It is bizarre that we are discussing making cars entirely autonomous as a way of improving safety, but refuse to consider the much more feasible option of technologically restricting speed on public roads.
While it is a no brainer to say every vehicle should be traveling sufficiently far behind another such that they have enough time to stop before they hit the one in front, this spacing out of vehicles will result in longer travel times as you are effectively reducing road capacity by having each vehicle take up more space on the road. Instead, it's (politically) easier to have each person take individual risks of getting into a collision.
However, with autonomous vehicles, it should be politically easier to force this constraint because the liability will be shifted from individuals to presumably the manufacturer so the manufacturer isn't going to stick their neck out so the individuals can save time on their commute.
This is for two reasons:
1) slower traffic requires a smaller safety gap between each vehicle.
2) the dominating factor in traffic jams is often people responding to the brake-lights of the people in front of them. People over compensate and therefore a "braking bubble" (Soltion: https://en.wikipedia.org/wiki/Soliton ) forms in the traffic which causes it to get even more spaced out.
Keeping traffic flowing is more important to throughput than keeping it flowing it fast. Constant braking and speeding up on a busy road means that the flow rate is constantly disrupted and this causes the traffic to tend towards clumping and congestion.
You're not "in traffic"; you "are traffic".
Maximum throughput at a fast speed with minimal spacing between vehicles is more than maximum throughput at a slower speed with minimum spacing between vehicles. I see this in every urban area, people sacrifice safety for speed.