I think the goal should be cars that drive the way people should, but cannot. There would be no actual traffic jams because the cars, networked together, could adjust speed, merge at speed and do all the things people cannot and will not because they view driving as a competition and not a team effort.
It would eliminate most reasons for car accidents. http://seriousaccidents.com/legal-advice/top-causes-of-car-accidents/
Distractions, speeding, intoxication, recklessness, redlights, stop signs, teen driving, night driving, lane changes. All the human factors would be removed. All the texters would be free to text their stupid little hearts out.
The only remaining source of accidents would be actual malfunctions of one kind or another. Weather conditions - rain, ice, fog, etc - could be drastically reduced by programing the cars to drive at more sensible speeds. Road conditions and malfunctions would be the remaining causes.
If you've seen the movie Minority Report, self driving cars were the ubiquitous mode of public transit and it was glorious.