eli5: would adding more lanes to a freeway/busy street really ease congestion or would you still get bottlenecks?

Question

I mean theoretically adding a lane or two should allow more cars to flow through, or would bad drivers still cause bottlenecks/gridlock despite the added capacity?

In: 28

Answer 1

Besides what everyone else have explained about induced demand, I remember reading in a book that after 3 lanes per side, lane changes becomes one of the big bottlenecks slowing down traffic. We humans are not good at driving; some people tend to do many unnecessary lane changes causing disruption that gets propagated trough the whole freeway, having extra lanes increases the amount of lane changes people perform exponentially, causing more disruption that eats away any gains from the extra lanes.