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

When freeway traffic is four lanes going 80 mph, the freeway isn’t the bottleneck. The exits are the bottlenecks. There is a benefit to expanding two lanes to maybe three or four. But expanding four lanes into six or seven just means that one guy who’s about to miss his exit will slow down and cross six lanes at the last second. There’s a real benefit to improving exits, adding lanes or device scanners to toll booths, anywhere people have to NOT “drive 80mph in a straight line”. Those are your bottlenecks.