Why not use a traffic sensor system (camera's/pressure sensors) plus highway lights/signs to monitor traffic and visibly relay the 'suggested driving speed' to cars further back in traffic? (i.e. take out the ACC automation and rely on people's acceptance of a more efficient system).

Eliminate the day dreamers and problem solved.

One day you won't have to drive. One day the car (if it's still known as such) will take you to your destination after you tell it where that is. You won't drive, it will be GPS guided all the way. You will just sit back and relax.
One day...

Much of the bunching up in section or what we in Toronto call the "accordion" effect is caused by ineffective civil engineering planning of the traffic light systems. You will have a very busy avenue that is pockmarked with slower side streets. For inexplicable reasons they will allow these side streets to dominate the ingress/egress traffic light times vs the heavily trafficked avenue. So instead of having a busy avenue with moving traffic, you have small side streets with traffic lights lasting 3 minutes dictating the flow of traffic on a busier street. Stupid

This is valuable work and eventually will be useful. I love the animation which does clearly prove the concept.
Sadly, until absolutely every vehicle on the road is fitted with ACC and the necessary modification, there would seem little chance of it being implementable.
I'd love to think this could happen sooner but it seems more likely to be twenty years away from utilisation on the road network.
Perhaps there are other potential applications ...perhaps the concept could be adapted for air traffic control to avoid 'stacking' while waiting for landing slots.

Rocky - that's nothing, you should try France. They do something similar, but without the traffic lights called "Priorité a droite", so small side roads have priority over the main roads they join. Except they repealed this law. Or maybe they didn't. Or maybe only in some places. Or on some days. Or when you see this sign (which might vary), or where you don't see this sign. Net result: total confusion; nobody has a clue who has right of way, and road deaths in France are double the UK, despite having less than half the traffic density. And how does the French presidency deal with this insanity? By giving an amnesty to all outstanding speeding offences on winning an election. Maybe they just want fewer voters?

I would wonder how this behaves when you include the possibility of cars changing lanes when they see a tie-up up ahead.

Much of the slowdown in highway traffic is due to turbulence caused by drivers who repeatedly pass vehicles moving at posted speed and return to the same lane. They advance to the next regular-speed vehicle and repeat the maneuver until there is no more room in the next lane to pass again. Those vehicles must then slow down to posted speed with the rest of the traffic ahead, creating a backup (bunching up) of cars where there used to be normal spacing. Vehicles traveling behind must now slow down, as the vehicles that were behind them are now crowded in front, using up all the safe gap space that used to be there. It takes only one jumper on a busy highway to have an effect; with many of them you can get a real slowdown that affects everyone, jumpers alike. When all traffic moves together at the same speed everyone gets down the road quicker.

An aftermarket adaptive cruise control addon would be very nice.
One more thing that causes these traffic snarls is when people do "pulse and glide". Slow acceleration to just above or right at the speed limit then take their foot off the accelerator pedal until they slow down to a certain speed under the limit, then they slowly accelerate again. There's even little microcontroller based computers that can do this automatically.
But some of the real snobby ones doing that have no care for anyone else on the road and will P&G on a busy road instead of just choosing a speed and sticking to it. They'd rather be a jerk and make it impossible for anyone behind them to use their cruise control.

no offense to the University of Exeter folks, but we knew about the backward travelling waves (2nd order differential wave equations) at MIT back in 1987.
Still really cool though