Erik, is your comment regarding the distance to the car in front of you not changing appreciably in 10km an example, or a real-life sample?

I ask because I would not be surprised that there might not be any visually noticeable difference when following a car for 6 minutes. And I would attribute that to the limits of human perception rather than the accuracy of the cruise control--judging distances can be difficult, especially in moving vehicles with no fixed frame of reference for comparison.

Now, if you followed a car for an hour--or maybe even a half hour--and observed the same thing then that would be a little more surprising to me.

For what it's worth, when I use cruise on the highway I almost always have my Palm-based GPS on the dashboard. My observation has been that the cruise control holds the vehicle speed *very* accurately to the point that my GPS doesn't show any variation in speed; since the GPS program shows one decimal point of precision that tells me the cruise control keeps the speed constant to within about 0.1 miles per hour.

To me the interesting part of your question isn't so much that the speed is very constant, but that two independent cars were able to randomly set the speed to the same value. Of course, that becomes less and less interesting if you had played with the decelerate/accelerate buttons a couple of times to fine-tune the speed before you were able to follow the car at a constant distance.

Regards,
Craig Steiner