[jeremysmyth]

Don't forget Amdahl's law though. You might be able to optimize away the reaction time with good AI, but you can't optimize away mechanical factors like engine failure, tire grip, and road surface friction. This affects the maximum speed and traffic density just like a human's reaction time.

This means that if one car in a densely packed column fails (blowout, engine seizure, ...) then the car immediately behind it is still subject to its mechanical ability to avoid a collision (swerve into empty space or brake to a hard stop at speed) no matter how fast it reacts.