I was driving on a roller coaster type road, speed limit was 40 mph. I set the cruise control to 45. While going down steep hills the speed went up to 62 mph. When going up hill the cruise control kept speed at 45. Is it normal for cruise control to work this way? I don't ever remember having to use the brake to keep the speed from rising above where it was set. I have had the car for 2 years and have 60,000 miles on it, but I don't use the cruise control very often.
Yes that is normal for how the Cruise control works, on all cars not just the prius. It is hard to find a that is steep enough for that to happen though.
Well, isn't that interesting. Not being a regular user of cruise control, I didn't know it would not control speed down a hill. Why wouldn't the car know when to use the brakes?
This feature is just not incorporated into the cruise control systems. It can obviously be done, but is a matter of cost I guess. Some cars have a "distance radar" as option now, where the car will brake if you get too close to the car in front - this works together with the cruise control system, so when the distance is over a certain lenght again, the car picks up it's speed.
The classic Prius could maintain downhill cruise control speed quite well in "B" but that has been disabled in the newer model.
Unlike conventional cruise control systems, BMW's ACC (Active Cruise Control) system is actually able to adjust the car's speed to suit the surrounding traffic conditions. It utilizes the distance radar concept I believe. It applys the brakes when going downill as needed to maintain a constant speed.
