You know what happens with those signs? I do. Took our neighborhood several months to get the city to remove the one from in front of my house and prevent them from putting it up somewhere else so the kids in my neighborhood didn't get killed.
What happens is this:
Safe drivers are already safe and the sign is retarded and nothing more than a pointless blinking visual distraction.
Unsafe drivers see the sign as a challenge and speed up so they can see how fast they can drive by the sign, meanwhile ignoring the children playing in the neighborhood so they can watch the sign to see their speed blink.
The theoretical psychology behind these systems maybe interesting, however theory isn't reality and these signs are most definitely far more dangerous than not having them as anyone who's actually been around them is aware.
In Portugal I saw a cute system - if you pass a sensor driving faster than the speed limit, then a traffic signal 200yards/metres down the road turns red for 10 seconds, making you (and again anyone behind you) stop.
Absolutely fucking retarded. Creating congestion never raises safety levels. Ever. What happens is people just go faster to run the light or run it anyway. You may think its cute, sounds pretty fucking dangerous to me. Its always a good idea to make speeders suddenly stop unexpectedly and have to hit the brakes hard ... especially with other people speeding behind them ... brilliant idea ... really ... who comes up with this stuff? How many accidents suddenly start happening right around that red light? Hmm? There are less speeding accidents, and twice as many accidents involving the red light being ran or people getting rear ended at it.
I love how someone invents a theory sitting behind a desk somewhere and without actually looking at what happens in the real world, they ignore all the other contributions to the equation and lose sight of reality resulting in a more dangerous situation that you started with.
You want safer driving? Require drivers have more of a clue. Don't let any random moron drive (Here in America if you can breath you can drive, and there are exceptions for non-breathers) and you won't have as many issues. Punish those who drive unsafe stiffer, take away their drivers license. Its not a right, its a privilege.
What you don't do is introduce more distractions and changes to throw unexpected things at the driver. They do this in video games to raise the difficultly level ... perhaps these scientists and others who think this is a good idea should play a few video games and get a clue.