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xkcd #2842: Inspiraling Roundabout
(imgs.xkcd.com)
Alt text:
Look, I just think we need to stop coddling those hedonistic roundabout hogs who get into the inner lane and circle for hours, wasting valuable capacity.
Simpler solution, just add a bottomless pit or small singularity in the middle to absorb excess traffic.
Sorry I'm late for work, I got sucked into a black hole again. No, I didn't take a picture of the event horizon, you should just take my word for it. I wouldn't even be late if it weren't for the time dilation.
An infinite spiral could easily solve these problems.