Anyone who’s led a tour probably knows the rule: the bigger the group, the slower you go. This is true for bicycling or walking, that it will generally take more time to cover the distances, to get through the intersections.
While not technically a chart, this animation from a German logistics company called PTV has some chart-like qualities, and illustrates well the relationship between transportation mode, complexity, space and time.
I don’t know the specifics of this model, but the basic equation is that the number of individual agents, where each agent is assigned individual qualities, things like reaction time or acceleration rates. Then you let them react to each other, and you can model a traffic environment.
It turns out that cars require a lot of space! Combined that with the sheer number of vehicles, and you get a sense for why [cars + density] = congestion.