Molson Hart

I'm trying to understand what kind of effect adding lanes has on the effectiveness of highway transport and I...can't. Suppose you have a single lane highway between A and B. In theory, its capacity is infinite.

In practice, cars can only go as fast as the slowest car on the highway (1). Merging causes slowdowns (2). And accidents stop traffic all together (3). When you add a second lane, you solve 1, you mitigate 2, and you sort of improve 3 (an accident increases merging which slows).