I’ve been following a forum thread by a traffic engineer. It’s been massively interesting, especially given my intense hatred for some of the cocked up road designs that have come out of GDOT in Atlanta. It turns out I’m largely correct: they’ve been screwing up. Several locations are poorly designed and introduce the dreaded ‘weaving’, where people are desperate to get out of and into a lane due to exit placement, a very dangerous trend (I-75 south between the I-285 ramp and the GA-85 exit, for instance).

One of the other things he’s touched on is speed limits versus how fast you can actually safely drive on a road. It’ll be no shocker to anyone: speed limits are very frequently artificially lowered due to political considerations (read: old people bitching).

He’s written an article on the subject that covers most of the good bits. It’s a little on the technical side but he does do a good job of explaining what he means. Well worth a read if you have a few.

http://www.deadcatbounce.com/features/featurescat/highway-handbook-why-we-speed