A physicist at the University of Michigan has built a computer simulation to model how "adaptive cruise-control" technology in cars may affect traffic flow. The system would use radar to keep vehicles from getting too close to each other. From Science News:
Its advantage is that it can respond much more quickly and precisely than human drivers can to any change in speed. A vehicle using adaptive cruise control typically brakes sooner and more smoothly than one without the system….
Intriguingly, at an average speed of 67 miles per hour, if only one in five vehicles used adaptive cruise control, no traffic jams would form and traffic would generally flow freely. At lower concentrations, however, intermittent episodes of traffic congestion would still be an issue.
