I've always wanted to run a traffic simulation to see if traffic is eliminated if the highway was partitioned (5-10 rows of car per partition) into several chunks going at a precise speed and requiring cars to maintain some distance between the next partitions behind them. This could be accomplished with some tracking laser following the cars against the wall. Of course this would be ruined as soon as drivers wanted to hop into the partition in front of them, change lanes, etc.

Another slightly relevant idea is to mark intersections with a large red no-go area placed at the calculated point, where, if you were going the speed limit, if the traffic signal changed to yellow and you were in this box you could not safely pass the stop line. I hate having to guess how long a yellow light is (3 to 6 seconds is a large gap).