Hi Willee,
The mathematical answer is, because straight lines create congestion on small roads. High-speed circles do the opposite, de-congest. Look at for example real world car circle-rounds known as round-abouts in American English, I believe, if I'm not mistaken. The similarity of reality is exactly this; except the ones we see here are highway-speed. So 100 or 110kph, if that makes sense, circle roads in a simulator. Oh man I love it.

Tyvm Cushy.

Tried this, it really kills the traffic flow.

why isn't the midddle just a straight road?