Do more lanes & buses curb congestion?

Your area has bad traffic? Just widen the roads! is the standard reaction.

Liberal politicians like this answer because it “creates jobs,” and developers like it subsidizes their housing development. But this latter fact suggests that maybe more lanes doesn’t actually reduce congestion: The developers want to build more houses out in Gainesville, and so they want more lanes. But those new houses in Gainesville — some of which wouldn’t be built without the new lanes — mean more cars, and thus maybe as much congestion, only on more lanes.