The laser rangefinder would probably the easiest. Instead of trying to monitor the speed of the car in front of you, you could monitor the distance. You would set how far back you wanted to stay and the cars cruse control would do the work. If the distance was greater than the set distance -- speed up, if it was less than the set distance -- slow down the computer already does the by monitoring the speed of the car so this would just be an addition. You would have to of course put in some kind of safety measure that if the distance changed dramatically very quickly (i.e., someone changing lanes in front of you) because you would want the computer to try and compensate for the sudden change and slow down to maintain the set space and the new car. Also of course if the car you were monitoring changed lanes it would compensate the other way and try and maintain a distance for the next car so it would accelerate very quickly. The main thing to think is there is no way any of this is going to work without human supervision. Maybe in the future when ALL the cars are controlled by computer and communicate with each other a totally computer driven car will be possible but all it would take would be one of us with our old beefed up Bonnies to cut a computer off and all hell would break loose. The computers wouldn't know what to do.

Parallelcircuits

humm.. with all this talks about sensors and stuff.. would there be some kinda delay to reflect real life environment like heavy rain, snow, fog, blowing leaves ( from us Dumb *** that has to deal with winter )

an interface into the control unit would work, where you could program the distance. I read an article in PopSci magazine awhile back and the big names in luxury cars have these coming out on thier cars pretty soon.