They tried that experiment in Tucson in the late 90s. They advertised the hell out of it, all over the radio and TV. There were large highly visible signs along the side of the road that varied as the traffic flow changed that said "Traffic Lights Synced for 40 mph" where the number 40 would vary from 40 down to about 30 depending on traffic.
Didn't help, not even a little. The city left that system in place for a full year if I remember right before giving up on it.
People really are that stoopid.
