Here's something fun and counter-intuitive:

From default settings, set speed variance to 50%, launch frequency to 120 cars/minute, and reaction time to 500ms. Unsurprisingly, this is chaos.

Then, keeping those settings, clear the cars and set the target speed to 150km/h. The traffic mostly clears up! Since the cars are going faster, they leave the road sooner, meaning fewer are on the road at a time, fixing most problems.

(Of course, in real life, this also makes the accidents that do occur worse.)