The irony is that when traffic builds up to the point of critical flow-density, such backwards waves are needed to allow space to grow between the vehicles. Traffic jams serve as bottlenecks that allow traffic in front of the jam to clear. Drivers accelerating out of the front of a traffic jam have room to drive precisely because the traffic jam held them back to allow that room to form.

People don't seem to realize that any bottlenecks clear the road in front of them in this way. Left-turn arrows that hold back left-turning traffic, for example, perform such a function. So do long traffic signals. So do accidents. So does narrowing a road down a lane before adding the lane back after some distance (literally a bottleneck). Remove all bottlenecks from traffic and you will eventually end up with one huge traffic jam.

Driverless cars could actually achieve a perfect singularity of a unified traffic jam if they were all steady enough and homogenously programmed. You would just need to keep adding one at a time to the roads until they all reach their simultaneous operating limitations. At that point, the backward wave would be total and everything would stop.

Hopefully at that point there will be a bike lane and sidewalks for everyone to get by the vast sea of frozen motor-traffic.