[tshaddox]

But there is some limit to the number of lanes you can add, even theoretically from a topological perspective, but more imminently from a practical standpoint of limited budgets and ability to tear down existing non-road infrastructure.

[AnthonyMouse]

The theoretical limit is irrelevant. It's like saying you can't always improve emergency response time because of the speed of light. Nobody is really up against the theoretical limit.

The practical limits are all trade offs. How much does it cost to add two lanes? How much does it cost to maintain low ridership bus service to low density suburbs? There are circumstances in which adding more lanes is the best available alternative.