What I'm missing is right lane preference, that would control how much people obey the rule that you shouldn't be on the leftmost lane unless you are faster then the cars in the right lane in front of you and if you aren't much faster then the car that's next to you on the right lane you should slow down and place yourself after it or speed up and place yourself in front of it.
It's horribly painful to watch two slow cars occupying both lanes next to each other.
Or indeed left-lane preference, for British and Japanese users.
But yes a more sophisticated simulation would use > 2 lanes, and have various controls for lane discipline, especially since poor lane discipline is a major contributor to congestion. This is a suggestion not a criticism btw, I had fun with this.
It's horribly painful to watch two slow cars occupying both lanes next to each other.