I heard about that one on the Neal Boortz show. It really raised the question of what are speed limits for. More people cause wrecks and aggressive driving by going at or under the speed limit than those who go over it. The worst cause of wrecks (in this study) was lane changes caused by people who fail to keep right except to pass.
As a side note, the college students who did that project were not obeying the keep right to pass law, but the point of their study was to show how rediculious a 55mph speed limit is on the Atlanta loop. It worked and has gotten LOTS of attention on the Atlanta talk radio.
Why don't they allow people to VOTE on speed limits? I don't know many people who would even WANT a speed limit, except maybe in towns, around schools and in residential areas.