find is the following behavior. The car substantially overshoots (by 10 mph or more) the set speed on the downhill portion of each hill, but then waits so long before reacting to the beginning of the next uphill portion, that it then undershoots the set speed by such a large amount (5 mph or more) that it has to "floor" the accelerator in order to catch up. Still on the uphill portion, it then proceeds to overshoot the set speed again, before finally settling down to the desired speed. This cycle of events repeats over and over again as one negotiates rolling hills with the cruise control "on." Why is the internal loop delay so long" why is the cruise control system not properly designed" (I happen to have expertise in control systems.) this control system really needs to be re-designed as a matter of priority! the cruise control's behavior could then be fixed by a simple firmware update.

- Waterloo, Ontario, Canada, 00, USA

Cruise control varies speed by 7 mph hour when engaged during non flat terrain causing a safety issue with cars following. When on flat terrain the cruise control maintains its target speed within +- 1 mph with no problems. The safety issues occurs when the vehicle encounters rolling hills, the cruise control will allow the speed to decrease by as much as 5 mph while descending down the hill, then as it begins to climb will aggressively accelerate to 2 mph over the target speed. When the road flattens out again it will maintain the original target speed. At highway speeds, 70 mph, this causes safety issues especially when traffic conditions are moderate to heavy in that traffic follow will not have any indication that the speed is slow by 5 mph. This in turn will cause a hazardous situation where a collision could occur. This has been reported to the local Toyota dealer and Toyota support responded that all is working within parameters and no adjusts are planned. Case # 200701250758 has been opened with Toyota customer relations with no promise of action.

- Georgetown, TX, USA