424
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.
It will deadlock in the center because the car lanes are used for two directions. Unless you upgrade those unidirectional lanes into bi-directional pairs of lanes.
And it will still deadlock, so you have to put a round-robin semaphore in the middle.
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.
No one should reach the center. The lines are dotted. If anyone ends up in the center they deserve a deadlock.
The center should put you on an out-spiraling bridge that feeds traffic back into the outermost lane. Then even the most indecisive drivers are accommodated. Or just a deep pit of punishment.