Here are a couple videos of the system in action. The first video is what it looks like in the cab, the second video shows the blinky lights on the FB.
http://www.youtube.com/watch?v=YFqfTlqF2NY
http://www.youtube.com/watch?v=YBoFKmAFVfc
Since I originally posted, I have added a yaw sensor to the system, which makes the steering much smoother. The only time I feel it make a steering adjustment is when I go through some rough ground. Even then, it is only a 3-6" steering move. I have gotten the line-holding ability down to staying within 6" of the line, and I'm still working on making the even smaller. My goal is 2-3".
And since you guys brought it up, I am told that there are city buses in Minneapolis that are being driven by GPS. The driver brings the bus to the curb, and puts it back in the traffic lane, but then the computer takes over and steers the bus along the route. The driver still has control of the throttle/brakes, and of course can manually steer to avoid a collision or whatever.
-Lance