...or why diverging diamonds won't work.
If you look closely at the diverging diamond fairy tale animations you will notice that one key ingredient of Atlanta traffic is missing. Assholes. Specifically the asshole that is three lanes to the left on southbound Ashford Dunwoody when she knows damn well she intends to get onto 285 westbound. And she expects at least two lanes of traffic to come to a complete halt so she can get over. At the last minute.
And she's not alone. That intersection is an asshole magnet, attracting some of the biggest and most obnoxious this region has to offer. If Dunwoody is number one in anything it is asshole drivers. Any day. Any time. Damn near anywhere, but especially there.
Why do these assholes do this? Because if they queued up in the correct lane whilst just north of Hammond, they might have to sit their self-righteous asses in a bit more traffic, that's why. Much better to zoom on down in what is clear to everyone is the wrong lane and push in just before the entrance ramp light. So they're not only assholes, they're arrogant assholes.
And arrogant assholes will deep six the best laid plans of our traffic engineers. You know, the same geniuses that brought the disaster known as the Lexus Lanes. Probably related to those that think that extending Peachford is something other than a road to nowhere. Unlike those two the diverging diamond looks like it should work. Problem is none of the traffic engineering accounts for assholes, and with the diverging diamond we can expect the current crop of last minute "left to right" assholes to be joined by a similar set of "right to left" assholes. While the diamond may diverge, what happens when the lefties and righties converge? You know they will.
Our only hope is that the scheme will be so confusing it scares folks away from the entire perimeter area.