I envision traffic as a viscous fluid. Unlike fluids that we are used to, like flowing water, maple syrup, or honey, this fluid wants to flow in multiple directions at once. If you can imagine a stream that flows both uphill and downhill at the same time, and sometimes acts like thick molasses, other times like corn starch suspension, and other times like mercury, you are ready to think about traffic.

This bizarre fluid does obey certain rules, which are consistent and discoverable. Once you have all the rules, you can model an entire system and run experiments.

That said, I hate roundabouts. They seem to combine the worst elements of multiple solutions to make all drivers equally unhappy and inconvenienced. It is somehow okay that no one wins, because everyone loses.